We examined channel bars at two sites in the lower reach of the Stung Sen River, which flows into Lake Tonle Sap, Cambodia, to identify sediment transport and accumulation processes during monsoon-related flood events and to investigate how sediment transport capacity changes as a result of enhanced backwater effect of the lake. Channel bars in the lower reach of the Stung Sen River that emerge in the dry season were classified into type A (lateral bars), type B (point bars), type C (concave-bank benches) and type D (diagonal and island bars, or fluvial dunes) based on Nagumo et al.'s previous study. Type B, type C, and type D channel bars were at our study sites of SEN-01 and SEN-02, about 83 and 77 km from the river mouth respectively. Computation of water surface profiles showed that sediment transport capacity of the Stung Sen River decreased abruptly after the peak flow stage because of the backwater effect from Lake Tonle Sap during the decreasing flow stage. Our observations suggest that alternating layers of sand and silt to clay layers accumulate to form type C channel bars, corresponding to changes in sediment transport capacity controlled by backwater effects from Lake Tonle Sap and by changes in flow depths and associated slackwater systems. The accumulation of alternating silt and sand layers of type B channel bars results from lateral sediment transportation that is accelerated with an increase of secondary flow, whereas development of type D channel bars is related to bedload mobility. (C) 2017 Elsevier B.V. All rights reserved.

Kolleru Lake, the largest freshwater wetland in India is highly degraded because of siltation, weed infestation and large-scale aquaculture encroachments. Restoration of the lake involves data on the original extent of this shrinking lake and on its extant condition. Previous studies indicated that the lake was a coastal lagoon abutting the Bay of Bengal during the mid-Holocene and later turned into a freshwater body as the seashore prograded 30 km and several rivulets continued to drain into the lake. However, the original extent of the lake is unknown. Mapping of geomorphic features from satellite images and facies recognition from the subsurface sediments recovered from 40 boreholes revealed that the lake initially extended over 1050 km(2). Analysis of time series satellite images indicated that aquaculture activity was absent in 1977 in the 493 km(2) designated Kolleru Wildlife Sanctuary within the 5 ft (similar to 1.5 m) contour but appeared in 12 % of the area in 1990 and expanded to 64 % by 2004. Despite the demolition of fishponds by the government during 2005-2006, they reappeared in 28 % of the sanctuary area by 2008 and further increased to 43 % by 2015, as encroachments continued unabated.

We investigated the Holocene evolution of the Godavari delta along the east coast of India, by analyses of landforms and 11 borehole cores collected from the delta plain during 2010-2013 with 113 C-14 dates. The Godavari delta covering an area of 5820 km(2) is one of the world's largest wave-dominated deltas fringed by a -30 km wide beach-ridge plain. Our analysis of sediment facies and their ages indicated that the Holocene marine sequence thickens seaward from -10 m to more than 50 m and that the local relative sea level rapidly rose from 43.5 m to 7.5 m below the present sea level during 10.9-8.0 cal ky BP followed by a slow rise up to its current level around 5 cal icy BP. Spatio-temporal variations in sediment accumulation rates and palaeo-shorelines for the last 6 Icy revealed successive changes of the main depocentre (delta lobe). We recognised six stages of delta evolution with distinct cyclic shifts of delta lobes controlled by avulsions. A linear beach ridge located 12-14 km inland from the present shoreline, which separates the first three lobes from the last three, represents the effect of coastal erosion of past cuspate delta lobes, as does the current linear shoreline of the central part of the delta. Our study documents continuous net progradation during the Holocene on millennial to centennial time scales. However, a considerable decrease of sediment discharge due to dam construction and water diversion since the 1970s has exacerbated coastal erosion, resulting in shrinking of the Godavari delta plain and tipping it into a persistent destruction phase. (C) 2015 Elsevier B.V. All rights reserved.

Tributaries of Lake Tonle Sap in the Lower Mekong Basin are strongly influenced by seasonal changes of water level in Lake Tonle Sap and discharge of the Mekong River. The aim of this research was to gain a better understanding of the fluvial geomorphology of the Stung Sen River, a tributary of Lake Tonle Sap. We used stereopairs of aerial photographs and satellite images to identify the microtopography of the floodplain and riverbed, and field surveys to observe bankside topography and deposits. We recognized four types of channel bar in the lower Stung Seng River: lateral bars (type A), point bars (type B), concave-bank benches (type C), and diagonal and island bars (type D). Type A appears to have a complementary relationship with type D. In some instances types A and D bars transition to type B bars and, in rare instances, into type C bars. These changes are probably related to channel sinuosity and changes in the volume of transported sediment. Sediment transport and construction of the channel bars appears to be controlled by shifts of the flow regime of the Stung Sen River related to differences in the rate of water level rise in the river compared to those in Lake Tonle Sap. The riverine environment differs greatly from that of the floodplain, where sediment is deposited from suspension during periods of inundation.

