The effect of climate change on flood risks; Menderes Basin example

Climate change causes significant effects on the water cycle and causes changes in precipitation regimes. Changing precipitation regimes also cause the Intensity-Duration-Frequency (IDF) curve, which shows the relationship between the intensity, duration, and frequency of precipitation, to change. Flood risks increase with more intense precipitation falling in shorter periods. Changing IDF curves requires re-evaluating flood risks since they change the designs and analyses based on these curves. This study aims to analyze the effects of climate change on flood risks by updating IDF curves and modeling the rainfall-runoff relationship in Tabakhane Stream in Aydın province, where floods have occurred many times before. Past and future IDF curves were determined using observation and climate projection data. Flow projections were calculated with the updated IDF curves using the Hydrologic Engineering Center-Hydrologic Modeling System (HEC-HMS) developed by the United States Army Corps of Engineers. In addition, flow projections were evaluated considering climate change scenarios and new scenarios based on land use that may change in the future. In the analyses, it was determined that there could be an increase of up to 10% in the distant future compared to the reference period in 100-year rainfall recurrences, and an increase of up to 80% in flow recurrences in the most adverse scenario, where land use is considered to have undergone the highest change. The study contributes to water resources planning by providing projections on how flood risks in the region will change in the future under the impact of climate change.