2022/05/19 更新

写真a

シバヤマ トモヤ
柴山 知也
所属
理工学術院 創造理工学部
職名
教授
プロフィール
1953年東京都文京区本郷生まれ。東京大学工学部土木工学科卒、同大大学院工学系研究科修士課程修了。工学博士。東京大学助手、同講師、同助教授、横浜国立大学助教授、教授を経て、2009年早稲田大学理工学術院教授(社会環境工学科)、横浜国立大学名誉教授。専門は土木工学(海岸工学、海洋開発、沿岸域防災、津波・高潮、建設社会学)。
著書:「Handbook of Coastal Disaster Mitigation for Engineers and Planners」Esteban・Takagi・Shibayama 共編著、Elsevier、2015年、「日本の海岸」 柴山知也・茅根創 編著、朝倉書店、2013年、「3.11津波で何が起きたか-被害調査と減災戦略」 単著、早稲田大学出版部、2011年、「Coastal Processes」 単著、World Scientific、2008年、「建設技術者の倫理と実践 増補・改訂版」 単著、丸善、2004年など。
2004年インド洋津波(スリランカ、インドネシア、タイ)、2005年カトリーナ高潮(米国)、2006年ジャワ島中部地震津波(インドネシア)、2007年シドル高潮( バングラデシュ)、2008年ナルジス高潮(ミャンマー)、2009年サモア津波(サモア)、2010年チリ津波(チリ)、2010年メンタワイ諸島津波(インドネシア)、2011年東北地方太平洋沖地震津波(日本)、2012年サンディー高潮(米国)、2013年ヨランダ高潮(フィリピン)等、いずれも調査隊長を務める。早稲田大学・東日本大震災復興研究拠点・複合災害研究所所長(2011年-2016)、土木学会海洋開発委員会委員長(2010年-2014年)、私立大学戦略的研究基盤形成事業『減災研究の国際展開のための災害研究基盤の形成』研究代表者(2013-2018)、早稲田大学・持続的未来社会研究所所長(2018年-現在)を務めた。過去にEditor in Chief, Coastal Engineering Journal、日本沿岸域学会副会長、神奈川県庁環境影響評価審査会会長、日本海洋工学会会長などを歴任し、現在は日本沿岸域学会会長を務めている。

兼担

  • 理工学術院   大学院創造理工学研究科

  • 附属機関・学校   グローバルエデュケーションセンター

学内研究所等

  • 2020年
    -
    2022年

    理工学術院総合研究所   兼任研究員

学歴

  •  
    -
    1979年

    東京大学   工学系研究科   土木工学  

  •  
    -
    1977年

    東京大学   工学部   土木工学科  

学位

  • 東京大学   工学博士

 

研究分野

  • 水工学

研究キーワード

  • 沿岸域防災

  • 海岸工学

論文

  • A Comparison between Agent-Based and GIS-Based Tsunami Evacuation Simulations: A Case Study for Tofino, BC

    Joseph Kim, Tomoyuki Takabatake, Ioan NISTOR, Tomoya Shibayama

    Canadian Journal of Civil Engineering    2021年06月

     概要を見る

    Soft measures such as evacuation planning are recommended to mitigate the loss of life during tsunamis. Two types of evacuation models are widely used: (1) Agent-based modelling (ABM) defines sets of rules that individual agents in a simulation follow during a simulated evacuation. (2) Geographical information systems (GIS) are more accessible to city planners, but cannot incorporate the dynamic behaviours found in ABMs. The two evacuation modelling methodologies were compared through a case study by assessing the state of evacuation preparedness and investigating potential mitigation options. The two models showed different magnitudes for mortality rates and facility demand but had similar trends. Both models agreed on the best solution to reduce the loss of life for the community. GIS may serve as a useful tool for initial investigation or as a validation tool for ABMs. ABMs are recommended for use when modelling evacuation until GIS methodologies are further developed.

    DOI

  • Engineering Lessons from September 28, 2018 Indonesian Tsunami: Scouring Mechanisms and Effects on Infrastructure

    Clemens Krautwald, Jacob Stolle, Ian Robertson, Hendra Achiari, Takahito Mikami, Ryota Nakamura, Tomoyuki Takabatake, Yuta Nishida, Tomoya Shibayama, Miguel Esteban, Nils Goseberg, Ioan Nistor

    Journal of Waterway, Port, Coastal and Ocean Engineering   147 ( 2 )  2021年03月  [査読有り]

     概要を見る

    The September 28, 2018 earthquake and tsunami, which occurred north of Palu City, Indonesia, attracted widespread interest from the scientific community due to the unusually large tsunami that occurred after a strike-slip earthquake with a relatively small moment magnitude (MW = 7.5). To understand the structural performance of buildings and infrastructure under hydrodynamic loads and their associated effects, the authors conducted field surveys in Palu City. Light wooden frame constructions and masonry infill walls were common in the area, some of which were severely damaged by the earthquake and tsunami. Reinforced concrete structures remained predominantly intact, although they suffered soil-related issues such as scour around rigid building members. Local structural failures caused by the loss of supporting soil were also observed during the field survey, resulting in an overall reduction in the stability of the inspected structures. Based on the observations made, knowledge gaps and research needs concerning coastal and structural scouring are discussed. These are tied into the latest community research activities and put in the context of a published ASCE standard chapter that discusses tsunami design.

    DOI

  • The mechanism of fluidization in mud beds under progressive waves

    Mohsen Soltanpour, Kourosh Hejazi, Mohammad Hadi Jabbari, Tomoya Shibayama, Shinsaku Nishizaki, Tomoyuki Takabatake

    Coastal Engineering Journal   63 ( 1 ) 32 - 51  2021年  [査読有り]

     概要を見る

    Wave-flume laboratory experiments were conducted to study the mechanism of fluidization of partially consolidated mud beds, under wave propagation. The mixture of commercial kaolinite and tap water was allowed to partially consolidate under its self-weight before initiating the progressive wave propagation. The vertical changes in pore water pressure in the mud bed were monitored by using sensitive pore pressure transducers, at three levels across the mud layer depth. The experiments revealed that the wave characteristics and bed properties strongly affect the complex fluidization process, in which the accumulated pore water pressure develops through four transitional stages. The accumulated pore water pressure increases sharply at the first stage, which is followed by further gradual increases in the next two stages, with different rates. The breakup of aggregated mud particles, i.e. the generation of fluid mud, is observed at the last stage, resulting in a partial dissipation of accumulated pore pressure and wave height attenuation. The measurements also revealed that the fluidization starts from the top of the mud layer, and proceeds to the underlying layers.

    DOI

  • Effect of translate speed of typhoon on wind waves

    Naoto Inagaki, Tomoya Shibayama, Miguel Esteban, Tomoyuki Takabatake

    Natural Hazards   105 ( 1 ) 841 - 858  2021年01月  [査読有り]

     概要を見る

    Quantitative assessments on the effect of translate speed of typhoons on wind waves were carried out.A WRF-SWAN coupled model that used observed meteorological data was applied to eight different typhoons in the vicinity of Shiono-Misaki, on the pacific side of Honshu Island, Japan. The authors proposed a new methodology to modify the translate speed and wind field of tropical cyclones using an empirical model in which the gross wind speed is expressed as the summation of two different types of wind generation. Two different trends of the relationship between the significant wave height (H ) and translate speed (V) were found, describing the most dominant parameter. Typhoons with a modest intensity and size (for the case of Japan) generally showed a positive correlation between the change in the maximum H and V, which means translation wind speed was the dominant parameter. In contrast, stronger typhoons were less sensitive to the change in V and could maintain high waves even when almost stationary. With reference to the results, it is important to raise awareness of the future problems that could be caused by large storms that stall for prolonged periods of time. s s

    DOI

  • Experimental and numerical investigation of tsunami behavior around two upright sea dikes with different heights

    Kotaro Iimura, Tomoya Shibayama, Tomoyuki Takabatake, Miguel Esteban

    Coastal Engineering Journal   63 ( 1 ) 1 - 16  2021年  [査読有り]

     概要を見る

    The 2011 Tohoku Tsunami caused severe damage to many coastal defenses along the Japanese coastline, including areas where two adjacent upright sea dikes of different heights met. There are many places along the coastline where structures of different heights and shapes meet due to the various design codes. In this study, the authors aim to examine the tsunami flow around such dikes by conducting three-dimensional hydraulic experiments in a tsunami wave basin and numerical simulations using the fluid dynamics model OpenFOAM. Twelve experimental cases were tested by changing the waveforms, and also by keeping the height of one side of the dike model constant while adjusting the dimensions of the other side. The results show that the difference in height between the structures significantly influences the volume of overtopping over the relatively lower dike and the inundation depth and velocity behind the dikes. Furthermore, different characteristics of inundation patterns are observed between the inundation depth and velocity. Hence, this study illustrates the necessity to re-assess the effectiveness of such structures against tsunami events.

    DOI

  • Influence of Edge Waves on Tsunami Characteristics along Kujukuri Beach, Japan

    Kentaro Koyano, Tomoyuki Takabatake, Miguel Esteban, Tomoya Shibayama

    Journal of Waterway, Port, Coastal and Ocean Engineering   147 ( 1 )  2021年01月  [査読有り]

     概要を見る

    The 2011 Tohoku Earthquake and Tsunami generated a massive tsunami that devastated Kujukuri Beach in Chiba Prefecture, Japan. The possibility that edge waves were involved in the propagation mechanism of the tsunami was investigated by using a numerical method. To detect the components of edge waves, the fluctuations of the simulated sea level, the variations of the power spectral and the phase, coherences, as well as the dispersed relations of the wavelength and the period, were analyzed. As a result, it was possible to conclude that there is a high probability that edge waves could have propagated around this coastline. In addition, to analyze the various types of edge waves that could be expected three additional earthquake scenarios were considered, each of them with a different magnitude and epicenter: The 1896 Sanriku Earthquake, the 1677 Empo Boso-oki Earthquake, and the 1703 Genroku Kanto Earthquake. This comparison indicates that there is a particular risk that edge waves can be generated by large earthquakes with their epicenter in the northern part of the Japan Trench.

    DOI

  • Extreme waves induced by cyclone Nargis at Myanmar coast: numerical modeling versus satellite observations

    Thit Oo Kyaw, Miguel Esteban, Martin Mäll, Tomoya Shibayama

    Natural Hazards    2021年  [査読有り]

     概要を見る

    The deltaic coast of Myanmar was severely hit by tropical cyclone Nargis in May 2008. In the present study, a top-down numerical simulation approach using the Weather Research and Forecasting (WRF) and Simulating WAves Nearshore (SWAN) models was conducted to study the meteorological and offshore wave characteristics of cyclone Nargis near the coast of Myanmar. The WRF simulation results agree well with the observed data from the India Meteorological Department. SWAN simulation results were compared with the WaveWatch 3 model by National Oceanic and Atmospheric Administration and validated against available measurement data from satellites. The model results show relatively good agreement, and hindcast with satellites data (significant wave height only) shows a correlation coefficient value of 0.89. The SWAN and satellite comparisons also show better fit for high wave conditions. The resulted maximum significant wave height of 7.3 m by SWAN is considerably higher in energy than the seasonal waves normally prevalent at Myanmar’s deltaic coast. The possibility of high energy waves due to cyclones should be considered during the design and operation of coastal and offshore projects in the area, particularly given the risks that climate change can intensify cyclones in the future. Since Myanmar lacks a dense network of in-situ observational stations, the methodology used in the current study presents the potential application of various numerical techniques and satellite data to estimate extreme wave conditions near the Myanmar coast.

    DOI

  • Tropical Cyclones in the Arabian Sea: overview and simulation of winds and storm-induced waves

    Mohsen Soltanpour, Zahra Ranji, Tomoya Shibayama, Sarmad Ghader

    Natural Hazards    2021年  [査読有り]

     概要を見る

    Three recent Tropical Cyclones (TCs) over the Arabian Sea, i.e., the super cyclone Gonu, the low intense cyclone Ashobaa, and cyclone Phet (with an unusual track), are studied using a high-resolution atmosphere-wave model and observations. The reliable performances of both atmospheric and wave models were established using the available field measurements, in which the modeling improvement in comparison with the previous studies is met. The effects of input parameterizations on the wave and wind estimations in the presence of TCs were examined. TCs track and intensity were more sensitive to the microphysics and cumulus schemes. Concerning the multi and single peaked wave spectra, three steps of wave generation, growth, and dissipation were addressed. Bimodal seas and swells exist in both generation and dissipation stages, whereas the seas are dominant in the growth stage. The performance of Westhuysen was better in modeling the combination of seas and swells.

    DOI

  • Physical modeling of tsunamis generated by subaerial, partially submerged, and submarine landslides

    Tomoyuki Takabatake, Martin Mäll, Dawn Chenxi Han, Naoto Inagaki, Daichi Kisizaki, Miguel Esteban, Tomoya Shibayama

    Coastal Engineering Journal   62 ( 4 ) 582 - 601  2020年12月  [査読有り]

     概要を見る

    In the present study, three different types of landslide-generated tsunamis (subaerial, partially submerged and submarine) were investigated through laboratory experiments that used 261 different experimental conditions. The results show that, for the near-field region, the subaerial landslide generated a higher leading wave, while the submarine landslide generated a higher second wave. However, frequency dispersion considerably influenced their propagation, with the leading wave decaying and the trailing waves being enhanced. The present study also revealed that the leading wave has higher values for wave celerity, period, and length than the second wave, regardless of landslide type. It was also shown that the celerity of the leading wave and second wave can be approximated by the solitary wave theory and third-order Stokes theory, respectively. Using the extensive experimental dataset obtained, predictive equations to estimate the maximum crest amplitudes generated by partially submerged and submarine landslides were also developed. A comparison with the experiments of previous researchers and field survey data from the 2018 Palu Tsunami indicated that these equations can estimate reasonably well the height of the generated tsunami. It was also shown that the relative mass and initial position of the landslide are influential nondimensional parameters to determine the tsunami amplitudes generated.

    DOI

  • Numerical Analysis of Seismic Water Level Oscillations in Canals

    Koichiro Ohira, Tomoyuki Takabatake, Miguel Esteban, Rafael Aranguiz, Martin Mäll, Tomoya Shibayama

    Journal of Waterway, Port, Coastal and Ocean Engineering   146 ( 6 )  2020年11月  [査読有り]

     概要を見る

    Water level oscillations induced by the ground motion of an earthquake have occasionally been observed in a closed or partially enclosed water system. The generated water disturbances can induce localized flooding, boat collisions, breakage/damage of moored cables due to water disturbances, or even the capsizing of vessels. In this study, the authors focused on cases of seismic water level oscillations in canals and attempted to investigate the potential hazards of and effective countermeasures against them through numerical simulations. The proposed numerical simulation model was first validated by reproducing the water level oscillation that was actually observed at a canal in Mexico City (Xochimilco Canal) during the 2017 Central Mexico Earthquake. The method was then applied to one of the canals in Tokyo (Keihin Canal) to clarify the potential water level fluctuations that can take place due to this phenomenon. The results indicate that while the risks of local inundation would be low, small boats, which can be found in many places in the canal, are at risk of capsizing. Finally, the use of wave-dissipating blocks was found to be an effective countermeasure to decrease the potential for a significant seismic water level oscillation to take place in this canal.

    DOI

  • Estimation of volcanic ashfall deposit and removal works based on ash dispersion simulations

    Yosuke Tomii, Tomoya Shibayama, Yuta Nishida, Ryota Nakamura, Non Okumura, Hideaki Yamaguchi, Yosuke Tanokura, Yu Oshima, Natsuko Sugawara, Kota Fujisawa, Takayuki Wakita, Takahito Mikami, Tomoyuki Takabatake, Miguel Esteban

    Natural Hazards   103 ( 3 ) 3377 - 3399  2020年09月  [査読有り]

     概要を見る

    Volcanic ashfall can cause considerable social impacts to a wide geographical area. Given the challenge to predict volcanic eruptions, it is essential to simulate the dispersion of ash as soon as possible after an event and promptly estimate the distribution of deposits and necessary removal works. In this study, a series of procedures to improve the accuracy of the WRF-FALL3D model for the case of the eruption of Mt. Kusatsu-Shirane in 2018 are proposed, which were verified through field surveys of ash deposits, showing that the accuracy of the model can be improved by selecting a range of column heights and promptly conducting field surveys following an event. Also, a methodology to estimate the amount of work necessary to clear road networks and river channels is proposed, which was applied to a volcanic event similar to that of the Hoei eruption of Mt. Fuji in 1707. The results also emphasize the need to improve the estimation of column heights in the future, which is of paramount importance to ensure the safety and operational continuity of human infrastructure in the vicinity of major active volcanoes.

    DOI

  • Suspended sand concentration models under breaking waves: Evaluation of new and existing formulations

    Gabriel Lim, Ravindra Jayaratne, Tomoya Shibayama

    Marine Geology   426  2020年08月  [査読有り]

     概要を見る

    A total of 7 reference concentration (C ) models (6 existing and 1 newly proposed) were validated against 119 test cases from 4 recently published datasets collected under the LIP, CROSSTEX, SandT-Pro and SINBAD experimental studies. These models were evaluated for performance in different cross-shore regions: the shoaling zone, breaking (outer surf) zone and inner surf zone, under regular and irregular breaking wave conditions. In almost all existing C models, substantial under-prediction was found particularly around the wave plunging point (point at which breaking wave plunges and surface generated turbulent kinetic energy, TKE, is injected into the water column) where strong localised increases in C were observed. This strong increase in concentration was attributed to the large-scale breaking-generated turbulent vortices invading the wave bottom boundary layer (WBBL) and entraining dense clouds of sediment near the plunging point. Models that were directly or indirectly driven by local wave climate such as the local wave height (H), breaker height (H ) or local water depth (d), were found to perform quite poorly in the breaking region under regular and irregular plunging breaker waves. Formulations that related C to the sand pickup rate (i.e. depending on exerted bed shear exceeding critical bed shear for entrainment) were adept in regions unaffected by external breaking-induced TKE (e.g. the shoaling zone) but could not account for the high levels of concentration observed at the plunging point. This is because these formulations were based on the implicit assumption that sediment entrainment is only induced by the local TKE generated by bed shear; not taking surface-generated breaking-induced TKE into account. This assumption was addressed in more recent studies, by including breaking-induced TKE into sediment pickup rate or reference concentration formulations. Though latest studies have shown promising relationships between near-bed TKE (k ) and reference concentration/sediment pickup, such formulations also face inherent limitations. These formulations are highly dependent on the accuracy of measured or modelled k and are also sensitive to the magnitude of k . For example, the magnitude of measured k was found to vary by a factor of 1.1–1.3 between regular and irregular wave conditions, with k being smaller under irregular wave conditions. This resulted in varied performance between datasets in k -driven reference concentration formulations. The Froude-scaled TKE produced smaller deviations in magnitude of TKE between datasets, suggesting that it may be a more suitable driving parameter for reference concentration models than k . A new reference concentration model, L19, was empirically derived from an inverse relationship observed between d and C , and from the roller energy dissipation rate. The newly proposed L19 model shows good agreement with measured C (with RMSE ranging between 0.36 and 1.79 kg/m over the different datasets) in regular and irregular wave conditions, even at the plunging point where concentration is highest. The modified concentration profile [C(z)] equation also performs well, generally capturing the vertical concentration profile accurately throughout the whole water column. 0 0 0 b 0 b b b b b b b 0 0 3

    DOI

  • Simulated effectiveness of a car evacuation from a tsunami

    Tomoyuki Takabatake, Kota Fujisawa, Miguel Esteban, Tomoya Shibayama

    International Journal of Disaster Risk Reduction   47  2020年08月  [査読有り]

     概要を見る

    © 2020 Evacuation plays an important role in saving lives during tsunamis. Although evacuation by vehicle is generally not recommended, it could be helpful for vulnerable people who cannot walk fast (e.g. the disabled, elderly, or infants). In the present study, the authors developed an agent-based tsunami evacuation model that considers the behaviour of both pedestrians and car evacuees, which can be important to formulate effective evacuation plans. The model developed was validated through comparisons with the actual traffic jams observed at Tagajyo City, Japan during the 2011 Tohoku Earthquake Tsunami. The model was then applied to another coastal city in Japan (Shinguu City) to investigate the effectiveness of an evacuation plan that considers vehicle use for evacuation during a future Nankai-Tonankai Earthquake Tsunami. The simulated results indicate that considering the capacity of evacuation places and the choice of route is important for a successful evacuation, especially for a coastal area where the number of evacuees could exceed the total capacity of its evacuation buildings.

    DOI

  • Comparative Analysis of Triggers for Evacuation during Recent Tsunami Events

    Takahito Mikami, Tomoya Shibayama, Miguel Esteban, Rafael Aránguiz

    Natural Hazards Review   21 ( 3 )  2020年08月  [査読有り]

     概要を見る

    © 2020 American Society of Civil Engineers. In the case of a near-field tsunami event, coastal residents must quickly become aware of the potential danger of a tsunami taking place and start taking actions to evacuate. The present paper aims to show which types of evacuation triggers worked amongst coastal residents with different characteristics and backgrounds by conducting a comparative analysis of four recent near-field tsunami events. The results of the analysis showed that basic knowledge about tsunamis had been spreading throughout the areas studied, which triggered many people to evacuate soon after feeling ground motion, almost regardless of how frequently each area had experienced tsunami events in the past. Educational activities and community-based efforts appear to be some of the reasons that can explain this finding. However, because some people in areas with fewer past experiences only evacuated after noticing last-minute signs and there is a nonnegligible number of visitors present in the coastline of certain communities, continuous efforts toward developing tsunami awareness are still needed. The results of the analysis also showed that in areas with fewer past experiences, people were more likely to wait for messages from the authorities to decide to evacuate. This finding highlights the importance of teaching local residents and visitors how a tsunami can reach a given area in a relatively short period of time.

    DOI

  • The 2018 Sulawesi tsunami in Palu city as a result of several landslides and coseismic tsunamis

    Rafael Aránguiz, Miguel Esteban, Hiroshi Takagi, Takahito Mikami, Tomoyuki Takabatake, Matías Gómez, Juan González, Tomoya Shibayama, Ryo Okuwaki, Yuji Yagi, Kousuke Shimizu, Hendra Achiari, Jacob Stolle, Ian Robertson, Koichiro Ohira, Ryota Nakamura, Yuta Nishida, Clemens Krautwald, Nils Goseberg, Ioan Nistor

    Coastal Engineering Journal   62 ( 4 ) 1 - 15  2020年06月  [査読有り]

    DOI

  • Effectiveness of hard and soft tsunami countermeasures on loss of life under different population scenarios

    Tomoyuki Takabatake, Miguel Esteban, Ioan Nistor, Tomoya Shibayama, Shinsaku Nishizaki

    International Journal of Disaster Risk Reduction   45  2020年05月  [査読有り]

     概要を見る

    © 2020 Elsevier Ltd The present study proposes a comprehensive investigation of the tsunami-evacuation plans for a popular coastal area considered to be at high risk for tsunami attack. If a coastal region constitutes a renowned sightseeing location or has a popular beach, numerous tourists and beach users could be at risk of a tsunami. However, tsunami risk management strategies have generally been developed considering only local residents, and the effects of the presence of tourist on the effectiveness of countermeasures have rarely been taken into account. To investigate changes in the effectiveness of tsunami countermeasures under different population scenarios, the authors further developed an existing agent-based tsunami evacuation simulation model. Through the application of this model to Yuigahama Beach in Kamakura City, Japan, it was found that the effectiveness of hard measures (i.e., elevating the road embankment) is slightly influenced by the numbers and types of evacuees who are present on or near the beach when a tsunami arrives. However, the effectiveness was greatly influenced by the type of soft measures (i.e., changing the evacuation behaviour) employed. It was also shown that, if there are many evacuees in a coastal area, soft measures merely aiming at early evacuation and guiding evacuees to the closest evacuation place via the shortest route could instead worsen the fatality rate. The present study thus sheds further light on the importance of establishing tsunami mitigation strategies that focus on the tourist population, in order to minimize the number of fatalities that could result from a future event.

    DOI

  • Pseudo-climate modelling study on projected changes in extreme extratropical cyclones, storm waves and surges under CMIP5 multi-model ensemble: Baltic Sea perspective

    Martin Mäll, Ryota Nakamura, Ülo Suursaar, Tomoya Shibayama

    Natural Hazards   102 ( 1 ) 67 - 99  2020年05月  [査読有り]

    DOI

  • Tsunami risk hazard in Tokyo Bay: The challenge of future sea level rise

    Ryutaro Nagai, Tomoyuki Takabatake, Miguel Esteban, Hidenori Ishii, Tomoya Shibayama

    International Journal of Disaster Risk Reduction   45  2020年05月  [査読有り]

     概要を見る

    © 2020 Sea level rise is one of the major challenges facing humanity in the 21st century, and could compound the risks posed by tsunamis to coastal cities. The authors conducted computer simulations of tsunami inundation and propagation into Tokyo Bay, and analysed the risks that such events pose to the cities of Yokohama and Kawasaki, for different sea level rise scenarios . The results show that unless significant investment in improved coastal defences is made, the area that can potentially be flooded by such events will gradually increase in the course of the 21st century. However, the risk to the life of the inhabitants of these cities will broadly remain unchanged until sea levels become +1.0 m higher than at present. From then, the risk of casualties taking place will rapidly increase, as the depth and velocity of the tsunami wave will substantially rise. Such results provide some indication regarding the long-term planning strategy to manage coastal defences around Tokyo Bay, highlighting the need to eventually reinforce coastal defences and the important contribution of tsunami evacuation to minimize casualties during such events.

    DOI

  • Effect of bed roughness on tsunami bore propagation and overtopping

    Miguel Esteban, Jochem Jan Roubos, Kotaro Iimura, Jorrit Thomas Salet, Bas Hofland, Jeremy Bricker, Hidenori Ishii, Go Hamano, Tomoyuki Takabatake, Tomoya Shibayama

    Coastal Engineering   157  2020年04月  [査読有り]

     概要を見る

    © 2019 The accurate modelling of overtopping of coastal defences by tsunami waves is of vital importance for the formulation of disaster management strategies. To improve knowledge of this phenomena the authors conducted experiments on coastal structure overtopping using bores that were generated by a dam-break mechanism. Three types of structures were tested, namely a coastal dyke, a wall, and a wall of infinite height. The results highlight the necessity to consider the energy present in a bore to determine if a structure will be overtopped or not. As a result of these experiments an empirical formula to determine the height of overtopping given the incident bore height and velocity was validated. The study highlights the importance of clearly modelling the velocity and Froude number of a tsunami. Such experiments should be conducted on rough beds, for which a suitable Manning's n seems to be around 0.06 sm-1/3. The study also contrasted the results obtained to those of the ASCE7 method, and concludes that the Manning's n values recommended in ASCE7 are probably too low.

    DOI

  • Post-event survey of locally concentrated disaster due to 2019 Typhoon Faxai along the western shore of Tokyo Bay, Japan

    Takayuki Suzuki, Yoshimitsu Tajima, Masashi Watanabe, Naoki Tsuruta, Hiroshi Takagi, Tomoyuki Takabatake, Kojiro Suzuki, Takenori Shimozono, Yoshinori Shigihara, Tomoya Shibayama, Shingo Kawaguchi, Taro Arikawa

    COASTAL ENGINEERING JOURNAL   62 ( 2 ) 146 - 158  2020年03月  [査読有り]

     概要を見る

    Typhoon Faxai caused severe damages along the western shore of Tokyo Bay, Japan in September 2019. Retaining a relatively small radius of maximum wind, Faxai passed across the center of Tokyo Bay and caused intensive wind and waves. While the sea level anomaly recorded at several tide gauge stations along Tokyo Bay were at most 1 m, and no significant surge-induced inundation was found, locally concentrated damages and wave-induced hazards were observed around Yokohama, on the middle-western shore of Tokyo Bay. The observed inundation height around Yokohama was TP (Tokyo Peil) 4.2 m on average, and the highest runup, TP 10.8 m, was observed at a small hill directly behind the seawall in Fukuura, Yokohama. The estimated wave overtopping directions at each location varied from the northeast to southeast, and no clear correlation was found between the wave overtopping directions and the extent of observed coastal hazards. Based on these findings and investigations of recorded data such as wind and waves, it was deduced that locally concentrated damages and hazards around the middle western shore of Tokyo Bay may be explained by the unique features of a relatively compact Faxai and the topographical characteristics of Tokyo Bay.

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  • Experimental and analytical investigation of the response of a mud layer to solitary waves

    Mohsen Soltanpour, S. Hadi Shamsnia, Tomoya Shibayama, Ryota Nakamura

    Ocean Dynamics   70 ( 2 ) 165 - 186  2020年02月  [査読有り]

    DOI

  • Evaluation of force exerted by tetrapods displaced by tsunami on caisson breakwater return wall

    Go Hamano, Hidenori Ishii, Kotaro Iimura, Tomoyuki Takabatake, Jacob Stolle, Miguel Esteban, Tomoya Shibayama

    COASTAL ENGINEERING JOURNAL   62 ( 2 ) 170 - 181  2020年02月  [査読有り]

     概要を見る

    Tsunamis can cause large damage to breakwaters and other protection structures placed along the coastline. The strong flows generated by such waves can move the armor units of composite breakwaters, leading to large impact forces on the caissons behind them. In the present work laboratory experiments were carried out in a flume to determine the forces that can result from such impacts. Then, an empirical equation that would allow the estimation of these forces was proposed, with the aim of facilitating the construction of returning walls and parapets situated on top of caissons.

    DOI

  • Tsunami awareness and evacuation behaviour during the 2018 Sulawesi Earthquake tsunami

    Anisa Shafiyya Harnantyari, Tomoyuki Takabatake, Miguel Esteban, Paolo Valenzuela, Yuta Nishida, Tomoya Shibayama, Hendra Achiari, Rusli, Abdul Gafur Marzuki, Muhammad Fadel Hidayat Marzuki, Rafael Aránguiz, Thit Oo Kyaw

    International Journal of Disaster Risk Reduction   43  2020年02月  [査読有り]

     概要を見る

    © 2019 Elsevier Ltd On September 28, 2018 significant tsunami waves, which are considered to have been generated by submarine landslides, struck the shorelines of Central Sulawesi, Indonesia. One month after the event, the authors conducted a questionnaire survey of the affected areas (Donggala Regency and Palu City) to collect information on the evacuation behaviour and tsunami awareness of local residents. In the present study, in addition to summarising the overall trend of the survey results using descriptive statistics, a chi-squared test was applied to analyse the significance of the relationship between tsunami awareness and evacuation behaviour and the demographic characteristics of respondents. The analysis of the results demonstrates that although the respondents generally have a high level of tsunami awareness, younger people and Donggala Regency residents have an overall lower understanding of the phenomenon. It was also found that 82.5% of the population evacuated after witnessing others evacuating during the event. As there was no official warning to residents before the arrival of the tsunami, this social trigger played a significant role in prompting evacuation and decreasing the number of casualties. The present study also revealed that many people faced congestion while evacuating (especially in Palu City). This highlights the need to introduce additional tsunami disaster mitigation strategies to ensure that all residents can swiftly evacuate during such incidents.

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  • Simulations of future typhoons and storm surges around Tokyo Bay using IPCC AR5 RCP 8.5 scenario in multi global climate models

    Ryota Nakamura, Tomoya Shibayama, Miguel Esteban, Takumu Iwamoto, Shinsaku Nishizaki

    Coastal Engineering Journal   62 ( 1 ) 101 - 127  2020年01月  [査読有り]

    DOI

  • Analysis of multi-layer safety in countries affected by recent tsunamis: Emergence of a global tsunami culture

    M. Esteban, V. Tsimopoulou, T. Mikami, N. Y. Yun, A. Suppasri, T. Shibayama

    Proceedings of the 7th International Conference on Asian and Pacific Coasts, APAC 2013     444 - 449  2020年

     概要を見る

    Since 2004, there is a growing awareness of the risks that tsunamis pose to coastal communities globally. Despite the fact that these events were already an intrinsic part of the culture of some countries such as Chile and Japan, many other places had virtually not heard about such phenomenon before 2004. Nevertheless, the frequent reoccurrence of major tsunamis in recent years has led to the emergence of a “tsunami culture” in many areas of the world, which has resulted in increased awareness, disaster preparedness and willingness of local populations to evacuate when the threat of these events arises. However, evacuation during a tsunami is still not successfully carried out by the different elements of society, pointing to lack of awareness, an over-reliance in defence mechanisms or lacking in the transmitting of knowledge from previous events. This paper will explore these cultural issues using as a basis questionnaires carried out by the authors during their own field visits to the last three major events (Chile in 2009, Indonesia in 2010 and Japan in 2011), and interpret these through the willingness of coastal communities to build protection measures along the shore and the impact that these can have on sustainable development. The existence of a “traditional tsunami culture” will be explored through an analysis of the existence of multi-layer safety system constructed by previous generations, and whether this is being preserved nowadays or past lessons are being forgotten.

  • Present and future tsunami and storm surge protections in Tokyo and Sagami bays

    T. Shibayama, K. Ohira, T. Takabatake

    Proceedings of the 7th International Conference on Asian and Pacific Coasts, APAC 2013     764 - 766  2020年  [査読有り]

     概要を見る

    © APAC 2013.All rights reserved. On March 11, 2011, a large earthquake that occurred offshore the northeast coast of Japan generated a large tsunami which devastated extensive areas of the Tohoku coastline and large casualties were recorded. Based on the experiences, coastal protection works in Japan are now in the process of modifications. In the present paper, Tokyo and Kanagawa are taken as examples and new methodologies are explained in the area. For the case of storm surge, a new model is applied to predict the future behavior of storm surge. For the case of tsunami, Genroku Kanto Earthquake (1703), Keicho Earthquake (1605) and Meiou Tokai Earthquake (1498) were mainly discussed in the numerical analysis, since tsunamis caused by these three earthquakes gave strong damages to coastal area of Kamakura, and left influences to Yokohama and Tokyo. New tsunami flood maps over coastal land area based on numerical simulations were presented to the residents of coastal region on April 2012 in Kanagawa prefecture. For Kamakura area, Keicho Earthqueke takes 90 minutes to reach the Kamakura coast and the height is over 12 m. But for the case of Genroku Kanto earthquake it takes 25 minutes and the height is 8 m. It appears that there are two different types of risk, 1) high wave comes but we have time for evacuation and 2) relatively small wave comes quickly and time is limited for evacuation. New countermeasures including soft and hard techniques are also required.

