Modeling the impacts of land use-land cover changes on soil erosion and sediment yield in the Andassa watershed, upper Blue Nile basin, Ethiopia

Understanding the impacts of land use-land cover (LULC) changes on soil erosion and sediment yield is necessary for watershed management planning purposes. This study was aimed at examining the impacts of LULC changes on soil erosion and sediment yield in the Andassa watershed during the past three decades and predicts the anticipated changes in the future. The hybrid land use classification technique for classifying time series Landsat images (1985-2015); the Cellular-Automata Markov (CA-Markov) model for prediction of the 2030 and 2045 LULC states; the Revised Universal Soil Loss Equation model for estimating the soil erosion rate; and the sediment delivery distributed model for sediment yield modeling were employed in the study. The different layers of the spatiotemporal changes on the LULC were used as the basis of analysis and the main factor for analyzing the changes in soil erosion and sediment yield over the period of analyses. The results showed that in the past three decades, cultivated land and built-up areas significantly increased while areas occupied by natural vegetation such as forest land, shrublands and grasslands dwindled at a rapid rate. The predicted results suggest continuation of the trend unless management interventions are made in the future. Consequently, the annual soil erosion rate has increased from 35.5 t ha(-1) year(-1) in 1985 to 55 t ha(-1) year(-1) in 2015, and sediment yield from 14.8 t ha(-1) year(-1) in 1985 to 22.1 t ha(-1) year(-1) in 2015. The model prediction suggests that the process of soil erosion and sediment yield from the watershed will continue to increase if the business as usual scenario of the land use is not changed in the next few decades. Despite the need for a planned use and management of the land resources in the watershed, the findings in this study also indicated a growing risk of sedimentation to power infrastructure in the upper Blue Nile basin.