EFFECTS OF LAND USE LAND COVER AND CLIMATE CHANGES ON SOIL EROSION IN LAGA ARBA WATERSHED, LOWER AWASH BASIN, ETHIOPIA

Abstract

Soil erosion is one of the major causes of soil degradation problems; which is sensitive in African countries including Ethiopia and Laga Arba watershed. This study was aimed to evaluate how soil erosion in watersheds is impacted by changes in land use land cover, and climate change. More specifically, this study was used to examine how future changes in rainfall will affect soil erosion, as well as to quantify and map the annual soil loss in the study area. GIS 10.4 software, and RUSLE model were used for analysis the rate of soil losses. K-factor of the study area was generated from the MoA. P-factor was generated from DEM and Landsat of the study area; whereas LS-factor was generated from DEM of the study area. The daily observed rainfall data were collected from meteorological stations, and projected bias corrected daily rainfall data were downloaded from MarkSim GCM model website. Then, both daily rainfall data were interpolated in ArcGIS 10.4 environment to output the rain erosivity (K-factor). Landsat TM of 1988 and 1998, Landsat ETM+ of 2008, and Landsat OLI of 2018 were used for the land use land cover classification. Then, LULC maps of the historical periods were delineated, and three land classes were identified for the land use land cover classification map. The four-land use land cover over all accuracy assessments were checked by using ground counter with classified lands. The land use land cover changes and matrices were evaluated for the periods of 1988, 1998, 2008, and 2018. The average rainfall erosivity is expected to increases by 13.45%, 14.80%, 14.91% and 21.54% under RCP 4.5(2040), 4.5(2070), 8.5(2040), and 8.5(2070) respectively. The estimated annual rate of soil loss was 19.66 ton-1 ha -1year in 1988, 20.45 ton-1 ha -1year in 1998, 20.85 ton-1 ha -1year in 2008, and 21.48 ton-1 ha -1year in 2018. And, the future average annual soil loss of study in RCP of 4.5 (2040), 4.5 (2070), 8.5 (2040) and 8.5 (2070) will be 22.23, 22.55, 22.57 and 24.14 ton-1 ha -1year respectively. Then, the rate of soil erosion is predicted to increase by 8.33, 9.89, 9.99 and 17.64% under RCP 4.5 (2040), 4.5 (2070), 8.5 (2040) and 8.5 (2070). Generally, land use land cover change increases soil erosion, future rainfall change was increased and soil loss estimated was high in all under impact of historical land use land cover and historical and projected rainfall.