A Flooding Simulation of Chi Basin

Abstract

A flooding simulation of Chi Basin is presented. Info Works RS was applied for flood routing along Chi River and its flood plain, in order to obtain basic information for flood warning. The essential data for the Info Works RS were including stage and discharge hydrograph at various stations along the river, the stream cross-sections, Manningn’s roughness coefficient (Manning’s n) of the stream and its flood plain, ground model which was created from GIS data base. The model employed a discharge hydrograph at the upstream, and a stage hydrograph at the downstream of the reach, as the upstream and the downstream boundary conditions respectively. The Manning’s n of the channel was obtained from a model calibration during the dry season, when the flow took pluce only in the channel. While, the Manning’s n of the flood plain was calculated and weighted according to its land use. A discharge hydrograph from each sub-basin was esrimated from the relationship between averaged annual stream flow and watcrshed area of the stream gauging stations in the basin. The relationship at a station was then adjusted by a correction factor corresponding to an index station to achieve a daily discharge hydrograph. The simulated outputs were including a boundary of flooding area over the basin, stage and discharge hydrograph at various locations along the river