Modeling flood hazard impacts using GIS-based HEC-RAS technique towards climate risk in Şanlıurfa, Türkiye

Climate change triggering extreme weather events and the fact that settlements are at risk have made flood disaster analysis a more critical issue. The economic, social, and environmental risk areas of Karakoyun, Sırrın, and Cavsak streams located in Şanlıurfa city center were determined using flood risk analysis. Thus, it aims to determine low, medium, high, and very high probability flood areas in the area, to collect the necessary data for establishing early warning systems and precaution packages, and to create an infrastructure for similar studies. While performing the risk analysis, we used Q5, Q10, Q25, Q50, Q100, Q500, and Q1000 flood recurrence flows of the mentioned streams. Many criteria were considered, including stream routes, natural water retention capacities, land topography, and general hydrological and geological features. In the light of the data provided, digital elevation models of the streams were created in the ArcGIS 10.3 program, all information was transferred to the hydraulic modeling HEC-RAS 5.07 software, and risky areas were determined by performing a 1D flood analysis. At Q2 flow rate, Karakoyun has 7.09, Cavsak 2.67, Sırrın 6.603 m3 s− 1, and at Q1000 flow rate, Karakoyun has 167.550, Cavsak 90.77, Sırrın 151.298 m3 s− 1 hydrograph peak values. As a result of the analysis, it was appointed that there was a flood risk in many parts of the stream sections. The flooding phenomenon has happened to be one of the most devastating floods for economic and environmental damages that occurred in Şanlıurfa City in 2023. People lost their lives, and many were injured during flooding; also, the urban economy affected nearly $15 million in the region. The risk of residences, shopping malls, and commercial areas in the city is revealed spatially.