  • IMPACT ASSESSMENT OF SLOSHING IN BAYS AND LAKES

    OHIRA Koichiro, TAKABATAKE Tomoyuki, MIKAMI Takahito, SHIBAYAMA Tomoya

    Journal of JSCE   8 ( 1 ) 13 - 25  2020年  [査読有り]

     概要を見る

    <p> Water–level fluctuations resembling long period waves, which differ from normal wind waves, were observed immediately after the Tohoku earthquake of 2011 in multiple locations, such as lakes in Yamanashi Prefecture, the fjords of Norway, and other sites located far away from the epicenter. Not many research on similar abnormal water–level fluctuations have been conducted thus far and, in many cases, these studies have treated the phenomena as seiches. However, researchers have not established concrete wave generation mechanisms and evaluation methods, and their awareness of this phenomenon and disaster prevention remains low. In this study, the authors sought to select a quantitative impact assessment method and learn more about this phenomenon. The authors used previous research and eyewitness accounts to judge that onsite slosh dynamics caused the waves to generate, and the authors attempted to recreate this phenomenon using a 3-D slosh dynamic analysis. After comparing laboratory results to verify the validity of the analysis, the authors recreated past examples of waves and also made future predictions. As a result, the authors were able to recreate abnormal water–level fluctuations based on this method. In addition, the authors identified water damage risks to in-land lakes and waterways of inner parts of bays. These are different from risks posed by tsunamis. The waves are formed immediately after the onset of an earthquake.</p>

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  • Field survey and evacuation behaviour during the 2018 Sunda Strait tsunami

    Tomoyuki Takabatake, Tomoya Shibayama, Miguel Esteban, Hendra Achiari, Nanda Nurisman, Mustarakh Gelfi, Trika Agnestasia Tarigan, Elsa Rizkiya Kencana, Muhammad Aldhiansyah Rifqi Fauzi, Satriyo Panalaran, Anisa Shafiyya Harnantyari, Thit Oo Kyaw

    COASTAL ENGINEERING JOURNAL   61 ( 4 ) 423 - 443  2019年10月  [査読有り]

     概要を見る

    On the 22nd of December 2018 the shorelines of Sunda Strait, Indonesia, were hit by tsunami waves generated by the flank collapse of the Anak Krakatau volcano. The authors conducted a field survey of the affected areas in both Sumatra and Java islands to collect information on tsunami inundation and run-up heights, damage patterns at each coastal community, and the evacuation behaviour and tsunami awareness of the affected people. The survey results showed that in Sumatra island inundation heights of more than 4 m were measured along the coastline that was situated to the north-north-east of Anak Krakatau, while less than 4 m were measured along the north-western direction. Inundation heights of over 10 m were measured at Cipenyu Beach (Pandeglang Regency) in Java island (south-south-eastern direction from Anak Krakatau). A questionnaire survey conducted by the authors revealed residents' perception of danger and evacuation patterns during the event. The results indicate the importance of having an operational tsunami warning system in Sunda Strait and the establishment of an appropriate evacuation plan so that residents can start evacuation immediately and reach a safe place without facing severe congestion along evacuation routes.

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  • Street-scale storm surge load impact assessment using fine-resolution numerical modelling: a case study from Nemuro, Japan

    Ryota Nakamura, Martin Mäll, Tomoya Shibayama

    Natural Hazards   99   391 - 422  2019年10月  [査読有り]

     概要を見る

    © 2019, Springer Nature B.V. Due to gradual sea level rise and changes in the climate system, coastal vulnerability to storm surge hazards is expected to increase in some areas. Studies regarding the effect of storm surge inundation on buildings and human lives, especially when it comes to relatively low-threat level events, have been few, however. In this research, storm surge load impact around coastal residential areas was quantitatively assessed, through fine-resolution numerical modelling. Meso- and street-scale simulation results for a storm surge event in Nemuro, Japan, were comprehensively validated against observations and field measurements, and the simulation results showed good accuracy for sea level, significant wave height and inundation area. A fine-resolution, street-scale coastal flood simulation was carried out with individual and grouped buildings, created with a building block model, and the results showed the significant role of buildings by realistically capturing inundation dynamics. Hydrodynamic results showed that coastal flood impact on buildings was insignificant (consistent with surveys). Lastly, the potential flood impact on people in the streets was investigated, using five human instability equations, where the most pessimistic results showed average values between 0.0 and 0.2 (max 0.6–0.7), and slightly below 0.4 for children and the elderly, respectively. These values indicated that threat levels during the Nemuro storm event were low, which corresponded with observations (no fatalities). This study framework could be applied wherever an accurate local storm surge threat estimate was required.

    DOI

  • Experimental investigation on the influence of arrangement of buil-dings on tsunami run-up flow

    Hidenori Ishiii, Tomoyuki Takabatake, Miguel Esteban, Go Hamano, Kotaro Iimura, Tomoya Shibayama

    Laboratory study of tsunami be-havior around two upright sea dikes with different heights    2019年09月  [査読有り]

  • Laboratory study of tsunami be-havior around two upright sea dikes with different heights

    Kotaro Iimura, Tomoya Shibayama, Tomoyuki Takabatake, Miguel Esteban, Hidenori Ishii, Go Hamano

    Proceedings of the Coastal Structures Conference 2019    2019年09月  [査読有り]

  • Numerical Simulation of Beach Changes on Seisho Coast by Typhoon Jongdari

    Proceedings of the 10th International Conference on Asian and Pacific Coasts    2019年09月  [査読有り]

  • Numerical modelling of coastal inundation from Cascadia Subduction Zone tsunamis and implications for coastal communities on western Vancouver Island, Canada

    Tomoyuki Takabatake, Philippe St-Germain, Ioan Nistor, Jacob Stolle, Tomoya Shibayama

    NATURAL HAZARDS   98 ( 1 ) 267 - 291  2019年08月  [査読有り]

     概要を見る

    In the present study, numerical simulations were conducted to estimate the spatio-temporal characteristics of tsunami inundation for municipalities on Vancouver Island, Canada, as a result of various potential Cascadia Subduction Zone earthquake deterministic scenarios. By varying the earthquake magnitude and associated slip distance, the influence of these parameters on the tsunami wave propagation, inundation, and the possible damage on infrastructure and buildings was investigated. A numerical tsunami inundation model based on nonlinear shallow water equations was constructed using publically available bathymetric and topographic data and applied to three study areas: the City of Port Alberni, the District of Ucluelet, and the District of Tofino. The numerical results obtained in this study show that the maximum tsunami inundation depth and spatial extent of inundation are sensitive to the earthquake magnitude, whereas the tsunami arrival time is not. For the worst-case earthquake scenario investigated (M-W 9.3), all of the three study areas were extensively inundated. Results of tsunami wave amplitude and overland inundation depth, flow velocity, hydrodynamic force, and depth-velocity product are analysed in detail to assess the impacts of the tsunami on inland buildings. The potential damage was estimated with previously proposed fragility curves for wood, reinforced concrete, and steel frame buildings. In conjunction with a site reconnaissance visit by the authors for better understanding the general characteristics of these areas, model results suggest that significant damage to buildings would occur, especially to wooden constructions, with considerable risk of loss of human life.

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  • Field Survey of the 2018 Sulawesi Tsunami: Inundation and Run-up Heights and Damage to Coastal Communities

    Takahito Mikami, Tomoya Shmayama, Miguel Esteban, Tomoyuki Takabatake, Ryota Nakamura, Yuta Nishida, Hendra Achiari, Rusli, Abdul Gafur Marzuki, Muhammad Fadel Hidayat Marzuki, Jacob Stolle, Clemens Krautwald, Ian Robertson, Rafael Aranguiz, Koichiro Ohira

    PURE AND APPLIED GEOPHYSICS   176 ( 8 ) 3291 - 3304  2019年08月  [査読有り]

     概要を見る

    On September 28, 2018, a large earthquake and its accompanying tsunami waves caused severe damage to the coastal area of Palu Bay, in the central western part of Sulawesi Island, Indonesia. To clarify the distribution of tsunami inundation and run-up heights, and damage to coastal communities due to the tsunami, the authors conducted a field survey 1 month after the event. In the inner part of Palu Bay tsunami inundation and run-up heights of more than 4 m were measured at many locations, and severe damage by the tsunami to coastal low-lying settlements was observed. In the areas to the north of the bay and around its entrance the tsunami inundation and run-up heights were lower than in the inner part of the bay. The tsunami inundation distance depended on the topographical features of coastal areas. The southern shore of the bay experienced a longer inundation distance than other shores, though generally severe damage to houses was limited to within around 200 m from the shoreline. The main lessons that can be learnt from the present event are also discussed.

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  • 2018 Typhoon Jebi post-event survey of coastal damage in the Kansai region, Japan

    Nobuhito Mori, Tomohiro Yasuda, Taro Arikawa, Tomoya Kataoka, Sota Nakajo, Kojiro Suzuki, Yusuke Yamanaka, Adrean Webb, Tomoyuki Takahashi, Sooyoul Kim, Susumu Araki, Yoko Shibutani, Takashi Yamano, Daiki Sakai, Tomohiro Takagawa, Naoki Tsuruta, Shingo Kawaguchi, Syota Asahi, Takashi Fujiki, Takumu Iwamoto, Yu Chida, Tomoya Shibayama, Miguel Esteban, Tomoyuki Takabatake, Ryota Nakamura, Kohji Uno, Tetsuya Kakinoki, Yasuo Nihei, Daisuke Inazu, Takaaki Shigematsu, Kazunori Sameshima, Kazuhiko Honda, Daiki Satomura, Ibuki Tsujisawa, Kentaro Kumagai, Noriki Sugahara, Shoichi Emoto, Yoshimitsu Tajima

    Coastal Engineering Journal   61 ( 3 ) 278 - 294  2019年07月  [査読有り]

     概要を見る

    © 2019 Japan Society of Civil Engineers. Typhoon Jebi in 2018 caused severe damage along areas of Osaka Bay, Japan. After the storm, a Japan Society of Civil Engineers (JSCE) coastal survey group surveyed the coastal impacts and recorded watermarks inside Osaka Bay and along the Pacific. The maximum storm tide recorded by a tide gauge was 3.29 m at the Osaka Tide Station, which is a historical high for Osaka Bay. Coastal flooding consisted of both storm surge and wave run-up in almost all locations, with flooding exceeding 5 m and 12 m in elevation from mean sea level in the inner parts of Osaka Bay and along the Pacific coast, respectively. Coastal damage was severe in areas located outside of coastal barriers, such as ports and harbors, while residential areas were mainly well protected and spared due to coastal protection systems. In addition, some inland flooding occurred in the Kobe-Ashiya regions due to the storm surge propagating up several small rivers. This survey report summarizes the findings of the post-event survey by JSCE and analyzes the relation between maximum water level and resulting damage.

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  • A semi-empirical formula for calculating the breaking depth of plunging waves

    Wenang Xie, Tomoya Shibayama, Miguel Esteban

    Coastal Engineering Journal   61   199 - 209  2019年04月  [査読有り]

     概要を見る

    © 2019 Japan Society of Civil Engineers. A new semi-empirical formula for calculating the breaking depth of plunging breakers is proposed in this study. The shallow water equation is used as the governing equation, and the wave front slope, which is one of the key parameters that governs the breaking criterion, is obtained from it analytically. The analytical formula was then modified based on both physical considerations and historical laboratory data. The accuracy of the resulting semi-empirical formula was examined using two sets of new laboratory data - including laboratory experiments performed by the authors - in order to verify its applicability. The results indicate that the proposed new formula is more accurate than existing formulas.

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  • Adaptation to sea level rise on low coral islands: Lessons from recent events

    Miguel Esteban, Ma. Laurice Jamero, Leonard Nurse, Lilian Yamamoto, Hiroshi Takagi, Nguyen Danh Thao, Takahito Mikami, Paul Kench, Motoharu Onuki, Angelie Nellas, Richard Crichton, Ven Paolo Valenzuela, Christopher Chadwick, John Erick Avelino, Nicholson Tan, Tomoya Shibayama

    OCEAN & COASTAL MANAGEMENT   168   35 - 40  2019年02月  [査読有り]

     概要を見る

    In the past two decades there have been fears that many low-lying atoll islands around the world could disappear as a consequence of climate change and sea level rise, leading to mass migration and threatening the existence of several island nations. Here we show how sea level rise does not inevitably lead to coastal areas becoming uninhabitable, and that humans have an innate and often underestimated capacity to adapt to changes in their environment. To do so we showcase three instances of human- and earthquake-induced land subsidence that have taken place in the 21st century, where the coastal/island areas are still inhabited despite the challenge of living with higher water levels: the Tohoku coastline following the 2011 Tohoku Earthquake Tsunami (subsidence similar to 0.4-1.0 m), the present day situation of coastal areas in Jakarta due to ground water extraction (> 5.0 m), and the islands of Tubigon, Bohol in central Philippines after the 2013 Bohol Earthquake (similar to 1.0 m). Humans are able to adapt and arrive at solutions even when confronted with cases of rapid rises in water levels, and thus it is likely that in the future vulnerable coastlines will be engineered and largely remain at present day locations, particularly in densely populated areas. If anything, around densely populated areas it is more likely that humans will continue to encroach on the sea rather than the reverse. We caution, however, that small islands are not homogeneous, and many are unlikely to respond to rising sea levels in the manner that atolls do (in fact, many might just resort to build at higher elevations). Where engineering and other adaptation responses become necessary, the financial and human resource requirements may well be beyond capacity of some small islands, which could lead to impoverishment and associated challenges in many communities.

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  • Engineering Lessons from the 28 September 2018 Indonesian Tsunami: Debris Loading

    Jacob Stolle, Clemens Krautwald, Ian Robertson, Hendra Achiari, Takahito Mikami, Ryota Nakamura, Tomoyuki Takabatake, Yuta Nishida, Tomoya Shibayama, Miguel Esteban, Ioan Nistor, Nils Goseberg

    Canadian Journal of Civil Engineering   47 ( 1 ) 1 - 12  2019年  [査読有り]

    DOI

  • Debris transport over a sloped surface in tsunami-like flow conditions

    Jacob Stolle, Tomoyuki Takabatake, Go Hamano, Hidenori Ishii, Kotaro Limura, Tomoya Shibayama, Ioan Nistor, Nils Goseberg, Emil Petriu

    COASTAL ENGINEERING JOURNAL   61 ( 2 ) 241 - 255  2019年  [査読有り]

     概要を見る

    Debris loading has been identified during several forensic engineering field surveys in the aftermath of the 2004 Indian Ocean and 2011 Tohoku Japan tsunamis as a critical design load. However, little research has addressed the assessment of debris loading hazards. The study presented herein examines the entrainment and transport of debris over a 1:10 sloped bed as well as over a flat, horizontal bed in tsunami-like conditions. The study was performed at a 1:50 scale and the debris was modelled as scaled-down shipping containers. The friction between the debris and the bed was varied by modifying the material installed on the slope as well as by covering the surface of the debris surface with materials with different degrees of friction. The debris-bed friction influenced the characteristics of the initial entrainment of the debris, which varied from sliding to rolling, depending on the magnitude of the static friction. This study also determined that the friction did not have a significant effect on the lateral spreading of the debris. However, a significant difference was observed in the case of the longitudinal displacement of debris (in the flow direction).

    DOI

  • Field Survey of 2018 Typhoon Jebi in Japan: Lessons for Disaster Risk Management

    Tomoyuki Takabatake, Martin Mall, Miguel Esteban, Ryota Nakamura, Thit Oo Kyaw, Hidenori Ishii, Justin Joseph Valdez, Yuta Nishida, Fuma Noya, Tomoya Shibayama

    GEOSCIENCES   8 ( 11 )  2018年11月  [査読有り]

     概要を見る

    Typhoon Jebi struck Japan on the 4 September 2018, damaging and inundating many coastal areas along Osaka Bay due to the high winds, a storm surge, and wind driven waves. In order to understand the various damage mechanisms, the authors conducted a field survey two days after the typhoon made landfall, measuring inundation heights and depths at several locations in Hyogo Prefecture. The survey results showed that 0.18-1.27 m inundation depths were caused by Typhoon Jebi. As parts of the survey, local residents were interviewed about the flooding, and a questionnaire survey regarding awareness of typhoons and storm surges, and their response to the typhoon was distributed. The authors also mapped the location of some of the containers that were displaced by the storm surge, aiming to provide information to validate future simulation models of container displacement. Finally, some interesting characteristics of the storm surge are summarized, such as possible overtopping at what had initially been thought to be a low risk area (Suzukaze town), and lessons learnt in terms of disaster risk management are discussed.

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  • Tsunami awareness: a comparative assessment between Japan and the USA

    Miguel Esteban, Jeremy Bricker, Ricardo San, Carlos Arce, Hiroshi Takagi, Namyi Y. Yun, Warathida Chaiyapa, Alexander Sjoegren, Tomoya Shibayama

    Natural Hazards   93   1507 - 1528  2018年09月  [査読有り]

     概要を見る

    © 2018, Springer Science+Business Media B.V., part of Springer Nature. Awareness about the threats posed by different types of coastal disasters has increased throughout the world, as people are exposed to the nature of these hazards through media reports on events in distant countries. This has resulted in coastal residents being aware about the destructive power of tsunamis, despite no such events having taken place in their country in recent times. Regardless of this increased awareness, it has been hypothesized that there is still need for local governments to enact adequate policies to raise the awareness of local residents, for example, by holding regular evacuation drills. The present research presents a comparative assessment of tsunami awareness in two tourist destinations in Japan and the USA, which was derived through structured questionnaire surveys of beach users in the city of Kamakura and various coastal cities in Florida. The results show how despite relatively high level of awareness tsunamis still pose a considerable risk to each of the communities, for example, due to shortcoming in evacuation knowledge and infrastructure.

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  • A study on mud particle velocities and mass transport in wave-current-mud interaction

    Mohsen Soltanpour, S. Hadi Shamsnia, Tomoya Shibayama, Ryota Nakamura

    Applied Ocean Research   78   267 - 280  2018年09月  [査読有り]

     概要を見る

    © 2018 Elsevier Ltd The upper fluid mud layer in muddy environments absorbs wave energy and, in turn, moves due to the wave action. In addition to these two major phenomena of wave-mud interaction, introduction of current in the wave field also changes the wave characteristics as well as the rates of mud mass transport. The present study offers an experimental investigation of wave-current-mud interaction to address the wave transformation and mud mass transport on a horizontal bed. A number of laboratory tests were conducted to measure the mud particle velocities as well as wave attenuation rates under following, opposing, and no current conditions. Both the wave energy dissipation and mud mass transport increase with the presence of opposing currents and decrease when following currents are introduced. A semi-analytical model was also presented and the numerical results are compared with the laboratory experiments, showing acceptable agreements.

    DOI

  • Experimental investigation of debris damming loads under transient supercritical flow conditions

    Jacob Stolle, Tomoyuki Takabatake, Ioan Nistor, Takahito Mikami, Shinsaku Nishizaki, Go Hamano, Hidenori Ishii, Tomoya Shibayama, Nils Goseberg, Emil Petriu

    COASTAL ENGINEERING   139   16 - 31  2018年09月  [査読有り]

     概要を見る

    Debris loading during extreme flooding events has been documented by many post-tsunami field surveys of disaster-stricken communities and, as such, it is now considered and accounted for as a critical design consideration in the design of resilient infrastructure. Debris damming is one of the debris loads of concern, occurring when solid objects entrained within the inundating flow accumulate at the face of a structure or structural element. The presence of the debris dam results in increased drag loads on the structure and can have other associated effects, such as flow runup and flow accelerations, that can influence design conditions. The focus of debris damming studies has been within river engineering: therefore, previous studies have been performed in steady-state conditions. The study presented here is the first to examine debris damming in transient, supercritical flow conditions. The study uses a modified dam-break wave as the hydrodynamic forcing condition and the debris are scaled down debris types common in coastal areas (shipping containers, hydro poles, and boards). The analysis includes a qualitative examination of the difference in the debris damming mechanisms as a result of distinct flow conditions associated with a dam-break wave interacting with a surface-piercing obstacle. Additionally, the study determined the influence of the debris dam resulted in a maximum loading condition that occurred earlier and was of greater magnitude than the clear water case.

    DOI

  • Advanced casualty estimation based on tsunami evacuation intended behavior: case study at Yuigahama Beach, Kamakura, Japan

    Tomoyuki Takabatake, Tomoya Shibayama, Miguel Esteban, Hidenori Ishii

    NATURAL HAZARDS   92 ( 3 ) 1763 - 1788  2018年07月  [査読有り]

     概要を見る

    Tsunamis are some of the most destructive types of natural hazards that can affect coastal areas. To optimize tsunami mitigation measures, it is important to estimate the potential casualties that can result from one of these events. Taking into account tsunami awareness and the possible evacuation behavior of at-risk individuals is necessary to estimate the number of casualties, though most of the research carried out to date has not considered detailed evacuation behavior when conducting simulations. In the present study, the authors proposed a new approach to estimating the number of tsunami casualties, based on a tsunami evacuation simulation model that considers the evacuation behavior of local residents, tourists and beach users. Such behavior parameters were incorporated by analyzing the results from previous questionnaires surveys. The model was applied to Yuigahama Beach in Kamakura City, Japan, with the aim of assessing potential tsunami casualties and providing suggestions regarding tsunami mitigation measures. The authors conducted seven tsunami inundation simulations for different earthquake scenarios, and then casualties were estimated considering six different evacuation scenarios. Based on the simulation results, it appears particularly important to attempt to improve the intended evacuation behavior of both the local population and visitors. Particularly, providing information about safe places and the routes to reach them is necessary, as prompt evacuation and heading to higher ground were found to be insufficient behavior to save lives during a tsunami event.

    DOI

  • Overtopping of structures by tsunami bores

    Esteban, M, Glasbergen, T, Takabatake, T, Hofland, B, Stolle, J, Nishida, Y, Nihizaki, S, Bricker, J, Nistor, I, Shibayama, T

    Proceedings of the 7thInternational Conference on the Application of Physical Modelling in Coastal and Port Engineering and Science (Coastlab)    2018年05月  [査読有り]

  • Debris damming loads and effect in tsunami-like events

    Stolle Jacob, Nistor Loan, Takabatake Tomoyuki, Goseberg Nils, Petriu Emil, Shibayama Tomoya

    6th International Disaster Mitigation Specialty Conference 2018, Held as Part of the Canadian Society for Civil Engineering Annual Conference 2018     70 - 80  2018年  [査読有り]

     概要を見る

    © 6th International Disaster Mitigation Specialty Conference 2018, Held as Part of the Canadian Society for Civil Engineering Annual Conference 2018. All rights reserved. Debris loading during extreme flooding events has been documented by many post-tsunami field surveys of disaster-stricken communities and, as such, it is now considered and accounted for as a critical design consideration in building resilient infrastructure. Debris damming is one of the debris loads of concern, occurring when solid objects entrained within the inundating flow accumulate at the face of a structure or a structural element. The presence of the debris dam results in increased drag loads on the structure and can have other associated effects, such as flow runup and flow accelerations, that can cause increased scouring at foundations. The focus of debris damming studies has been within river engineering: Therefore, previous studies have been performed in steady-state conditions. The study presented here is the first to examine debris damming in transient, supercritical flow conditions. The study uses a modified dam-break wave as the hydrodynamic forcing condition and the debris are scaled down debris types common in coastal areas (shipping containers, hydro poles, and boards). The study qualitatively examines the difference in the debris damming mechanisms as a result of distinct flow conditions associated with a dam-break wave interacting with a surface-piercing obstacle. Additionally, the study aimed to determine the influence of the debris dam. It was found that maximum loading condition occurred earlier and of greater magnitude than for the clear water case.

  • Hindcasting of Wave Climate along the Pacific Coast of Japan in October 2014

    Shinsaku Nishizaki, Tomoya Shibayama, Tomoyuki Takabatake, Ryota Nakamura

    ASIAN AND PACIFIC COASTS 2017: PROCEEDINGS OF THE 9TH INTERNATIONAL CONFERENCE ON APAC 2017     129 - 138  2018年

     概要を見る

    One-month wave simulations were performed from Oct. 1st to Nov. 1st in 2014. The one-way numerical models composed of WRF (Weather Research and Forecasting) and SWAN (Simulating WAve Nearshore) were used. This research focused on evaluations of both a resolution of wind data and a difference between structured SWAN (STSWAN) and unstructured SWAN (UNSWAN). The results show some differences among case studies. High resolution wind data affect peak values of significant waves at typhoon periods. In addition, the overestimation of swell caused by typhoons decreased at the nearshore points, in particular at Shimoda by using UNSWAN. As a conclusion, there is little difference between STSWAN and UNSWAN on the overall simulation of wave climate. However, UNSWAN is useful for simulating nearshore waves and has possibility to predict wave climate with higher precision than STSWAN.

    DOI

  • A semi-empirical formula for wave attenuation over muddy bed under current

    Wenang Xie, Tomoya Shibayama

    Proceedings of the 9th International Conference on APAC 2017     34 - 43  2018年01月

     概要を見る

    © 2018 World Scientific Publishing Co. Pte. Ltd. Theoretical and laboratory studies are performed to analyze the wave attenuation phenomenon over fluid mud under current. In the theoretical part, a semi-empirical formula is derived to model the attenuation process under current. Based on the linear wave theory, the change of wave amplitude is related with the averaged damping effect of the muddy bed. By solving a differential equation, the exponential decay of the wave amplitude is confirmed. A function called damping function is used in the formula, and it is expanded into a series of wave parameters and some undetermined coefficients called auxiliary damping factors. Based on the assumption that the mud properties do not change under current, the formula is combined with the dispersion relation for linear wave under uniform current to describe the attenuation process under current. Laboratory experiments are conducted first without current. The data of wave attenuation are collected and inserted to the formula obtained in the theoretical analysis to figure out the values of the auxiliary damping factors. The second set of experiments is conducted under current and the collected data are compared with the calculated values obtained by using the newly proposed formula with the dispersion relation. The result of comparison shows good applicability of the new formula to the wave attenuation under current.

  • Debris impacts and effects on structures

    Jacob Stolle, Nils Goseberg, Ioan Nistor, Tomoya Shibayama

    Handbook of Coastal and Ocean Engineering: Expanded Edition   1-2   457 - 479  2017年12月

     概要を見る

    © 2018 by World Scientific Publishing Co. Pte. Ltd. All rights reserved. The entrainment of debris within inundating flows in extreme hydrodynamic events results in impact loads and other effects that need to be considered in the design of at-risk structures. The analysis of debris impact loads has been performed following field investigations as well as in an experimental setting. The emphasis of this research has primarily been focused on determining the debris impact loads. Additionally, some work has been performed for assessing the risk of debris impact and entrainment characteristics of the debris. This chapter provides a review of the current research on debris motion, impacts and loads, and analyzes existing design guidelines related to debris loads. The chapter presents the current stateoftheart in the field and also provides recommendations for future research.

    DOI

  • Overtopping of Coastal Structures by Tsunami Waves

    Miguel Esteban, Toni Glasbergen, Tomoyuki Takabatake, Bas Hofland, Shinsaku Nishizaki, Yuta Nishida, Jacob Stolle, Ioan Nistor, Jeremy Bricker, Hiroshi Takagi, Tomoya Shibayama

    GEOSCIENCES   7 ( 4 ) 1 - 17  2017年12月  [査読有り]

     概要を見る

    Following the 2011 Tohoku Earthquake and Tsunami, Japanese tsunami protection guidelines stipulate that coastal defences should ensure that settlements are shielded from the coastal inundation that would result from Level 1 tsunami events (with return periods in the order of about 100 years). However, the overtopping mechanism and leeward inundation heights of tsunami bores as they hit coastal structures has received little attention in the past. To ascertain this phenomenon, the authors conducted physical experiments using a dam-break mechanism, which could generate bores that overtopped different types of structures. The results indicate that it is necessary to move away from only considering the tsunami inundation height at the beach, and also consider the bore velocity as it approaches the onshore area. The authors also prepared a simple, conservative method of estimating the inundation height after a structure of a given height, provided that the incident bore velocity and height are known.

    DOI

  • Modelling a storm surge under future climate scenarios: case study of extratropical cyclone Gudrun (2005)

    Martin Mall, Ulo Suursaar, Ryota Nakamura, Tomoya Shibayama

    NATURAL HAZARDS   89 ( 3 ) 1119 - 1144  2017年12月  [査読有り]

     概要を見る

    Weather Research and Forecasting atmosphere model and Finite Volume Community Ocean Model were for the first time used under the pseudo-climate simulation approach, to study the parameters of an extreme storm in the Baltic Sea area. We reconstructed the met-ocean conditions during the historical storm Gudrun (which caused a record-high +275 cm surge in Parnu Bay on 9 January 2005) and simulated the future equivalent of Gudrun by modifying the background conditions using monthly mean value differences in sea surface temperature (SST), atmospheric air temperature and relative humidity from MIROC5 in accordance with the IPCC scenarios RCP4.5 and RCP8.5 for 2050 and 2100. The simulated storm route and storm surge parameters were in good accordance with the observed ones. Despite expecting the continuation of recently observed intensification of cyclonic activity in winter months, our numerical simulations showed that intensity of the strongest storms and storm surges in the Baltic Sea might not increase by the end of twenty-first century. Unlike tropical cyclones, which derive their energy from the increasing SST, the extratropical cyclones (ETCs) harvest their primary energy from the thermal differences on the sides of the polar front, which may decrease if the Arctic warms up. For climatological generalizations on future ETCs, however, it is necessary to re-calculate a larger number of storms, including those with different tracks and in different thermal conditions.

    DOI

  • 来訪者を対象とした避難シミュレーションに基づく津波対策効果の検討

    高畠 知行, 柴山 知也

    土木学会論文集B2(海岸工学)   73 ( 2 ) I_1507 - I_1512  2017年11月  [査読有り]

    DOI CiNii J-GLOBAL

  • How to Carry Out Bathymetric and Elevation Surveys on a Tight Budget: Basic Surveying Techniques for Sustainability Scientists

    Esteban, M, Takagi, H, Mikami, T, Bahbouh, L, Becker, A, Nurse, L, Shibayama, T, Nagdee, M

    INTERNATIONAL JOURNAL OF SUSTAINABLE FUTURE FOR HUMAN SECURITY   5 ( 2 ) 86 - 91  2017年11月  [査読有り]

    DOI

  • Experimental Investigation of Debris-Induced Loading in Tsunami-Like Flood Events

    Jacob Stolle, Tomoyuki Takabatake, Takahito Mikami, Tomoya Shibayama, Nils Goseberg, Ioan Nistor, Emil Petriu

    GEOSCIENCES   7 ( 3 )  2017年09月  [査読有り]

     概要を見る

    Debris loads during flood events have been well-documented by forensic engineering field surveys of affected communities. Research has primarily focused on debris impact loading and less emphasis has been placed into quantifying the loads and effects associated with debris damming, which occurs when solid objects accumulate at the front of structures. The formation of the debris dam has been shown to results in increased drag forces, backwater rise, and flow accelerations which can influence the stability of the structure. This study examined the formation of a debris dam in steady-state conditions of debris common to flood-prone communities. The study determined that the hydraulic conditions, in particular flow velocity, influenced the formation of the debris dam. Additionally, the study examined the influence of the blockage ratio on the backwater rise as well as the drag coefficient.

    DOI

  • A method for tsunami risk assessment: a case study for Kamakura, Japan

    Non Okumura, Sebastiaan N. Jonkman, Miguel Esteban, Bas Hofland, Tomoya Shibayama

    NATURAL HAZARDS   88 ( 3 ) 1451 - 1472  2017年09月  [査読有り]

     概要を見る

    This paper presents a methodology for tsunami risk assessment, which was applied to a case study in Kamakura, Japan. This methodology was developed in order to evaluate the effectiveness of a risk-reducing system against such hazards, also aiming to demonstrate that a risk assessment is possible for these episodic events. The tsunami risk assessment follows these general steps: (1) determination of the probability of flooding, (2) calculation of flood scenarios, (3) assessment of the consequences and (4) integration into a risk number or graph. The probability of flooding was approximated based on the data provided by local institutes, and the flood scenarios were modeled in 1D using the Simulating WAves till SHore model. Results showed that a tsunami in Kamakura can result in thousands of casualties. Interventions such as improvements in evacuation systems, which would directly reduce the number of casualties, would have a large influence in risk reduction. Although this method has its limits and constraints, it illustrates the value it can add to existing tsunami risk management in Japan.

    DOI

  • Entrainment and Transport Dynamics of Shipping Containers in Extreme Hydrodynamic Conditions

    Jacob Stolle, Ioan Nistor, Nils Goseberg, Takahito Mikami, Tomoya Shibayama

    COASTAL ENGINEERING JOURNAL   59 ( 3 )  2017年09月  [査読有り]

     概要を見る

    An experimental study was performed to examine multiple debris entrainment and transport in tsunami-like flow conditions. The study was performed in the Tsunami Wave Basin at Waseda University. The wave basin used a falling-head driven elongated solitary wave that broke at the edge of a horizontal apron to generate a tsunami-like surge. The debris, modeled as scaled-down (1:40 length scale) 20-foot standard shipping containers, was placed on the horizontal apron. The debris was tracked using a camera-based object tracking algorithm. The study examined the effect of the debris configuration, the number of debris, and orientation of debris on the entrainment and transport within the inundating surge. In examining the transport of multiple debris, the debris tended to be transported within the surge as an agglomeration. Using a previously derived model of debris transport, the study determined experimentally derived coefficients to explain the difference in debris transport between various configurations.

    DOI

  • Risk awareness and intended tsunami evacuation behaviour of international tourists in Kamakura City, Japan

    Ricardo San Carlos Arce, Motoharu Onuki, Miguel Esteban, Tomoya Shibayama

    INTERNATIONAL JOURNAL OF DISASTER RISK REDUCTION   23   178 - 192  2017年08月  [査読有り]

     概要を見る

    The present study focuses on analysing the state of the tsunami risk communication strategies, awareness and intended evacuation behaviour amongst tourists in Kamakura City, Japan. A mixed methodologies approach was utilized, using key informant interviews, site surveys and questionnaire surveys to understand the risk awareness of this transient group of the population. The results of the survey showed a relatively high risk awareness and willingness to evacuate, though there was some confusion regarding the direction of evacuation, mode of transportation, and location of evacuation areas in the city. A majority of respondents stated that they would expect to be warned of a threat by an official warning or announcement, whereas a minority mentioned social cues as a way to understand what to do, possibly thus requiring changes to the city's risk management strategies. In Japan, the concept of tendenko has been getting more attention since the 2011 Tohoku Earthquake and Tsunami, which calls for each individual to immediately initiate evacuation by himself or herself, requiring the trust that other members of the family and community will be doing the same. Based on these findings the authors outlined a number of recommendations to improve disaster risk management for the case of tourists visiting Kamakura city.

