Mapping Flood Zone in Khorram Abad River by Integrating Hydrological and Hydraulic Models

The aim of this study is to investigate the application of an integrated hydrological-hydraulic modeling approach to simulate river flows, flood hydrographs, and flood-prone areas in the Khorram Abad (Iran) drainage basin. In this study, the WetSpa hydrological model and the LISFLOOD-FP hydraulic model were used to simulate river flows and flood zones. Ten years of meteorological data (water years 2005–2006 to 2014–2015) were employed for the simulations. The models were calibrated using data from the first five years, while the subsequent five years of data were used for validation. The WetSpa model was applied to simulate daily flows, and the LISFLOOD-FP model was used to simulate flood-prone areas for different return periods. The WetSpa model successfully simulated daily flows with acceptable accuracy, achieving performance metrics such as the Nash-Sutcliffe Efficiency (NSE) of 0.53 and the Kling-Gupta Efficiency (KGE) of 0.68. For high-flow events, the NSE coefficient reached 0.7, indicating the model's effectiveness in flood prediction. The results from the LISFLOOD-FP model showed that the maximum flood extent for the 200-year return period was 627,100 square meters. The water balance analysis revealed that 25.5% of the precipitation was converted into runoff, comprising 2.34% surface runoff, 1.6% subsurface runoff, and 21.57% groundwater flow. This study demonstrates that the integration of hydrological and hydraulic models can effectively predict flood behavior and delineate high-risk areas.