Determining the effect of urbanization on flood hazard zones in Kahramanmaras, Turkey, using flood hazard index and multi-criteria decision analysis.

Floods are the most destructive natural hazard throughout the world. Identifying flood hazard zones is the first step in flood risk management. Land use changes, especially urbanization, is the key factor in the destructiveness of flood events and change in flood risk. Therefore, determining the effect of urbanization on the changes in flood hazard zones presents a valuable data for effective flood risk management and urban development planning. In this context, the aim of this study is to reveal the effect of urbanization on flood hazard zones in Kahramanmaras city. In this study, an index-based approach was used to identify the flood hazard zones. To calculate a flood hazard index, the susceptibility map was multiplied by the land use map by using the raster calculator tool in the ArcGIS. The susceptibility map was generated by combining the maps of flow accumulation, distance to stream, slope, and elevation parameters based on parameter weights obtained from the analytical hierarchy process (AHP) method. Two land use maps for the years 1990 and 2018 were separately overlaid with the susceptibility map to reveal the effects of urbanization on flood hazard zones. According to the results, it was found that very low, low, and moderate hazard zones decreased by 0.01%, 0.09%, and 1.2%, respectively whereas the high and very high zones increased by 3.30% and 0.58%, respectively due to urbanization. It was also determined that the main reason for the increase in the high zone was the expansion of urban areas into agricultural areas in the study area.