Development of integrated hydrologic and hydrodynamic models for flood modeling in Radiša catchment at Western Slovakia using HEC-HMS and HEC-RAS

Integrated hydrological and hydrodynamic models could help in understanding the dynamics of floods and developing effective strategies for flood management and mitigation to diminish the risk to people, communities, and the environment. This study aims to develop integrated hydrological and hydrodynamic models using HEC-HMS and HEC-RAS for flood modeling in the Radiša catchment at Western Slovakia. First, the design flood hydrographs for the Radiša catchment were generated using hydrologic modeling (HEC-HMS). Curve Number (CN) was used as the loss method, and its initial values were estimated based on Corine Land Cover (CLC) data. Design hyetographs were generated with the alternating block technique from intensity duration frequency (IDF) curves, which were estimated by annual maxima analysis (AMA) and simple downscaling of daily precipitation. The results were compared with the hyetographs produced by the regional method and EBA4SUB modelling and AMA of discharge measurements at Bánovce and Bebravou. Afterward, by using the obtained hydrographs, 2D hydrodynamic modeling (HEC-RAS) was performed to analyze the flood extensions of various peak discharge hydrographs. The hydrological results showed that the developed methodology can generate realistic design flood hydrographs for higher return periods, while peak discharges for low return periods are underestimated. In addition, the comparison of different methodologies showed an overestimation of peak discharges when using the AMCIII CN class. Moreover, the regional method was found to give the most consistent results in terms of peak discharges when considering both low and high return periods. The HEC-RAS outputs showed that the area is safe for the 2 and 5-year peak obtained discharge values. However, for higher frequency income discharge values, the dimensions of the river are insufficient to safely transfer the water downstream. Results indicated that accurate hydrological and hydrodynamic flood modeling can help to minimize life and property losses of the catchment.