Hydrodynamic Simulation of Flood Dynamics in a Himalayan River Basin Using HEC-RAS and Geospatial Integration

Abstract

Floods represent extreme natural occurrences that lead to devastating damage and adversely impact communities. To effectively mitigate and manage the consequences of such events, decision makers and disaster management authorities rely on reliable data related to flood depth, discharge, magnitude and specialized datasets. This research article prepared to employ the upgradedsoftware model of HEC-RAS to perform  one-dimensional hydrodynamic flood modeling along the mountainous ‘Sutlej’ river, spanning of 23 km from ‘Karcham Dam’ to ‘Nathpa Dam’ in Himachal Pradesh, India, with a specific focus on leveraging geospatial techniques. The study seeks to showcase the geospatial analytical capabilities of HEC-RAS v5. River data, including bank lines, flow path lines, and cross-section cut lines, as extracted from ALOS-PALSAR Digital Elevation Model (DEM) for flood modeling purposes. Steady flow analysis was conducted to simulate a one-dimensional hydrodynamic model. The model’s outcomes presented as flood elevation ranging from 1779.6m to 1596.2m (R.L) can be visualized in the geospatial RAS Mapper window, Flood depth maps for maximum flood highlight the susceptibility of low-lying areas on both sides of Sutlej River when river discharge exceeds 6740 m³/s.The model simulation results depicted different arrival time of flood at different places on downstream with water surface elevations varying from 1790.8m to 1520.2m and backwater affect starts approximately 2 km before reaching Nathpa Dam reservoir. The velocity of flood water varies from 0 to 8m/s. By effectively integrating geo-spatial techniques with HEC-RAS, it is witnessed to create more accurate data-driven models and the results from the one-dimensional modeling demonstrate promise and accuracy.