Flood Inundation Mapping in “Ghed Topography” Using Hydrodynamic Modelling and Google Earth Engine – A case of Combined Approach for Flood Assessment.

Floodwaters, though a natural phenomenon, can be managed through effective flood assess-ment. This study employs satellite imagery and two-dimensional (2D) hydrodynamic analysis to evaluate the inundated Ghed region (Gujarat state, India) using HEC-RAS v6 and Google Earth Engine (GEE). HEC-RAS v6 leverages open-source digital elevation models (DEMs) to generate hazard maps, while GEE’s machine-learning algorithms analyze Sentinel 1-C band synthetic- aperture radar (SAR) data from 2017 to 2021 to visualize flooding. The flood mapping algorithm (FMA) in GEE provides data that is compared with 2D model outputs, showing that floodwaters disperse into a large depressed zone. Validation of the 2D model, based on water depth analysis at four sites, yields statistical values of 0.82 for the coefficient of determination (R2), 0.26 for Root Mean Squared Error (RMSE), and 0.76 for Nash-Sutcliffe Efficiency (NSE). Floodwaters annually affect an area of over 170 km2 in the Ghed region, emphasizing the need for effective flood management strategies.

https://www.tandfonline.com/doi/full/10.1080/09715010.2025.2479839