Application of latest HEC-RAS version 6 for 2D hydrodynamic modeling through GIS framework: a case study from coastal urban floodplain in India

Hydrodynamic models play an important role in efficient flood management by identifying flood risk zones. The present study is carried out using GIS-integrated 2D hydrodynamic modeling to appraise the flood event of the year 2006 and find inundation in the low-lying regions of Surat city. In this study, terrain data of Surat city and Lower Tapi Basin obtained from Shuttle Radar Topographic Mission (SRTM) 30 m digital elevation model (DEM) and flood data of 2006 were used to develop a 2D hydrodynamic model in HEC-RAS-v6.1. The discharge from the Ukai Dam during the flood event and the normal depth at downstream are considered as upstream and downstream boundary conditions, respectively, to simulate the model under unsteady flow condition. The simulated flood showed satisfactory performance when compared with the observed flood level map of the flood event prepared by Surat Municipal Corporation (SMC), with R 2 value of 0.96, NSE value of 0.90, and RMSE value of 0.66 m. Additionally, the simulation yield information such as flood water depth, flow velocity, flood arrival time, and water surface elevation (WSE). The west and north zone of Surat city are topographically low-lying areas and are most vulnerable to flooding with greater flood extent, higher water depth, and longer flood duration. The decision-makers can use the simulated results to take proper decisions at the appropriate time to reduce the number of casualties and destruction of property. The study can assist in reducing the flood risks in vulnerable areas by planning and implementing appropriate flood control measures.