Modeling future flood frequency under CMIP5 Scenarios in Hare watershed, Southern Rift Valley of Ethiopia

Climate-related disasters like floods are one of the serious challenges, especially on economies and human life. Thus, this study aimed to model future flood frequency under CMIP5 scenarios in the Hare watershed important for sustainable flood management and preparedness. In this study, the projected climate sequences was used as input to soil water assessment tool (SWAT) to simulate projected changes in the watershed over the mid-term (2040–2069) and end-term (2070 2099) periods. The SWAT model was calibrated for the period (1994–1998) and validated for the period (1999–2001) using monthly stramflow data in the watershed. Flood frequency distribution (FFD) package was employed to analyze flood magnitude and frequency curves for future periods. The result of the SWAT model performance evaluation statistics for calibration showed high potential in the prediction of future streamflow. In the watershed, the maximum and minimum temperature is projected to increase by 0.75 to 2.86 °C and 0.68 to 2.46 °C, respectively. Similarly, the future mean annual precipitation is projected to increase by 2.94 to 20.35%. The projected change in monthly streamflow results shows an increasing trend by 7.5 to 64.9% and 25.8 to 75.9% in mid-term and end-term periods, respectively. The future annual peak flow shows an increasing trend by 82 to 114% in the mid-term and 107 to 135% in the end-term periods. Because of the impact of future climate change, the future design flood is expected to increase by 13.9 to 194.9% in the mid-term and 7.5 to 127% in the end-term periods. Future flood modeling provides valuable information to support flood risk management and reduce flood impact in the watershed. © 2021, Saudi Society for Geosciences.