Hydraulic modelling and flood hazard zoning in rivers of the urban basin of Sulaymaniyah using 2D modelling with HEC-RAS and GIS

The preparation of flood zoning maps is crucial in global urban development studies, serving as fundamental information for investment and project implementation assessments by relevant organisations. This study focused on hydraulic modelling and flood zoning in Sulaymaniyah urban basin using hydrologic model HEC-RAS and GIS. Given the escalating urban flood frequency, effective solutions are imperative. The 2D hydraulic model HEC-RAS was employed for a more accurate simulation of flow patterns, especially in flood-prone areas. Hydrological data, digital elevation model, and urban structure data were utilised for modelling, with the aim to identify vulnerable areas and propose damage reduction solutions. The study generated water surface profile maps, width, depth, and flow velocity for return periods of 2, 5, 10, 25, 50, and 100 years. With a 25-year return period, flood vulnerability was classified based on depth and flow velocity, revealing substantial risks in urban areas. H5 and H6 hazard zones covered 43.5% and 24.5% of these areas, posing threats to individuals, vehicles, and structures. The H4 hazard zone, comprising 8.8% of the flood-prone area, presented risks to people and vehicles. Also, the correctness of choosing Manning's roughness coefficient was evaluated. This research provides valuable insights for urban flood management and hazard mitigation.