Effect of land use-land cover and projected rainfall on soil erosion intensities of a tropical catchment in Sri Lanka

Soil erosion has become a severe environmental issue due to its detrimental effects on land productivity, agricultural production, hydropower generation and water quality. Land use-land cover and rainfall are two factors affecting soil erosion. This study estimated the spatial variation of soil erosion in the Nalanda Oya catchment in Sri Lanka using Revised Universal Soil Loss Equation (RUSLE) model supported with a GIS. The study assesses the changes in erosion with time in relation to the changes of land use-land cover and climate change impacted rainfall. The findings of the study would help on the land management to minimize erosion potential under changing climate. The mean annual soil loss value of the catchment is 2.99 t ha(-1) yr(-1), and the expected changes in land use-land cover and projected rainfall could increase the mean annual soil loss in 2030's to be 3.43 t ha(-1) yr(-1) and 3.66 t ha(-1) yr(-1) under Representative Concentration Pathway (RCP) 4.5 and RCP 8.5 scenarios, respectively. The results highlighted that about 18.78% of the catchment is under moderate to high (> 5 t ha(-1) yr(-1)) erosion risk which may increase to about 20.83% to 21.58% in 2030s, for RCP 4.5 and RCP 8.5, respectively. About 32% of the land area would show an increase in soil erosion mostly due to the climate change impacted changes in rainfall. Improving the land use to mitigate the increase in potential erosion may require reforestation and conservation practices, as a climate adaptation measure to protect sensitive ecosystems and ensure continued ecosystem services.