    DOI

  • Simulated tsunami evacuation behavior of local residents and visitors in Kamakura, Japan

    Tomoyuki Takabatake, Tomoya Shibayama, Miguel Esteban, Hidenori Ishii, Go Hamano

    INTERNATIONAL JOURNAL OF DISASTER RISK REDUCTION   23   1 - 14  2017年08月  [査読有り]

     概要を見る

    Currently, it is believed that evacuation is the most effective method of protecting lives from tsunamis, in particular after the events of the 2011 Tohoku Earthquake Tsunami. In many coastal areas tsunamis pose a threat not only to local residents, who know the area well, but also to visiting tourists, and thus it is important to consider both these groups when preparing evacuation plans. However, while numerous studies and simulations on tsunami evacuation have been made, research focusing on the influence of visitors on evacuation processes is limited. To clarify this the authors developed an agent-based tsunami evacuation model which considers the different behavior of local residents and visitors, which can estimate the evacuation time, number of individuals reaching each evacuation area, the location of bottlenecks and the number of casualties. The model was applied to study the case of Yuigahama Beach, Kamakura, Japan, with results indicating that the behavior and number of visitors have a significant impact on evacuation processes, especially the location of bottlenecks and the number of casualties. Results also show that heavy congestion will occur during evacuation in places where there are many visitors and thus, in such a situation, the decrease of the moving speed owing to the congestion needs to be appropriately taken into account to simulate the evacuation process. It can be concluded that reducing congestion (i.e., widening roads, guiding visitors to less congested roads) is a crucial countermeasure for a sightseeing location to reduce the casualties that can result from a tsunami.

    DOI

  • Experimental Investigations of Debris Dynamics over a Horizontal Plane

    Ioan Nistor, Nils Goseberg, Jacob Stolle, Takahito Mikami, Tomoya Shibayama, Ryota Nakamura, Shunya Matsuba

    JOURNAL OF WATERWAY PORT COASTAL AND OCEAN ENGINEERING   143 ( 3 )  2017年05月  [査読有り]

     概要を見る

    This study presents the results of an experimental research program dealing with spatial debris motion on a horizontal apron depicting a typical harbor wharf. Accordingly, scaled-down 6.1-m (20-ft) shipping containers were equipped with a novel yet nonintrusive real-time tracking system and motion sensors. The instrumentation allowed for the spatiotemporal tracking of debris specimens moving across the apron while entrained by an incoming tsunami-like broken bore. The system proved its capabilities and accuracy; this was particularly challenging since this was the first time the system was used in water. The experiments involved using various numbers of shipping containers that were either arranged in one layer or stacked in two layers. In addition, the effect of different numbers of container rows was also investigated to study the influence of the overall container count and placement with respect to their longitudinal displacement and dispersion (spreading) across the apron. Linear relationships were derived for both parameters, suggesting potential guidelines for future design efforts and disaster risk reduction and mitigation. (C) 2016 American Society of Civil Engineers.

    DOI

  • Tralck analysis, simulation, and field survey of the 2013 Typhoon Haiyan storm surge

    H. Takagi, M. Esteban, T. Shibayama, T. Mikami, R. Matsumaru, M. De Leon, N. D. Thao, T. Oyama, R. Nakamura

    JOURNAL OF FLOOD RISK MANAGEMENT   10 ( 1 ) 42 - 52  2017年03月  [査読有り]

     概要を見る

    The authors have examined the characteristics of Typhoon Haiyan (Yolanda), which made landfall on the coast of the Philippines on November 2013, generating a substantial storm surge. In order to better understand the storm surge phenomenon, its nature and severity were analysed by means of a numerical simulation and a field survey. Unlike most other tropical cyclones that weaken before they hit land, Haiyan struck Leyte Island at near peak strength, with maximum sustained wind speeds of 160 knots, the strongest in the recorded history of the Western North Pacific. Haiyan approached very quickly with a forward speed of 41 km/ h towards Leyte, which was also the fastest among typhoons with similar intensities. As a result of these extreme gusts and the exceptionally low central pressure of the typhoon (895 hPa), Haiyan caused the largest storm surge in the recorded history of the Philippines. Numerical simulations show that the maximum storm surges occurred in Leyte Island and Samar Island. A stormsurge field survey conducted by the authors corroborated this, with maximum inundation height of 7 m recorded in Tacloban, located at the northern end of Leyte Gulf. The simulation results also corroborate the fact that water levels at some locations first lowered and then rapidly began to increase after an hour.

    DOI

  • 2016年11月22日福島県沖地震における津波避難に関する一考察―宮城県塩釜市の聞き取り調査より―

    三上 貴仁, 荒木 優介, 田中 直樹, 妹尾 光平, 高畠 知行, 柴山 知也

    自然災害科学   36 ( 1 ) 43 - 50  2017年  [査読有り]

    J-GLOBAL

  • 湾湖でのスロッシング現象と影響評価

    大平 幸一郎, 高畠 知行, 三上 貴仁, 柴山 知也

    土木学会論文集B3(海洋開発)   73 ( 1 ) 56 - 66  2017年  [査読有り]

    DOI

  • Failure Mechanisms and Local Scour at Coastal Structures Induced by Tsunami

    Mantripathi Prabath Ravindra Jayaratne, Buddhika Premaratne, Abimbola Adewale, Takahito Mikami, Shunya Matsuba, Tomoya Shibayama, Miguel Esteban, Ioan Nistor

    COASTAL ENGINEERING JOURNAL   58 ( 4 )  2016年12月  [査読有り]

     概要を見る

    On 11 March 2011, an exceptionally large tsunami event was triggered by a massive earthquake offshore, the northeast coast of Japan, which affected coastal infrastructure such as seawalls, coastal dikes and breakwaters in the Tohoku region. Such infrastructure was built to protect against the Level 1 tsunamis that previously hit the region, but not for events as significant as the 2011 Tohoku tsunami, which was categorized as a Level 2 tsunami [Shibayama, T., Esteban, M., Nistor, I., Takagi, H., Thao, N. D., Matsumaru, R., Mikami, T., Aranguiz, R., Jayaratne, R. & Ohira, K. [2013] "Classification of tsunami and evacuation areas," Nat. Hazards 67(2), 365-386]. The failure mechanisms of concrete-armored dikes, breakwaters and seawalls due to Level 2 tsunamis are still not fully understood by researchers and engineers. This paper investigates the failure modes and mechanisms of damaged coastal structures in Miyagi and Fukushima Prefectures, following the authors' post-disaster field surveys carried out between 2011 and 2013. Six significant failure mechanisms were identified for the coastal dikes and seawalls affected by this tsunami: (1) Leeward toe scour failure, (2) Crown armor failure, (3) Leeward slope armor failure, (4) Seaward toe scour and slope armor failure, (5) Overturning failure, and (6) Parapet wall failure, in which leeward toe scour being recognized as the major failure mechanism in most surveyed locations. The authors also propose a simple practical mathematical model for predicting the scour depth at the leeward toe of the coastal dikes, by considering the effects of the tsunami hydrodynamics, the soil properties and the type of structure. The key advantage of this model is that it depends entirely on quantities that are measurable in the field. Furthermore this model was further refined by conducting a series of hydraulic model experiments aimed to understand the governing factors of the leeward toe scour failure. Finally, based on the results obtained, key recommendations are given for the design of resilient coastal defense structures that can survive a level 2 tsunami event.

    DOI

  • Nonintrusive Spatiotemporal Smart Debris Tracking in Turbulent Flows with Application to Debris-Laden Tsunami Inundation

    N. Goseberg, I. Nistor, T. Mikami, T. Shibayama, J. Stolle

    JOURNAL OF HYDRAULIC ENGINEERING   142 ( 12 )  2016年12月  [査読有り]

     概要を見る

    Flood disasters such as dam breaks and surges from extreme hurricanes or tsunamis entrain and transport substantial amounts of submerged or floating debris. Understanding of motion and spatiotemporal distribution of debris entrained by a flood is thus of great importance to hydraulic, coastal, and structural engineers; the displacement of debris to a location where it may eventually impact critical infrastructure requires scientific attention at the laboratory scale first. In this context, the design and application of a novel smart debris system utilizing off-the-shelf components is presented and discussed. The system tracks the spatial location and orientation of a multitude of debris specimens and it proposes an accurate tool to assess their individual trajectory, velocity, and momentum in a laboratory environment. Contrary to the traditional camera-based approach of video tracking, which often fails once objects are submerged, the proposed smart debris system delivers six-degree-of-freedom (6DOF) data in a reliable, timely manner. Miniaturized inertial measurement units (IMU), commonly called motion sensors, which are used for attitude heading reference systems are deployed to output time series of spatial orientation along with filtered 3D acceleration readings. A Bluetooth low-energy (BLE) tracking system is applied along with the motion sensor to track the 3D debris positions. A detailed investigation in controlled laboratory conditions reveals the detailed individual performance of the tested spatial orientations and positions. As an application, debris transport tests were conducted in a newly built tsunami wave basin at Waseda University in Tokyo, Japan. For this test series, a typical harbor layout with a vertical quay wall adjacent to a horizontal container-stacking platform was constructed. The advection by a broken tsunamilike bore of multiple down-scaled shipping containers in basic arrangements was then tracked from their initial position. The performance of the innovative smart debris system is qualitatively tested in order to provide guidance for their future application in hydraulic and coastal engineering as well as to provide a solid basis for its application in field studies. (C) 2016 American Society of Civil Engineers.

    DOI

  • Experimental analysis of debris motion due the obstruction from fixed obstacles in tsunami-like flow conditions

    N. Goseberg, J. Stolle, I. Nistor, T. Shibayama

    COASTAL ENGINEERING   118   35 - 49  2016年12月  [査読有り]

     概要を見る

    Experimental research was conducted focusing on debris motion over a horizontal apron featuring vertical obstacles in the path of the debris propagation. The apron was designed as a typical representation of a harbor threatened by an inundating tsunami. The experimental setup idealized often complex harbor settings. The debris was a scaled-down 20-foot shipping container modelled at a 1 in 40 Froude length scale. Offand onshore regions were separated by a vertical quay wall which allowed the incoming elongated solitary wave used to represent the first part of a tsunami to steepen, break and propagate over the initially dry surface as a tsunami-like bore. In the path of propagation, a varying number of debris were entrained within the inundating bore over the horizontal apron. The entrained debris interacted with regularly spaced vertical obstacles representing infrastructure and houses within the propagation path. Varying debris and obstacle arrangements were tested to evaluate the effects the obstacles would have on the debris' maximum longitudinal displacement and the spreading angle. The main conclusion is that the spreading angle of the debris is not as significantly altered by the presence of obstacles on the harbor apron whereas the maximum longitudinal displacement of the debris was significantly affected. (C) 2016 Published by Elsevier B.V.

    DOI

  • Erratum for Stability of Breakwater Armor Units against Tsunami Attacks (vol 140, pg 188, 2014)

    Esteban Miguel, Jayaratne Ravindra, Mikami Takahito, Morikubo Izumi, Shibayama Tomoya, Nguyen Danh Thao, Ohira Koichiro, Ohtani Akira, Mizuno Yusuke, Kinoshita Mizuho, Matsuba Shunya

    JOURNAL OF WATERWAY PORT COASTAL AND OCEAN ENGINEERING   142 ( 4 )  2016年07月  [査読有り]

    DOI

  • Future typhoon and storm surges under different global warming scenarios: case study of typhoon Haiyan (2013)

    Ryota Nakamura, Tomoya Shibayama, Miguel Esteban, Takumu Iwamoto

    NATURAL HAZARDS   82 ( 3 ) 1645 - 1681  2016年07月  [査読有り]

     概要を見る

    The present work evaluates potential future typhoon and storm surges around the islands of Samar and Leyte in the Philippines taking into account monthly mean sea surface temperatures, atmospheric air temperature, and relative humidity (hereafter, SST, AAT, and RH) from MIROC5 according to four scenarios proposed by IPCC AR5. Super-typhoon Haiyan (2013), which caused catastrophic damage to coastal areas in the Philippines due to its high winds and storm surge, was used as the case study storm given that it was one of the tropical cyclones recorded in modern history. In this study, the Advanced Research Weather Research and Forecasting Model (ARW-WRF) is used to estimate the characteristics of both the present-day Haiyan and a typhoon with a similar return period under the climate condition of the year 2100. The unstructured, Finite Volume Community Ocean Model (FVCOM) was used to estimate both the present and potential future storm surges. The research has two main focuses. First, both the historical event and its storm surge are simulated and contrasted with field measurements of the storm surge height in order to prove the accuracy of the model. Second, the future typhoon and storm surge are estimated using the monthly mean value differences in SST, AAT, and RH from MIROC5 between 2011-2020 and 2091-2100 for the different scenarios. The characteristics of the simulated typhoon route and storm surge heights agree well with those of the best track data and field measurements. The numerical results of the future typhoon show that, if climate change is considered to only increase SST, its intensity and storm surge will be larger than under the present climate. The minimum sea-level pressure (hereafter, MSLP) of the future typhoon under scenario RCP 8.5 would be about 21 hPa lower and the storm surge 2.7 m higher than in the present climate. However, if SST, AAT, and RH are also taken into account, then the increase in typhoon intensity will not be as marked as if only SST is considered, with the MSLP under RCP 8.5 decreasing only by 13 hPa and the storm surge increasing by 0.7 m. The results of the present research thus suggest that while increases in SST can contribute to the intensification of future typhoons, increases in AAT and RH will somehow moderate this effect. Nevertheless, all scenarios considered point out to stronger typhoons and higher storm surges, clearly highlighting the perils posed by future climate change.

    DOI

  • Erratum to "Stability of breakwater armor units against tsunami attacks" [J. Waterway, Port, Coastal, Ocean Eng., (2014), 188-198] DOI:10.1061/(ASCE)WW.1943-5460.0000227

    Miguel Esteban, Ravindra Jayaratne, Takahito Mikami, Izumi Morikubo, Tomoya Shibayama, Nguyen Danh Thao, Koichiro Ohira, Akira Ohtani, Yusuke Mizuno, Mizuho Kinoshita, Shunya Matsuba

    Journal of Waterway, Port, Coastal and Ocean Engineering   142 ( 4 )  2016年07月  [査読有り]

    DOI

  • Storm Surge Heights and Damage Caused by the 2013 Typhoon Haiyan Along the Leyte Gulf Coast

    Takahito Mikami, Tomoya Shibayama, Hiroshi Takagi, Ryo Matsumaru, Miguel Esteban, Nguyen Danh Thao, Mario De Leon, Ven Paolo Valenzuela, Takahiro Oyama, Ryota Nakamura, Kenzou Kumagai, Siyang Li

    COASTAL ENGINEERING JOURNAL   58 ( 1 )  2016年03月  [査読有り]

     概要を見る

    Typhoon Haiyan (Yolanda) struck the islands of Leyte and Samar, the central part of the Philippines, on 8 November 2013, bringing large-scale devastation to coastal areas due to the high winds and large storm surge and waves associated with it. In order to obtain the distribution of storm surge heights and damage covering the wide stretch of affected coastline, the authors carried out a series of field surveys in the aftermath of the typhoon (in December 2013, May 2014, and October 2014). In the present paper, the authors detailed the results of these field surveys and summarized the characteristics of the storm surge and main causes of the damage, especially focusing on the Leyte Gulf coast, which is surrounded by the eastern coast of Leyte and the southern coast of Samar. Finally, the wide range of types of storm surge disasters were also discussed by comparing Typhoon Haiyan with other recent major events.

    DOI

  • Storm Surge Awareness in the Philippines Prior to Typhoon Haiyan: A Comparative Analysis with Tsunami Awareness in Recent Times

    Miguel Esteban, Ven Paolo Valenzuela, Ryo Matsumaru, Takahito Mikami, Tomoya Shibayama, Hiroshi Takagi, Nguyen Danh Thao, Mario De Leon

    COASTAL ENGINEERING JOURNAL   58 ( 1 )  2016年03月  [査読有り]

     概要を見る

    Category 5 Typhoon Haiyan was one of the strongest typhoons to hit the Philippines in modern times, and introduced the term "storm surge" to the vocabulary of many local residents, who had not heard about such phenomena prior to this event. The storm surge manifested itself on the 8th November 2013 as Haiyan made landfall, devastating large areas in the islands of Leyte and Samar. To attempt to gain an understanding of the level of awareness that local residents had about storm surges the authors conducted structured questionnaires (n = 172) and focus group interviews with local residents, and discussed the results obtained with key informants (government officers and disaster risk managers). One of the key problems identified during the interviews was how people were not able to clearly understand the concept of a storm surge, with many respondents emphasizing how it would have been better for authorities to describe it as a "tsunami". A discussion is also made on the recent evolution in world-wide coastal disaster awareness, comparing it to recent developments in storm surge awareness in the Philippines and other countries in the area, such as Vietnam and Japan. The authors conclude that, in terms of its influence on worldwide disaster awareness, typhoon Haiyan constitutes an event of similar importance to major recent high-impact tsunami events such as the 2004 Indian Ocean and 2011 Tohoku events. As a result, the authors will outline a number of lessons learnt from Haiyan, such as the necessity for creating multi-layer safety strategies and improving how information about storm surges is transmitted to local residents.

    DOI

  • Storm surge and evacuation in urban areas during the peak of a storm

    Hiroshi Takagi, Siyang Li, Mario de Leon, Miguel Esteban, Takahito Mikami, Ryo Matsumaru, Tomoya Shibayama, Ryota Nakamura

    COASTAL ENGINEERING   108   1 - 9  2016年02月  [査読有り]

     概要を見る

    The present paper examines the impact of floodwater caused by the storm surge brought about by Typhoon Haiyan in 2013, focusing on downtown Tacloban in Leyte Island, the Philippines. A reliable numerical model for predicting such flooding was developed by calibrating the results of field investigations, including footage from a video clip taken during the storm surge. The simulation reveals that flow velocities along the streets in downtown Tacloban reached up to 7 m/s due to flow contraction along the high-density blocks of houses, and how water levels reached their peak in just 10 min. According to the depth-velocity product criteria, often used for evaluating the vulnerability of people and buildings to floodwaters, only 8% of the length of streets in downtown Tacloban were within the safe limits that allow pedestrian evacuation. Based on these findings, the present research concludes that pedestrian evacuation in the middle of a storm surge generated by a strong typhoon is a high-risk behavior. Thus, clearly and objectively, evacuation during this time should not be encouraged, even when seawater intrudes the houses of local residents. In this respect, it would appear imperative that prior to the arrival of the typhoon all residents should evacuate areas at risk of being flooded. Though the flood height was significant in the downtown area, the damage to these houses was limited. If it was not possible for some reason to evacuate prior to the arrival of the typhoon, those in solid houses should first consider vertical evacuation and the possibility that they could survive in their place, rather than courageously evacuating in an unpredictable water flow. (C) 2015 Elsevier B.V. All rights reserved.

    DOI

  • 東京湾における津波による石油タンクの安全性評価および油の移流拡散予測

    森永 貴之, 三上 貴仁, 柴山 知也

    土木学会論文集B2(海岸工学)   72 ( 2 ) I_433 - I_438  2016年  [査読有り]

    DOI

  • Estimation of increase in storm surge damage due to climate change and sea level rise in the Greater Tokyo area

    Sayaka Hoshino, Miguel Esteban, Takahito Mikami, Hiroshi Takagi, Tomoya Shibayama

    NATURAL HAZARDS   80 ( 1 ) 539 - 565  2016年01月  [査読有り]

     概要を見る

    Sea level rise and an increase in typhoon intensity are two of the expected consequences from future climate change. In the present work, a methodology to change the intensity of tropical cyclones in Japan was developed, which can be used to assess the inundation risk to different areas of the country. As a result, the probability of a storm with an equivalent return period in the year 2100 to that of the worst storm in the 20th century overcoming sea defences around Tokyo Bay could be calculated. The risk of higher storm surges, coupled with different sea-level-rise scenarios, highlights how the dykes around Tokyo or Kawasaki could fail unless adaptation measures against climate change are attempted. The cost of adapting to both of these effects by building higher coastal dykes and raising port areas outside them was quantified. Finally, an estimation of the cost of allowing the areas behind the defences to be flooded was also made, clearly showing that the cost of adaptation measures is clearly lower than the cost of inaction.

    DOI

  • Spectral analysis of irregular waves in wave–mud and wave–current–mud interactions

    Samsami, Farzin, Soltanpour, Mohsen, Shibayama, Tomoya

    Ocean Dynamics   65 ( 9-10 ) 1305 - 1320  2015年09月  [査読有り]

     概要を見る

    © 2015, Springer-Verlag Berlin Heidelberg. The dissipation of irregular waves passing over muddy beds is investigated through two series of wave flume laboratory experiments with and without currents, where commercial kaolinite is used as the muddy sediment bed material. The changes in spectral characteristics of waves along the muddy bed and the effects of following and opposing currents are investigated. A numerical multi-layered model was also employed to simulate the attenuation of regular/irregular waves assuming viscoelastic rheological behavior for fluid mud, and the outputs were compared with the laboratory data. The first series of the experiments show that propagation of a wave spectrum over a short fluid mud section does not result in a shift in peak frequencies of wave spectra. The comparisons of spectral width parameters of various wave spectra also reveal that higher values of spectral peakedness parameters generally result in higher rates of wave energy dissipation. This can be related to the frequency dependency of wave energy dissipation on the mud layer. The results of the second series of experiments show higher dissipation rates in the opposing current and lowe

    DOI

  • 2004 Indian Ocean tsunami

    Tomoya Shibayama

    Handbook of Coastal Disaster Mitigation for Engineers and Planners     3 - 19  2015年07月

    DOI

  • Adaptation to sea level rise in Tokyo Bay: Opportunities for a storm surge barrier?

    Miguel Esteban, Sebastiaan N. Jonkman, Sayaka Hoshino, María José Ruiz-Fuentes, Takahito Mikami, Hiroshi Takagi, Tomoya Shibayama, Mathijs Van Ledden

    Handbook of Coastal Disaster Mitigation for Engineers and Planners     723 - 747  2015年07月

    DOI

  • Stability of breakwaters against Tsunami attack

    Miguel Esteban, Nguyen Danh Thao, Hiroshi Takagi, Ravindra Jayaratne, Takahito Mikami, Tomoya Shibayama

    Handbook of Coastal Disaster Mitigation for Engineers and Planners     293 - 323  2015年07月

    DOI

  • Estimation of the current risk to human damage life posed by future tsunamis in Japan

    Sho Yamao, Miguel Esteban, Nam Yi Yun, Takahito Mikami, Tomoya Shibayama

    Handbook of Coastal Disaster Mitigation for Engineers and Planners     257 - 275  2015年07月

    DOI

  • Tsunami disasters in remote islands: 2009 Samoan and 2010 Mentawai Islands tsunamis

    Takahito Mikami, Tomoya Shibayama

    Handbook of Coastal Disaster Mitigation for Engineers and Planners     75 - 91  2015年07月

    DOI

  • Storm surge in New York City caused by hurricane Sandy in 2012

    Takahito Mikami, Miguel Esteban, Tomoya Shibayama

    Handbook of Coastal Disaster Mitigation for Engineers and Planners     115 - 131  2015年07月

    DOI

  • Storm surge due to 2008 cyclone Nargis in Myanmar and post-cyclone preparedness activities

    Khandker Masuma Tasnim, Miguel Esteban, Tomoya Shibayama, Hiroshi Takagi

    Handbook of Coastal Disaster Mitigation for Engineers and Planners     55 - 74  2015年07月

    DOI

  • 2005 storm surge by hurricane Katrina

    Tomoya Shibayama

    Handbook of Coastal Disaster Mitigation for Engineers and Planners     21 - 34  2015年07月

    DOI

  • Destruction of coastal structures after the 2011 Great East Japan earthquake and tsunami

    Ravindra Jayaratne, Buddhika Premaratne, Takahito Mikami, Shunya Matsuba, Tomoya Shibayama, Miguel Esteban, Martin Marriott

    Handbook of Coastal Disaster Mitigation for Engineers and Planners     349 - 362  2015年07月

    DOI

  • Observations and numerical simulation of storm surge due to cyclone sidr 2007 in Bangladesh

    Khandker Masuma Tasnim, Miguel Esteban, Tomoya Shibayama

    Handbook of Coastal Disaster Mitigation for Engineers and Planners     1 - 35  2015年07月

    DOI

  • Stochastic design of caisson breakwaters: Lessons from past failures and coping with climate change

    Hiroshi Takagi, Miguel Esteban, Tomoya Shibayama

    Handbook of Coastal Disaster Mitigation for Engineers and Planners     635 - 673  2015年07月

    DOI

  • Handbook of Coastal Disaster Mitigation for Engineers and Planners

    Miguel Esteban, Hiroshi Takagi, Tomoya Shibayama

    Handbook of Coastal Disaster Mitigation for Engineers and Planners     1 - 765  2015年07月

     概要を見る

    The world's population is expected to increase to over 8 billion by 2020. About 60% of the total population of the world lives in coastal areas and 65% of the cities with a population of over 2.5 million are located in coastal areas. Written by an international panel of experts in the fields of engineering and risk management, The Handbook of Coastal Disasters Mitigation presents a coherent overview of 10 years of coastal disaster risk management and engineering, during which some of the most relevant events of recent time have taken place, including the Indian Ocean tsunami, hurricanes Katrina and Sandy in the United States or the 2011 Japanese tsunami. International case studies offer practical lessons on how disaster resilience can be improved in the future. Contains tools and techniques for analyzing and managing the risk of coastal disasters. Provides engineering measures for mitigating coastal vulnerability to tsunamis, tropical cyclones, and hurricanes. Includes crucial tactics for rehabilitation and reconstruction of the infrastructure.

    DOI

  • Preface

    Shibayama, Tomoya

    Handbook of Coastal Disaster Mitigation for Engineers and Planners    2015年07月

  • Lessons from the last 10 years of coastal disasters

    Esteban, Miguel, Takagi, Hiroshi, Shibayama, Tomoya

    Handbook of Coastal Disaster Mitigation for Engineers and Planners     xxv - xxx  2015年07月

  • Estimation of Maximum Possible Wave Heights in Surf Zone

    Winyu Rattanapitikon, Khiem Quang Tran, Tomoya Shibayama

    COASTAL ENGINEERING JOURNAL   57 ( 2 )  2015年06月  [査読有り]

     概要を見る

    The breaking-limited (or depth-limited) approach is a traditional method to determine the maximum possible wave height for the design of coastal structures in the surf zone. It is well recognized that the maximum wave height in the surf zone is limited by wave breaking. The maximum possible wave height is usually determined from a breaker height formula. The present study was undertaken to examine the applicability of 14 existing breaker height formulas for computing the maximum possible wave heights. The existing breaker height formulas were examined against measured regular and irregular wave heights. A total of 17 863 data points from 30 sources of published experimental data were used to examine the formulas. The experiments cover a wide range of wave and bottom topography conditions including small-scale, large-scale, and field experiments. It was found that the errors of existing formulas for regular and irregular waves have the same tendency. The existing formulas give considerable underestimation of the maximum possible wave heights in shallow water. The top three formulas were modified by including a new form of relative depth into each formula. Overall, the modified formulas give a considerable better estimation than those of existing formulas.

    DOI

  • Estimation of maximum possible wave heights in surf zone

    Winyu Rattanapitikon, Khiem Quang Tran, Tomoya Shibayama

    Coastal Engineering Journal   57  2015年06月  [査読有り]

     概要を見る

    © 2015 World Scientific Publishing Company and Japan Society of Civil Engineers. The breaking-limited (or depth-limited) approach is a traditional method to determine the maximum possible wave height for the design of coastal structures in the surf zone. It is well recognized that the maximum wave height in the surf zone is limited by wave breaking. The maximum possible wave height is usually determined from a breaker height formula. The present study was undertaken to examine the applicability of 14 existing breaker height formulas for computing the maximum possible wave heights. The existing breaker height formulas were examined against measured regular and irregular wave heights. A total of 17 863 data points from 30 sources of published experimental data were used to examine the formulas. The experiments cover a wide range of wave and bottom topography conditions including small-scale, large-scale, and field experiments. It was found that the errors of existing formulas for regular and irregular waves have the same tendency. The existing formulas give considerable underestimation of the maximum possible wave heights in shallow water. The top three formulas were modified by including a new form of relative depth into each formula. Overall, the modified formulas give a considerable better estimation than those of existing formulas.

    DOI

  • Typhoon Haiyan 2013 Evacuation Preparations and Awareness

    Esteban, M, Valenzuela, V, P. Yun, N. Y, Mikami, T, Shibayama, T, Matsumaru, R, Takagi, H, Thao, N. D, De Leon, M, Oyama, T, Nakamura, R

    INTERNATIONAL JOURNAL OF SUSTAINABLE FUTURE FOR HUMAN SECURITY   3 ( 1 ) 37 - 45  2015年03月  [査読有り]

    DOI

  • A two-dimensional experimental-numerical approach to investigate wave transformation over muddy beds

    Mohsen Soltanpour, S. Abbas Haghshenas, Tomoya Shibayama

    OCEAN DYNAMICS   65 ( 2 ) 295 - 310  2015年02月  [査読有り]

     概要を見る

    The effect of a thin fluid mud layer on nearshore two-dimensional wave transformation is studied through numerical modeling and wave basin experiments. The wave basin experiments were conducted on both muddy and fixed beds. A mixture of commercial kaolinite and tap water was used as fluid mud layer, where its rheological viscoelastic parameters were derived from rheometer cyclic tests. The results can be utilized for better understanding of the complex wave transformation phenomena under real field conditions where the combined effects of shoaling, refraction, and diffraction as well as wave energy dissipation due to existing mud beds and wave breaking jointly occur. A dissipation model was coupled to the combined refraction and diffraction 1 (REF/DIF 1) wave model to develop a numerical wave height transformation model for muddy beaches. The proposed model was utilized to analyze the experimental data on muddy beds. Comparing the computed values of wave heights over mud layer with the corresponding measurements shows a fair agreement.

    DOI

  • 2014年12月に北海道で発生した温帯低気圧による根室の高潮被害の現地調査と発生機構の解明

    中村 亮太, 岩本 匠夢, 柴山 知也, 三上 貴仁, 松葉 俊哉, Martin MAELL, 舘小路 晃史, 田野倉 祐介

    土木学会論文集B3(海洋開発)   71 ( 2 ) I_31 - I_36  2015年  [査読有り]

    DOI

  • 海岸堤防を越流する津波の挙動に及ぼす防潮林の効果

    松葉 俊哉, 三上 貴仁, 柴山 知也

    土木学会論文集B2(海岸工学)   71 ( 2 ) I_871 - I_876  2015年

     概要を見る

    2011年東北地方太平洋沖地震津波では,陸地への浸水を防ぐ海岸堤防が多数破壊され被害が拡大した.現地調査より,堤防の主たる破壊原因は,津波が堤防を長時間越流することによって引起こされた洗掘であると考えられる.さらに,堤防被害や洗掘規模と堤防背後の防潮林被害の関係から,堤防とその周辺の状況が,堤防被害に影響を及ぼす可能性があることが分かった.そこで本研究では,海岸堤防を越流する津波に対して防潮林が与える影響を水理実験により検討した.その結果,防潮林により堤防背後に流下する津波が射流から常流へと変化することが分かった.堤防裏法尻部に流下する流速が4割低減され,また堤防裏法肩部に作用する負圧が低減されることが分かった.以上より,背後に防潮林を有することで堤防周囲で生じる津波の挙動が変化し,越流する津波による堤防への被害を軽減し得ることが分かった.

    DOI CiNii

  • 貞山運河の津波減衰効果に関する実験的研究

    渡邊 峻, 三上 貴仁, 柴山 知也

    土木学会論文集B2(海岸工学)   71 ( 2 ) I_301 - I_306  2015年

     概要を見る

    東日本大震災時において,仙台平野沿いに流れる貞山運河を境に津波高さの減少が見られた.本研究では,運河の津波減衰効果を明らかにすることを目的として,現地調査結果の分析および水理実験を行った.現地調査結果の分析から,複数の地点において貞山運河による津波減衰効果を確認することができた.水理実験ではチャンバー式平面津波水槽を用いた.運河の津波減衰効果を明らかにするため,運河模型を越えた越流量に注目した.実験は津波高さ,長さ,運河内水深を変化させて行った.水理実験から運河に越流量を減衰させる効果があることが判明した.また,同一の断面では運河内水深を浅くするほど越流量は減少することや波形によっても越流量は変化することが確認できた.

    DOI CiNii

  • 秋谷海岸礫養浜の経過とその評価

    柴山 知也, 泉 正寿, 佐藤 映, 澤野 靖, 平尾 淳

    土木学会論文集B2(海岸工学)   71 ( 2 ) I_769 - I_774  2015年

     概要を見る

    神奈川県三浦半島の相模湾岸に位置する秋谷海岸では,平成10年代から海岸侵食が顕在化したために,平成19年から8年間にわたって92,600m&lt;sup&gt;3&lt;/sup&gt;の中央粒径15mmの礫を用いた養浜を行った.礫養浜工法の選択は,4年間に及ぶ地元での合意形成会議の議論に基づいて行われている.礫養浜の進行に伴い,地形,底質,生物の各項目について,モニタリングを行っている.モニタリング結果を用いて合意形成会議において順応的な管理方法について話し合いを行い,部分的な手直しを行ってきた.8年を経て,礫浜は岸沖方向には安定しているが,沿岸方向には礫の分布が広がりつつあり,両端部での礫移動の管理方法が課題となっている.

    DOI CiNii

  • Field observation and numerical simulation of past and future storm surges in the Bay of Bengal: case study of cyclone Nargis

    Khandker Masuma Tasnim, Tomoya Shibayama, Miguel Esteban, Hiroshi Takagi, Koichiro Ohira, Ryota Nakamura

    NATURAL HAZARDS   75 ( 2 ) 1619 - 1647  2015年01月  [査読有り]

     概要を見る

    Storm surges are one of the most important risks to coastal communities around the Bay of Bengal, and it is feared that the threat they pose will increase with climate change in the future. To understand the threats that these events pose, a summary of the field surveys performed in Yangon River Basin after cyclone Nargis in Myanmar in 2008 is presented. Though due to government restrictions survey activities were limited to the area near Yangon city, it was found out that the tide due to the storm surge was probably between 3 and 4 m high and travelled around 50 km upstream of the river mouth of Yangon River. Cyclone Nargis could be accurately reproduced using a numerical model that integrated weather, wave, coastal ocean models, and tide prediction system. The application of such an integrated model is relatively new for storm surge simulation and has never been used for the Bay of Bengal storms. The model was then used to also simulate future cyclones over the Bay of Bengal considering a future climate change scenario.

