Erosion Rate Estimates in Relation to Land-use Change: A Case Study in Samin Watershed, Central Java, Indonesia

Abstract

Soil erosion, as a critical land parameter, disrupts ecosystem balance. In alignment with Sustainable Development Goal 15 (life on land), mitigating land degradation is essential for maintaining environmental quality. Erosion estimations are empirically influenced by climate (R), soil properties (K), slope (LS), also vegetation cover and conservation practices (CP). Remote sensing is used to estimate soil erosion, a phenomenon where soil material is transported by surface runoff, influenced by land-use changes driven by human activities. This study applies Random Forest classification to assess land-use as a CP-factor in estimating erosion rates in the Samin sub-watershed for 2017 and 2024, integrating spectral values from Landsat-8 and physical characteristics from Alos Palsar DSM. Samin sub-watershed, located upstream of Bengawan Solo watershed in Central Java, Indonesia, is part of volcanic landform of Lawu Volcano. R-factor was calculated for two distinct periods to account for its dynamic nature. The results of the R-factor range from 151.548 to 197.175 MJ.mm/ha.hour, the K-factor ranges from 0.23 to 0.42, the LS-factor ranges from 0.01 to 56.58, and the CP-factor values extracted from land use range from 0 to 1. The smallest CP value indicates low erosion potential, while higher values correspond to greater susceptibility to erosion. RUSLE model for 2017 ranges from 0 to 1984.9 tons/ha/year, and for 2024 ranges from 0 to 1174.61 tons/ha/year. A Pearson correlation analysis between erosion rate and CP-factor extracted from land use classification yields a coefficient of 0.95, indicating that 90% of the variation in the erosion rate is influenced by land use changes. Land areas without vegetation cover have high erosion potential, while dense vegetation exhibits lower erosion potential. Vegetation cover reduces the impact of rainwater by dissipating its energy, retaining and absorbing water, and decreasing surface runoff.