The Stung Sen River, the biggest tributary to Lake Tonle Sap in the Lower Mekong Basin in Cambodia, is characterized by large seasonal changes of water discharge under the Asian monsoon climate and seasonal changes in water level that reach at least 7 m and are controlled by the water level of the lake. The Stung Sen River floodplain consists of two geomorphic units: meander belt along the river channel and backmarsh. Coupled observations of outcrops along the river channel and arrays of sediment cores across the floodplain north of Kampong Chheuteal village and Kampong Thom City, c. 150 km and c. 70 km, respectively, reveal that floodplain environmental changes at c. 11 ka were possibly associated with the Holocene onset of the southeast Asian monsoon and probably with the emergence of Lake Tonle Sap. These observations also show that the present backmarsh-meander belt system was established about 5.5 ka along with the unique Mekong-Tonle Sap connection, characterized by a reversal in flow direction during the monsoon season. The meander belt materials are replaced as the river channel shifts on a decadal to centennial timescale. Backmarsh sediments at sites Kampong Chheuteal and Kampong Thom had a constant accumulation rate of about 0.5 mm/y during the Holocene, contrasting with rates of 0.1 mm/y during the late Pleistocene. At around 11 ka, a sand layer was deposited over all of the valley around Kampong Chheuteal, while wetlands enlarged around Kampong Thom, probably because of increased rainfall triggered by an enhancement of the Asian summer monsoon. This 11 ka horizon has since been covered by clayey sediments keeping pace with the accumulation of lacustrine sediments in Lake Tonle Sap. (C) 2013 Elsevier B.V. All rights reserved.

We conducted field research around Phnom Penh in the Cambodian lower Mekong plain, which was damaged by heavy flooding between August and October 2011. Flooded areas shown by satellite images and inundation depths measured in the field corresponded to the distribution of micro landforms. Flood water flowed through the Mekong River floodplain, and the area along the Tonle Sap River was heavily inundated. The flood water also reached higher alluvial surfaces, which are rarely inundated during the usual monsoon season. Although the flooding was comparable to that occurring in 2000, there was relatively less damage to infrastructure. In this region with cyclic annual flooding, people in local settlements make adaptations to maintain traditional lifestyles and land use patterns to minimize the risk of floods.

A geomorphological survey map of the Arakawa Lowland (the lower Arakawa River basin in the Kanto Plain, central Japan) documents several groups of paleomeanders suggestive of channel shifts of the Arakawa River during historical times (last ca. 2,000 years). However, the sequence and timing of these changes of the river are unclear. I examined geomorphological features of paleomeanders and lithological analyses of natural levee deposits, along with historical records on channel modifications, to summarize the current state of knowledge. I differentiate four groups of paleomeanders with different meander wavelengths along the present Arakawa River. The set with the smallest wavelengths is on the Moto-Arakawa River, considered to be a distributary prior to river modifications starting in the 17th century. The second smallest is of late 19th century derived from earlier topographic maps. The set with middle-sized wavelengths can be correlated with the main trunk in the Middle Ages, and the set with the largest wavelengths is suggested to be from an ancient large river that combined the flows from the Tone and Arakawa Rivers. Lithological analyses of deposits along the large paleomeander indicate sediment input from the Tone River watershed. More historical and geomorphological evidence and dating results are required to confirm these arguments.

The Stung Sen River is a major tributary of the Tonle Sap River systems, and several pre-Angkor strongholds are located in its drainage basin. Geomorphological characteristics and development of floodplain in lower reach of the Stung Sen River is discussed by sedimentary core analysis and field survey. The floodplain is composed of more than 10m of fluvial deposits which overlay the heavily weathered basement. Five depositional units and alternation of sandy channel deposits and suspended deposits are distinguished. The accumulation rate of the successive floodplain deposits is calculated as 0.1-0.6mm/yr by AMS-^<14>C ages, while the rate near the Stung Sen main channel is large, to be replaced frequently by the channel shifts. Fluctuation in the groundwater level is shown by the deposits color. This represents distinct seasonal environmental changes caused by monsoon.