    DOI

  • A CROSS-SHORE BEACH PROFILE EVOLUTION MODEL

    Mantripathi Prabath Ravindra Jayaratne, Md Rezaur Rahman, Tomoya Shibayama

    COASTAL ENGINEERING JOURNAL   56 ( 4 )  2014年12月  [査読有り]

     概要を見る

    Developing an accurate and reliable time-averaged beach profile evolution model under storm and nonstorm conditions is a challenging task. Over the last few decades, a number of beach deformation models have been developed under limited experimental conditions and uncertainties, and sometimes they required a long computation time. It is quite evident that a large amount of wave, current, sediment and beach profile data is available today. The present study leads to the development of a simple two-dimensional beach profile evolution model with on-offshore sand bar formation under nonstorm and storm conditions based on the time-averaged suspended sediment concentration models of Jayaratne and Shibayama [Jayaratne, M. P. R. and Shibayama, T. [2007] "Suspended sediment concentration on beaches under three different mechanisms," Coastal Eng. J., JSCE 49( 4), 357-392.] and Jayaratne et al. [Jayaratne, M. P. R., Sritharan, S. and Shibayama, T. [2011] "Examination of the suspended sediment concentration formulae using full-scale rippled bed and sheet flow data,"Coastal Eng. J., JSCE 53(4), 451-489.]. These models were formulated for computing sediment concentration in and outside the surf zone under three different mechanisms: (1) suspension due to turbulent motion over sand ripples, (2) suspension from sheet flow layer and (3) suspension due to turbulent motion under breaking waves. The suspended load is calculated by the product of time-averaged sediment concentration and undertow velocity from edge of the wave boundary layer to wave trough and mass transport velocity from wave trough to crest (bore-like wave region). Sediment transport in wave boundary layer is computed from the modified Watanabe [Watanabe, A. [1982] "Numerical model of nearshore currents and beach deformation model,"Coastal Eng. Jpn., JSCE 25, 147-161.] model. Rattanapitikon and Shibayama [Rattanapitikon, W. and Shibayama, T. [1998] "Energy dissipation model for regular and irregular breaking waves,"Coastal Eng. J., JSCE 40(4), 327-346.] wave model is used to calculate the average rate of energy dissipation due to wave breaking. The beach deformation is calculated from the conservation of sediment mass while the avalanching concept of Larson and Kraus [Larson, M. and Kraus, N. C. [1989] SBEACH: Numerical model for simulating storm induced beach change, Report 1, Technical Report CERC-89-9, US Army Eng. Water. Exp. Station.] is used to re-distribute the sediment mass in neighboring grids for a steady solution. Published field-scale experimental and natural beach profiles from five high-quality data sources from 1983-2009 [Kajima et al., 1983; Kraus and Larson, 1988; Port and Airport Research Institute, Japan, 2005, 2009; Hasan and Takewaka, 2007, 2009; Ruessink et al., 2007] are used to verify the performance of the proposed numerical model. The key feature in this process-based model is that it takes about a couple of minutes to simulate beach profiles of a 2-3 days storm qualitatively at a fairly satisfactory level using a standard personal computer. It is found that the present numerical predictions are not better than the null hypothesis as the model is in a stage of ongoing development.
    Therefore, it is believed that the final model is often of more value to a practical coastal engineer than a very detailed study of hydrodynamics and sediment transport study, however an incorporation of swash dynamics, more precise evaluation of offshore sand bar formation and continuation to a longer time scale with precise beach deformation are recommended as the next stage of the model.

    DOI

  • A cross-shore beach profile evolution model

    Mantripathi Prabath, Ravindra Jayaratne, Md Rezaur Rahman, Tomoya Shibayama

    Coastal Engineering Journal   56  2014年12月  [査読有り]

     概要を見る

    © 2014 World Scientific Publishing Company and Japan Society of Civil Engineers. Developing an accurate and reliable time-averaged beach profile evolution model under storm and nonstorm conditions is a challenging task. Over the last few decades, a number of beach deformation models have been developed under limited experimental conditions and uncertainties, and sometimes they required a long computation time. It is quite evident that a large amount of wave, current, sediment and beach profile data is available today. The present study leads to the development of a simple two-dimensional beach profile evolution model with on-offshore sand bar formation under nonstorm and storm conditions based on the time-averaged suspended sediment concentration models of Jayaratne and Shibayama [Jayaratne, M. P. R. and Shibayama, T. [2007] &quot;Suspended sediment concentration on beaches under three different mechanisms,&quot; Coastal Eng. J., JSCE 49(4), 357-392.] and Jayaratne et al. [Jayaratne, M. P. R., Sritharan, S. and Shibayama, T. [2011] &quot;Examination of the suspended sediment concentration formulae using full-scale rippled bed and sheet flow data,&quot; Coastal Eng. J., JSCE 53(4), 451-489.]. These models were formulated for computing sediment concentration in and outside the surf zone under three different mechanisms: (1) suspension due to turbulent motion over sand ripples, (2) suspension from sheet flow layer and (3) suspension due to turbulent motion under breaking waves. The suspended load is calculated by the product of time-averaged sediment concentration and undertow velocity from edge of the wave boundary layer to wave trough and mass transport velocity from wave trough to crest (bore-like wave region). Sediment transport in wave boundary layer is computed from the modified Watanabe [Watanabe, A. [1982] &quot;Numerical model of nearshore currents and beach deformation model,&quot; Coastal Eng. Jpn., JSCE 25, 147-161.] model. Rattanapitikon and Shibayama [Rattanapitikon, W. and Shibayama, T. [1998] &quot;Energy dissipation model for regular and irregular breaking waves,&quot; Coastal Eng. J., JSCE 40(4), 327-346.] wave model is used to calculate the average rate of energy dissipation due to wave breaking. The beach deformation is calculated from the conservation of sediment mass while the avalanching concept of Larson and Kraus [Larson, M. and Kraus, N. C. [1989] SBEACH: Numerical model for simulating storm induced beach change, Report 1, Technical Report CERC-89-9, US Army Eng. Water. Exp. Station.] is used to re-distribute the sediment mass in neighboring grids for a steady solution. Published field-scale experimental and natural beach profiles from five high-quality data sources from 1983-2009 [Kajima et al., 1983; Kraus and Larson, 1988; Port and Airport Research Institute, Japan, 2005, 2009; Hasan and Takewaka, 2007, 2009; Ruessink et al., 2007] are used to verify the performance of the proposed numerical model. The key feature in this process-based model is that it takes about a couple of minutes to simulate beach profiles of a 2-3 days storm qualitatively at a fairly satisfactory level using a standard personal computer. It is found that the present numerical predictions are not better than the null hypothesis as the model is in a stage of ongoing development. Therefore, it is believed that the final model is often of more value to a practical coastal engineer than a very detailed study of hydrodynamics and sediment transport study, however an incorporation of swash dynamics, more precise evaluation of offshore sand bar formation and continuation to a longer time scale with precise beach deformation are recommended as the next stage of the model.

    DOI

  • Tsunami vulnerability evaluation in the Mentawai islands based on the field survey of the 2010 tsunami

    Takahito Mikami, Tomoya Shibayama, Miguel Esteban, Koichiro Ohira, Jun Sasaki, Takayuki Suzuki, Hendra Achiari, Teguh Widodo

    NATURAL HAZARDS   71 ( 1 ) 851 - 870  2014年03月  [査読有り]

     概要を見る

    On October 25, 2010, a large earthquake occurred off the coast of the Mentawai islands in Indonesia, generating a tsunami that caused damage to the coastal area of North Pagai, South Pagai, and Sipora islands. Field surveys were conducted soon after the event by several international survey teams, including the authors'. These surveys clarified the tsunami height distribution, the damage that took place, and residents' awareness of tsunamis in the affected islands. Heights of over 5 m were recorded on the coastal area of the Indian Ocean side of North and South Pagai islands and the south part of Sipora island. In some villages, it was difficult to evacuate immediately after the earthquake because of the lack of routes to higher ground or the presence of rivers. Residents in some villages had taken part in tsunami drills or education; however, not all villages shared awareness of tsunami threats. In the present paper, based on the results of these field surveys, the vulnerability of these islands with regards to future tsunami threats was analyzed. Three important aspects of this tsunami disaster, namely the geographic disadvantage of the islands, the resilience of buildings and other infrastructure, and people's awareness of tsunamis, are discussed in detail, and corresponding tsunami mitigation strategies are explained.

    DOI

  • Tsunamis from the Arica-Tocopilla source region and their effects on ports of Central Chile

    Rafael Aranguiz, Tomoya Shibayama, Yoshiki Yamazaki

    NATURAL HAZARDS   71 ( 1 ) 175 - 202  2014年03月  [査読有り]

     概要を見る

    The last great earthquake in northern Chile took place in 1877, and the ensuing tsunami affected not only that region but also Central Chile. For example, the Bay of Concepcin, which is located 1,500 km south of the tsunami source, experienced an inundation height of around 3 m. Ports are important in the Chilean economy, due to the fact that a large percentage of Chilean exports (excluding copper) use ports located in Central Chile. With this in mind, the authors investigated the potential effect of an 1877-like tsunami on the main ports of Central Chile. To do this, the dispersive wave model Non-hydrostatic Evolution of Ocean WAVEs was used. In addition, the first tsunami forecast model for Talcahuano, inside the Bay of Concepcin, was developed by means of numerical simulation of several events of different moment magnitudes. The results showed that most of the important ports (Valparaiso, San Antonio, San Vicente and Coronel) had inundation heights on the order of just 1 m, while inundation levels in Talcahuano reached up to 3.5 m. The forecast model for Talcahuano uses only earthquake magnitude, focal depth and tide level to determine tsunami inundation heights. In addition, the tsunami arrival time was computed to be 3 h, and the maximum tsunami amplitude takes place at 4 h and 45 min after the earthquake.

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  • 気象-高潮-潮汐 結合モデルを用いた東京湾におけるRCP8.5シナリオ下での高潮予測

    岩本 匠夢, 中村 亮太, 大山 剛弘, 水上 亮, 柴山 知也

    土木学会論文集B2(海岸工学)   70 ( 2 ) I_1261 - I_1265  2014年

     概要を見る

    The aims of this study are to examine the reproducibility of new Meteorological-Surge-Tide coupled model and to estimate the effect of global warming to storm surge. In order to examine the model, the case of typhoon Roke (2011) is taken to be an example since the sea level elevation in this case is the highest record in Tokyo Bay during recent 10 years. For the case of typhoon Roke, the tendency of time history of water level is well reproduced though the maximum value is underestimated. The future case of typhoon Roke is also calculated. The sea level at Shibaura is increased for around 20cm and it is also increased around 40cm at Funabashi. These results imply that the coupled model has good performance but there are still some differences of sea level at Tokyo Bay due to the effect of complex geography.

    DOI CiNii

  • Typhoon Yolandaによるフィリピンの高潮被災の高潮追算と現地調査の比較

    中村 亮太, 大山 剛弘, 柴山 知也, 松丸 亮, 高木 泰士, ESTEBAN Miguel, 三上 貴仁

    土木学会論文集B2(海岸工学)   70 ( 2 ) I_236 - I_240  2014年  [査読有り]

    DOI

  • 2013年台風Yolanda(Haiyan)時の災害情報の伝達と住民の避難行動に関する分析

    Esteban Miguel, 松丸 亮, 高木 泰士, 三上 貴仁, 柴山 知也, Mario P. de Leon, Ven Paolo Valenzuela, Nguyen Danh Thao

    土木学会論文集B3(海洋開発)   70 ( 2 ) I_1218 - I_1223  2014年  [査読有り]

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  • 2013年台風Yolanda(Haiyan)の統計的分析および高潮の調査と数値解析

    高木 泰士, 三上 貴仁, 柴山 知也, 松丸 亮, Mario P. de Leon, Esteban Miguel, Nguyen Danh Thao, 中村 亮太

    土木学会論文集B3(海洋開発)   70 ( 2 ) I_1206 - I_1211  2014年  [査読有り]

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  • 2013年台風Yolanda(Haiyan)による高潮災害の調査と分析

    柴山 知也, 松丸 亮, 高木 泰士, Mario P. de Leon, Esteban Miguel, 三上 貴仁, 大山 剛弘, 中村 亮太

    土木学会論文集B3(海洋開発)   70 ( 2 ) I_1212 - I_1217  2014年  [査読有り]

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  • Nationwide post event survey and analysis of the 2011 Tohoku earthquake tsunami

    Nobuhito Mori, Tomoyuki Takahashi, Shun Etsu Hamaura, Kazuya Miyakawa, Katsuhiko Tanabe, Keisuke Tanaka, Mitsuyuki Tanaka, Tsukasa Watanabe, Hideo Matsutomi, Kazunori Naoe, Takuya Noumi, Erika Yamaguchi, Shoichi Ando, Yushiro Fujii, Toshihide Kashima, Yasuo Okuda, Bun'ichiro Shibazaki, Tsutomu Sakakiyama, Masafumi Matsuyama, Takumi Yoshii, Kazuhisa Goto, Takashi Aida, Yuuji Kurata, Mabumi Miyazaki, Katuya Shutou, Jun Suzuki, Hikari Takeuchi, Takayuki Nakamura, Osamu Fujiwara, Kyoko Kagohara, Haruo Kimura, Junko Komatsubara, Yukari Miyashita, Yuichi Namegaya, Yuki Sawai, Masanobu Shishikura, Koichiro Tanigawa, Hermann Fritz, Ken Ichi Uzaki, Mikio Sasaki, Masato Minami, Hitoshi Endou, Masaki Hashimoto, Yutaka Kobashigawa, Masamitsu Kumagai, Masahiro Ietsune, Kazuhiko Nakamura, Aditya Gusman, Kazuomi Hirakawa, Kei Loki, Yugo Nakamura, Takafumi Nakayama, Yuichi Nishimura, Puma Putra, Ayumi Saruwatari, Yasunori Watanabe, Tomohito Yamada, Yasunori Nabetani, Hisamichi Nobuoka, Takashi Tamada, Yuriko Matsubayashi, Toshinori Ogasawara, Shigeki Sakai, Masao Abe, Yutaka Hayashi, Hideki Iino, Kazuhiro Iwakiri, Kazuhiro Kimura, Kenji Maeda, Masami Okada, Hiroaki Tsushima, Taro Kakinuma, Kei Yamashita, Shinya Umeda, Takahiro Nakamura, Shuji Seto, Kurokawa Takahiro, Tetsuya Torayashiki, Gozo Tsujimoto, Kohji Uno, Shoichi Yoshioka, Norio Dewa, Tetsuya Hayashi, Mitsuyoshi Kitamura, Shusaku Kuroda, Akihiko Nakahira, Takeshi Nozawa, Kazuya Taniwaki, Kunio Ohtoshi, Takashi Aoyama, Tatsuo Chiba, Hiroshi Enomoto, Kazunori Hirahara, Shigeki Murai, Hiroshi Narayama, Satoshi Yamanaka, Hitoshi Yamazaki, Satoshi Yoshiiri, Ryoukei Azuma, Yasuyuki Baba

    Coastal Engineering Journal   54  2014年01月  [査読有り]

     概要を見る

    At 14:46 local time on March 11, 2011, a magnitude 9.0 earthquake occurred off the coast of northeast Japan. This earthquake generated a tsunami that struck Japan as well as various locations around the Pacific Ocean. With the participation of about 300 researchers from throughout Japan, joint research groups conducted a tsunami survey along a 2,000 km stretch of the Japanese coast. More than 5,200 locations have been surveyed to date, generating the largest tsunami survey dataset in the world. The inundation height and run-up height were surveyed by laser, GPS, and other instruments, and the tidal correction has been accurately adjusted using a tidal database and a numerical simulation for Tohoku, an area where tide gauges were destroyed by the tsunami. Based on the survey dataset, the regional and local scale analyses were conducted to understand the basic characteristics of this event. Maximum run-up heights greater than 10 m are distributed along 500 km of coast in direct distance. The affected area of this event was several times larger than historically recorded in Tohoku. The mean inundation height in the southern Sanriku region is 1015 m and there are several peaks of inundation along the coast from the northern to middle part of Sanriku. © 2012 World Scientific Publishing Company and Japan Society of Civil Engineers.

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  • Smoothed-Particle Hydrodynamics Numerical Modeling of Structures Impacted by Tsunami Bores

    Philippe St-Germain, Ioan Nistor, Ronald Townsend, Tomoya Shibayama

    JOURNAL OF WATERWAY PORT COASTAL AND OCEAN ENGINEERING   140 ( 1 ) 66 - 81  2014年01月  [査読有り]

     概要を見る

    Recently, major tsunami events have resulted in considerable damage to low-lying coastal developments as well as significant loss of life. This is owing to the fact that coastal communities and associated infrastructure are not able to withstand the extreme hydrodynamic forces induced by the overland progression of large tsunami waves. This paper reports the findings of a study, which is part of an ongoing comprehensive (hydraulic-structural engineering) research program initiated at the University of Ottawa in Canada. The goals of the latter are to contribute to the understanding and quantification of extreme hydrodynamic impacts on structural elements, and to the development of design guidelines for structures located in tsunami-prone areas. In this study, a single-phase three-dimensional (3D) weakly compressible smoothed-particle hydrodynamics (WCSPH) model is used to investigate the hydrodynamic forces, induced by the impact of rapidly advancing tsunami-like hydraulic bores, on a freestanding column of a square cross section. Numerical time histories of the water surface elevation and net base horizontal force acting on the column are compared with the results of large-scale physical experiments, conducted by the authors as part of an experimental component of this research program. The experiments were performed on the basis of analogies between tsunami bores and dam-break waves. The bore-structure interaction is analyzed in detail as the validated numerical model is subsequently applied to additionally investigate the influence of laboratory channel geometry on the results. (C) 2014 American Society of Civil Engineers.

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  • Stability of breakwater armor units against tsunami attacks

    Miguel Esteban, Ravindra Jayaratne, Takahito Mikami, Izumi Morikubo, Tomoya Shibayama, Nguyen Danh Thao, Koichiro Ohira, Akira Ohtani, Yusuke Mizuno, Mizuho Kinoshita, Shunya Matsuba

    Journal of Waterway, Port, Coastal and Ocean Engineering   140 ( 2 ) 188 - 198  2014年  [査読有り]

     概要を見る

    The design of breakwater armor units against tsunami attacks has received little attention in the past because of the comparative low frequency of these events and the rarity of structures designed specifically to withstand them. However, field surveys of recent events, such as the 2011 Tohoku Earthquake Tsunami and the Indian Ocean tsunami in 2004, have shown flaws in the design of protection structures. During these extreme events, many breakwaters suffered partial or catastrophic damage. Although it is to be expected that most normal structures fail because of such high-order events, practicing engineers need to possess tools to design certain important breakwaters that should not fail even during Level 2 events. In the future, research into the design of critical structures that only partially fail (i.e., resilient or tenacious structures) during very extreme Level 2 tsunami events should be a priority
    in this sense, the present paper proposes a formula that allows the estimation of armor unit damage depending on the tsunami wave height. © 2014 American Society of Civil Engineers.

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  • EFFECT OF SUBMARINE CANYONS ON TSUNAMI PROPAGATION: A CASE STUDY OF THE BIOBIO CANYON, CHILE

    Rafael Aranguiz, Tomoya Shibayama

    COASTAL ENGINEERING JOURNAL   55 ( 4 )  2013年12月  [査読有り]

     概要を見る

    The 2010 Chile tsunami had different effects along the Chilean coast. Seawater surged hundred meters into many rivers, though field surveys showed that the 2 km wide Biobio River did not experience any flooding. In a similar manner, the coastal zones south of the river had an inundation height of less than 2m. To ascertain why these areas were not greatly affected by the event, the behavior of tsunami waves propagating over a submarine canyon was investigated by means of numerical simulations over a simplified and idealized bathymetry. The main variables which define the size of the canyon were varied, and three different tsunami wave lengths were tested. The results show that submarine canyons have a strong influence on tsunami propagation and run-up such that there is a spatial variation of wave amplitude along the coast and this behavior is very sensitive to the canyon size. The run-up directly behind the canyon is lower than in the case without the canyon, while there are zones of wave amplification at both sides of the canyon. These idealized results compare well with what happened during the 2010 Chile tsunami, and provide a useful insight into the behavior of tsunamis around other submarine canyons in other regions of the world.

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  • Analysis of Evacuation Patterns in Countries Affected by Recent Tsunamis: Emergence of a Global Tsunami Culture

    Esteban, M, Tsimopoulou, V, Mikami, T, Yun, N, Suppasri, A, Shibayama, T

    7th International Conference on Asian and Pacific Coasts (APAC2013)    2013年09月  [査読有り]

  • Recent tsunamis events and preparedness: Development of tsunami awareness in Indonesia, Chile and Japan

    M. Esteban, V. Tsimopoulou, T. Mikami, N. Y. Yun, A. Suppasri, T. Shibayama

    INTERNATIONAL JOURNAL OF DISASTER RISK REDUCTION   5   84 - 97  2013年09月  [査読有り]

     概要を見る

    Since the 2004 Indian Ocean Tsunami, there is a growing awareness of the risks that tsunamis pose to coastal communities. Despite the fact that the population of some countries such as Chile and Japan were aware of such events, many other places had virtually not heard about such phenomenon before 2004. Nevertheless, the frequent reoccurrence of major tsunamis in recent years has led to a heightened state of tsunami awareness in many areas of the world, which can be described by an increased knowledge, disaster preparedness and willingness of local populations to evacuate when the threat of these events arises. However, the response of different elements of society to tsunami warnings nowadays still appears to be inadequate a times, pointing to lack of awareness by at least some individuals, an over-reliance in defence mechanisms or lacking in the transmission of knowledge from previous events. This paper will explore these cultural issues using as a basis observations made by the authors during field visits to areas afflicted by the last three major events (Chile, Indonesia, and Japan). The level of tsunami awareness prior to these events will be explored through an analysis on the existence of multiple layers of safety against tsunami developed by previous generations, and whether these had been preserved over time. The potential impact of these major tsunamis in the development of tsunami awareness will be analysed based on questionnaires that indicate the willingness of local coastal communities to invest in disaster preparedness. (C) 2013 Elsevier Ltd. All rights reserved,

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  • VERIFICATION AND EXTENSION OF GODA FORMULAS FOR COMPUTING REPRESENTATIVE WAVE HEIGHTS TRANSFORMATION

    Winyu Rattanapitikon, Tomoya Shibayama

    COASTAL ENGINEERING JOURNAL   55 ( 3 )  2013年09月  [査読有り]

     概要を見る

    The present study concentrates on the empirical formulas of Goda [1975, 2009]. The formulas were proposed for computing the transformation of three common representative wave heights (i.e. H-1/3, H-max and H-m0) on plane beaches. The objectives of the present study are to verify the Goda formulas for computing the transformation of H-1/3, H-max and H-m0 on unbarred beaches and to extend the formulas for computing the transformation of H-m, H-rms and H-1/10. Laboratory data from small-scale and large-scale wave flumes with unbarred beach conditions are used to verify the formulas. The verification shows that the formulas give very good predictions of H-1/3 and H-m0, but give fair prediction of H-max. The formulas are rewritten in the form of a general formula. The general form of Goda formulas is recalibrated and extended to compute other representative wave heights (i.e. H-m, H-rms and H-1/10). The general formula gives very good predictions of H-m, H-rms, H-1/3, H-1/10, H-max and H-m0.

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  • Classification of Tsunami and Evacuation Areas

    Tomoya Shibayama, Miguel Esteban, Ioan Nistor, Hiroshi Takagi, Nguyen Danh Thao, Ryo Matsumaru, Takahito Mikami, Rafael Aranguiz, Ravindra Jayaratne, Koichiro Ohira

    NATURAL HAZARDS   67 ( 2 ) 365 - 386  2013年06月  [査読有り]

     概要を見る

    On March 11, 2011, a large earthquake that occurred offshore the north-east coast of Japan generated a large tsunami which devastated extensive areas of the Tohoku coastline. Despite Japan being considered a country well prepared for these types of disasters, large casualties were recorded, with numerous discussions amongst the Japanese coastal engineering community ensuing. As a result, two different levels of tsunamis have been proposed and now recognized in Japan, depending on the frequency of such extreme events. The idea that hard measures can protect the lives of inhabitants of coastal areas has been abandoned, and these measures are only considered to be effective in protecting properties against the more frequent but lower magnitude events. Soft measures should always be used to protect against the loss of lives, and to this respect, the authors of the paper propose the introduction of a Classification of Evacuation Areas, to show which of these should be prioritized by residents as they seek to evacuate.

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  • Analysis of Tsunami Culture in Countries Affected by Recent Tsunamis

    Miguel Esteban, Vana Tsimopoulou, Tomoya Shibayama, Takahito Mikami, Koichiro Ohira

    3RD INTERNATIONAL CONFERENCE ON SUSTAINABLE FUTURE FOR HUMAN SECURITY, SUSTAIN 2012   17   693 - 702  2013年  [査読有り]

     概要を見る

    Since 2004 there is a growing global awareness of the risks that tsunamis pose to coastal communities. Despite the fact that these events were already an intrinsic part of the culture of some countries (such as Chile and Japan), in many other places they had been virtually unheard of before 2004. Nevertheless, the frequent reoccurrence of these events in recent years has led to the emergence of a "tsunami culture" in many areas of the world, which has resulted in increased awareness, disaster preparedness and willingness of local populations to evacuate when the threat of these events arises. This paper will explore these cultural issues using as a basis questionnaires carried out by the authors during their own field visits to the last three major events (in Japan, Chile and Indonesia), and interpret these through the willingness of coastal communities to build protection measures along the shore and the impact that these can have on sustainable development. (C) 2013 The Authors. Published by Elsevier B.V.

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  • SEA LEVEL RISE AND THE INCREASE IN RUBBLE MOUND BREAKWATER DAMAGE

    Miguel Esteban, Hiroshi Takagi, Tomoya Shibayama

    COASTAL STRUCTURES 2011, VOL 1 & 2     130 - 140  2013年  [査読有り]

     概要を見る

    Sea level rise could threaten the stability of rubble mound breakwaters in the future, as greater water depth will allow larger waves to reach these structures. Particularly worrying, however, is the prospect of an acceleration in the pace of sea level rise as a result of climate change, especially after 2050. This could lead to a change in the philosophy behind the design of breakwaters and ports, leading to substantial increases in the cost to build and maintain these costly structures. Particularly there would have to be a shift in the main parameter used to calculate breakwater sections from the significant wave height (H-s) to the limiting breaker height (H-b), due to future uncertainties in wave climate. The likely increases in breakwater costs due to this shift in design philosophy were evaluated for 4 different rates of sea level rise showing that for the more extreme cases of sea level rise (for a sea level rise of 1.3m over 50 years) a breakwater designed in 2050 would be between around 8% and 66% more expensive than one designed in the 20th century not taking into account sea level rise.

  • Present and future tsunami and storm surge protections in Tokyo and Sagami bays

    Shibayama Tomoya, Ohira Koichiro, Takabatake Tomoyuki

    Proceedings of the 7th International Conference on Asian and Pacific Coasts (APAC)     764 - 766  2013年  [査読有り]

  • 2012年ハリケーンサンディによる高潮災害のニューヨークにおける現地調査に基づく臨海都市域の浸水災害と減災策に関する考察

    三上 貴仁, 柴山 知也, ESTEBAN Miguel

    土木学会論文集B3(海洋開発)   69 ( 2 ) I_982 - I_987  2013年  [査読有り]

    DOI

  • 東京湾における高潮被災予測と沿岸防護手法の提案

    星野 さや香, 柴山 知也, ESTEBAN Miguel, 高木 泰士, 三上 貴仁, 高畠 知行

    土木学会論文集B3(海洋開発)   69 ( 2 ) I_994 - I_999  2013年  [査読有り]

    DOI

  • 津波越流時の堤防周辺における流体運動の分析

    三上 貴仁, 松葉 俊哉, 柴山 知也

    土木学会論文集B2(海岸工学)   69 ( 2 ) I_991 - I_995  2013年  [査読有り]

    DOI

  • EFFECT OF SEA LEVEL RISE AND INCREASE IN TYPHOON INTENSITY ON COASTAL STRUCTURES IN TOKYO BAY

    Sayaka Hoshino, Miguel Esteban, Takahito Mikami, Tomoyuki Takabatake, Tomoya Shibayama

    COASTAL STRUCTURES 2011, VOL 1 & 2     141 - 152  2013年

     概要を見る

    Sea level rise and an increase in typhoon intensity are two of the results expected from future climate change. In the present work a methodology to change the intensity of tropical cyclones in Japan is developed based on the work of Knutson and Tuleya (2004). An example of how this would affect one of the worst typhoons to hit the Tokyo Bay area in the 20th century was thus developed, highlighting the considerable dangers associated with this event, and how current sea defences could be under danger of failing by the end of the 21st century.

  • WAVE BEHAVIOR IN TOKYO BAY CAUSED BY A TSUNAMI OR LONG-PERIOD GROUND MOTIONS

    Koichiro Ohira, Tomoya Shibayama

    COASTAL STRUCTURES 2011, VOL 1 & 2     1313 - 1324  2013年

     概要を見る

    This work aims to ascertain the wave behavior and possible damage in Tokyo Bay caused by the double effect of a tsunami and long-period ground motion using numerical analysis. Tsunami behavior in Tokyo Bay has not been given enough consideration in the past, though the study of such behavior is very important to develop an adequate protection strategy. The generation of a tsunami-type wave which is affected by long-period ground motion in a bay is a new concept. The target earthquakes, which could occur directly beneath or far from Tokyo Bay, are forecasted to take place within the next 20 years.

  • WAVE BEHAVIOR IN TOKYO BAY CAUSED BY A TSUNAMI OR LONG-PERIOD GROUND MOTIONS

    Koichiro Ohira, Tomoya Shibayama

    COASTAL STRUCTURES 2011, VOL 1 & 2     1313 - 1324  2013年

     概要を見る

    This work aims to ascertain the wave behavior and possible damage in Tokyo Bay caused by the double effect of a tsunami and long-period ground motion using numerical analysis. Tsunami behavior in Tokyo Bay has not been given enough consideration in the past, though the study of such behavior is very important to develop an adequate protection strategy. The generation of a tsunami-type wave which is affected by long-period ground motion in a bay is a new concept. The target earthquakes, which could occur directly beneath or far from Tokyo Bay, are forecasted to take place within the next 20 years.

  • EFFECT OF SEA LEVEL RISE AND INCREASE IN TYPHOON INTENSITY ON COASTAL STRUCTURES IN TOKYO BAY

    Sayaka Hoshino, Miguel Esteban, Takahito Mikami, Tomoyuki Takabatake, Tomoya Shibayama

    COASTAL STRUCTURES 2011, VOL 1 & 2     141 - 152  2013年

     概要を見る

    Sea level rise and an increase in typhoon intensity are two of the results expected from future climate change. In the present work a methodology to change the intensity of tropical cyclones in Japan is developed based on the work of Knutson and Tuleya (2004). An example of how this would affect one of the worst typhoons to hit the Tokyo Bay area in the 20th century was thus developed, highlighting the considerable dangers associated with this event, and how current sea defences could be under danger of failing by the end of the 21st century.

  • MODIFIED HEEL PRESSURE FORMULA TO SIMULATE TILTING OF A COMPOSITE CAISSON BREAKWATER

    Miguel Esteban, Hiroshi Takagi, Tomoya Shibayama

    COASTAL ENGINEERING JOURNAL   54 ( 4 )  2012年12月  [査読有り]

     概要を見る

    Susami West Breakwater, a composite caisson breakwater located in Japan, was damaged by high waves caused by typhoon Tokage on the 20th of October 2004. The failure mode was characterized by the sliding/tilting of the caissons and the removal of the concrete armoring units. The failure of these armor units is believed to increase the pressures exerted by the waves on the caisson, and thus exacerbate the expected deformations in the rubble mound foundation, a fact which has thus far been ignored in previous research. The present paper proposes a methodology to take into account the effect of these concrete armor units to estimate the deformations that took place in the rubble mound foundation. The methodology uses a modification of the method by Goda [1985] proposed by Esteban et al. [2009] that can approximate to the right order of magnitude the vertical deformations at the back of the caisson by using a Monte Carlo simulation.

    DOI

  • Applicability of suspended sediment concentration formulae to large-scale beach morphological changes

    Ravindra Jayaratne, Yasufumi Takayama, Tomoya Shibayama

    Proceedings of the Coastal Engineering Conference    2012年12月

     概要を見る

    Study of beach morphological changes under storm conditions and its prediction capability are of paramount importance in coastal zone management. Seabed sediment is picked up violently in and outside the surf zone due to suspension mechanisms, therefore a considerable amount of sand is transported in coastal waters due to such mechanisms. For the construction of an accurate beach morphological model, it is necessary to elucidate the sediment suspension and to introduce it properly into the modelling of sediment transport. Jayaratne and Shibayama (2007) developed a complete set of explicit theoretical formulae to predict the time-averaged concentration on sandy beaches due to three suspension mechanisms: a) vortical motion over wave-generated sand ripples, b) from sheet flow, and c) turbulent motion under breaking waves. The present paper focuses on the development of a quasi-3D beach deformation model using the sediment concentration models of Jayaratne and Shibayama (2007), the bed load model of Watanabe (1982), the wave propagation model of Onaka et al. (1988), the nearshore current model of Philips (1977) and the undertow model of Okayasu et al. (1990) to predict the large-scale morphodynamics of sandy beaches. The predicted beach profiles and total sediment transport rates were compared with two sets of large-scale laboratory experimental data [Kajima et al. (1983); Kraus and Larson (1988)] and Seisho beach at Kanagawa Prefecture, Japan. It can be concluded that the present numerical model is capable of predicting sediment transport direction, on-offshore sand bar formation and the general trend of the beach profiles of large-scale erosive- and accretive-type sandy beaches to a satisfactory level.

