Hydrodynamic flood modeling of Dikrong River in Arunachal Pradesh, India: a simplified approach using HEC-RAS 6.1

An attempt has been made in this study to simplify the conventional approach of hydrodynamic modeling using HEC-RAS 6.1. Conventionally, the ArcGIS extension HEC-GeoRAS has been used to perform hydrodynamic modeling for HEC-RAS application. However, the new tool RAS Mapper, available with the latest version of HEC-RAS 6.1 has been found to be capable of performing complex hydrodynamic modeling. In this study, the flood inundation maps are generated using the RAS Mapper rather than the widely used HEC-GeoRAS. To assess the accuracy of the simplified approach, velocities, and water surface elevations at the return periods of 25 years, 50 years, and 100 years are stimulated using DEM and compared with the results obtained using total station data. The comparison of results shows that the coefficient of correlation ranges between 92 to 94 percent for velocity and 96 to 98 percent for water surface elevation. The flood inundation map for the return periods of 25 years, 50 years, and 100 years reveals There is an increase in channel depth as well as the extent of inundation as the return period of flood even increases. Furthermore, the simplified technique is demonstrated to be effective and reliable for hydrodynamic flood modeling. As per the findings, the two most vulnerable locations in the study area are Banderdewa and Harmuty. As a result, the government of Arunachal Pradesh has recommended building sheet pile spurs on the river's right bank long with earthen embankments on both banks to mitigate the flood problems in the study area.