INFLUENCE ANALYSIS OF OBSERVED RIVER CHANNEL CONDITIONS ON THE INUNDATION PROCESS IN THE LOWER MEKONG RIVER BASIN

This study aims to analyze the influence of observed river channel conditions on inundation simulation in terms of discharge within a river channel and inundation area and depth over a floodplain. The target area is the Lower Mekong River Basin, which suffered from severe floods in 2000 and 2011. First, measurement using an acoustic Doppler current profiler is conducted to understand the longitudinal distribution of cross-sectional shapes and roughness change during a flood in a river channel. Based on the observation results, inundation simulation with the Rainfall-Runoff-Inundation model is conducted. The calculation results show that the reproducibility of discharge improves by taking the longitudinal distribution of the width and depth of the river reach into consideration, and that the water depth over the floodplain has a high sensitivity to both cross-sectional shapes and roughness change during the flood.