  • FIELD SURVEY OF THE 2011 TOHOKU EARTHQUAKE AND TSUNAMI IN MIYAGI AND FUKUSHIMA PREFECTURES

    Takahito Mikami, Tomoya Shibayama, Miguel Esteban, Ryo Matsumaru

    COASTAL ENGINEERING JOURNAL   54 ( 1 )  2012年03月  [査読有り]

     概要を見る

    At 14:46 on March 11, 2011 (local time), a large earthquake of magnitude Mw9.0 took place, generating a tsunami that caused severe damage to the east coast of Japan. To comprehensively record tsunami trace heights and impacts along the coastal region, the Tohoku Earthquake Tsunami Joint Survey Group was organized immediately after the event. As part of this group, the authors conducted a field survey in Miyagi and Fukushima Prefectures. The surveyed area can be divided into 2 parts from the point of view of its geographical features: the northern part (a rias coastal area) and the southern part (a coastal plain area). In this paper, the characteristics of the damage due to the tsunami in each area are analyzed by using both the results of the authors' by using both the results of the authors' own field survey and the Joint Survey Group. In the rias coastal area, inundation heights were more than 10 m, which resulted in the flooding of the low-lying grounds located at the inner part of the bays. The tsunami wave caused widespread destruction in this area, and coastal buildings (including reinforced concrete buildings) suffered severe damage. In the southern coastal plains, inundation heights were 5-10 m and the tsunami reached a few kilometers inland, though unfortunately there were not enough high locations or buildings for the residents to evacuate. In addition, an extensive line of coastal dikes and forests, which had been placed to protect the wide plains behind them, also suffered extensive damage. From these geographically dependent inundation and destruction patterns, a number of important lessons on how to modify and improve future risk management strategies can be obtained.

    DOI

  • 東北地方太平洋沖地震津波における津波襲来時の映像の解析と津波の数値計算

    久木田 駿一, 柴山 知也

    土木学会論文集B3(海洋開発)   68 ( 2 ) I_49 - I_54  2012年

     概要を見る

    2011年3月11日に発生した東北地方太平洋沖地震津波の映像の解析を行った. この津波の伝播及び氾濫について気仙沼を対象とした数値計算を行い, 映像から求めた結果と数値計算による結果と比較し, 数値計算の結果の妥当性の検討を行った. 映像の解析結果と数値計算による結果との比較により, 陸上に氾濫した津波の計測結果と数値計算結果がほぼ一致するということ, 氾濫シミュレーションにおいて津波の水位変化が再現できているということがわかった, また津波の陸上部における水位変化の挙動について津波防潮堤の存在が水位の立ち上がりを遅くしていたことも判明した.

    DOI CiNii

  • 長周期地震動による震源遠隔地での波の発生

    大平 幸一郎, 柴山 知也

    土木学会論文集B3(海洋開発)   68 ( 2 ) I_55 - I_59  2012年

     概要を見る

    本研究では,地震発生の際に長周期地震動により発生する遠隔地での高波に注目し,その発生メカニズムを検討する.2011年3月11日に東北地方太平洋沖でモーメントマグニチュードMw9.0の地震が発生した際,震源より約470km離れた西湖(最大水深73.2m,面積2.12km2)において,波高約1mの波が観測された.本研究では西湖で発生した波浪現象を,現地調査と数値計算を用いて再現した.さらに今後30年以内に70%の確率で発生すると予測されている東南海地震と東海地震の想定に同じ計算モデルを適用し,震源より離れた東京湾での長周期地震動により発生する波の予測を行った.その結果,波が不規則に発生することが分かった.地震が発生した際に,津波とともに注意すべき現象の一つとして,長周期地震動により発生する波を指摘した.

    DOI CiNii

  • 東京港における高潮・津波の危険予測

    高畠 知行, 柴山 知也

    土木学会論文集B3(海洋開発)   68 ( 2 ) I_894 - I_899  2012年  [査読有り]

    DOI CiNii J-GLOBAL

  • Field Survey of Tsunami Disaster on Sipora Island, Indonesiaafter Sumatra Earthquake 2010

    8th INTERNATIONAL CONFERENCE ON COASTAL AND PORT ENGINEERING IN DEVELOPING COUNTRIES    2012年

  • EXAMINATION OF THE SUSPENDED SEDIMENT CONCENTRATION FORMULAE USING FULL-SCALE RIPPLED BED AND SHEET-FLOW DATA

    Mantripathi Prabath Ravindra Jayaratne, Sritharan Srikanthan, Tomoya Shibayama

    COASTAL ENGINEERING JOURNAL   53 ( 4 ) 451 - 489  2011年12月  [査読有り]

     概要を見る

    A set of theoretical models is deduced for computing suspended sediment concentration in coastal waters under the influence of suspension on the bottom boundary layer due to turbulent motion over full-scale sand ripples and sheet-flow, following on from the work of Jayaratne and Shibayama [2007]. Dimensional analysis and best-fit technique are the main methods for the formulation of reference concentrations and vertical distribution of diffusion coefficients of the models. Model parameters (e.g. calibration coefficients) are calibrated with the help of full-scale measured data. Time-averaged concentration profiles are derived from the steady diffusion equation. Two distinct suspension layers (i.e., lower and upper) were identified within the suspension over rippled bed, therefore predictive models were given separately for each layer. In the case of sheet-flow regime, predictive models were given for suspension and upper-sheet-flow layers. Published experimental data from 4 different data sources in the SANTOSS database (75 and 80 full-scale experiments for rippled bed and sheet-flow regimes respectively) from 1994 to 2007 [Van der Werf et al., 2009] are better explained by the proposed formulae, however different sets of calibration coefficients were assigned in each data set primarily due to the flow type (regular or irregular flows) and nature of the laboratory experiments (wave flume and wave tunnel).

    DOI

  • ASSESSMENT OF FUTURE STABILITY OF BREAKWATERS UNDER CLIMATE CHANGE

    Hiroshi Takagi, Hidehiro Kashihara, Miguel Esteban, Tomoya Shibayama

    COASTAL ENGINEERING JOURNAL   53 ( 1 ) 21 - 39  2011年03月  [査読有り]

     概要を見る

    Climate change is expected to lead to increases in both sea level and typhoon intensity, which could threaten the stability of break waters in the future. In this study, calculations using the SWAN model showed that a 10% potential increase in the future wind speed of typhoons resulting from the warming of surface sea temperatures can lead to a 21% increase in the significant wave heights generated by these winds. To understand the effect that this would have on break water stability, the expected sliding distances for the break waters at Shibushi Ports in Japan were estimated using a probabilistic design method. The results show that in the future the expected sliding distances may be come five times greater than at present, due to a combination of increases in sea level and wave height.

    DOI

  • Field survey and analysis of tsunami disaster in the Samoan Islands 2009

    Proc. of 6th Int. Conf. Coastal Structures, CD-Rom    2011年

  • Field Survey of the 2011 off the Pacific Coast of Tohoku Earthquake Tsunami Disaster and Future Tsunami Protections

    Proceedings of the Sixth International Conference on Asian and Pacific Coasts (APAC 2011)    2011年

  • Field survey and analysis of tsunami disaster in the Samoan Islands 2009

    Proc. of 6th Int. Conf. Coastal Structures    2011年

  • 2010年チリ沖地震津波災害の現地調査

    木学会論文集B3(海洋開発)   67  2011年

    DOI

  • 2011年東北地方太平洋沖地震による津波災害の宮城県以南における現地調査

    土木学会論文集B2(海岸工学)   67 ( 2 ) 1301 - 1305  2011年

    DOI

  • Erratum to: The economic impact of future increase in tropical cyclones in Japan (Nat Hazards, 10.1007/s11069-010-9522-9)

    Christian Webersik, Miguel Esteban, Tomoya Shibayama

    Natural Hazards   56 ( 1 ) 407 - 408  2011年  [査読有り]

    DOI

  • ENERGY DISSIPATION MODEL FOR COMPUTING TRANSFORMATION OF SPECTRAL SIGNIFICANT WAVE HEIGHT

    Winyu Rattanapitikon, Tomoya Shibayama

    COASTAL ENGINEERING JOURNAL   52 ( 4 ) 305 - 330  2010年12月  [査読有り]

     概要を見る

    The objective of this study is to propose the most suitable dissipation model for computing the transformation of spectral significant wave height (H-m0). A wide range of experimental conditions, covering small-scale, large-scale, and field experiments, were used to examine the models. Fourteen existing dissipation models, for computing root-mean-square wave heights (H-rms) were applied to compute H-m0. The coefficients of the models were re-calibrated and the accuracy of the models was compared. It appears that the model of Janssen and Battjes [2007] with new coefficients gives the best overall prediction. The simple model proposed in the present paper was modified by changing the formula of stable wave height in the dissipation model. Comparing with the existing models, the modified model is the simplest one but gives better accuracy than those of existing models.

    DOI

  • The economic impact of future increase in tropical cyclones in Japan

    Christian Webersik, Miguel Esteban, Tomoya Shibayama

    NATURAL HAZARDS   55 ( 2 ) 233 - 250  2010年11月  [査読有り]

     概要を見る

    This article estimates the non-first-order economic loss in Japan due to a future increase in tropical cyclones. One possible effect of global warming could be the increase in intensity of tropical cyclones. Using historical storm tracks between the years 1978 and 2007 and altering their intensities due to this potential increase in their intensity, this paper calculates the future potential regional GDP loss in a certain area that is affected by tropical cyclones. Most of the literature is concerned with physical damage and the loss of lives due to tropical cyclones. However, there are additional economic costs when sustained wind speeds are higher than 30 knots (55.56 km/h), a level that generally will lead to a precautionary cessation of many human activities. Using a Monte Carlo simulation, the paper calculates the potential economic costs for the year 2085 under a climate change scenario with a linear one-per cent yearly increase in CO2. Using a spatial distribution of economic activity in Japan, it is possible to forecast which parts of the country are likely to experience the highest loss risk.

    DOI

  • Methodology for the estimation of the increase in time loss due to future increase in tropical cyclone intensity in Japan

    Miguel Esteban, Christian Webersik, Tomoya Shibayama

    CLIMATIC CHANGE   102 ( 3-4 ) 555 - 578  2010年10月  [査読有り]

     概要を見る

    The present paper develops a methodology for estimating the risks and consequences of possible future increases in tropical cyclone intensities that would allow policy makers to relatively quickly evaluate the cost of different mitigation strategies. The methodology simulates future tropical cyclones by modifying the intensity of historical tropical cyclones between the years 1978 and 2007. It then uses a Monte Carlo Simulation to obtain the expected number of hours that a certain area can expect to be affected by winds of a given strength. The methodology outlined has a range of applications, and the present paper shows as an example the calculation of the expected cost of mitigation of the increased downtime for Japanese ports by 2085 for a variety of economic growth scenarios.

    DOI

  • サイクロンNARGISによる高潮調査と氾濫挙動の分析

    海洋開発論文集   26   429 - 434  2010年

  • サモア諸島沖地震津波の調査と分析

    土木学会論文集B2(海岸工学)   66 ( 1 ) 1376 - 1380  2010年

    DOI

  • Effect of a global warming-induced increase in typhoon intensity on urban productivity in Taiwan

    Miguel Esteban, Christian Webersik, Tomoya Shibayama

    SUSTAINABILITY SCIENCE   4 ( 2 ) 151 - 163  2009年10月  [査読有り]

     概要を見る

    A number of scientists have recently conducted research that shows that tropical cyclone intensity is likely to increase in the future due to the warming effect of greenhouse gases on surface sea temperatures. The aim of this paper is to establish what would be the likely decrease in the productivity of urban workers due to an increase in tropical cyclone-related downtime. The methodology used simulates future tropical cyclones by magnifying the intensity of historical tropical cyclones between the years 1978 and 2008. It then uses a Monte Carlo simulation to obtain the expected number of hours that a certain area can expect to be affected by winds of a given strength. It shows how annual downtime from tropical cyclones could increase from 1.5% nowadays to up to 2.2% by 2085, an increase of almost 50%. This decrease in productivity could result in a loss of up to 0.7% of the annual Taiwanese GDP by 2085.

    DOI

  • METHODOLOGY FOR THE SIMULATION OF THE CONSTRUCTION OF A BREAKWATER TAKING INTO ACCOUNT CLIMATE AND CONSTRUCTION ACCIDENT RISK

    Miguel Esteban, Hiroshi Takagi, Tomoya Shibayama

    COASTAL ENGINEERING JOURNAL   51 ( 1 ) 49 - 68  2009年03月  [査読有り]

     概要を見る

    This paper presents a method to simulate the construction of a caisson breakwater in order to evaluate the risks involved in its construction. A computer model of the construction process that a contractor would follow to build a caisson breakwater was developed, with the wave climate for each month of the duration of works modeled using data obtained from the NOWPHAS Reports. Possible damage to the caisson was determined using a deformation-based reliability design method that included sliding, tilting, overturning of the caisson and erosion of the toe armour and foundation material. The model included possible delays due to adverse weather, reconstruction of damaged sections and construction accidents. By using the Monte Carlo simulation technique, the expected cost and time to finish the breakwater could be obtained, allowing to determine the risk associated with the breakwater construction. Thus, it is possible to determine when would be the most appropriate time to begin construction and the likelihood of encountering problems during the construction phase. A case study of the breakwater construction for Honshu island in Japan is shown, with the results comparing well with the experience of Japanese contractors.

    DOI

  • A two-dimensional horizontal wave propagation and mud mass transport model

    Ali Oveisy, Kevin Hall, Mohsen Soltanpour, Tomoya Shibayama

    CONTINENTAL SHELF RESEARCH   29 ( 3 ) 652 - 665  2009年03月  [査読有り]

     概要を見る

    The present study offers a two-dimensional horizontal wave propagation and morphodynamic model for muddy coasts. The model can be applied on a general three-dimensional bathymetry of a soft muddy coast to calculate wave damping. fluid mud mass transport and resulting bathymetry change under wave actions. The wave propagation model is based on time-dependent mild slope equations including the wave energy dissipation due to the wave-mud interaction of bottom mud layers as well as the combined effects of the wave refraction, diffraction and breaking. The constitutive equations of the visco-elastic-plastic model are adopted for the rheological behavior of fluid mud. The mass transport velocity within the fluid mud layer is calculated combining the Stokes&apos; drift, the mean Eulerian velocity and the gravity-driven mud flow. The results of the numerical model are compared against a series of conducted wave basin experiments, wave flume experiments and field observations. Comparisons between the computed results with both the field and laboratory data reveal the capability of the proposed model to predict the wave transformation and mud mass transport. (C) 2008 Elsevier Ltd. All rights reserved.

    DOI

  • Quantitative Evaluation of Vulnerabilities in Coastal Structures due to Climate Change -Case Studies for Breakwaters-

    高木 泰士, 柏原 英広, 柴山 知也

    土木学会論文集B2(海岸工学)   65 ( 1 ) 891 - 895  2009年

     概要を見る

    Climate change is expected to lead to increases in both sea level and typhoon intensity. Such changes may threaten the stability of breakwaters. In this study, calculations using the SWAN model showed that a 10% increase in wind speed can lead to a 20% increase in wave height. The expected sliding distances for the breakwaters at Shibushi Ports were estimated using a probabilistic method proposed by Takagi et al. (2008). It is noteworthy that in the future sliding distances may become three times greater than current ones due to a combination of increases in sea level and wave height.

    DOI CiNii

  • FAILURE MODE AGAINST IMPACT AND SOLITARY WAVES OF ARMOURED CAISSON BREAKWATERS PROTECTED BY A PARTIALLY FAILED ARMOUR LAYER

    Miguel Esteban, Hiroshi Takagi, Tomoya Shibayama

    PROCEEDINGS OF COASTAL DYNAMICS 2009    2009年  [査読有り]

  • Field survey of storm surge disaster due to cyclone Sidr in Bangladesh

    Tomoya Shibayama, Yoshimitsu Tajima, Taro Kakinuma, Hisamichi Nobuoka, Tomohiro Yasuda, Raquib Ahsan, Mizanur Rahman, Shariful Islam

    Proc. Coastal Dynamics 2009    2009年  [査読有り]

  • Coastal Processes—Concepts of Coastal Engineering and Their Applications to Multifarious Environments

    World Scientific     215  2009年

  • 港湾構造物に及ぼす気候変動の影響とその定量的予測

    海岸工学論文集 B2(海岸工学)   65 ( 1 ) 891 - 895  2009年

  • サイクロンNargisによる高潮被害の調査

    海岸工学論文集,土木学会論文集B2(海岸工学)   65 ( 1 ) 1376 - 1380  2009年

    DOI

  • スリランカにおける津波警報発令時の情報伝達・避難行動の実態―2007年9月の事例―

    松丸亮, 内倉嘉彦, 落合知帆, WIJAYARATNA Nimal, 柴山知也

    海岸工学論文集   55 ( 2 ) 1421 - 1425  2008年10月

     概要を見る

    2007年9月にインド洋地域に津波警報が発令された際のスリランカ防災当局における災害対応の参与観察およびその後の対応に係る聞き取り調査等の分析。

    DOI J-GLOBAL

  • Total quality management implementation in the Egyptian construction industry

    Tarek Elghamrawy, Tomoya Shibayama

    JOURNAL OF MANAGEMENT IN ENGINEERING   24 ( 3 ) 156 - 161  2008年07月  [査読有り]

     概要を見る

    Total quality management (TQM) has been recognized as a successful management philosophy that can be successfully implemented in the construction industry. By examining the Japanese contractors working in Egypt and comparing their managing systems to the local ones, a comparative analysis of the two contractors working in the Egyptian field is presented in this paper to illustrate how TQM can be implemented effectively in the Egyptian construction industry. Bearing in mind the location bound nature of the production process, the competitive bidding, which emphasizes cost and the absence of the quality culture of the clients, subcontractors and site operatives are some of the constraining factors for implementing the quality policy. Based on the research findings, the paper presents some features of the Japanese construction industry that could be implemented in the Egyptian field in addition to a new model for TQM implementation that appropriates the Egyptian construction industry.

    DOI

  • NUMERICAL MODELING OF WAVE TRANSFORMATION ON MUDDY COASTS

    Mohsen Soltanpour, Ali Oveisy, Tomoya Shibayama

    COASTAL ENGINEERING JOURNAL   50 ( 2 ) 143 - 160  2008年06月  [査読有り]

     概要を見る

    The present study offers a two-dimensional horizontal wave transformation model that can be applied on a general three-dimensional bathymetry of soft muddy coasts. The wave transformation model is based on time-dependent mild slope equations including the high energy dissipation of bottom mud layers as well as the combined effects of wave refraction, diffraction and breaking. The constitutive equations of visco-elastic-plastic model are adopted for rheological behavior of fluid mud. The results of the numerical model are compared with a series of the conducted wave-basin experiments. The performance of the application of the numerical model on a real field condition, i. e. Kumamoto Port of Japan, is also examined. Comparison between the simulated results and measured values in both laboratory and field conditions reveal the capability of the proposed wave transformation model to consider the wave attenuation on fluid mud layers.

    DOI

  • Landslide susceptibility analysis using quantitative method with GIS for mountaneous road

    Proc. of Global Environmental Eng., 16     15 - 25  2008年

    DOI

  • 東京湾における陸棚波に起因した異常潮位の分析とその将来影響

    海岸工学論文集   55   1306 - 1310  2008年

    DOI

  • Landslide susceptibility analysis using quantitative method with GIS for mountaneous road

    地球環境研究論文集   16   15 - 25  2008年

    DOI

  • サイクロンSidrによるバングラデシュ海岸・河川高潮災害の現地調査

    海岸工学論文集   55   1396 - 1400  2008年

    DOI

  • Suspended sediment concentration on beaches under three different mechanisms

    Mantripathi Prabath Ravindra Jayaratne, Tomoya Shibayama

    COASTAL ENGINEERING JOURNAL   49 ( 4 ) 357 - 392  2007年12月  [査読有り]

     概要を見る

    A set of predictive models is formulated for computing suspended sediments concentration in and out surf zone under three different mechanisms:
    (1) suspension due to turbulance motion over sand ripples,
    (2) suspension from sheet flow layer, and
    (3) suspension due to turbulance motion under breaking waves.
    Dimensional analysis ans best-fit technique are the main methods for the formulation of reference concentration and diffusion coefficient and the model parameters are calibrated with the help of a large amount of published data. Time-averaged concentration profiles are derived from the steady diffusion equation. Published experimental data from 19 sources from 1977 to 1966 are better explained by the proposed formulae than the preceding formulae of Sleath [1982]. Nielsen [1986 and 1988] and, Rattanapitikon and shibayama [1994]. Due to scale effects, models are given for small-scale and large-scale cases seperately. Predominance of each suspension mechanism is verified with newly developed explicit formula. Finally, the applicability of the above sub models for irregular waves is also confirmed by the measured data sets.

    DOI

  • Improvement in calculation of resistance force on caisson sliding due to tilting

    Miguel Esteban, Hiroshi Takagi, Tomoya Shibayama

    COASTAL ENGINEERING JOURNAL   49 ( 4 ) 417 - 441  2007年12月  [査読有り]

     概要を見る

    The aim of the present paper is to investigate the long-term deformations of the rubble mound of a breakwater during its working life. Understanding these deformations is essential for the sliding and tilting to be able to be measured effectively. In order to do so, laboratory experiments were carried out, from which probability distribution functions of sliding and tilting were obtained for a series of three storms of similar intensity. The laboratory results were then reproduced using a computer model, which decomposed the movement of the caisson into its vertical and horizontal components. The horizontal movement uses the equation of Shimosako and Takahashi [1998] as modified by Kim and Takayama [2005], whereas for the vertical deformation the method of Esteban and Shibayama [2006] is employed. A new methodology for the calculation of the resistance force caused by the caisson tilting is proposed. The results obtained overestimate the deformation slightly during the first storm but can predict well the deformation during the subsequent storms.

    DOI

  • Estimation of shallow water representative wave heights

    Winyu Rattanapitikon, Tomoya Shibayama

    COASTAL ENGINEERING JOURNAL   49 ( 3 ) 291 - 310  2007年09月  [査読有り]

     概要を見る

    If the Rayleigh distribution of wave heights is valid, the representative wave heights can all be converted one to another through the known relationships. In shallow water, it has been pointed out by many researchers that the wave height distribution deviates from the Rayleigh distribution. However, it is not clear whether this deviation can lead to significant errors on the estimation of representative wave heights or not. Experimental data from small-scale, large-scale, and field experiments were used to examine the errors of the relationships derived from the Rayleigh distribution one stimating representative wave heights. The examination indicates that if H-rms is given, the relationships give overall very good estimations on (H) over bar and H-1/3 ,good estimation on H-1/10 but fair estimation on H-max. the effect of wave breaking was empirically incorporated in to the relationships. The new relationships give better estimation than the relationships derived from the Rayleigh distribution.

    DOI

  • Irregular wave attenuation and mud mass transport

    Mohsen Soltanpour, Tomoya Shibayama, Yugo Masuya

    COASTAL ENGINEERING JOURNAL   49 ( 2 ) 127 - 147  2007年06月  [査読有り]

     概要を見る

    The major aspects of interactive effects between irregular waves and a soft muddy bed, i. e. wave height attenuation and mud mass transport, are examined using numerical simulation and laboratory experiments. The irregular waves are simulated by spectral calculation method and joint distribution of wave height and wave period. The possibility of applying the representative wave method is also examined. The constitutive equations of visco-elastic-plastic model are selected for the complex rheological behavior of fluid mud. A series of wave flume experiments have been performed to obtain the required data for the veri. cation of the numerical model. The results of the numerical model are also compared with the laboratory data of Zhang and Zhao [1999]. It is concluded that both wave spectra modeling and individual wave analysis are capable to simulate the interactive effects between irregular waves and fluid mud. The wave energy dissipation can also be simulated by using common representative waves. However, mean wave is the only representative wave that offers an acceptable approximation for the prediction of mud mass transport.

    DOI

  • A numerical study of intermittent sediment concentration under breaking waves in the surf zone

    Takayuki Suzuki, Akio Okayasu, Tomoya Shibayama

    COASTAL ENGINEERING   54 ( 5 ) 433 - 444  2007年05月  [査読有り]

     概要を見る

    A three-dimensional Large Eddy Simulation (LES) model is presented together with a sediment pickup/advection module for the study of spatial and temporal variation of sediment concentration due to three-dimensional fluid motion under breaking waves on a sloping beach. The LES flow module calculates the turbulent flow due to wave breaking where a large-scale turbulence can be directly solved by the governing flow equations and a small-scale turbulence can be evaluated using a sub-grid-scale (SGS) model. In the sediment pickup/advection module, the sediment pickup rate is estimated by a sediment pickup function using the Shield's number at the bottom of the fluid layer, and suspended sediment particles are assumed to move with the ambient fluid. The numerical results show that the flow field including the wave breaking is represented well by the LES model and the sediment pickup/advection module is able to simulate spatial and temporal intermittency of the sediment suspension. Three noticeable sediment pickup areas are defined, namely around the breaking point, break impact area and run-up zone. In the inner region of the surf zone, the sediment concentration distribution shows strong three-dimensionality. The calculated results of the time-averaged and the equi-phase-averaged sediment concentration distributions are compared to earlier laboratory experiment results. The sediment concentration distribution and advection calculated by the model show general correspondence to the experimental results, but the averaged sediment concentration is approximately 1.5 times greater than the experimental value. (c) 2006 Elsevier B.V. All rights reserved.

    DOI

  • Tsunami disaster survey after Central Java tsunami in 2006

    Tomoya Shibayama, Jun Sasaki, Hiroshi Takagi, Hendra Achiari, Andojo Wurjanto

    ASIAN AND PACIFIC COASTS 2007     323 - +  2007年

  • Proposal of Simple pavement deterioration model by using in-service survey data

    Proceedings of Japan-China 4th Workshop on Pavement Technologies, Sapporo Japan     297 - 306  2007年

  • Numerical simulation of wave impact pressure on vertical breakwater

    Nguyen Danh Thao, Tomoya Shibayam

    ASIAN AND PACIFIC COASTS 2007     125 - 128  2007年

  • Management of pavement network maintenance and rehabilitation planning using shuffled complex evolution

    Journal of Construction Management and Engineering   14   143 - 153  2007年  [査読有り]

    DOI

  • Integrated Model for Estimating Sediment Discharge to Coastal Area from River Basin -A Case Study of Sakawa River

    Journal of Global Environment Engineering   12   13 - 32  2007年  [査読有り]

  • Evaluation of the active depth of foundations under a caisson breakwater subjected to impact waves

    Coastal structures 2007,CD-Rom     123 - 126  2007年

  • Determination of Risk Scores for Road Network in Bhutan

    Journal of Research and Development, Royal University of Bhutan    2007年

  • Application of the methodology for risk assessment of a caisson breakwater during construction to evaluate the insurance premium

    Miguel Esteban, Hiroshi Takagi, Tomoya Shibayama

    ASIAN AND PACIFIC COASTS 2007     645 - 648  2007年

  • Expansion of the reliability design method for caisson-type breakwaters towards deep water using the fourth order approximation of standing waves

    Hiroshi Takagi, Tomoya Shibayama, Miguel Esteban

    ASIAN AND PACIFIC COASTS 2007     661 - +  2007年

  • Breaking wave formulas for breaking depth and orbital to phase velocity ratio

    Winyu Rattanapitikon, Tomoya Shibayama

    COASTAL ENGINEERING JOURNAL   48 ( 4 ) 395 - 416  2006年12月  [査読有り]

     概要を見る

    This study was undertaken to find out the suitable breaking wave formulas for computing breaker depth, and corresponding orbital to phase velocity ratio and breaker height converted with linear wave theory. A large amount and wide range of published laboratory data (695 cases collected from 26 sources of published laboratory data) were used to examine and develop the breaker formulas. Examination of some existing formulas indicates that none of them can be used for a wide range of experimental conditions. New breaker formulas were developed based on the re-analysis of the existing formulas. Overall, the new formulas give good predictions over a wide range of experimental conditions.

    DOI

  • スマトラ島沖地震とインド洋津波/2004 インドネシア・バンダアチェにおける津波痕跡高と海岸侵食調査

    柴山知也, 岡安章夫, 佐々木淳, 鈴木崇之, 松丸亮, MASIMIN, ARIFF Zouhrawaty A

    月刊地球     146 - 153  2006年10月

    J-GLOBAL

  • 途上国における環境変化の土砂環境への影響−メコン川を例として−

    第14回地球環境シンポジウム講演論文集     115 - 120  2006年

    DOI

  • ベトナムDa Rang川における長期河口変動の解析

    日本沿岸域学会研究討論会2006講演概要集     284 - 289  2006年

  • 3次元LESモデルによる傾斜式防波堤周辺の乱流特性の数値的検討

    海岸工学論文集   53   751 - 755  2006年

    DOI

  • Hurricane Katrinaによる高潮被害の調査

    海岸工学論文集   53   401 - 405  2006年

    DOI

  • Topography Changes of Da Rang Coastal River Mouth,Shorelines and River Profile

    Techno-Ocean 2006    2006年

  • Laboratory Study on the Progression of Damage on Caisson Breakwaters Under Impact Waves

    Techno-Ocean 2006    2006年

  • Integrated Model for Estimating Sediment Discharge to Coastal Environment from River Basin−A Case Study of Sakawa Riber

        109 - 114  2006年

  • インド洋津波の被害調査と今後の沿岸域の環境研究協力

    柴山 知也, 岡安 章夫, 佐々木 淳, 鈴木 崇之

    地球環境シンポジウム講演論文集   13   289 - 291  2005年

     概要を見る

    Surveys were performed on disasters caused by Indian Ocean tsunami which occurred in December 26, 2004. Surveys were done in Sri Lanka and in Indonesia. Cooperative works with professors of domestic universities, who graduated from Japanese universities were the core of the survey works. From the survey results, varieties of disaster mechanisms were found. Local natural conditions and social conditions give big influences on the mechanism. In order to promote an appropriate post tsunami rehabilitation and environmental restoration process, cooperative works with local professors and engineers are essential.

    DOI CiNii

  • 流域から海岸への土砂供給量の検討−酒匂川を例として−

    海岸工学論文集   52   621 - 625  2005年

    DOI

  • 波による底泥移動量の評価方法−不規則波浪下と平面波浪場への適用

    海岸工学論文集   52   446 - 450  2005年

    DOI

  • アマモ群落における底質輸送機構と底質安定性向上効果について

    海岸工学論文集   52   1001 - 1005  2005年

    DOI

  • 2004年スマトラ沖地震津波のスリランカ南部被害調査

    海岸工学論文集   52   1401 - 1405  2005年

    DOI

  • 2004年スマトラ沖地震津波のインドネシア・バンダアチェ被害調査

    海岸工学論文集   52   1371 - 1375  2005年

    DOI

  • GIS-Based Estimation of Soil Erosion and Sediment Delivery to Coastal Environment from the River Basin. A Case Study of Rufiji River in Tanzania

    Asian and Pacific Coasts 2005     1695 - 1704  2005年

  • 途上国の環境変動研究の文献調査と開発の進展を時間軸とした比較:途上国研究小委員会報告

    柴山 知也

    地球環境シンポジウム講演論文集   12   7 - 9  2004年

     概要を見る

    A comparative study is performed for environmental problems in developing countries. Examples of environmental problems are collected, classified and discussed in relation to the stages of economic development in these countries. Time history of occurrences of these engineering problems is compared with socioeconomic development stage of each country. It is found out that environmental problems are closely related with industrialization and development stages. The developing countries in Asian region including ASEAN nations are accomplishing economic development well for the long terms before the recession period starting in 1997. Industry, agriculture, and the resort development were rapidly advanced. As a result, Asian region faces a rapid change of environmental system as having not experienced by the human race before. Also in African countries, for examples in Tanzania, we can observe the same type of environmental problems.

    DOI CiNii

  • 砕波帯内浮遊砂量の評価法−現地規模の現象に着目して−

    海岸工学論文集   51   386 - 390  2004年

    DOI

  • 「健全な議論による終結」を目指す住民参加型協議会運営方法の分析

    建設マネジメント研究論文集   11   15 - 26  2004年

    DOI

  • Irregular wave height transformation using representative wave approach

    W Rattanapitikon, R Karunchintadit, T Shibayama

    COASTAL ENGINEERING JOURNAL   45 ( 3 ) 489 - 510  2003年09月

     概要を見る

    Many researchers have pointed out that the use of representative wave approach can give erroneous results in the computation of irregular wave height transformation. However, the representative wave approach seems to be an efficient tool incorporated into beach deformation models because of its simplicity and computational efficiency. It will be useful for practical work, if this approach can be used to compute the irregular wave height transformation. Therefore, this study is carried out to investigate the possibility of simulating irregular wave height transformation by using representative wave approach. A large amount and wide range of experimental conditions, covering small-scale, large-scale, and field experimental conditions, are used to calibrate and examine the model. The rms wave height transformation is computed from the energy flux conservation law. Various energy dissipation models of regular wave breaking are directly applied to the irregular wave model and test their applicability. Surprisingly, it is found that by using an appropriate energy dissipation model with new coefficients, the representative wave approach can be used to compute the rms wave height transformation with very good accuracy.

    DOI

  • Cross-shore mud transport and beach deformation model

    M Soltanpour, T Shibayama, T Noma

    COASTAL ENGINEERING JOURNAL   45 ( 3 ) 363 - 386  2003年09月

     概要を見る

    The present study aims to simulate the various features of wave-mud interaction on fine-grained shore profiles including wave height attenuation, wave-induced mud mass transport, gravity-driven flow of fluid mud and the reconfiguration of profile shape. A two-dimensional mud beach deformation model is presented considering the transport of fluid mud under continued wave action and downward gravity force. The wave height transformation is computed from the energy flux conservation law combining the effects of mud bed, shoaling and wave breaking. The rheological constitutive equations of visco-elastic-plastic model (Shibayama et al., 1990) are selected for numerical simulation. Wave flume experiments are carried out and the results are utilized for the verification of numerical model. The results of the numerical model are also compared with the laboratory data of Nakano (1994). It is concluded that the model is capable to predict the observed phenomena.

    DOI

  • Application of GIS to Evaluate Long-term Variation of Sediment Discharge to Coastal Environment(共著)

    Coastal Engineering Journal   45 ( 2 ) 275 - 293  2003年06月

    DOI

  • A proposal of new breaker height formula

    W Rattanapitikon, T Vivattanasirisak, T Shibayama

    COASTAL ENGINEERING JOURNAL   45 ( 1 ) 29 - 48  2003年03月

     概要を見る

    A new breaker height formula is developed based on a re-analysis of available laboratory data. The analysis shows that the breaking wave steepness is mainly governed by its deepwater wave steepness. The power form could be used to fit the relationship between breaking wave steepness and its deepwater wave steepness. This finding is new. Although the breaker height has been a subject of study for a century, no researcher has tried to relate the breaking wave steepness to the deepwater wave steepness. Bottom slope effect is included explicitly into the present formula. The present formula and existing formulas are examined and compared with a large number and wide range of published laboratory data (695 cases collected from 26 sources). Overall, the present formula gives very good predictions over a wide range of experimental conditions and is better than existing formulas.

