Flood inundation mapping under climate change scenarios in the Boyo watershed of Southern Ethiopia

Abstract

This research aims to map flood inundated areas under changing climate in the Boyo watershed of Southern Ethiopia. A semi-distributed physically based Hydrologic Engineering Center-Hydrologic Modeling System (HEC-HMS) and Hydrologic Engineering Center-River Analysis System (HEC-RAS) were used to simulate the flood events and maps, respectively, for climate scenarios. The bias-corrected data of four climate models were used for the baseline (1976–2005), mid-term (2041–2070) and long-term (2071–2100) cycles under RCP4.5 and RCP8.5 scenarios. The 50- and 100-year return period flood events were generated from the baseline and future period streamflow data. The HEC-RAS model was used to simulate the inundation areas and depths from the flood events. The result exhibited that the average annual rainfall and maximum and minimum temperatures of the catchment will increase in the future with an increase in annual runoff. The severity of annual floods would increase in the future under RCP4.5 and RCP8.5 scenarios. Approximately, 193 ha of the study may be flooded with flood events having a return period of 100 years under the RCP8.5 scenario in the long-term period, which is an extreme case. The result is a benchmark to reduce the flood risk and management of floodplains in this watershed.

Assessment of surface water resource and allocation optimization for diverse demands in Ethiopia's upper Bilate Watershed

“…An ARCGIS 10.3 version and ARC HYDRO 10.3 version have been applied for stream delineation, which was an input for HEC-GeoHMS and terrain pre-processing. To process data in the watershed execution, create a Basin Models file, and import it into HEC-HMS, HEC-GeoHMS, and HEC-HMS have been utilized [ 21 , 22 , 29 , 30 ]. The assessed area's peak flow, peak time, and peak discharge volume were all determined using the HEC-HMS model.…”

“…The HEC-HMS (Hydrologic Engineering Centre - Hydrologic Modelling System) is a popular hydrological tool for simulating streamflow and runoff in river basins [ 21 , 22 ]. This hydrological model is essential for predicting rainfall-runoff processes, forecasting floods, and managing water resources in Ethiopia's UBW, where managing water resources is essential for agriculture, energy, and water supply.…”