Flood Inundation Mapping Using GIS and Hydraulic Model (HEC-RAS): A Case Study of the Burhi Gandak River, Bihar, India

Abstract

The Burhi Gandak River in north Bihar (India) affects agricultural land, industrial areas, commercial areas, and populations nearby riverbank. Therefore, the study focused on identifying areas exposed to hydrological risks and creating management plans for emergencies. The flood map makes it easy to spot flood-affected areas near the river. For analyzing flood inundation of the study area, discharge data of 50 years (1956–2005) for Sikandarpur gauge station are analyzed, and the same is forecasted for 5, 10, 20, 50, 100, 150-years return period. For flood frequency analysis, well-known probability distributions including generalized Pareto, generalized extreme value (GEV), log normal, Gumbel, and Weibull (1) were tested to calculate extreme flows for different return periods. The Kolmogorov–Smirnov test indicates the Gumbel distribution to be the most appropriate probability distribution for the study. To precisely identify and draw the flood inundation map, the HEC-RAS that models the river flow hydraulics used for the study area together with an extension of ArcGIS is known as HEC-GeoRAS. The main objective of the study is to define HEC-RAS model to find two flow variables (water depth and flow velocity).