    DOI

  • 不規則波による底泥移動と波高減衰に関する実験的研究

    海岸工学論文集   50   466 - 470  2003年

    DOI

  • 砕波帯内浮遊砂量の評価方法

    海岸工学論文集   50   451 - 455  2003年

    DOI

  • 公共海岸事業の選択における専門家と一般市民

    海岸工学論文集   50   1351 - 1355  2003年

    DOI

  • 数値地図情報を用いた流域から海岸に供給される土砂収支の地球規模での算定方法

    海岸工学論文集   49   606 - 610  2002年

    DOI

  • 砕波帯内乱流モデルの波打ち帯(Swash Zone)への拡張

    海岸工学論文集   49   451 - 455  2002年

    DOI

  • 海岸原風景の回復を目指したエネルギー逸散型岸沖構造物の検討

    海岸工学論文集   49   1386 - 1390  2002年

    DOI

  • 集合表象による景観解析を用いた波浪制御の提案

    海岸工学論文集   48   1331 - 1335  2001年

    DOI

  • 砕波帯内戻り流れ(undertow)の推定方法

    海岸工学論文集   48   111 - 115  2001年

    DOI

  • A comparative study of coastal processes in Asian countries

    T Shibayama, LT Tuan

    PROCEEDINGS OF THE FIRST ASIAN AND PACIFIC COASTAL ENGINEERING CONFERENCE, VOLS 1 AND 2 (APACE 2001)   2   909 - 917  2001年

     概要を見る

    A comparative study was per-formed for coastal processes in Asian countries including Japan, Thailand, and Vietnam. The examples of coastal erosion problems were collected, classified and discussed in relation to the stages of economic development in these countries. Time history of occurrences of these engineering problems was compared with socioeconomic development stage of each country. It was found out that coastal problems were closely related with industrialization and development stages.

  • Verification and modification of breaker height formulas

    Rattanapitikon, V, T Shibayama

    COASTAL ENGINEERING JOURNAL   42 ( 4 ) 389 - 406  2000年12月  [査読有り]

     概要を見る

    This study is undertaken to find out the most reliable breaker height formulas that predict well for a wide range of hydraulic conditions. The applicability of 24 existing formulas, for computing breaking wave heights, is examined by using wide range and large amount of published laboratory data (574 cases collected from 24 sources). It is found that most formulas predict well for the breaking waves on the gentle slope (0 &lt; m &lt;less than or equal to&gt; 0.07), but the prediction is unsatisfactory for the breaking waves on the steep slope (0.1 &lt; m &lt;less than or equal to&gt; 0.44). Three formulas are selected and are modified by including the new form of bottom slope effect into the formulas. The new breaker height formulas predict well for wide range of wave and bottom slope conditions.

    DOI

  • Simple model for undertow profile

    W Rattanapitikon, T Shibayama

    COASTAL ENGINEERING JOURNAL   42 ( 1 ) 1 - 30  2000年03月

     概要を見る

    Based on a re-analysis of the existing undertow models and the experimental results, a proper explicit model is proposed for computing undertow profile inside the surf zone. The model has been derived by using the eddy viscosity approach. The model is examined using published laboratory data from six sources covering small-scale and large-scale experiments, i.e. the experiments of Nadaoka et al. (1982), Hansen and Svendsen (1984), Okayasu et al. (1988), Cox et al. (1994), CRIEPI (Kajima et al., 1983) and SUPERTANK (Kraus and Smith, 1994). The present undertow model is considerably simpler than most of existing models. Although the model is simple, it shows good agreement with the experimental results above the bottom boundary layer. The calculation is so simple that the undertow profile can be calculated by using a pocket calculator.

    DOI

  • 信頼関係と技術者の行動選択

    建設マネジメント研究論文集   8   247 - 253  2000年

    DOI

  • 砕波帯内底面乱流境界層のモデル

    海岸工学論文集   47   501 - 505  2000年

    DOI

  • ベトナムの経済発展に位置づけた海岸問題発現の比較研究

    海岸工学論文集   47   1341 - 1345  2000年

  • Energy Dissipation Formulas for Regular Breaking Waves

    Proc. of the 4th International Conf. on Hydrodynamics     545 - 550  2000年

  • Comparative Study of Coastal Problems in Vietnam

      47   1341 - 1345  2000年

  • Calculation of Wave-Induced Longshore Current in Surf Zone by Boussinesq Equations

    Proc. of 27th Coastal Eng. Conf.,ASCE     334 - 335  2000年

  • A Unified Numerical Model for the Bottom Boundary Layer and the Upper Layer in the Surf Zone

    Proc. of Coastal Eng. Conf.,ASCE   27 ( 1 ) 120 - 133  2000年

  • A Model of Sediment Transport in the Bottom Boundary Layer

    Proc. of Coastal Eng. Conf.,ASCE   27   134 - 147  2000年

  • A Model for Bottom Boundary Layer in the Surf Zone

      47   501 - 505  2000年

  • Simple model for undertow profile

    Winyu Rattanapitikon, Tomoya Shibayama

    Coastal Engineering Journal   42 ( 1 ) 1 - 30  2000年  [査読有り]

     概要を見る

    Based on a re-analysis of the existing undertow models and the experimental results, a proper explicit model is proposed for computing undertow profile inside the surf zone. The model has been derived by using the eddy viscosity approach. The model is examined using published laboratory data from six sources covering small-scale and large-scale experiments, i.e. the experiments of Nadaoka et al. (1982), Hansen and Svendsen (1984), Okayasu et al. (1988), Cox et al. (1994), CRIEPI and SUPERTANK. The present undertow model is considerably simpler than most of existing models. Although the model is simple, it shows good agreement with the experimental results above the bottom boundary layer. The calculation is so simple that the undertow profile can be calculated by using a pocket calculator.

    DOI

  • A 2-DV numerical solution for the turbulent wave boundary layer under breaking waves

    NT Duy, T Shibayama, A Okayasu

    COASTAL ENGINEERING 1998, VOLS 1-3     484 - 497  1999年

     概要を見る

    This paper presents a numerical solution for the bottom boundary, layer (BBL) in the surf zone. The upper boundary of the BBL is determined through the solution of a breaking waves model. Different turbulence models have been tested to determine the distribution of turbulent kinetic energy, energy dissipation and eddy viscosity in the BBL. Finally, the vertical profiles of horizontal velocity can be found out through the solution of the governing equations of the BBL.

  • 掃流砂と浮遊砂を統一的に取り扱う砕波帯内漂砂量モデルとその検証

    海岸工学論文集   46 ( 1 ) 601 - 605  1999年

    DOI

  • 傾斜泥層の波による輸送量モデルとその実験による検証

    海岸工学論文集   46 ( 1 ) 581 - 585  1999年

    DOI

  • Mud Transport Model over Sloping Bottom

      46 ( 1 ) 581 - 585  1999年

  • Integrated Model Including Bed Load and Suspended Load for Sediment Transport in the Surf Zone

      46 ( 1 ) 601 - 605  1999年

  • 粘弾塑性体多層モデルを用いた二次元泥浜の変形予測

    海岸工学論文集   45   521 - 525  1998年

    DOI

  • Two-Dimensional Mud Beach Deformation Model

      45   521 - 525  1998年

    DOI

  • Random Wave Modelling Approach Included in a Beach Deformation Model

    Proc. of 26th Coastal Eng. Conf. , ASCE     3008 - 3021  1998年

  • Modeling of Time-Dependent Sand Transport at the Bottom Boundary Layer in the Surf Zone(共著)

    Coastal Engineering Journal, JSCE   40 ( 3 ) 1 - 22  1998年

  • Energy dissipation model for regular and irregular breaking waves

    Winyu Rattanapitikon, Tomoya Shibayama

    Coastal Engineering Journal   40 ( 4 ) 327 - 346  1998年

     概要を見る

    Based on a large amount of published laboratory results, reliable models are developed for computing the average rate of energy dissipation in regular and irregular breaking waves The average energy dissipation rate is assumed to be proportional to the difference between the local mean energy density and stable energy density. Wave height transformation is computed from the energy flux conservation law based on the linear wave theory. The models are examined and verified extensively for a variety of wave and bottom conditions including small and large scale laboratory and field experiments. Reasonable good agreements are obtained between the measured and computed wave heights and root mean square wave heights.

    DOI

  • Energy Dissipation Model for Irregular Braking Waves

    Proc. of 26th Coastal Eng. Conf. , ASCE     112 - 125  1998年

  • Modelling of time-dependent sand transport at the bottom boundary layer in the surf zone

    Tomoya Shibayama, Ioan Nistor

    Coastal Engineering Journal   40 ( 3 ) 241 - 263  1998年  [査読有り]

     概要を見る

    The present paper is aimed to formulate a numerical model for calculating the time-dependent velocity field and the space and time distribution of sand concentration inside the bottom boundary layer in the surf zone. The numerical results are compared with recent laboratory data. The 2DV (two-dimensional vertical) numerical module for the velocity field is based on the Reynolds averaged form of the Navier-Stokes equations while the sand transport module uses the turbulent convection-diffusion equation. The equiphase mean values for the horizontal and vertical velocities within the bottom boundary layer (the flow field) and the equi-phase mean values for the sand concentration are obtained. A transformation of the coordinate system is performed in order to enable the easy implementation of the numerical modelling. Details of the numerical modelling together with discussions on the boundary conditions are also presented. The comparison of numerical and laboratory results reveals relatively good agreement within certain limitations of the present model. The laboratory data, which are used to compare the hydrodynamic numerical model have been obtained in the surf zone while the ones for verifying the sand concentration numerical model are obtained as a result of pure oscillatory movement.

    DOI

  • Energy dissipation model for regular and irregular breaking waves

    Winyu Rattanapitikon, Tomoya Shibayama

    Coastal Engineering Journal   40 ( 4 ) 327 - 346  1998年  [査読有り]

     概要を見る

    Based on a large amount of published laboratory results, reliable models are developed for computing the average rate of energy dissipation in regular and irregular breaking waves The average energy dissipation rate is assumed to be proportional to the difference between the local mean energy density and stable energy density. Wave height transformation is computed from the energy flux conservation law based on the linear wave theory. The models are examined and verified extensively for a variety of wave and bottom conditions including small and large scale laboratory and field experiments. Reasonable good agreements are obtained between the measured and computed wave heights and root mean square wave heights.

    DOI

  • A Convection-Diffusion Model for Suspended Sediment in the Surf Zone(共著)

    Journal of Geophysical Research, Oceans   102 ( C10 ) 23169 - 23186  1997年10月

    DOI

  • Beach Deformation Model under Irregular Waves

    Offshore Mechanics and Arctic Engineering. OMAE Conf.   1   124 - 138  1997年

  • 途上国の発展段階に位置づけた海岸問題発現の比較研究 (共著)

    海岸工学論文集   43 ( 2 ) 1291 - 1295  1996年

    DOI

  • 砕波帯内底面乱流境界層の数値モデルとその検証

    海岸工学論文集   43 ( 1 ) 446 - 450  1996年

    DOI

  • 工学高等教育分野における途上国援助の方策

    国際開発研究   5   81 - 88  1996年

  • Development Stages of Engineering School and Construction Industry in Asia

    Proc. of CIB Conf. on Construction Modernization and Education, CD-ROM    1996年

  • Cross-Shore Sediment Transport and Beach Deformation Model

    Proc. of 25th Coastal Eng. Conf. , ASCE     3062 - 3075  1996年

  • A Turbulent Flow Model for Braking Waves

    Proc. of 25th Coastal Eng. , ASCE     200 - 213  1996年

  • A Proposal for Higher Education Support in Engineering Field

      5   81 - 88  1996年

  • 乱流方程式を用いたさ砕波帯流速場・圧力場の計算法の検証 (共著)

    海岸工学論文集   42 ( 1 ) 21 - 25  1995年

    DOI

  • 乱流下の移流拡散方程式を用いた砕波帯内浮遊砂濃度の予測数値モデル (共著)

    海岸工学論文集   42 ( 1 ) 441 - 445  1995年

    DOI

  • 浮遊漂砂量予測を取り入れた二次元海浜変形モデル (共著)

    海岸工学論文集   42 ( 1 ) 446 - 450  1995年

    DOI

  • Three Examples of Japanese Experiences of Coastal Environment Changes due to Construction Works

    Proc.of (]G0004[) COPEDEC.    1995年

  • Suspended sediment concentration profiles under non-breaking and breaking waves

    Rattanapitikon Winyu, Tomoya Shibayama

    Proceedings of the Coastal Engineering Conference   3   2813 - 2827  1995年01月

     概要を見る

    Simple formulas to predict time-averaged suspended sediment concentration are formulated using steady diffusion equation. Empirical formulas are developed to compute reference concentration (boundary condition) and diffusion coefficient. For suspended sediment concentration in the field, the same formulas with regular wave condition can be applied by using root mean square wave height and average wave period. Total 139 data sets are used for calibration of empirical formulas and 175 data sets are used for verification.

  • 乱流方程式を用いた砕波帯内波浪場の数値モデル (共著)

    海岸工学論文集   41 ( 1 ) 151 - 155  1994年

    DOI

  • 土木工学におけるパラダイム転換論と新しい土木事業執行制度の枠組みについて-力学中心からポストモダン、協同的人間活動への転換をめざして- (共著)

    土木学会誌   79 ( 10 ) 42 - 45  1994年

  • 砕波帯内の浮遊漂砂量の算定モデル (共著)

    海岸工学論文集   41 ( 1 ) 431 - 435  1994年

    DOI

  • 国際開発工学に向かって

    土木学会誌   79 ( 3 ) 35 - 37  1994年

  • 技術開発力の発展とその背景 (共著)

    国際開発研究   3 ( 1 ) 177 - 184  1994年

  • 河口周辺の海浜変形モデルとその検証 (共著)

    海岸工学論文集   41 ( 1 ) 466 - 470  1994年

    DOI

  • Coastal Disasters in Asia and Education of Leading Engineers in Japanese Universities

    Towards Natural Disaster Redution, Proc.of (]G0007[) PSA Workshop     149 - 153  1994年

  • A 2-D Vertical Model for Wave and Current in the Surf Zone Based on the Turbulent Flow Equations (共著)

    Coastal Engineering in Japan, JSCE   37 ( 1 ) 41 - 66  1994年

  • 波流れ共存下での底泥質量輸送 (共著)

    海岸工学論文集   40 ( 1 ) 361 - 365  1993年

    DOI

  • 持続可能なアジアの沿岸開発

    国際開発研究   2 ( 2 ) 105 - 112  1993年

  • 砕波帯を含む浮遊砂濃度の鉛直分布の評価 (共著)

    海岸工学論文集   40 ( 1 ) 306 - 310  1993年

    DOI

  • 砕波による運動量輸送を考慮した海浜流の準3次元数値モデル (共著)

    海岸工学論文集   40 ( 1 ) 251 - 255  1993年

    DOI

  • Vertical Distribution of Suspended Sediment Concentration in and Outside Surfzone (共著)

    Coastal Engineering in Japan, JSCE   36 ( 1 ) 49 - 65  1993年

  • Opening of Engineering Graduate Education of Japanese Universities to Developing Countries

    Proc.of (]G0010[)(]G0010[)(]G0005[) IAHR Congress   (]G0007[)   222 - 225  1993年

  • A Visco-Elastic-Plastic Model for Wave-Mud Interaction (共著)

    Coastal Engineering in Japan, JSCE   36 ( 1 ) 67 - 90  1993年

    DOI

  • 東京湾の流動と物質拡散 (共著)

    海岸工学論文集   39 ( 2 ) 916 - 920  1992年

    DOI

  • 底泥特性の周期依存性に着目したモデルとその検証 (共著)

    海岸工学論文集   39 ( 1 ) 511 - 515  1992年

    DOI

  • 大学院教育の国際化 (共著)

    工業教育   40 ( 4 ) 97 - 101  1992年

  • 斜面上に設置した大口径円柱周辺の地形変化機構 (共著)

    海岸工学論文集   39 ( 1 ) 486 - 490  1992年

    DOI

  • 斜め入射波による砕波帯内定常流の3次元分布 (共著)

    海岸工学論文集   39 ( 1 ) 66 - 70  1992年

    DOI

  • 砕波帯内長周期波の漂砂量への効果 (共著)

    海岸工学論文集    1992年

    DOI

  • アジアの開発途上国における高等教育の課題とわが国の取り組み

    国際協力研究   8 ( 2 ) 31 - 39  1992年

  • Multi-Level Model for Hydrodynamic Circulation and Dispersion Process in Bays (共著)

    Coastal Engineering in Japan, JSCE   35 ( 1 ) 49 - 66  1992年

  • 底泥の粘弾性特性の計測と数値モデルへの応用 (共著)

    海岸工学論文集   38 ( 1 ) 471 - 475  1991年

  • タイ国の海岸問題-東南アジアにおける一例- (共著)

    海岸工学論文集   38   371 - 375  1991年

  • 底泥移動に関する粘弾塑性体モデルの波流れ場への適用 (共著)

    海岸工学論文集   37   240 - 243  1990年

    DOI

  • 長周期波の局所漂砂量に及ぼす効果 (共著)

    海岸工学論文集   37   279 - 283  1990年

    DOI

  • Laboratory Study on Sand Suspension Due to Breaking Waves (共著)

    Coastal Engineering in Japan   33 ( 2 ) 219 - 231  1990年

  • Breaking Conditions of Composite and Random Waves (共著)

    Coastal Engineering in Japan   33 ( 2 ) 133 - 143  1990年

  • 波と流れが任意角度で斜交する場での漂砂量 (共著)

    海岸工学論文集   36   304 - 308  1989年

    DOI

  • 粘弾塑性体モデルによる底泥移動量の評価法 (共著)

    海岸工学論文集   36   334 - 338  1989年

    DOI

  • 東京湾の津波計算と海上交通の安全性 (共著)

    日本沿岸域会議論文集     37 - 42  1989年

  • 砕波による底質の巻き上げ量に関する実験的研究 (共著)

    海岸工学論文集   36   279 - 283  1989年

    DOI

  • 海浜変形数値シミュレ-ションにおける浮遊砂の移流過程とundertowの効果 (共著)

    海岸工学論文集   36   394 - 398  1989年

    DOI

  • Sediment Transport Rate in Wave-Current Coexistent Field (共著)

    Coastal Engineering in Japan   32 ( 2 ) 161 - 171  1989年

  • Long-wave Component in Near-bottom Velocities under Randam Waves on a Gentle Slope (共著)

    Coastal Engineering in Japan   32 ( 2 ) 149 - 159  1989年

  • 緩勾配斜面上における不規則波の底面流速変動特性に関する研究

    佐藤愼司, 諌山太郎, 柴山知也

    第35回海岸工学講演会論文   35   78 - 82  1988年  [査読有り]

    DOI

  • MUD MASS TRANSPORT DUE TO WAVES.

    Tomoya Shibayama, Hiroshi Takikawa, Kiyoshi Horikawa

    Coastal Engineering Journal   29   151 - 161  1986年12月  [査読有り]

     概要を見る

    Theoretical and laboratory investigations were performed in order to estimate the rate of mud mass transport under wave action. In the theoretical work, the behavior of soft mud over which waves were propagating was assumed to be similar to a viscous fluid. Then a formula to calculate the rate of mud mass transport was derived by using the analytical solution of mud velocity field. In the laboratory work, spatial distributions and time histories of the mud mass transport rate were measured in a wave flume using kaolinite as a bed material.

  • Mud Mass Transport due to Waves (共著)

    Coastal Engineering in Japan   29   151 - 162  1986年

  • NUMERICAL MODEL FOR TWO-DIMENSIONAL BEACH TRANSFORMATION.

    Tomoya Shibayama, Kiyoshi Horikawa

    Doboku Gakkai Rombun-Hokokushu/Proceedings of the Japan Society of Civil Engineers     167 - 176  1985年05月  [査読有り]

     概要を見る

    A simplified simulation model for predicting two-dimensional beach transformation was developed The on the recent results of research works on wave transformation, near bottom velocity and sediment transport. The wave field was calculated by the energy flux method based on either cnoidal or linear wave theory in the linear zone, and by Mizuguchi&#039;s energy dissipation model in the surf zone. The velocity field was calculated by the approximate method of Koyama and Iwata using the cnoidal wave profile or by linear wave theory. The sediment transport formula of Shibayama and Horikawa, which includes the effect of suspended sediment caused by vortices created in the vicinity of ripples, was used to calculate transport rates. The model was found to give reasonable results. The results were compared with various laboratory data and the feasibility of the model was discussed.

  • A Numerical Model for Two-Dimensional Beach Transformation (共著)

      357 ( (]G0002[)-3 ) 167 - 176  1985年

    DOI

  • Sediment Suspension due to Breaking Waves (共著)

    Coastal Engineering in Japan,JSCE   25   163 - 176  1982年

  • SEDIMENT SUSPENSION DUE TO BREAKING WAVES.

    Tomoya Shibayama, Kiyoshi Horikawa

    Coastal Engineering in Japan   25   163 - 176  1982年01月  [査読有り]

     概要を見る

    In order to investigate on-offshore sediment transport mechanism and two-dimensional beach transformation, sediment movement under the agitation of wave breaking was considered. Sediment movement in the vicinity of wave breaking point was observed in a wave flume and sediment concentration was measured both in the wave flume and on natural beaches. The rate and direction of sediment transport at wave breaking point were calculated by using the data of two-dimensional beach profile change. The governing factors to determine the rate and direction are wave period, sediment fall velocity and suspended distance of sediment particles above bottom.

  • Laboratory Study on Sediment Transport Mechanism due to Wave Action (共著)

      ( 296 ) 131 - 141  1980年

    DOI

  • Bed Load Measurement and Prediction of Two-Dimensional Beach Trnasformation

    Coastal Engineering in Japan, JSCE (共著)   23   191 - 203  1980年

  • BED LOAD MEASUREMENT AND PREDICTION OF TWO-DIMENSIONAL BEACH TRANSFORMATION DUE TO WAVES.

    Tomoya Shibayama, Kiyoshi Horikawa

    Coastal Engineering in Japan   23   179 - 190  1980年01月  [査読有り]

     概要を見る

    Model and experimental investigations have been performed to examine a bed load formula and to predict two-dimensional beach transformation. Laboratory experiments were carried out to count the number of sand particles in motion and to measure water particle velocity at each instant of a wave cycle in a wave flume. The results were compared with a bed load formula derived by modifying the Madsen-Grant bed load formula.

  • 首都直下地震による東京湾内津波の挙動と災害危険度の評価

    海洋開発論文集   26   219 - 223

▼全件表示

書籍等出版物

  • 海岸工学 -- よくわかる海岸と港湾

    ( 担当: 編集)

    森北出版  2021年05月

  • 水理学解説

    柴山 知也( 担当: 編集)

    コロナ社  2019年09月

  • Handbook of Coastal Disaster Mitigation for Engineers and Planners

    ( 担当: 共編者(共編著者))

    2015年01月 ISBN: 9780128010600

  • 図説 日本の海岸

    柴山知也, 茅根創( 担当: 共編者(共編著者))

    朝倉書店  2013年05月 ISBN: 9784254160659

  • 3.11津波で何が起きたか

    柴山 知也

    早稲田大学出版部  2011年12月 ISBN: 9784657113047

  • Coastal Processes--Concepts in Coastal Engineering and Their Application to Multifarious Environment

    Tomoya Shibayama

    World Scientific  2009年01月

  • 建設技術者の倫理と実践 増補・改訂版

    柴山知也

    丸善  2004年 ISBN: 4621074075

  • 漂砂環境の創造に向けて

    土木学会, 海岸工学委員会, 編集代表, 河田恵昭, 柴山知也( 担当: 共編者(共編著者))

    土木学会・丸善(株)  1998年07月 ISBN: 4810602222

  • 建設社会学-土木技術者・国際開発技術者のための社会学入門-

    柴山知也

    山海堂  1996年 ISBN: 4381009371

▼全件表示

Misc

  • 九十九里沿岸部を対象とした津波によるエッジ波の特性に関する研究

    小谷野賢太朗, 高畠知行, 柴山知也

    海洋工学シンポジウム(CD-ROM)   28th  2020年

    J-GLOBAL

  • 深層学習を用いた波浪予測手法の開発と日本沿岸域への適用性

    馬渡竜輝, 高畠知行, KYAW Thit Oo, 柴山知也, 澁谷容子, 小竹康夫

    海洋工学シンポジウム(CD-ROM)   28th  2020年

    J-GLOBAL

  • Correction to: Street-scale storm surge load impact assessment using fine-resolution numerical modelling: a case study from Nemuro, Japan (Natural Hazards, (2019), 99, 1, (391-422), 10.1007/s11069-019-03746-6)

    Ryota Nakamura, Martin Mäll, Tomoya Shibayama

    Natural Hazards   99   423 - 424  2019年10月

     概要を見る

    © 2019, Springer Nature B.V. This correction stands to correct two discrepancies reported to the publisher soon after publication. The authors and publisher regret the errors as they were caused by a proofing oversight and stress the following to be noted: First, under the Methods and Material section (3.4), where the erroneous equation is:(Formula presented.).

    DOI

  • Study on the risks of tsunami inundation via underground pipelines

    T. Takabatake, T. Shibayama

    Proceedings of the 9th International Conference on APAC 2017   ( 213039 ) 268 - 279  2018年

     概要を見る

    When a tsunami comes to seaside industrial areas, seawater would enter landside areas through underground pipelines and induce inundation disasters. In the present study, the authors aim to investigate the risks of this tsunami inundation via the pipelines using the numerical simulation model. The results indicated that the influence of the tsunami inundation via the pipelines on seaside areas is not small and especially it will likely to influence the initial phase of evacuation. It is therefore important for port authorities and city planners to consider such risks when developing tsunami mitigation plans.

    DOI

  • Coastal flooding-induced debris motion

    Ioan Nistor, Nils Goseberg, Jacob Stolle, Tomoya Shibayama, Takahito Mikami

    Proceedings of the Coastal Engineering Conference   36  2018年01月

  • Tsunami-induced hydrodynamics and scour around structures

    Ravindra Jayaratne, Mara Nicholas, Behnaz Ghodoosipour, Sophie Mugnaini, Ioan Nistor, Tomoya Shibayama

    Proceedings of the Coastal Engineering Conference   36  2018年01月

  • Future wave projection during the typhoon and winter storm season

    Shinsaku Nishizaki, Ryota Nakamura, Tomoya Shibayama, Jacob Stolle

    Proceedings of the Coastal Engineering Conference   36  2018年01月

  • Physical and Numerical Modelling of the Flow Structure behind Structure in Tsunami-like Flow

    Hidenori Ishii, Tomoya Shibayama, Jacob Stolles

    Proceedings of the Coastal Engineering Conference   36  2018年01月

  • Numerical simulation of Cyclone nargis (2008) and its related wave field at Myanmar coast by using WRF-SWAN model

    Thit Oo Kyaw, Tomoya Shibayama

    Proceedings of the Coastal Engineering Conference   36  2018年01月

  • Inter-comparison of coastal models: Case study of storm surge at Nemuro in Japan

    Ryota Nakamura, Martin Mäll, Tomoya Shibayama, Shigeru Kato

    Proceedings of the Coastal Engineering Conference   36  2018年01月

  • Tsunami casualty estimation considering intended evacuation behavior of local residents and visitors

    Tomoyuki Takabatake, Tomoya Shibayama, Esteban Miguel

    Proceedings of the Coastal Engineering Conference   36  2018年01月

  • A numerical model of cross-shore beach profile evolution: Theory, model development and applicability

    Mohammad Tabasi, Mohsen Soltanpour, Ravindra Jayaratne, Tomoya Shibayama, Akio Okayasu

    Proceedings of the Coastal Engineering Conference   36  2018年01月

     概要を見る

    © 2018 American Society of Civil Engineers (ASCE). All rights reserved. A practical numerical model was developed to simulate cross-shore profile evolution at two coastal sites in Iran. The model consists of three sub-models for calculating wave and current, sediment transport, and bed level changes. Validation and calibration of the model was carried out using the measured field data on the north and south coasts of Iran, where historic measurements of cross-shore beach profiles and wave conditions have been recorded. The model is formulated for calculating cross-shore sediment transports in and outside the surf zone by the product of time-averaged suspended sediment concentration under three different mechanisms and undertow velocity. The comparisons between the model results and field data show reasonable agreement for both coastal sites and will be capable of applying it to other coastal sites with modifications to the free parameters.

  • An evaluation of suspended sediment concentration models under breaking waves

    Gabriel Lim, Ravindra Jayaratne, Tomoya Shibayama

    Proceedings of the Coastal Engineering Conference   36  2018年01月

  • Modelling parameters and impacts of four extratropical cyclones under future climate scenarios

    Martin Mäll, Ryota Nakamura, Tomoya Shibayama, Ülo Suursaar

    Proceedings of the Coastal Engineering Conference   36  2018年01月

  • Comparison of Two Recent Storm Surge Events Based on Results of Field Surveys

    Ryota Nakamura, Tomoya Shibayama, Takahito Mikami, Miguel Esteban, Hiroshi Takagi, Martin Maell, Takumu Iwamoto

    PROCEEDINGS OF THE INTERNATIONAL CONFERENCE OF GLOBAL NETWORK FOR INNOVATIVE TECHNOLOGY AND AWAM INTERNATIONAL CONFERENCE IN CIVIL ENGINEERING (IGNITE-AICCE'17): SUSTAINABLE TECHNOLOGY AND PRACTICE FOR INFRASTRUCTURE AND COMMUNITY RESILIENCE   1892  2017年

     概要を見る

    This paper compares two different types of storm surge disaster based on field surveys. Two cases: a severe storm surge flood with its height of over 5 m due to Typhoon Haiyan (2013) in Philippine, and inundation of storm surge around Nemuro city in Hokkaido of Japan with its maximum surge height of 2.8 m caused by extra-tropical cyclone are taken as examples. For the case of the Typhoon Haiyan, buildings located in coastal region were severely affected due to a rapidly increase in ocean surface. The non-engineering buildings were partially or completely destroyed due to their debris transported to an inner bay region. In fact, several previous reports indicated two unique features, bore-like wave and remarkably high speed currents. These characteristics of the storm surge may contribute to a wide-spread corruption for the buildings around the affected region. Furthermore, in the region where the surge height was nearly 3 m, the wooden houses were completely or partially destroyed. On the other hand, in Nemuro city, a degree of suffering in human and facility caused by the storm surge is minor. There was almost no partially destroyed residential houses even though the height of storm surge reached nearly 2.8 m. An observation in the tide station in Nemuro indicated that this was a usual type of storm surge, which showed a gradual increase of sea level height in several hours without possessing the unique characteristics like Typhoon Haiyan. As a result, not only the height of storm surge but also the robustness of the buildings and characteristics of storm surge, such as bore like wave and strong currents, determined the existent of devastation in coastal regions.

    DOI

  • 東京湾における沿岸域災害対策の費用便益分析

    大矢淳, 柴山知也, 中村亮太, 岩本匠夢

    土木学会論文集 B3(海洋開発)(Web)   72 ( 2 )  2016年

    J-GLOBAL

  • A predictive model for scour depth of coastal building failures due to tsunamis

    Mara Nicholas, Ravindra Jayaratne, Takayuki Suzuki, Tomoya Shibayama

    Proceedings of the Coastal Engineering Conference   35  2016年01月

     概要を見る

    The 2011 Great East Japan Earthquake and Tsunami was one of the strongest earthquakes which generated a major tsunami in modern history. The tsunami disaster had an estimated cost of 16.9 trillion yen (US 217.3 billion) and affected the Coastal buildings, services, infrastructure and industrial sectors. Approximately 61% of damaged cost was from the building sector. A practical predictive scour depth model at seaward face was developed to highlight the scour failure of Coastal buildings in Miyagi, Fukushima and Iwate prefectures affected by the 2011 Great East Japan Earthquake and Tsunami. The predictive model for representative scour depth was developed in terms of various hydraulic, geometrical and soil properties affecting Coastal buildings. An analysis was undertaken to investigate the effectiveness of the authors&#039; predictive scour model against the existing models. The results of the authors&#039; proposed model suggested that the tsunami velocity played a significant role on tsunami-induced scour, other scour models such as Tonkin et al.&#039;s model (2003) is reliant on the accuracy of sub models and hydrodynamic forces while the Colorado State University model as modified by Nadal et al. (2010) is reliant on the geometric parameter of the structure.

  • Ensemble forecast of extreme storm surge: A case study of 2013 typhoon haiyan

    Ryota Nakamura, Tomoya Shibayama

    Proceedings of the Coastal Engineering Conference   35  2016年01月

     概要を見る

    The object of this study is to evaluate an ensemble forecast of extreme storm surge by using a case of Typhoon Haiyan (2013) and its associated storm surge. A simple numerical model composed of ARW-WRF, FVCOM and SWAN is employed as a forecast system for storm surge. This ensemble system can successfully forecast storm surge 3-4 days before it happened. However, the typhoons in almost all ensemble members were underpredicted probably because of its difficulty in forecasting a track and central pressure of highly intense typhoon. This leads to the underestimation of a prediction of storm surges around Leyte Gulf. Compensating the underestimation of forecasted extreme storm surge, it can be important to not only examine the ensemble mean among members but also consider the phase-shifted manipulation and the worst ensemble member in the case where the extreme storm surge is forecasted. In addition, the ensemble forecast system can have a potential to determine the time at which the peak of extreme surge appears with a high precision.

  • A study on wave-induced particle velocities in fluid mud layer

    Mohsen Soltanpour, Hadi Shamsnia, Tomaya Shibayama, Ryota Nakamura, Akifumi Tatekoji

    Proceedings of the Coastal Engineering Conference   35  2016年01月

     概要を見る

    Cohesive sediments can be found in many coastal zones all over the world. The upper layer of these muddy coasts may be fluidized under the wave action. Fluid mud is also formed by settlement of fine particles when the waves and currents exert a small shearing stress on the bed. When the waves pass over the fluid mud layer, it absorbs wave energy and, in turn, moves due to the wave action. The present study offers a numerical and experimental study of wave-mud interaction on a horizontal bed. A number of wave flume laboratory tests are presented to investigate wave attenuation, particle velocities in fluid mud layer and mud mass transport under different wave characteristics. The laboratory results are also compared with a developed semi-Analytical model.

  • Influence of historical bathymetric changes due to urbanization on the vulnerability of storm surge in Tokyo bay

    Akifumi Tatekoji, Ryota Nakamura, Tomoya Shibayama

    Proceedings of the Coastal Engineering Conference   35  2016年01月

     概要を見る

    In this study, the influence of historical changes on bathymetry to the intensity and features of the storm surge in the Tokyo Bay is evaluated using the meteorology-ocean-Tide models. In detail, storm surge of 1917 is reproduced using an artificial Taisho Typhoon of 1917 in order to quantify the influence of bathymetric changes. This paper possesses two important findings. The first is that past storm surge occurred mainly because of shallow water area spanning over the inner bay which can be characteristics of past bathymetry. The second is that the high vulnerable area affected by storm surge has been shifted from mudflat shallow area in the inner bay to the below-sea-level inland area, due to landfill and urbanization which have continued approximately 100 years after the storm. As a conclusion, the bathymetry shifting due to human activity has a great influence to changing the effects of coastal disasters even in the same location.

