Spatio Temporal Analysis of the Effect of Slope Gradient on the Magnitude of Erosion and Deposition in the Endikat Watershed

Erosion is a natural process caused by rainfall (R), slope gradient (λ), slope length (LS), soil type (K), and changes in land cover. These factors drive the erosion of the surface layer of the soil, intensified by steep slopes and shifts in land use. The extent of this erosion has significant implications as it contributes to a reduction in the distribution of ecosystem services (ES) both spatially and temporally in various sub-watershed areas. To analyze the magnitude of erosion, modern methodologies including the Universal Soil Loss Equation (USLE) and the refinement, the Revised Universal Soil Loss Equation (RUSLE) have been adopted particularly focusing on the slope length (LS) factor for more accurate assessments. From this analysis and the direction of deposition spatially, the results can be used to assess and consider the actual value of ES in watersheds. The results can also be used for policy in decision-making, assessing the quality and quantity of water resources, as well as managing land resources better in an economically, environmentally, and socially beneficial manner. Therefore, this study aimed to analyze the classification of the magnitude of slope in the RLKSi equation to predict the estimated spatial pattern of both erosion and deposition as well as assess the level of vulnerability to soil loss in the Endikat sub-watershed which was upstream of the Lematang watershed. The equation used was SEDRET which included the level of soil resistance to the magnitude of soil loss (RUSLE) minus actual erosion (USLE). The results of the highest erosion value of 2,205.14 tons/Ha/year occurred in an area with slope of > 45% and soil type Association & yellow brown podzolic with shrub land use. Although the highest eroded retention rate of - 6,710.17 tons/Ha/year occurred on slope of 39.09% with yellowish brown podzolic soil type and dry agricultural land use. Additionally, the area experiencing the greatest sedimentation occurred on slope of 5.79% with Andosol Brown & Regosol soil types as well as shrub land use.