82-Flood Inundation Simulation for the Delta Region of Mahanadi River Basin Using MIKE FLOOD.

Abstract

In this study, a coupled 1D-2D hydrodynamic model, MIKE FLOOD is used to simulate the flood inundation extent and flooding depth in the delta region of Mahanadi River basin in India. Initially, the 1D model MIKE 11 is calibrated using river water level data of two gauging sites for the monsoon period (June to September) of the year 2001. Subsequently, the calibrated set up is validated using water level data for the same period for the year 2002. The performance of the calibration and validation results of MIKE 11 are evaluated for all the years using the error functions, modeling efficiency (E) and index of agreement (d). The simulated water levels are found to be in close agreement with the observed water levels. A bathymetry (equivalent to a Digital Elevation Model (DEM)) of the study area with a spatial resolution of 250 m is prepared and provided as an input to the 2D model, MIKE 21. MIKE 11 and MIKE 21 models are then linked to form the MIKE FLOOD model set up for simulating the two dimensional flood inundations in the study area. MIKE FLOOD model is calibrated for the year 2001 by comparing the maximum flood inundation extent simulated by the model with the corresponding actual inundated area obtained from remote sensing data of IRS-1D WiFS. The calibration is carried out by changing the Manning's roughness coefficient (n) of the flood plain, which is assessed from the land use map of the study area developed using IRS-1D LISS III data. The results of calibration show a close agreement between the simulated maximum flood inundation extent and the inundation extent obtained from remote sensing data. The calibrated MIKE FLOOD model set up is then validated for the year 2003 by comparing the model simulated inundation extent with inundation extent obtained from the flood reports prepared by the State Water Resources Department (SWRD) and United Nations Development Program (UNDP). The aerial extent of the maximum flood inundation is found to be 514.7 km2 for the year 2003, which is in close agreement with the observed maximum inundation extent of 550.0 km2 as reported by the SWRD and UNDP.