  • Evaluation of Storm Surge Caused by Typhoon Yolanda (2013) and Using Weather - Storm Surge - Wave - Tide Model

    Ryota Nakamura, Oyama Takahiro, Tomoya Shibayama, Esteban Miguel, Hiroshi Takagi

    8TH INTERNATIONAL CONFERENCE ON ASIAN AND PACIFIC COASTS (APAC 2015)   116   373 - 380  2015年

     概要を見る

    This paper presents a comparison between numerically estimated storm surge invoked by typhoon Yolanda (2013) and field survey results. In order to estimate the typhoon more accurately, TC-Bogus scheme is used in typhoon simulation. This scheme has a potential to improve an initial atmospheric field and give a better results, in terms of routes and minimum sea surface pressure of the typhoon. In the results of calculated storm surge, a height of the estimated storm surge reached approximately 5.0 m at Tacloban. This value is a good agreement with the measured height. The timing of the storm surge was 00:00 UTC 8th November 2013. The estimated time of the storm surge invoked by Yolanda is almost the same with that of information from residents. Thus, the storm surge model composed of the WRF, FVCOM, SWAN and WX-tide has a potential to reproduce the storm surge realistically. (C) 2015 Published by Elsevier Ltd.

    DOI

  • Detached Breakwaters Effects on Tsunamis around Coastal Dykes

    Takahito Mikami, Mizuho Kinoshita, Shunya Matsuba, Shun Watanabe, Tomoya Shibayama

    8TH INTERNATIONAL CONFERENCE ON ASIAN AND PACIFIC COASTS (APAC 2015)   116   422 - 427  2015年

     概要を見る

    The Japanese coastal areas have a lot of different types of coastal structures with different purposes, and it is important to understand each structure's effects on tsunami. In the present paper, the authors focused on detached breakwaters effects on tsunami flow around coastal dykes with a field data investigation and laboratory experiments using a tsunami basin. The field data obtained from the 2011 Tohoku Earthquake and Tsunami showed that tsunami flow was not uniform along a coastal dyke with the specific arrangement of detached breakwaters. The laboratory experiments performed in a tsunami basin showed that a detached breakwater with a small detached breakwater parameter (distance from the shoreline/length of the opening) had a tsunami mitigation effect along the shoreline just behind the main body of the breakwater, but did not have a tsunami mitigation effect along the shoreline just behind the opening. The results obtained from the laboratory experiments agreed with the field data of the 2011 tsunami. (C) 2015 The Authors. Published by Elsevier Ltd.

    DOI

  • Field Surveys of Recent Storm Surge Disasters

    Tomoya Shibayama

    8TH INTERNATIONAL CONFERENCE ON ASIAN AND PACIFIC COASTS (APAC 2015)   116   179 - 186  2015年

     概要を見る

    In these ten years since 2004, there were more than ten big disasters in coastal area including six storm surge events and five tsunami events. The author performed post disaster surveys on all these events as the team leaders of survey teams. Based on those experiences, the author describes lessons of these events. Tsunami is now generally well known to coastal residents. Evacuation plans gradually become common for tsunami disasters. Storm surges arise more frequently due to strong storms but coastal residents are not well protected and not informed how to evacuate in case of surge emergency. From the field surveys conducted, it appeared that the damage depend on the geographical and social conditions of each of the areas that were visited by the author. It is now clear that such issues play important roles in disaster mechanisms. Therefore disaster risk management should carefully include local topography and social conditions of each area during the formulation of disaster prevention plans. In order to establish a reliable disaster prevention system, appropriate protection structures should be constructed, and these should be accompanied by a clear and concise evacuation plan for residents of a given area. (C) 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

    DOI

  • Flood-Induced Debris Dynamics over a Horizontal Surface

    J. Stolle, I. Nistor, N. Goseberg, T. Mikami, T. Shibayama, R. Nakamura, S. Matsuba

    Coastal Structures and Solutions to Coastal Disasters 2015: Tsunamis - Proceedings of the Coastal Structures and Solutions to Coastal Disasters Joint Conference 2015     54 - 64  2015年

     概要を見る

    This paper reports on an experimental test program investigating the motion and entrainment of flow-entrained debris. The motion of debris in large scale hydraulic events can cause severe damage to the impacted communities: the dynamic characteristics of the debris' motion is crucial in identifying high-risk areas in affected communities. Determining the motion of flow-entrained debris has been historically difficult to quantify as many traditional techniques, such as post-mortem site assessment, cannot provide sufficient information about the kinematic and environmental conditions that affect the debris motion. This paper presents a novel non-invasive system for tracking the 6 degrees-of-freedom debris motion. The experiments examined the effect of various debris configurations on their entrainment as well as their overall motion. Using video footage, the debris entrainment mechanisms and surrounding flow features common to all experiments were examined and using this tracking system, the motion of the debris was accurately tracked and further used to validate other debris spreading observed in real field conditions.

    DOI

  • Assessment of Vietnam Coastal Erosion and Relevant Laws and Policies

    Le Van Cong, Nguyen Van Cu, Tomoya Shibayama

    Coastal Disasters and Climate Change in Vietnam: Engineering and Planning Perspectives     81 - 106  2014年06月

     概要を見る

    The main purpose of this chapter is to provide an assessment of the coastal erosion situation in Vietnam, covering its present status of erosion at the national and the subnational levels. Erosion can be caused by a number of factors, including the impacts of sea level rise (SLR). Relevant laws and policies for addressing coastal erosion, various types of measures for coastal erosion, gaps and needs to address coastal erosion in terms of national policies, and legal and institutional arrangements to address coastal erosion are also given.

    DOI

  • Preface

    Tomoya Shibayama

    Coastal Disasters and Climate Change in Vietnam: Engineering and Planning Perspectives    2014年06月

    DOI

  • 気象-高潮-潮汐 結合モデルを用いた東京湾におけるRCP8.5シナリオ下での高潮予測

    岩本匠夢, 中村亮太, 大山剛弘, 水上亮, 柴山知也

    土木学会論文集 B2(海岸工学)(Web)   70 ( 2 )  2014年

    J-GLOBAL

  • Analysis of Tsunami behavior and the effect of coastal forest in reducing Tsunami force around coastal dikes

    Shunya Matsuba, Takahito Mikami, Ravindra Jayaratne, Tomoya Shibayama, Miguel Esteban

    Proceedings of the Coastal Engineering Conference   2014-January  2014年01月

     概要を見る

    Many coastal dikes in Iwate, Miyagi and Fukushima prefectures in Japan were damaged due to the 2011 Great Eastern Japan Earthquake Tsunami. The primary failure mode of these dikes was scour failure at the leeward toe by the overflowing tsunami. However, the forces exerted by the tsunami wave against the dikes were reduced to the presence of some obstacles (such as trees) located behind the dikes, increasing the tsunami inundation height immediately behind the structure and actually helping to reduce the force on the dike itself. In order to analyze how tsunamis affected coastal dikes, the authors carried out post-tsunami field surveys and laboratory tests using dikes and different coastal forest models. The critical failure mechanism of dikes was analyzed and co-related to tsunami overflowing pattern. In addition, the experimental results show how coastal forest can help to reduce the damage caused by the tsunami to coastal dikes by increasing water depth and changing the tsunami motion pattern. Thus, the placement of coastal forests behind dikes can help to increase their resilience against tsunami attack, and should be considered as part of a disaster management strategy for certain tsunami prone areas.

  • Tsunami resonance in the bay of Concepcion, Chile

    Rafael Aránguiz, Mauricio Villagrán, Miguel Esteban, Tomoya Shibayama

    Proceedings of the Coastal Engineering Conference   2014-January  2014年01月

     概要を見る

    Natural oscillation modes of the Bay of Concepcion are determined by means of Empirical Orthogonal Functions. Simulations of the 2010 and 1960 tsunamis were performed using 4 nested grids of 120, 30, 6 and 1″ arc resolution with the NEOWAVE model. In addition, a spectral analysis of tsunami waveforms at both the continental shelf and inside the Bay of Concepcion was performed, and the results were contrasted with natural oscillation periods. The results showed that the natural oscillation period of the first, second and third modes of the Bay were found to be 95, 37 and 32 min. It was found that large tsunami amplifications at the southern shore of the Bay of Concepcion were due to tsunami resonance and coupling between the shelf resonance and bay oscillations. Large inundations heights during 2010 tsunami were caused by the tsunami exciting the fundamental oscillation mode of the Bay. The relative low inundation during the 1960 tsunami was due to the tsunami exciting the higher frequency.

  • Flow geometry of overflowing tsunamis around coastal dykes

    Takahito Mikami, Shunya Matsuba, Tomoya Shibayama

    Proceedings of the Coastal Engineering Conference   2014-January  2014年01月

     概要を見る

    Japan has a long stretch of coastal dykes along its shoreline to protect against many types of coastal disasters. The 2011 Tohoku Tsunami caused serious damage to these coastal dykes along the long coastaline. One of the main reasons of the coastal dyke failure was overflowing tsunamis. Thus, after the 2011 Tohoku Tsunami, many studies on coastal dyke failure due to overflowing tsunamis have been conducted. The present study aimed to analyze the basic hydraulic characteristics of overflowing tsunamis on coastal dykes. First, the characteristics of overflowing tsunamis on coastal dykes observed during the 2011 tsunami were described using field data. The field data showed that there were different types of overflowing tsunamis during the 2011 tsunami and these types could be related to coastal dyke failure. Then, flow geometry were discussed based on the classification presented by Hom-ma (1940). Finally, the relationships between the hydraulic characteristics of overflowing tsunamis around coastal dykes (velocity field and pressure profile) and coastal dyke failure were discussed in detail by means of both laboratory investigations and numerical experiments.

  • Study of irregular wave-current-mud interaction

    Mohsen Soltanpour, Farzin Samsami, Tomoya Shibayama, Sho Yamao

    Proceedings of the Coastal Engineering Conference   2014-January  2014年01月

     概要を見る

    The dissipation of regular and irregular waves on a muddy bed with the existence of following and opposing currents are investigated through a series of wave flume laboratory experiments. The commercial kaolinite is used as fluid mud layer. The laboratory results show the increase of both regular and irregular wave heights due to opposing currents. On the other hand, the following currents result to the decrease of the wave heights. In the numerical treatment, the deformation of wave due to current was first calculated based on the conservation equation of wave action and then the attenuation of this deformed wave due to the muddy bed is simulated by a multi-layered wave-mud interaction model. Acceptable agreements were observed between the numerical results and laboratory data.

  • Predictive model for scour depth of coastal structure failures due to tsunamis

    Ravindra Jayaratne, Adewale Abimbola, Takahito Mikami, Shunya Matsuba, Miguel Esteban, Tomoya Shibayama

    Proceedings of the Coastal Engineering Conference   2014-January  2014年01月

     概要を見る

    Post-tsunami field surveys carried out after the 2011 Great Eastern Japan Earthquake Tsunami revealed that scour around the landward side of concrete sea dikes and seawalls was the most dominant failure mechanism. To better understand this phenomenon, detailed scour data were collected and soil samples from the surveyed locations in Miyagi and Fukushima Prefectures of Japan were comprehensively analysed. Mathematical modeling technique was employed with various combinations of input variables considered in order to determine the effective variables needed to predict the representative scour depth at the leeward of a concrete sea dike or seawall and possible design of these coastal structures against tsunami impact. Parameters such as impact overflowing pressure, height of structure measured at the landward side, inundation height, inundation velocity, angle of landward slope, Darcy&#039;s coefficient of permeability and scour depth were found to be the effective parameters essential to generate proposed scour depth predictive model. The results indicate that the hydrodynamic parameters, soil properties and physical geometry of coastal structure play a crucial role in the scour process of such structures. In addition to that, numerical experiments were also performed in order to understand the characteristics of tsunami flow around a typical coastal dike, and to propose preliminary guidelines for structure resilience against future tsunamis.

  • Climate change adaptation in Tokyo Bay: The case for a storm surge barrier

    Miguel Esteban, Takahito Mikami, Tomoya Shibayama, Hiroshi Takagi, Sebastiaan N. Jonkman, Mathijs Van Ledden

    Proceedings of the Coastal Engineering Conference   2014-January  2014年01月

     概要を見る

    Increases in typhoon intensity and sea level rise could pose significant challenges to coastal defences around Tokyo Bay. In order to analyse the extent of future problems the authors determined the increase storm surge that could result from an increase in typhoon intensity and sea level rise to this area around the turn of the 21st century. Results show how the various settlements around Tokyo Bay are at considerable risk of storm surges and sea level rise in the future. If defences are breached the potential direct economic consequences could be significant, potentially in excess of 100 trillion yen, with the indirect costs likely to be even greater. As a result it is likely that sea defences will have to be strengthened around Tokyo Bay in the future, which could cost in the order of 370bn yen to defend against a 1 in 100 year storm by the year 2100. Alternatively, a storm surge barrier could be built, which would be more expensive (possibly in the range of 700-800bn yen), though it could increase the protection level and would be able to cope with 1 in 200 or 500 year events, amongst other benefits.

  • Numerical simulation of cyclonic storm surges over the bay of bengal using a meteorology-wave-surge-tide coupled model

    Khandker Masuma Tasnim, Koichiro Ohira, Tomoya Shibayama, Miguel Esteban, Ryota Nakamura

    Proceedings of the Coastal Engineering Conference   2014-January  2014年01月

     概要を見る

    The purpose of this study was to evaluate the performance of an integrated meteorology and storm surge model for both the hind casting and prediction of future climate change intensified cyclones over the Bay of Bengal. This meteorology based storm surge model was developed and applied by integrating a mesoscale WRF model with the wave model SWAN and coastal ocean model FVCOM. The coupled model could capture the actual phenomena of historical cyclone Nargis, which made landfall in Myanmar in 2008, accurately and reproduce the total water level rise due to this event. The model was then used to also simulate future cyclones over the Bay of Bengal taking into account climate change by the year 2100.

  • Investigation of coastal structure failures due to the 2011 great eastern Japan earthquake tsunami

    R. Jayaratne, T. Mikami, M. Esteban, T. Shibayama

    Coasts, Marine Structures and Breakwaters 2013: From Sea to Shore - Meeting the Challenges of the Sea   2   1241 - 1250  2014年01月

     概要を見る

    © Thomas Telford Limited 2014. The authors have highlighted critical failure mode of coastal structures, particularly sea dikes and seawalls affected by the 2011 Great Eastern Japan Earthquake Tsunami, based on their two extensive field surveys conducted in the summers of 2011 and 2012 (UEL-Waseda Research Partnership), and numerical modelling at Waseda University. Further, the authors have attempted to simulate overflowing wave pressure, vorticity and velocity over a coastal dike which will be useful for a practicing engineer to check whether a certain level of overflowing pressure, vorticity and velocity is likely to cause a structure to fail catastrophically during a given tsunami event.

  • Analysis of the stability of armour units during the 2004 Indian ocean and 2011 Tohoku Tsunami

    Miguel Esteban, Ravindra Jayaratne, Takahito Mikami, Tomoya Shibayama, Yusuke Mizuno, Mizuho Kinoshita, Shunya Matsuba

    Coasts, Marine Structures and Breakwaters 2013: From Sea to Shore - Meeting the Challenges of the Sea   1   562 - 572  2014年

     概要を見る

    The relative lack of frequency of major tsunami events has meant that little attention was paid in the past to the development of formulas to design breakwater armour against these events. However, field surveys of recent events such as the 2011 Great Eastern Japan Earthquake Tsunami and 2004 Indian Ocean Tsunami have shown flaws in the design of protection structures. In the present work, the authors have set out to improve the accuracy of the formula of Esteban et al. (2012) by expanding the analysis to a number of other ports that were affected by the 2011 Great Eastern Japan Earthquake Tsunami and the 2004 Indian Ocean Tsunami. The aim is to obtain a formula that can easily be applied by a practicing engineer to check whether a certain armour unit is likely to catastrophically fail during a given tsunami event. The improved formula proposed is based on that of Hudson but combining damage progression elements from the Van der Meer formula. The design of structures that only partially fail (i.e. "resilient" or "tenacious" structures) during an extreme level 2 tsunami event should be prioritized in future important protection works. Accordingly, the present paper makes recommendations on the acceptable level of damage for each tsunami level for various types of port installations.

    DOI

  • Climate change and coastal defences in Tokyo bay

    Sayaka Hoshino, Miguel Esteban, Takahito Mikami, Tomoyuki Takabatake, Tomoya Shibayama

    Proceedings of the Coastal Engineering Conference    2012年12月

     概要を見る

    Sea level rise and an increase in typhoon intensity are two of the expected consequences from future climate change. In the present work a methodology to change the intensity of tropical cyclones in Japan was developed, which can be used to assess the inundation risk to different areas of the country. An example of how this would affect one of the worst typhoons to hit the Tokyo Bay area in the 20th century was thus developed, highlighting the considerable dangers associated with this event, and how current sea defences could be under danger of failing by the end of the 21st century.

  • A laboratory and field study on 2DH spectral wave transformation in muddy environments

    Mohsen Soltanpour, S. Abbas Haghshenas, Tomoya Shibayama

    Proceedings of the Coastal Engineering Conference    2012年12月

     概要を見る

    The present paper offers a set of wave basin experiments on muddy beds together with field measurements data at Hendijan Mud Coast in the north-west corner of the Persian Gulf in order to investigate the 2DH spectral wave transformation over muddy beds. A dissipation model was added to REF/DIF S wave model to develop a numerical wave spectrum transformation model for muddy beaches. The proposed model was utilized to analyze the experimental and field measurements data on muddy beds. The simulated wave spectra over-mud bed are in fair agreement with the measurements.

  • Stability of rubble mound breakwaters against solitary waves

    Miguel Esteban, Izumi Morikubo, Tomoya Shibayama, Rafael Aranguiz Muñoz, Takahito Mikami, Nguyen Danh Thao, Koichiro Ohira, Akira Ohtani

    Proceedings of the Coastal Engineering Conference    2012年12月

     概要を見る

    No formulas currently exist to design armour units against tsunami attack. To develop such formulae, laboratory experiments were carried out to clarify the failure mechanism of these types of structures. Also, the behavior of armour units against real cases of tsunami attack during the 2011 Tohoku tsunami were evaluated. Both the results of the laboratory experiments and the breakwaters studied in the field where then analyzed in terms of well established formulas such as that of Van der Meer or Hudson. The design of structures that only fail partially during a given tsunami event (&quot;resilient&quot; or &quot;tenacious&quot; structures) should be prioritized in future counter-measures, and in order to make it possible to construct such structures a modification of the Hudson formula for their design is proposed.

  • Numerical analysis of tsunami propagation on wide reef platform

    Takahito Mikami, Tomoya Shibayama

    Proceedings of the Coastal Engineering Conference    2012年12月

  • Comprehensive numerical simulation of waves caused by typhoon using a meteorology-wave-storm surge-tide coupled model

    Koichiro Ohira, Tomoya Shibayama, Miguel Esteban, Takahito Mikami, Tomoyuki Takabatake, Makito Kokado

    Proceedings of the Coastal Engineering Conference    2012年12月

     概要を見る

    The present study focuses on the risks of storm surge caused by future increases in typhoon intensity due to climate change. These risks were analyzed by integrating weather, wave, storm surge and tide prediction systems into a new simulation methodology. This model, which the authors developed by themselves, makes it possible to calculate the weather fields of typhoons in the past as well as in the future on the basis of meteorology and can simulate waves in a complex geographical area, in contrast with many previous storm surge simulation methods which were not based on accurate meteorological models. The model was verified to accurately reproduce historical typhoons and waves and thus is a useful tool for the analysis of future climate risks.

  • Increase in Port Downtime and Damage in Vietnam Due To a Potential Increase in Tropical Cyclone Intensity

    Miguel Esteban, Nguyen Danh Thao, Hiroshi Takagi, Tomoya Shibayama

    Climate Change Management     101 - 125  2012年01月

     概要を見る

    © 2012, Springer-Verlag Berlin Heidelberg. It is currently feared that the increase in surface sea temperature resulting from increasing levels of greenhouse gases in the atmosphere could result in an increase in tropical cyclone intensity in the future. Although the economic consequences have been studied for a number of developed countries, very little work has been done on developing countries. The present paper attempts to indicate what are the likely economic effects of this, by using a Monte Carlo simulation that magnifies the intensity of historical tropical cyclones between the years 1978 and 2008. This tropical cyclone model is then coupled with a socioeconomic model that attempts to provide a projection of the likely development course of the Vietnamese economy and society. The simulation shows how annual downtime from tropical cyclones could increase from 0.23 to 0.37% by 2085 which could cause the loss of between 0.015 and 0.035% of GDP growth per year (between 600 bn and 1,400 m USD after factoring in the likely growth in the Vietnamese economy by this time). The effect that this could have on port operations and a preliminary assessment on the potential for increases in direct damage due to high winds are also made, showing a typical 33 to 65% increase for the centre and north of the country.

    DOI

  • The economic impact of future increase in tropical cyclones in Japan (vol 55, pg 233, 2010)

    Christian Webersik, Miguel Esteban, Tomoya Shibayama

    NATURAL HAZARDS   56 ( 1 ) 407 - 408  2011年01月

    その他  

    DOI

  • Field survey of the 2011 off the pacific coast of tohoku earthquake tsunami disaster and future tsunami protection

    Tomoya Shibayama

    Asian and Pacific Coasts, 2011 - Proceedings of the 6th International Conference     79 - 82  2011年01月

     概要を見る

    © 2019, World Scientific. All rights reserved. On March 11, 2011, a large earthquake of magnitude 9.0 took place, generating a tsunami that caused a severe damage to the east coast of Japan. Field surveys were performed to know tsunami inundation heights and disasters in Iwate, Miyagi, Fukushima, Ibaraki and Chiba prefectures. The results of these surveys are reported. Inundation heights were more than 10 m in the north part of Miyagi, 5 to 10 m along the coast of Sendai Bay and around 5 m in Ibaraki and Chiba. Buildings, including reinforced concrete structures, were washed away and ships were stranded in land. Coastal structures such as dikes and coastal forests also suffered extensive damage. Possible evacuation measures are also discussed based on the observations.

    DOI

  • Modification of the Goda formula to evaluate the movement of a caisson breakwater protected by failed armour

    Miguel Esteban, Hiroshi Takagi, Tomoya Shibayama

    Coasts, Marine Structures and Breakwaters: Adapting to Change - Proceedings of the 9th International Conference   2   402 - 413  2010年12月

  • Comparisons of storm surge disasters in Asia-Cases of cyclones Sidr in 2007 and Nargis in 2008

    Tomoya Shibayama

    Proceedings of the Coastal Engineering Conference    2010年12月

     概要を見る

    Field surveys were performed in the southwest of Bangladesh after cyclone Sidr in 2007 and in Yangon River Basin after Cyclone Nargis in Myanmar in 2008 in order to learn lessons out of severe disasters due to storm surges. Spatial distributions of inundation heights were measured around the most damaged areas. Both Bangladesh and Myanmar were severely damaged, but the preparedness against storm surge and the experiences were different. The resultant total losses in these two countries were significantly different. In Bangladesh, many people witnessed that storm surges inundated with bore-like waves. Counter measured against storm surges should account for the physical mechanisms for the development of such bore-like waves and possible damages due to such waves. Embankment showed significant roles to minimize the damage. Development of riverbanks especially around the river mouth is one of most essential counter-measures to be carried out in Bangladesh. Shelter functioned well to save significant number of lives in Bangladesh. But in Myanmar, there were few experiences on storm surge and no countermeasures such as shelters. These differences results the difference of losses. They were 4,234 including deaths and unknowns in Bangladesh but 138,366 in Myanmar.

  • Applicability of the predictive formulae for supended sediment concentration on full-scale rippled bed and sheet flow

    Ravindra Jayaratne, Tomoya Shibayama

    Proceedings of the Coastal Engineering Conference    2010年12月

  • Modified Goda formula to simulate sliding of composite caisson breakwater

    Miguel Esteban, Hiroshi Takagi, Tomoya Shibayama

    Proceedings of the Coastal Engineering Conference    2010年12月

     概要を見る

    Caisson breakwaters can continue to maintain their function if a limited amount of sliding or tilting occurs. Although this has been the focus of much research during the last years, little attention has been paid to the design of composite caisson breakwaters (i.e. caissons protected with armour layers). The present paper outlines laboratory experiments that were carried out to propose a modification of the Goda formula (1974) that takes into account the increased pressures that can be exerted by waves due incomplete armour layers at the seaside face of the caisson. The effect that this modification can have on the expected deformations in the rubble mound after one storm are also evaluated by means of a Monte Carlo Simulation, showing how incomplete armour layers will result in much greater expected vertical movements in the caisson.

  • ON THE MECHANISM OF ORGANIC-RICH SEDIMENT ACCUMULATION AT THE HEAD OF TOKYO BAY

    Jun Sasaki, Yuta Sato, Thamnoon Rasmeemasmuang, Tomoya Shibayama

    PROCEEDINGS OF THE 5TH INTERNATIONAL CONFERENCE ON ASIAN AND PACIFIC COASTS, VOL 2   2   67 - +  2010年

     概要を見る

    Extensive accumulation of soft mud at the head of Tokyo Bay, Japan, is one of the major causes Of deterioration of water quality and ecosystems. We performed field observation of sediment quality and numerical simulation of sediment accumulation and grain size distribution to reveal the mechanism of its accumulation and provide suggestions for the future restoration strategy in the bay. We reveal the detailed variation in sediment quality and found that one of the causes is attributed to the lower decomposition rate of organic matter clue to the long-term exposure to hypoxic waters along with the higher rate of accumulation of very fine particles reflecting hydrodynamic properties.

  • ESTIMATING THE INDIRECT COSTS OF NON ADAPTING INFRASTRUCTURE TO AN INCREASE IN TYPHOON INTENSITY IN THE ASIA-PACIFIC REGION

    Miguel Esteban, Christian Webersik, Tomoya Shibayama

    PROCEEDINGS OF THE 5TH INTERNATIONAL CONFERENCE ON ASIAN AND PACIFIC COASTS, VOL 2   2   170 - +  2010年

     概要を見る

    The present paper develops a methodology for estimating the risks and consequences of possible future increases in tropical cyclone intensities that can allow for the cost of mitigation strategies in port infrastructure to be evaluated It uses a Monte Carlo Simulation to obtain the expected number of hours that a certain area can expect to be affected by winds of a certain strength, and then evaluates the relationship between port infrastructure and Japanese economic growth. Finally, the expected increase in expenditure due to climate change can be evaluated.

  • DISASTER SURVEY AFTER THE CYCLONE NARGIS IN 2008

    Tomoya Shibayama, Hiroshi Takagi, Ngun Hnu

    PROCEEDINGS OF THE 5TH INTERNATIONAL CONFERENCE ON ASIAN AND PACIFIC COASTS, VOL 2   2   190 - +  2010年

     概要を見る

    The cyclone 'Nargis' hit the southern part of Myanmar on May 2(nd) and 3(rd) 2008. This devastating cyclone caused enormous number of casualties its well as fatal damages to houses and paddy fields, particularly both the downstream areas of the Irrawaddy and Yangon Rivers. In the present field survey, thought the activities were limited to the area near Yangon city due to certain governmental restrictions, it was found out that the tide due to the storm surge was probably up to 3 - 4m and came up to around 50 kilometers upstream of the river month of Yangon River.

  • Pressure exerted by a solitary wave on the rubble mound foundation of an armoured caisson breakwater

    Miguel Esteban, Nguyen Danh Thao, Hiroshi Takagi, Tomoya Shibayama

    Proceedings of the International Offshore and Polar Engineering Conference     1137 - 1144  2009年12月

     概要を見る

    Although a lot of attention has been paid to develop formulas and methodologies to assess the effect of wind waves on caisson breakwaters, there is still limited understanding of the loadings due to tsunami waves. More specifically, no methodology exists to determine the effect that a partially destroyed armour layer would have on the overall stability of an armoured caisson breakwater. Although Esteban et al. (2008) developed a method to estimate the deformation of a caisson breakwater subjected to solitary wave attack, this method is known the be greatly influenced by the presence of an armour layer in front on the caisson. Thus, laboratory experiments with solitary waves were carried out to clarify the failure mechanism of an armoured caisson breakwater against a comprehensive range a tsunami type events (bore-type, breaking and non-breaking). The results of the experiments show how the load which is exerted by the caisson onto the foundation depends on the depth of water in front of it, the shape of the armour layer and whether the wave strikes the caisson or the armour layer first. Of particular interest, it was found how the presence of armour (in particular a failed or partially constructed armour layer) can sometimes be detrimental to the stability of the caisson itself. Copyright © 2009 by The International Society of Offshore and Polar Engineers (ISOPE).

  • 港湾構造物に及ぼす気候変動の影響とその定量的予測?防波堤を対象として?

    高木泰士, 柏原英広, 柴山知也

    海岸工学論文集   56 ( 2 ) 891-895  2009年10月

    DOI J-GLOBAL

  • IMPACT PRESSURES DUE TO BREAKING SOLITARY WAVE EXERTED ON A VERTICAL WALL

    Nguyen Danh Thao, Miguel Esteban, Hiroshi Takagi, Tomoya Shibayama

    COASTAL ENGINEERING 2008, VOLS 1-5     3186 - +  2009年

     概要を見る

    Breaking waves impacts on vertical or sloping breakwaters are one of the most severe and dangerous loads that maritime structures can suffer. The present study is concerned with a theoretical approach, which is based on the momentum impulse, to simulate the impact pressures of solitary wave exerted on a vertical breakwater. The theoretical impact pressures are determined using varied velocity before impact process. The advancing solitary wave can simply be considered as a two-dimensional mass of water moving toward a vertical rigid wall with initial velocity. The impulse momentum is calculated by using the velocities just in front of the breakwater between the time the impact pressure first begins to act and the time when the forward velocity becomes almost zero. By using precise velocity field, the general mechanism of impact pressure histories on vertical breakwater obtained is more reasonable than those obtained by previous researchers. The simulation results show reasonable agreements with the laboratory data.

  • PROPOSED METHODOLOGY FOR EVALUATING THE POTENTIAL FAILURE RISK FOR EXISTING CAISSON-BREAKWATERS IN A STORM EVENT USING A LEVEL III RELIABILITY-BASED APPROACH

    Hiroshi Takagi, Miguel Esteban, Tomoya Shibayama

    COASTAL ENGINEERING 2008, VOLS 1-5     3655 - +  2009年

     概要を見る

    In this study, an effective methodology for evaluating the potential failure risk of caisson breakwaters has been developed. In the proposed model, two indexes, ETSD and EFEC, are used to evaluate the sliding failure and bearing capacity failure, respectively. Based on these indices, the degree of damages of the breakwaters can be estimated stochastically and quantitatively. Hence, using this method it is expected that planners will be able to prioritize the implementation of breakwater reinforcements amongst a large number of breakwaters, and designers will be able to better determine appropriate caisson geometries for a given future storm.

  • AN INTEGRATED WAVE-MUD-CURRENT INTERACTION MODEL

    Mohsen Soltanpour, S. Abbas Haghshenas, Tomoya Shibayama

    COASTAL ENGINEERING 2008, VOLS 1-5     2852 - +  2009年

     概要を見る

    This study presents an integrated wave-mud-current interaction model to simulate energy dissipation of traveling waves over non-rigid muddy beds and mud mass transport in the presence of current. Assuming the water layer to be inviscid with a uniform current field, the governing Navier-Stokes equations are solved for fluid mud sub-layers. The constitutive equations of visco-plastic material are adopted for the fluid mud rheological behavior. The comparison between the wave attenuation and mud mass transport results of the numerical model and the laboratory data of An and Shibayama (1994) shows a good agreement.

  • Concepts in coastal engineering and their applications to multifarious environments

    Tomoya Shibayama

    Advanced Series on Ocean Engineering   28   1 - 227  2008年12月

    DOI

  • 2008年サイクロンNargisの被災状況調査報告(速報)

    柴山 知也, 高木 泰士, Hnu Ngun

    自然災害科学   27 ( 3 ) 331 - 338  2008年11月

     概要を見る

    The cyclone &#039;Nargis&#039; hit the southern part of Myanmar on May 2^&lt;nd&gt; and 3^&lt;rd&gt; 2008. This devastating cyclone caused enormous number of casualties as well as fatal damages to houses and paddy fields, particularly both the downstream areas of the Irrawaddy and Yangon Rivers. In the present field survey, thought the activities were limited to the area near Yangon city due to certain government restrictions, it was found that the tide due to the storm surge was probably up to 3-4m around 50 kilometers upstream of the river mouth of Yangon River. According to interviews with the local residents, it also appears that significant flooding took place at inland areas as a result of the upsurge through the tributaries or channels from the main river. Even though the situation was catastrophic, it seems that most residents had not evacuated. One of the reasons for this could be related to the fact that the cyclone passed through the area investigated in the late night to the early morning of May 3^&lt;rd&gt;. Another reason might be because of an underestimation or the lack of perception of the threat of storm surge. Apart from the investigation, the tracks for the present and past cyclones (1945-

    CiNii

  • Chapter 26 An integrated hydrodynamic model on muddy coasts

    Mohsen Soltanpour, S. Abbas Haghshenas, Tomoya Shibayama

    Proceedings in Marine Science   9   379 - 390  2008年

     概要を見る

    A numerical cross-shore model to simulate two features of wave-mud interaction on fine-grained shore profiles, i.e. fluidization of mud layer and wave height attenuation, is presented. The analytical model of Foda et al. (1993) is used to determine the fluidized depth of mud layer. The wave height transformation is computed from the energy flux conservation law combining the effects of mud bed, shoaling and wave breaking. The rheological constitutive equations of visco-elastic (VE) material are used for numerical simulation of fluid mud behavior. A preliminary application of the model shows its capability to predict wave height transformation along soft muddy profiles. © 2008 Elsevier B.V. All rights reserved.

    DOI

  • Analysis of Rubble Mound Foundation Failure of a Caisson Breakwater Subjected to Tsunami Attack

    Miguel Esteban, Nguyen Danh Thao, Hiroshi Takagi, Tomoya Shibayama

    PROCEEDINGS OF THE EIGHTEENTH (2008) INTERNATIONAL OFFSHORE AND POLAR ENGINEERING CONFERENCE, VOL 4     528 - +  2008年

     概要を見る

    Presently, there is no methodology to evaluate the deformation that the rubble mound of a caisson breakwater would suffer if it was attacked by a tsunami. The present paper proposes a methodology to evaluate this deformation based on the method of Esteban and Shibayama (2006), which originally was developed for wind waves. The method was verified by carrying out laboratory experiments using solitary waves and comparing the results to those obtained using the new methodology.