The Sambor Prei Kuk archaeological site in lower reach of the Stung Sen River, central Cambodia, is the site of the capital city of the pre-Angkor state of Chen la. The location of Sambor Prei Kuk is discussed in relation to the geomorphological characteristics of lower reach of the Stung Sen River and the requirements of the inhabitants. The uplands were divided into upland I, which is characterized by hills, and uplands II and III, both of which have flat surfaces, with upland III lower than upland II. The present river follows a meandering course within a conspicuous meander scroll zone, and deposits along the channel are repeatedly eroded and redeposited. Back marsh areas have gradually filled with suspended flood water sediments during the last 4600 years at an accumulation rate of 0.6 mm/yr. The floodplain and lake plain were divided into five zones to evaluate the monsoonal flood risk and accessibility to upland, considering uplands distribution. Sambor Prei Kuk on upland II with the port town adjacent the river is situated on the place where water transport is feasible and the risk of monsoonal flood is low, which means the people accommodated to the highly different dry and monsoonal environment. (C) 2010 Lavoisier SAS. All rights reserved

We constructed a GIS-based digital map named Japan Engineering Geomorphological Land Classification Map (JEGM) that covers all over Japan with unified category, consisting of a total of approximately 380, 000 grid cells of c. 1 * 1 km each in size. For constructing the JEGM, we had been referred various kind of geomorphologic maps, geologic maps, reports and papers. This paper examines source data and maps for constructing the JEGM, and presents some problems in the existing maps such as the geomorphologic database that included the Digital National Land Information of National Land Agency. For example, the geomorphologic database in the National Land Information has problems in land classification criteria that are not unified over all prefectures. It was compiled from separate geomorphological maps of 1 : 200, 000 prepared by each prefecture in 1970s.

The Sagami River mouth faces the Sagami Trough without a distinct continental shelf, and the lower Sagami plain has well-developed marine and fluvial terraces. This area is also favorable for interpreting the tephrochronology of the Last Glacial Cycle using tephras from Fuji and Hakone volcanoes. The subaerial terraces and their constituent deposits in the lower Sagami plain correspond to the Marine Isotope Stages (MIS) 5c-5a (S1-S3 terraces), 3 (N and T) and 2 (M), respectively.<br>The buried terraces were examined by bore-hole logs and correlated with subaerial ones in the upper reaches using morphological continuity and tephra sequence lying on the terraces. These buried terraces and deposits correspond to the MISs 5a, 4, 3, and 2, based on tephrostratigraphy.<br>The landform development of the lower Sagami plain since the MIS 5a is as follows: A broad fan-deltaic plain was formed in the culmination of the MIS 5a. A deep and narrow valley incised the plain during the MIS 4, because of the sea-level drop. During the MIS 3, this deep valley was filled, and a relatively wide plain of compound fans developed. A deep and narrow valley was formed again in the MIS 2. Sagami Bay has intruded into the lower Sagami plain in the MIS 1.<br>Relative sea-level changes are shown by subtracting tectonic components from the observed heights of buried terraces near the present river mouth. The tectonic component (average uplift rate) is estimated to be 0.07m/ky near the present river mouth. The calculated sea-level height at the culmination of each stage was as follows: -30 to -40m in the MIS 5a, ; -95 to 110m in the MIS 4; -80 to -90m in the MIS 3; and -100 to -110m in the MIS 2. These results suggest a low sea level for the MIS 4 and that a relatively low sea-level remained throughout the MIS 3.

The northwest region of Bangladesh is divided into four geomorphological units which show different flood features. The region has suffered severe flood damage both in 1987 and 1988. After these floods Bangladesh Action Plan for Flood Control was established by the World Bank. In the northwest region the plan proposed two major projects, namely, an interceptor drain and a diversion channel. A Polder Project is also going on in this region. However these major projects are mainly on structural methods and require much cost for long embankments. The author suggests smaller but reasonable projects combining structural and non-structural methods in the region. © 1993 Kluwer Academic Publishers.

