Characteristics of Flood Disasters in Low Floodplain Along a Big River Due to Overflow Levee Breach

Abstract

During flooding season, large amount of water flows through Bangladeshi river and it causes earthen levee failure and huge damage occurs in the inhabitants inside the levees. Thus it is important to recognize the process of inundation and we have attempted to do through numerical simulation. As for simulation scheme, schematic model area is considered with main channel, levee and floodplain, and they are roughly composed of the same sediment characteristics because the flood plain have been formed by flooding sediment, the levees have been made by piling up the sediment dredged from the river bed. Therefore, we treat these three components simultaneously in the simulation model. The main channel, levee, floodplain and flow parameters are selected in conformity with the study field of Sirajganj district and Jamuna River in Bangladesh. And RIC-Nays a two-dimensional numerical model for flood flow and morphology is utilized in this study upon confirmation through the experimental and other numerical study. Based on the calculated results, inundation of water and sediment in the floodplain and evolution process of levee breach are investigated. Levee breach is considered to initiate in the middle of the levee with crest opening. We change the opening size in vertical and longitudinal scales, and the inflow discharge. For the floodplain slope is also taken into account.