Floodplain Characteristics of the Mekong Delta in Cambodia

抄録

The purpose of this study was to examine the floodplain characteristics of the inner Mekong Delta, on the lower part of the Mekong River in Cambodia. Previous works have not investigated the floodplain characteristics of the fluvial dominated area of the Mekong Delta. To grasp the morphology of the study area, we first constructed topographical profiles from hydrologic maps and Space Shuttle Radar Topography Mission 3 data. Then, focusing on the morphology of the floodplain, we produced a land classification map based on aerial photo interpretation and field survey and identified the morphological structures of the study area. We classified the delta landforms as natural levee, back marsh, abandoned channel, alluvial terrace, swamp, point bar, and artificial landforms, including colmatages. We identified four floodplain zones. Zone A floodplains, along the upper part of the Mekong River, have cut-off point bar patterns. Those in zone B, along the lower part of the Mekong River, are linear, and develop back marsh widely. In zone C, along the Bassac River, the floodplains follow the river meanders, and are characterized by unevenly distributed artificial colmatages. Floodplains in zone D, along the Tonle Sap River, which has an extremely low gradient, display a unique geomorphology caused by seasonally reversed river flows.