Flood Inundation Mapping In Belsiri River Basin Linking HEC-RAS and HEC-GeoRAS Model and Flood Frequency Analysis

Flood is basically a natural phenomenon which has its obvious impacts on floodplain environment.It is a high magnitude episodic discharge of river, which, in turn brings about significant changes in the adjacent floodplains.In this paper an attempt is made to map the flood inundation areas of Belsiri river basin in HEC-GeoRAS model integrating the empirical methods of flood frequency analysis.For mapping the flood inundation areas, covering the period 1991-2011, the calculated design floods with 5, 10, 20, 50, 100 and 200 years return periods are integrated in HEC-GeoRAS and the resultant inundation areas are estimated, mapped and demarcated using the model the design floods of 126,139,147,158,163 and 168 m 3 s -1 with return periods of 5, 10, 20, 50, 100 and 200 years estimated following Log Pearson Type III method correspond to inundation areas of 22.704, 22.946, 23.138, 23.303, 23.394 and 23.442 km 2 respectively.These data are similar to flood inundation data estimated using HEC-GeoRAS.It is evident in the flood inundation map prepared in HEC-GeoRAS that the extents of flood inundation are increasing.