Shonai Plain is located in the lower reach of the Mogami River, which flows into the Japan Sea in Northeast Japan. The Amarume Anticline, where Amarume and other oil fields are located, runs from north to south in the eastern part of the plain. Deformations of the plain surface are seen as evidences of an active fold on this plain.<br>During the revision of the "Geomorphologic Land Classification Map of the Shonai Plain illustrating features of flooding and soil liquefaction" (Oya et al., 1982, 1989), it was found that the Amarume Anticline influenced the river courses in the Shonai Plain. By studying historical maps based on a geomorphologic land classification map, I found that the Mogami River has changed its course repeatedly within a entrenched meandering belt of the river along the Amarume Anticline from 17th century to the present. The relative height of a natural levee from the former Mogami river bed is 2.65m along the anticline. Furthermore, the Aizawa River, a small tributary which flows into the Mogami River near Sagoshi, is entrenching the alluvial surface of the plain with its relative height of 4.5m. The Kyoden River from Mt. Haguro shows an incised meander along the Amarume Anticline. These phenomena descrived above can be used to determine the existence of an active fold—Amarume Anticline.<br>Geomorphologic land classification maps serve many purposes. For example, one was used to determine the site of bridge at the Brahmaputra-Jamna River by Oya (1979). Geomorphologic land classification maps can also be used to indicate the presence of an active fold. Moreover, they illustrate how river cources change with time.

Landforms of the main part of Tokyo Metropolis consist of Pleistocene uplands and Holocene lowlands. The original forms of upland surfaces are sea bottoms of the Last Interglacial Age, or the fluvial surface of the Last Glacial. These terrace surfaces are covered with thick air-laid tephra layers. They were supplied by westerly sitting volcanoes such as Mt. Fuji and the Hakone Caldera during the late Pleistocene. The uplands are dissected by valleys whose heads are situated on the upland surface. Some valleys in the upland were formed by remnant streams on the upland surface where tephras were accumulated. The origin of these valleys dates back to the Last Glacial. The lowlands were the places where some large valleys were cut during the Last Glacial. The marine deposits of the Postglacial Transgression buried these valleys. Fluvial systems, including the Japan's largest river Tone, developed after that. These deposits formed the “soft ground”. The outline of the evolution of Tokyo Lowland during the late Holocene is shown by the method of historical ge-omorphology. Since the 17th century, river courses have been changed artificially and the coastal area along Tokyo Bay has been reclaimed and filled up. The Tokyo Lowland is the most transformed area by human activities in Japan. The characteristics of the mobile belt such as crustal movements and volcanic activities have played as important a role as the eustatic changes in the landform of the uplands and lowlands of Tokyo. Human activities are increasing on the landform of Tokyo. © 1990, The Association of Japanese Geographers. All rights reserved.

In this study, geomorphological and geological features of valleys which dissect the diluvial uplands of Sagamino and Musashino, unto Plain, are investigated and a model of their evolution is also shown.<br> Diluvial uplands of the Kanto Plain such as Sagamino and Musashino have thick air-laid tephra layers on their surfaces. These tephras were supplied from westward volcanoes such as Haone and Fuji, and are estimated to have been supplied constantly by many intermittent eruptions father than by a few eruptions in short duration.<br> There must have been two processes on the upland surfaces following the formation of the uplands: stream erosion and tephra deposition for which the evolution of these valleys can be understood as a result of these reciprocal processes.<br> The purpose of this study is to clarify the evolution of these valleys under the conditions mentioned above. Geornorphological features are investigated in their planforms, longitudinal profiles and cross section forms of valleys. Geological stratigraphy along the valleys is analysed from boring data and observations of outcrops in the investigated areas.<br> Valleys investigated are those of Sakai River, Hikiji River and Hato River in Saamino and Kanda R., Shakujii R., Sen R., No R., urome R. and Toshitorazu R. in Musashlno (Fig. 1).<br> The Saamino Upland consists of some terraces groups: Zama Hills (lama stage), Koza Hills (Simosueyoshi stage), Sagamihara Surface (usasino stage), Tanahara Surface and Minahara Surface (both Tacikawa stage). The surfaces from Sagamihara Surface on are dissected fan terraces, and are covered with thick tephra layers: 17-20m on Sagamihara Surface, 6-7m on Tanahara. Surface and 2-4m on Minahara Surface. Thickness varies depending on their forming age (Figs. 2 and 3). formed by the removal of tephras along the former river courses. The model (Fig. 17) shows the evolutional history of these valleys: 1) A former river course remains on a terrace surface; 2) Remnantstreams flows away falling tephras along the former river course; 3) Tephras accumulated on both side of the stream form a &ldquo;valley&rdquo; and 4) A water spring may create another valley.<br> When additional &ldquo;fossil channels&rdquo; on diluvial uplands are discovered, they will offer further data for reconstructing river hydrology or palaeoenvironmental studies.