Modelling the Impact of Climate Change on Flood Hazard in Rift Valley Basin of Ethiopia

Abstract

The increase of climate change-induced events, such as flooding, has intensified, particularly impacting developing countries over the last few decades. It is essential to develop flood hazard maps to identify and protect vulnerable regions. This will also help establish early warnings system execute both structural and non-structural measures effectively. The study area is the Rift Valley basin of Ethiopia, which has experienced 11 out of 15 recorded flood events in the past. The aim is to forecast the impacts of climate change on flooding, considering both present and future climate scenarios. Through the participatory approach by engaging stakeholders, this study evaluates the reliability of conventional flood risk assessment approaches. Primary and secondary datasets were acquired through field visits and from both non-governmental and governmental organizations. To achieve the objectives of the study, eight flood risk indicators namely, rainfall, DR, land elevation, slope, TRI, TWI, LULC, and soil type were chosen. Two climate scenarios namely SSP245 and SSP585 were used to project the near and far future rainfall based on CMIP6. The study makes use of three standout climate models namely, NoRESM2, CNRM-ESM2-1, and CanESM5. The AHP model and PGIS were used for relative importance analysis, including affected communities from Bilate, Kulfo Gina, Sile-sego, and Lake Hassa sub-basins. The finding revealed that in 2060, both SSP245 and SSP585 scenarios show an increasing trend in high and very high flood-risk areas, with SSP585 indicating a more considerable rise. By 2100, the spatial distribution of very high and high class concentrates in the northern and central parts, emphasizing greater risk under SSP585. Comparison with the baseline period reveals a spatiotemporal change, suggesting climate change's potential contribution to increased flood likelihood and extent in the Rift Valley basin