Evaluation of the impact of land use/cover change on potential soil erosion in Alto Molócuè Watershed - Mozambique

Abstract:

Soil erosion is a global environmental problem, which affects the sustainability and productivity of agriculture, the siltation of reservoirs, and the degradation of water quality. One of the main causes of soil erosion is the change of land use/cover in a region. During the last 20 years, a significant change in land use/cover and a considerable increase in soil erosion has been observed in Alto Molócuè watershed, but no studies have been done to quantify and map potential soil erosion and its driving factors. Many researchers evaluated the influence of a specific land use class on soil erosion; however, they did not consider the mathematical relationship between land use change and soil erosion. The objective of this study is to map soil erosion potential, and evaluate the impact of land use change (forest/shrub to agriculture/urban) on soil erosion and to develop a specific regression model to explain the dependence of soil loss and land use change. Landsat images from the years 1998, 2008 and 2018 were downloaded from Earth Explorer and processed in ArcGIS. Using Land Change Modeler tool from Terrset, it was possible to assess the accuracy of the image classification and the transition matrix to quantify land cover change over the 10-year periods. We used the Revised Universal Soil Loss Equation (RUSLE) to calculate and map annual soil loss and we classified the soil loss per land use in the study area. The accuracy of classification shows values of 87.9 %, 80.4 % and 85.2% with Kappa coefficient of 0.8, 0.85 and 0.97 for 1998, 2008 and 2018, respectively. The results showed a decrease in plant cover (11% in forest and 4% in shrubland), while on the other hand an increase in agricultural land and urban area (11% and 3%, respectively) occurred as shown below:

Mean annual soil erosion from RUSLE shows values of 0.93, 1.63 and 3.3 t/ha/year respectively for the years 1998, 2008 and 2018. Since data availability is a major problem in many developing countries, a specific regression model to explain change in land use and soil loss can be a starting point for future studies on soil erosion affected by land use.