  • Laboratory Experiments on the Sliding Failure of a Caisson Breakwater Subjected to Solitary Wave Attack

    Miguel Esteban, Nguyen Danh Thao, Hiroshi Takagi, Tomoya Shibayama

    PROCEEDINGS OF THE EIGHTH (2008) ISOPE PACIFIC/ASIA OFFSHORE MECHANICS SYMPOSIUM: PACOMS-2008     291 - +  2008年

     概要を見る

    At present no methodology exists to evaluate the failure mode of a caisson breakwater subjected to a tsunami attack. The present paper investigates the sliding and tilting failure of a caisson breakwater subjected to a solitary wave attack, and establishes a relationship between the sliding and vertical movement. The vertical movement of the caisson is evaluated using the method of Esteban and Shibayama (2006), originally was developed for wind waves. The method was verified by carrying out laboratory experiments using solitary waves and comparing the results to those obtained using the new methodology. The sliding failure will be discussed and a general expression for an upper bound limit to the sliding will be proposed.

  • Numerical and experimental study on wave propagation over mud

    A. Oveisy, M. Soltanpour, T. Shibayama, Y. Masuya

    Proceedings of the Coastal Engineering Conference     472 - 481  2007年12月

     概要を見る

    Due to high wave energy dissipation of wave-mud interaction, the common 2D horizontal hydrodynamic models for the simulation of wave field can not be applied to muddy coasts. The present study offers a multi-layered numerical model to simulate the wave transformation on 2D horizontal plane under regular waves. Time dependent mild slope equations are employed including the combined wave refraction, diffraction and breaking. A series of wave basin experiments have been performed to obtain the required data for the verification of the numerical model. © 2007 World Scientific Publishing Co. Pte. Ltd.

  • Irregular wave transformation on mud profiles including the fluidization of mud layer

    M. Soltanpour, S. A. Haghshenas, T. Shibayama

    Proceedings of the Coastal Engineering Conference     482 - 490  2007年12月

     概要を見る

    The present study offers a numerical cross-shore wave-mud interaction model that can be used to predict fluid mud thickness and irregular wave transformation along soft mud profiles. The rheological constitutive equations of visco-elastic (VE) material are adopted for the behavior of fluid mud layer under the wave action. Extending an analytical model of fluidization to irregular waves, the fluidized depth of mud layer under overlaying wave action is determined. Spectral calculation method is used for the simulation of irregular wave transformation. The capability of the model to predict the fluidized depth and the wave height transformation along muddy profiles is also examined. © 2007 World Scientific Publishing Co. Pte. Ltd.

  • Numerical simulation of 3-d wave breaking on breakwater

    Danh Thao Nguyen, Tomoya Shibayama

    Proceedings of the Coastal Engineering Conference     261 - 273  2007年12月

     概要を見る

    This paper presents a three-dimensional breaking wave model to investigate the spatial and temporal variation of fluid motions under breaking waves. A three-dimensional Large Eddy Simulation (LES) is used to solve the governing equations for the flow parameters. Fluid motions in the area near the breakwater and its turbulences as well as wave overtopping on an inclined breakwater are investigated. Through the model, the spatial and temporal variations of the hydrodynamic problems of breaking waves on a breakwater are examined. © 2007 World Scientific Publishing Co. Pte. Ltd.

  • Disaster survey of indian ocean tsunami in South Coast of Sri Lanka and Aceh, Indonesia

    Tomoya Shibayama, Akio Okayasu, Jun Sasaki, Nimal Wijayaratna, Takayuki Suzuki, Ravindra Jayaratne, Masimin, Zouhrawaty Ariff, Ryo Matsumaru

    Proceedings of the Coastal Engineering Conference     1469 - 1476  2007年12月

     概要を見る

    Field surveys were performed on disasters caused by Indian Ocean tsunami that occurred in December 26, 2004. Surveys were done in the south part of Sri Lanka and in Aceh of Indonesia. From the survey results, varieties of disaster mechanisms were found. Local natural conditions and social conditions gave big influences on the disaster mechanism. In order to promote an appropriate post tsunami rehabilitation and environmental restoration process, cooperative works with local engineers and university professors are essential since the restoration process should include the local social and natural conditions. © 2007 World Scientific Publishing Co. Pte. Ltd.

  • Violent Wave Impact on Vertical Wall using Pressure-Impulse Theory

    Thao Nguyen Danh, 高木 泰士, 柴山 知也

    海岸工学論文集   54   811 - 815  2007年

     概要を見る

    Breaking waves on coastal structures produce impulse pressures that are high in magnitude and short in duration, compared with pressures exerted by non-breaking waves. The present study is concerned with a theoretical approach, which is based on the momentum impulse, to simulate the impact pressures on a vertical wall. The theoretical impact pressures are determined using varied velocity before impact process. The velocity field in the vicinity of structure is calculated by LES model including turbulence. The necessary coefficient λ* to evaluate impulse pressures is tentatively obtained through a comparison between the laboratory tests and the numerical results. The computational results using the coefficient obtained show time-histories of pressure with nonlinearity rather than linearity considered ever.

    DOI CiNii

  • Time dependent mud fluidization and irregular wave transformation on muddy profiles

    Mohsen Soltanpour, S. Abbas Haghshenas, Tomoya Shibayama

    Coastal Sediments '07 - Proceedings of 6th International Symposium on Coastal Engineering and Science of Coastal Sediment Processes    2007年

     概要を見る

    A numerical cross-shore model for wave-mud interaction is presented that can be used to predict time dependent variations of fluid mud thickness and irregular wave transformation along soft mud profiles. The rheological constitutive equations of visco-elastic (VE) material are adopted for the behavior of fluid mud layer under the wave action. Spectral calculation method is used for the simulation of irregular wave transformation. The application of the numerical model at a field site shows the capability of the model to predict the wave height transformation along muddy profiles.

    DOI

  • Wave attenuation and mud mass transport under irregular waves

    M Soltanpour, T Shibayama, Y Masuya, Sabzevari, I

    Coastal Engineering 2004, Vols 1-4   2005-January   1851 - 1860  2005年

     概要を見る

    Two major aspects of wave-mud interaction, i.e. wave height attenuation and mud mass transport, under irregular waves are studied in this paper. Spectral calculation method and joint distribution of wave height and wave period are used for the simulation of irregular wave-mud interaction. A series of wave flume experiments have been performed to obtain the required data for the verification of the numerical model. It is concluded that the phenomena can be better predicted by the method of modeling spectra.

    DOI

  • An evaluation method of suspended sediment concentration in and outside the surf zone

    MPR Jayaratne, T Shibayama

    Coastal Engineering 2004, Vols 1-4   2005-January   1715 - 1727  2005年

     概要を見る

    Simple formulas are proposed to predict time-averaged reference concentration, diffusion coefficient and vertical distribution of suspended sediment concentration over ripple-covered bed, sheet flow layer and under agitation of breaking waves separately. Formulas of reference concentration and diffusion coefficient are in terms of wave, sediment and flow properties and reference concentrations are defined at levels where they can be measured without disturbance to the bed. Time-averaged concentration profiles are computed from steady diffusion equation. Published experimental data are better explained by the predictive models.

    DOI

  • Landscape analysis by using collective unconscious and its application to design coastal structures

    Tomoya Shibayama, Yuki Sakai, Yuichirou Morichika

    Asian and Pacific Coasts, 2003 - Proceedings of the 2nd International Conference    2004年01月

     概要を見る

    © 2004, World Scientific. All rights reserved. In order to design coastal structures, it is required to consider landscape of coastal area. The present paper analyze classic Japanese common recognition of coastal view and proposed to include view of breaking waves into design of coastal structures. An appropriate coastal structure is selected. The performance of structure is examined from the view of landscape of breaking waves and energy dissipation.

    DOI

  • WAVE-MUD INTERACTION under IRREGULAR WAVES

    Mohsen Soltanpour, Tomoya Shibayama

    Proceedings of the Coastal Engineering Conference   2003-January   2949 - 2958  2003年01月

     概要を見る

    © 2003 World Scientific Publishing Co. Pte. Ltd. The present study aims to simulate two major aspects of wavemud interaction, i.e. wave height attenuation and mud mass transport, under irregular waves. The rheological constitutive equations of viscoelastic-plastic model (Shibayama et al., 1989) are selected for numerical simulation. The results of the numerical model are compared with the laboratory data of of Zhang and Zhao (1999). It is concluded that the model is capable to predict the phenomena.

    DOI

  • THE SIMULATION of SWASH OSCILLATIONS by A BREAKING WAVES MODEL

    Nguyen The Duy, Tomoya Shibayama, Akio Okayasu

    Proceedings of the Coastal Engineering Conference   2003-   904 - 916  2003年

     概要を見る

    This paper presents a breaking waves model in which the wave boundary layer and the swash zone are also included in the model domain. The model is based on the Reynolds equations for incompressible turbulent flows. The numerical solution of the model is performed in a non-uniform grids system so that high resolution can be obtained in the near-bottom area, where the velocity gradients are very large due to viscous effect. Numerical results of the present model are verified by laboratory data for the surf zone, the bottom boundary layer and the swash zone. The comparisons show that the model can predict reasonably the water motions in the surf zone, the bottom boundary layer and the swash zone.

    DOI

  • Calculation of wave-induced longshore current in surf zone by using Boussinesq equations

    Shaowu Li, Tomoya Shibayama

    Coastal Engineering 2000 - Proceedings of the 27th International Conference on Coastal Engineering, ICCE 2000   276   X334 - 345  2000年

     概要を見る

    This paper aims to propose a widely applicable numerical method for the computation of longshore current on the basis of Boussinesq equations. Laboratory data of longshore current of Visser (1991) are used to be compare with the numerical results. The effects of side boundary conditions to the longshore current are discussed. A socalled 'numerical pump' method is proposed in handling the side boundaries for the purpose to obtain a relatively uniform longshore distribution of longshore current and to diminish the circulation of flow outside the surf zone.

    DOI

  • Energy dissipation model for irregular breaking waves

    W Rattanapitikon, T Shibayama

    COASTAL ENGINEERING 1998, VOLS 1-3   1   112 - 125  1999年

     概要を見る

    A simple model is presented to compute the average rate of energy dissipation in irregular breaking waves. The average rate of energy dissipation rate is assumed to be proportional to the difference between the local mean energy flux and stable energy flux. The local fraction of breaking waves is determine from the derivation of Battles and Janssen (1978). Root mean square wave height deformation is computed from the energy flux conservation. The model is validated using root mean square wave height data from small and large scale laboratory and field experiments. Total 144 wave height profiles are used in the calibration and verification of the model. Reasonable good agreement is obtained between the measured and computed root mean square wave heights. The root mean square relative error of the model is 10.2 %.

  • A 2-DV numerical solution for the turbulent wave boundary layer under breaking waves

    NT Duy, T Shibayama, A Okayasu

    COASTAL ENGINEERING 1998, VOLS 1-3   1   484 - 497  1999年

     概要を見る

    This paper presents a numerical solution for the bottom boundary, layer (BBL) in the surf zone. The upper boundary of the BBL is determined through the solution of a breaking waves model. Different turbulence models have been tested to determine the distribution of turbulent kinetic energy, energy dissipation and eddy viscosity in the BBL. Finally, the vertical profiles of horizontal velocity can be found out through the solution of the governing equations of the BBL.

  • A nearshore wave breaking model

    Li Shaowu, Wang Shangyi, Tomoya Shibayama

    Acta Oceanologica Sinica   17   121 - 132  1998年12月

     概要を見る

    A wave breaking model is proposed on the basis of turbulent energy equation and the relationship of energy dissipation due to wave breaking in the surf zone. The model is established by introducing turbulent dissipation terms into the Boussinesq equations and involves the breaking process of individual wave. The model is verified by experiment data in terms of wave height and mean surface elevation. Good agreements are obtained.

  • Turbulent flow model for breaking waves

    Nguyen The Duy, Tomoya Shibayama, Akio Okayasu

    Proceedings of the Coastal Engineering Conference   1   200 - 213  1997年01月

     概要を見る

    This paper presents the formulation and solution of a numerical model for breaking waves on uniform sloping bottoms. The model is based on the two-dimensional vertical (2DV) Reynolds-averaged Navier-Stokes equations. The effect of breaker-generated turbulence is modeled by the Reynolds stress terms in the momentum equations, together with an eddy viscosity model. A transformation technique is utilized to solve numerically the governing equations in a variable grid system. At each time level of computation, it is possible to determine directly the following wave quantities for the surf zone: water surface elevation, pressure field and velocity field. The numerical results are verified with various cases of laboratory data.

  • Cross-shore sediment transport and beach deformation model

    Rattanapitikon Winyu, Tomoya Shibayama

    Proceedings of the Coastal Engineering Conference   3   3062 - 3075  1997年01月

     概要を見る

    Based on a large amount of published laboratory results, reliable model is developed for computing beach profiles under regular wave actions. The sediment transport is separated into suspended load and bed load. The suspended load is computed as the product of the time-averaged suspended concentration and the time-averaged velocity. The bed load is developed following the similar step as Watanabe (1983) but the applied area is different. The wave model of Dally et al. (1985) is modified and used to compute wave height transformation. The beach profile change is computed from the conservation of sediment mass. The beach deformation model is verified with small scale and large scale experiments. Reasonably good agreement is obtained between measured and computed beach profiles.

  • Numerical model for beach deformation around river mouth due to waves and currents

    Tomoya Shibayama, Akiko Yamada

    Proceedings of the Coastal Engineering Conference   3   3295 - 3304  1995年01月

     概要を見る

    A numerical model is proposed for beach deformation under wave and current in river mouth area. The model includes three major driving forces for sediment transport which are wave, wave-induced current and river discharge. Interaction of wave and current is also included. Laboratory experiments are performed to be compared with numerical results. Wave field, current field and beach deformation are compared between laboratory and numerical results and good agreements are obtained.

  • Laboratory experiments on 3-D nearshore current and a model with momentum flux by breaking waves

    Akio Okayasu, Koji Hara, Tomoya Shibayama

    Proceedings of the Coastal Engineering Conference   3   2461 - 2475  1995年01月

     概要を見る

    Laboratory experiments are performed in a wave basin to investigate the characteristics of three dimensional distribution of the nearshore current. Direction and amplitude of the nearshore current significantly change along the vertical axis and have spiral distribution. A quasi 3-D model which gives the 3-D distribution of nearshore current is proposed. Momentum flux due to the large vortexes formed on the front face of breaking waves is included in the model to evaluate the depth averaged current. The model is examined with the experimental results.

  • Wave-current interaction with mud bed

    Nguyen Ngoc An, Tomoya Shibayama

    Proceedings of the Coastal Engineering Conference   3   2913 - 2927  1995年01月

     概要を見る

    A series of wave flume experiments for wave-current-mud system has been performed. The results reveal that the rate of wave attenuation increases in the opposing currents and decreases in the following currents. The results are the same with the waves on the fixed bed. Another important result is that the mud mass transport velocity increases in the opposing currents and decreases in the following currents. The visco-elastic-plastic model which was proposed by Shibayama and An (1993) for wave-mud interaction has further been extended to the wave-current-mud system by taking a wave deformation effect into considerations. The extended model succeeds in predicting the laboratory results. The model shows that due to pressure gradient in wave propagating direction, the largest mud mass transport velocity occurs in the strongest opposing current and the smallest one in the strongest following current.

  • Long period wave and suspended sand transport in the surf zone

    Tomoya Shibayama, Akio Okayasu, Mikio Kashiwagi

    Proceedings of the Coastal Engineering Conference   3   2438 - 2449  1993年01月

     概要を見る

    The effect of long period wave to local sand transport rate in the surf zone is analyzed by laboratory and numerical experiments. In the laboratory experiment, surface profile, near-bottom velocity and suspended sand concentration are measures simultaneously and resultant net sand transport rate is measured by mass difference during the experimental runs. It appears that the net sand transport rate is determined by three driving forces which are undertow, long wave and short wave. In mild slope condition, the effect of long wave becomes large. In order to simulate this process, a new numerical model is formulated.

  • Local scour around a large circular cylinder on the uniform bottom slope due to waves and currents

    Eiichi Saito, Tomoya Shibayama

    Proceedings of the Coastal Engineering Conference   3   2799 - 2810  1993年01月

     概要を見る

    Investigation for mechanism of the local scouraround a large circular cylinder installed on the uniform bottom slope due to waves and currents were performed experimentally and numerically.

  • Mud transport rate in mud layer due to wave action

    Tomoya Shibayama, Masakazu Okuno, Shinji Sato

    Proceedings of the Coastal Engineering Conference   3   3037 - 3049  1991年01月

     概要を見る

    In order to calculate mud transport rate, two forms of transport should be considered, which are (1) mud mass transport in mud layer, and (2) suspended mud transport in water layer. The first type of transport (mass transport in mud layer) is greater than the second one in quantity under soft mud or fluid mud condition, therefore the first type of transport is mainly considered. The previously proposed methods to calculate the first type of transport are summarized and discussed. Then a new transport model called visco-elastic-plastic model is derived and some of the results of the model are shown. The model is based on the assumption that the fluid mud layer can be assumed to be visco-elastic fluid and when the magnitude of stress in mud layer exceeds the value of yield stress, the mud layer is modeled as visco-plastic fluid. Results of the new numerical model are compared with laboratory results and some discussions are given.

  • Local scour around a large circular cylinder due to wave action

    Eiichi Saito, Shinji Sato, Tomoya Shibayama

    Proceedings of the Coastal Engineering Conference   2   1795 - 1804  1991年01月

     概要を見る

    Laboratory experiments were performed in a wave basin to reproduce the local sea bed scour around large-scale maritime structures. Experiments suggested that the mass transport velocity and wave-induced steady currents were essential in modeling sand transport. Based on experimental observations, a numerical model was presented for the local scour around a large circular cylinder. The applicability of the model was confirmed with experiments. Although some discrepancies are still present between experiments and computation, the model seems to provide a basic framework for the local scour around large-scale structures. Future studies are expected on the three-dimensional boundary layer flow as well as on the wave nonlinearity.

  • Effect of long waves to local sediment transport rate

    Tomoya Shibayama, Eiichi Saito, Akio Okayasu

    Coastal Sediments '91     129 - 138  1991年01月

     概要を見る

    When irregular waves travel to the shoreline, long wave component becomes important in the surf zone. In the surf zone, sands are transported by both wave motion and turbulence due to wave breaking. The wave motion consists of variety of periods of waves from long wave to short wave. In the present study, the role of long wave to local sediment transport rate is analyzed by laboratory experiments and numerical experiments. It is concluded that the long wave component gives a important effect to the local net sand transport rate, in particular in the vicinity of shoreline.

  • Vertical variation of undertow in the surf zone

    Akio Okayasu, Tomoya Shibayama, Kiyoshi Horikawa

        478 - 491  1988年12月

     概要を見る

    In order to establish a model of the vertical distribution of the undertow, laboratory experiments were performed on uniform slopes of 1/20 and 1/30. The turbulent velocity in the surf zone including the area close to the bottom was measured by using a two-component laser doppler velocimeter. The distributions of the mean Reynolds stress and the mean eddy viscosity coefficient were calculated. Based on the experimental results, a model to predict the vertical profile of the undertow was presented.

  • Sediment transport due to breaking waves.

    T. Shibayama, K. Horikawa, A. Higuchi

    IN: PROC. TWENTIETH INT. CONF. ON COASTAL ENGINEERING, (TAIPEI, TAIWAN: NOV. 9-14, 1986), B.L. EDGE (ED.)   II, New York, U.S.A., Am. Soc. Civ. Engrs., 1987, Part II, Chapter 111   1509 - 1522  1987年01月

     概要を見る

    Sand movement in the surf zone was studied in a wave flume. The two categories of movement were suspension due to the vortex created by wave plunging, and deposition under turbulent flow. The suspension process could be explained in terms of the deep water wave steepness and the bottom slope. A numerical model of the process was formulated.

  • Velocity field under plunging waves.

    A. Okayasu, T. Shibayama, N. Mimura

    IN: PROC. TWENTIETH INT. CONF. ON COASTAL ENGINEERING, (TAIPEI, TAIWAN: NOV. 9-14, 1986), B.L. EDGE (ED.)   I, New York, U.S.A., Am. Soc. Civ. Engrs., 1987, Part I, Chapter 50   660 - 674  1987年01月

     概要を見る

    In order to clarify the characteristics of the velocity field in the surf zone, three sets of detailed and precise two dimensional laboratory experiments were performed. Spatial distributions and time histories of velocity were measured by using a hot film velocimeter with a split type probe or a two components laser Doppler velocimeter for regular wave conditions. Typical plunging breakers were formed during the experiments. Based on the experimental results, a model was investigated in order to estimate the two dimensional distribution of the on-offshore steady current below the through level.

  • VELOCITY FIELD UNDER PLUNGING WAVES.

    Akio Okayasu, Tomoya Shibayama, Nobuo Mimura

    Proceedings of the Coastal Engineering Conference   1   660 - 674  1987年01月

     概要を見る

    In order to clarify the characteristics of the velocity field in the surf zone, three sets of detailed and precise two dimensional laboratory experiments were performed. Spatial distributions and time histories of velocity were measured by using a hot film velocimeter with a split type probe or a two components laser doppler velocimeter for regular wave conditions. Typical plunging breakers were formed during the experiments. Based on the experimental results, a model was investigated in order to estimate the two dimensional distribution of the on-offshore steady current below the trough level.

  • SEDIMENT TRANSPORT DUE TO BREAKING WAVES.

    Tomoya Shibayama, Akihiko Higuchi, Kiyoshi Horikawa

    Proceedings of the Coastal Engineering Conference   2   1509 - 1522  1987年01月

     概要を見る

    In the surf zone, the agitation of the bed materials by breaking waves is strong and the suspended sand concentration in the vicinity of the wave plunging point is extremely high. Sand movement in this region was observed and sand concentration was measured in a wave flume. The sand movement in the region was divided into the following two categories: 1) sand suspension due to the large vortex which is created by wave plunging, and 2) sand deposition under turbulent flow. The condition for exciting this suspension process was considered and the result was well explained by the two parameters which are the deep water wave steepness and the bottom slope. Then a numerical model of the sediment suspension process was formulated and the process was well simulated by the model.

  • On-offshore sediment transport rate due to irregular waves.

    T. Shibayama, Y. Irie

    IN: 1987 PROC. COASTAL &amp; PORT ENGINEERING IN DEVELOPING COUNTRIES, SECOND INT. CONF., (BEIJING, CHINA: SEP. 7-11, 1987)   II, Nanjing, China, China Ocean Press, 1987, Group D, p.1500-1511. (ISBN 7-5027-0052-8)  1987年01月

     概要を見る

    Laboratory experiments on two dimensional beach transformation were performed under irregular wave conditions. Wave deformations, near bottom velocities, ripple dimensions and beach profile changes were measured. The net sediment transport rate was calculated from beach profile changes. The rate was also obtained by applying the sediment transport model of Shibayama and Horikawa (1985) to individual half wave of irregular wave history. These two results of transport rate were compared and a good agreement was seen.

  • SEDIMENT TRANSPORT AND BEACH TRANSFORMATION.

    Tomoya Shibayama, Kiyoshi Horikawa

    Proceedings of the Coastal Engineering Conference   2   1439 - 1458  1983年01月

▼全件表示

受賞

  • 濱口梧陵国際賞

    2019年11月   国土交通大臣   津波・高潮の研究  

    受賞者: 柴山 知也

共同研究・競争的資金等の研究課題

  • 北極圏の沿岸防災に関するカナダとの国際共同研究

    日本学術振興会  科学研究費助成事業 国際共同研究加速基金(国際共同研究強化(B))

    研究期間:

    2020年10月
    -
    2026年03月
     

    柴山 知也, 高畠 知行, 三上 貴仁, 中村 亮太

  • 令和元年台風15号による停電の長期化に伴う影響と風水害に関する総合調査

    日本学術振興会  科学研究費助成事業 特別研究促進費

    研究期間:

    2019年10月
    -
    2021年03月
     

    丸山 喜久, 能島 暢呂, 庄司 学, 永田 茂, 宮島 昌克, 大庭 哲治, 梶谷 義雄, 佐藤 翔輔, 筆保 弘徳, 小林 文明, 竹見 哲也, 飯塚 聡, 宮本 佳明, 益子 渉, 丸山 敬, 松井 正宏, ガヴァンスキ 江梨, 野田 稔, 中嶋 唯貴, 西嶋 一欽, CRUZ Ana・Maria, 高橋 徹, 友清 衣利子, 劉 ウェン, 有川 太郎, 柴山 知也, 高木 泰士, 平石 哲也, 清野 聡子, 田中 規夫, 八木澤 順治, 竹林 幹雄, 大西 正光, 畑山 満則, 平田 輝満, 轟 朝幸, 大石 哲

     概要を見る

    令和元年台風15号(房総半島台風)が主として千葉県で引き起こした長期間に渡る停電と風水害の総合調査を行った.本研究は,ライフライン,気象,風工学,海岸・港湾,水工学,交通の6分野で構成される.ライフライン分野では,ライフライン被害・復旧の概要と災害間比較,ライフライン停止による生活支障の実態調査などを行った.近年の自然災害の中でも台風15号による停電は復旧進捗の遅さは群を抜いており,かなり特異な傾向を示していることがわかった.気象分野では,台風15号の発生・発達環境場の概要調査,数値シミュレーションによる台風上陸前の強度・構造変化メカニズムの解明などを行った.令和元年台風15号は,発生期から発達期前半までは顕著に発達しなかったが,その後発達期を迎えて台風急速発達が起きたことがわかった.さらに,成熟期から衰弱期では,衰弱過程が弱くなる環境場であった.風工学分野では,現地調査による構造物の強風被害状況の把握,UAV空撮画像による屋根被害の検出などを行った.千葉県鋸南町,南房総市および館山市の一部地域で行われた現地被害調査では,何らかの被害を受けた住宅の被害率は約60%であった.海岸・港湾分野では,横浜市および南房総における高潮・高波の調査,船舶漂流挙動の予測と対策などを行った.神奈川県では,明らかな高波被害が東京湾に面した横浜市中区や金沢区の港湾区域で確認された.水工学分野では,降雨特性,流域特性からみた浸水メカニズムの比較と住民避難状況の調査を行った.調査結果に基づいて,千葉県で浸水が生じた河川に対して,実際の浸水形態を広域かつ簡易に説明できるような判定図を作成した.交通分野では,成田空港における利用者滞留問題の調査,航空貨物輸送への影響評価などを行い,空港アクセス交通機関で何が起こったのかをとりまとめた.

  • 不規則波浪作用下の海浜過程に関する研究

    科学研究費助成事業(東京大学)  科学研究費助成事業(一般研究(A))

  • 波による軟らかい底質粘土の輸送機構

    科学研究費助成事業(東京大学)  科学研究費助成事業(一般研究(C))

  • 堆積底泥の波による再浮遊機構に関する研究

    科学研究費助成事業(東京大学)  科学研究費助成事業(環境科学特別研究)

  • 臨海型高密度都市域の地震に対する災害危険度

    科学研究費助成事業(横浜国立大学)  科学研究費助成事業(重点領域研究)

  • 多方向不規則波浪場における漂砂量の推定法に関する研究

    科学研究費助成事業(横浜国立大学)  科学研究費助成事業(一般研究(B))

  • 任意断面地形上の砕波帯における不規則波浪のエルネギ-変換過程

    科学研究費助成事業(横浜国立大学)  科学研究費助成事業(一般研究(B))

  • 海洋環境下での底泥移動予測三次元モデルの開発

    科学研究費助成事業(横浜国立大学)  科学研究費助成事業(一般研究(C))

  • 開発に伴うアジア地域の沿岸環境変化の調査

    科学研究費助成事業(横浜国立大学)  科学研究費助成事業(国際学術研究)

  • 波流れ作用での底泥移動量の評価

    科学研究費助成事業(横浜国立大学)  科学研究費助成事業(一般研究(C))

  • 新形式縦型離岸堤の開発

    科学研究費助成事業(横浜国立大学)  科学研究費助成事業(一般研究(A))

  • 沿岸開発による環境変化機構の調査

    科学研究費助成事業(横浜国立大学)  科学研究費助成事業(国際学術研究)

  • 不規則波浪場の下での底泥移動機構解明と三次元数値モデルの構成

    科学研究費助成事業(横浜国立大学)  科学研究費助成事業(基盤研究(B))

  • 砕波に伴う3次元流体運動と底質移動に関する実験・現地観測および数値モデルの開発

    科学研究費助成事業(横浜国立大学)  科学研究費助成事業(基盤研究(B))

  • 工学倫理教育の方法論開発

    科学研究費助成事業(横浜国立大学)  科学研究費助成事業(萌芽研究)

  • アジア諸国における海岸ネットワークの構築と海岸工学上の諸問題の整理

    科学研究費助成事業(名古屋工業大学)  科学研究費助成事業(基盤研究(C))

  • 内湾における富栄養化履歴の解読とその数値再現に基づく長期環境予測に関する研究

    科学研究費助成事業(横浜国立大学)  科学研究費助成事業(基盤研究(B))

  • 開発による沿岸域環境変化機構の調査

    科学研究費助成事業(横浜国立大学)  科学研究費助成事業(基盤研究(B))

  • 化学量論に基づく地球温暖化後の内湾生態系応答シナリオに関する基礎的検討

    科学研究費助成事業(横浜国立大学)  科学研究費助成事業(萌芽研究)

  • 東京湾環境情報ネットワークの構築と新たな研究実施枠組みの提案

    科学研究費助成事業(横浜国立大学)  科学研究費助成事業(基盤研究(C))

  • 技術者における倫理観形成過程の発達心理学的研究

    科学研究費助成事業(鎌倉女子大学)  科学研究費助成事業(基盤研究(C))

  • 浚渫窪地の環境影響の解明と新しい環境マネジメント手法の提案

    科学研究費助成事業(横浜国立大学)  科学研究費助成事業(基盤研究(B))

  • 建設現場での意志決定プロセスの建設社会学的研究

    科学研究費助成事業(横浜国立大学)  科学研究費助成事業(萌芽研究)

  • アジア・アフリカ地域における沿岸災害脆弱性変容の調査

    科学研究費助成事業(早稲田大学)  科学研究費助成事業(基盤研究(B))

▼全件表示

特定課題研究

  •  陸上に氾濫する津波の三次元的挙動解明と減災への応用

    2018年   石井秀憲, 高畠知行, Miguel Esteban

     概要を見る

     陸上に氾濫した津波では周辺に存在する構造物の遮蔽効果を用いれば、波力を低減できる。水理実験では、津波水槽内で角柱構造物周辺の流速場をPIVを用いて計測し、流速・渦度の時間的・空間的変化を計測した。汀線と平行方向に構造物を配置した場合、浸水深は角柱間の距離に依存して変化し、運動量流束が角柱を設置しない場合と比較して40~140%程度変化した。この他にもいくつか配置を検討し、構造物の配置により運動量流束の最大値が10~140%変化することが解った。 また、乱流モデル(DES)を用いた3次元数値計算により、流速場及び浸水深を再現し、運動量流束の低減効果の高い配置パターンを提示した。この結果は、構造物配置を設計する上で有用である。

  • 首都圏での噴火による火山灰降下分布予測と対策の立案

    2015年   大島 優, 山口秀明, 奥村 暖, 田野倉祐介, 菅原 奈津子, 三上貴仁

     概要を見る

     メソスケール化学輸送モデルを用いて噴火後迅速に火山灰の降灰範囲を予測し、速報型の予測手法を提案した。噴火後24時間以内に必要な情報を収集し、噴火の翌日から数値計算を行うことで数日間の降灰範囲の予測を行う場合を想定し、これを速報型の予測手法と定義した。この手法を用いて噴火後の降灰範囲を予測することで、全国の自治体に所属する土木技術者が迅速に降灰への対策を講じることが可能となる。具体的にはメソスケール気象予測モデルWRF(Weather Research and Forecasting)と大気化学プロセスが組み込まれたメソスケール領域気象・化学輸送モデルWRF-Chem (Weather Research and Forecasting and Chemistry)を用いている。

  • 沿岸域の高潮・津波災害脆弱性の分析

    2009年  

     概要を見る

     アジア、アフリカの対象地域に対して既に筆者が構築した広範なネットワークを利用して、具体的な海外現地調査データの集積を行い、各地域の特性を把握し、その結果を基に総合的な防災、環境モニタリングのシステムを検討した。まず、2009年9月初旬に大隈小講堂において「アジアとアフリカにおける沿岸域の防災・環境・管理に関する研究集会」を開催し、ベトナム、インドネシア、タイ、スリランカ、タンザニア、イギリス、日本、カナダなど各国の研究者が沿岸域の防災、環境、マネジメントなどに関するそれぞれの国での最新の研究状況、研究成果について発表した。参加者は途上国や欧米の大学で教鞭をとる研究者たちで、本研究集会の成果により新しい沿岸域研究プロジェクトを開始することを決定した。 また、2009年9月中旬には、上記の研究集会参加所の協力を得て、ベトナムでの現地調査を実施した。その結果、環境変動に伴う高潮・高波被害の変化、高潮・高波対策、および土壌の浸食対策については、海外調査の結果による情報を解析し、環境変動あるいは流域内の浸食量を推定する方法をシステム化するための資料を得た。 一方、2009年9月29日に発生したサモア諸島沖地震津波により,サモア独立国と米領サモアの沿岸部は大きな被害を受けた.本研究では,現地調査と数値計算を実施することにより両国での津波被災の特徴を明らかにした。地震発生から約1カ月後の2009年10月28日から11月1日にかけて,サモア独立国・ウポル島および米領サモア・トゥトゥイラ島の2島において津波痕跡高の測量と被災住民への聞き取り調査を実施した.サモア諸島沿岸には地震発生後20分程度で第一波が襲来し,高さは最大で9m に及び,広い範囲で甚大な被害をもたらした.サモア諸島は島を取り囲むサンゴ礁のリーフの幅が広く,これらのリーフ上で波が砕けながら進んでくる様子がはっきりと見え,沿岸部の住民はいち早く危険に気付き逃げることができた.いくつかの村では津波の挙動を教える教育を実施しており,津波の危険を感じたら安全な場所へ避難するという意識が住民の中に備わっていた.サモア社会の特徴として地域社会の構造が極めて強固であり,酋長であるマタイの権限が強いことが挙げられる.住み慣れた沿岸の居住地を離れ高地への移転を決断した村では,このマタイのリーダーシップというサモア社会の特徴がうまく機能していたと考えられる. 

 

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