Investigating the Two-Dimensional HEC-RAS Model Capability for Flood Risk Mapping in the Qarachai River in Ramian, Golestan Province

Changes in precipitation patterns and its intensity due to the global climate change has led to intensifying floods as the most occurent natural disaster. ‏Flooding cannot be fully prevented, but its impacts can be mitigated by accurately identifying flood-prone areas and implmenting appropriate risk-based management measures. The Qarachai Watershed, located in the upstream of the Gorganrood River Basin in Golestan Province, Iran, was chosen as the study area, which has experienced several flood events in recent decades. ‏In this study, flood risk was assessed using the HEC-RAS, a two-dimensional hydraulic model. ‏Flood discharge values occured in the early 2019 were considered as model input, and based on ground truth, the manning roughness coefficient values were measured. To evaluate the results of the HEC-RAS model, some statistical criteria were used reflecting a good performance of the model. ‏The analysis showed that by increasing the return period, the extent, depth, and amount of flood risk increase. Moreover, the analysis showed that the flood zone in 100 year return period, affects parts of Seyedkalate Village. Approximately, half of the flood zone identified in this study was attributed with very low-risk. The results of the study are used to adopt appropriate strategies and plans to adapt to climate change and as an appropriate tool for identifying flood exposed and flood-prone zones.