The Development of Coupled 1D–2D Hydrodynamic Flood Model by Using HEC-RAS: a Case Study of the Panchganga River Basin, Kolhapur District, Maharashtra, India

The flood related problems have amplified greatly in the Panchganga River (PR) basin. Thus, the present research work developed coupled 1D–2D hydrodynamic model by using Hydrological Engineering Centre-River Analysis System (HEC-RAS) for mapping of flood on the PR reach between Shinganpur to Ichalkaranji gauging stations. In this study, 1D unsteady model is calibrated and validated for flood events occurred in 2021 and 2019, respectively. The developed 1D model is then coupled with 2D floodplain model. The capabilities of 1D and coupled 1D–2D models are evaluated by RMSE, NSE, PBIAS and R² values, these values lie in range; RMSE = 0.64 to 0.85, NSE = 0.33 to –0.35, PBAIS = –0.0011 to 0.089 and R² = 0.70 to 0.97. The floodplain’s Manning’s n is selected on the basis of six available observed data locations in the Kolhapur City. The inundation map is developed for the Kolhapur City. The fairly accurate flooding depth and inundation extent is observed from inundation map developed in 1D–2D coupled HEC-RAS model.