Evaluation of Simulation Results of HEC-RAS Coupled 1D/2D and 2D Modeling Approaches Through Scenario-Based Analysis

While 1D, 2D, and coupled 1D/2D models are widely used in flood extent mapping, a significant research gap remains in comparative analyses of 2D and coupled 1D/2D approaches. Study of the Dinsiz Stream Basin is of critical importance due to its proximity to industrial zones and residential areas, as well as its susceptibility to flood risk. Due to the lack and insufficiency of flow data in the basin, only long-term rainfall data were used in the analysis. Rainfall return periods of 50, 100, 200, and 500 years were estimated using statistical methods, and these values were utilized to generate flood hydrographs for this study. These values were then transferred to HEC-HMS, and the resulting hydrographs were input into HEC-RAS to establish coupled 1D/2D and 2D models for comparison. Flood mapping was performed for different return periods to evaluate the flood impact. This study revealed that maximum water levels in the 1D/2D models were higher than in the 2D models. The results showed that Dinsiz Stream could cause major losses for the second organized industrial zone located nearby when it overflows. The accuracy of the model was ensured with photographs of the flood event that occurred in 2021, ensuring the reliability of the findings.