Land-use and land-cover change and its impact on flood hazard occurrence in Wabi Shebele River Basin of Ethiopia

Land-use and land-cover (LULC) changes can impact hydrological conditions such as land surface coefficient, runoff, and infiltration. This study investigates the changes in LULC and its impact on water resources of the Wabi Shebele basin using the soil and water assessment tool (SWAT) and a separation method. Surface and groundwater parameters in the northwestern; and soil and surface parameters in the eastern highland and southern lowland parts of the basin are identified as sensitive parameters in water production. The coverage of cropland was increased by 48.63% while forest and woodland decreased by 49.14 and 14.76%, respectively, between the 1980s and 2010. Streamflow simulated during this period indicates increases in those watersheds showing significant cropland increases and forest coverage decreases particularly in Wabi at Dodola, Maribo, Robe, and Erer watersheds. Flood indices (i.e., AMAX, SMW, SMSp, and SMSu) calculated from simulated daily streamflow under different LULC map indicates an increase in the middle and northwestern watersheds up to 1.83 and 0.44%, respectively. The impact level of LULC change on flood discharge shows a comparable level with climate change impact on flood hazard particularly in the middle part of the basin.