The nexus between land use land cover dynamics and soil erosion hotspot area of Girana Watershed, Awash Basin, Ethiopia

Abstract

Maintaining hilly agriculture and food security remains challenging due to the ongoing degradation of the land caused by soil erosion on Ethiopia's highlands. . Soil erosion is one of the major problems affecting land and water resources. With the increase of land-use change, erosion and soil degradation increase significantly, leading to a loss of fertile soil every year. This study was therefore designed to identify erosion hotspot areas and their spatial and temporal alteration with land use land cover (LU/LC) change in the Girana watershed to give an option to local government decisions makers towards watershed management strategies. An attempt was made to combine a set of factors such as topographic wetness index (TWI), soil type, land use (1989 and 2019), slope, rainfall, and gully locations using geographic information system (GIS) based multi-criteria decision analysis (MCDA) to achieve the stated objective. Criterion maps of each factor have been processed and the factors were weighted using analytical hierarchy process (AHP) based pair-wise comparison methods, and weights have been combined using weighted overlay analysis to obtain the final erosion hotspots areas of the two-time references (1989 and 2019). The result found that 0.01%, 8.01%, 84.06%, and 7.92% of the total area fall under highly sensitive, moderately sensitive, marginally sensitive, and currently not sensitive erosion risk zone respectively for the year 1989 and 0.06%, 17.42%, 80.88% and 1.63% of the total area fall under highly sensitive, moderately sensitive, marginally sensitive, and not sensitive erosion risk zone respectively for the year 2019. Parts of the area that are highly sensitive, and moderately sensitive to Soil erosion classes increased markedly for the last thirty years in the Girana watershed, as a result of the conversion of thousands of forest areas to cultivated land and residential area. Therefore an urgent soil conservation intervention in hotspot areas is compulsory in the Girana watershed.