Integrated Assessment and Mapping of Soil Water Erosion in a Tropical Urban Catchment Using Google Earth Engine: A Case Study of the Gourou Watershed (Abidjan, C？te d’Ivoire)
Water erosion constitutes a major threat to soil sustainability in tropical urban catchments exposed to intense rainfall and rapid urban expansion. This study assesses and maps soil loss in the Gourou watershed (Abidjan, C？te d’Ivoire) using the Revised Universal Soil Loss Equation (RUSLE) model implemented within the Google Earth Engine (GEE) platform. The methodological approach integrates multi-source data, including remote sensing products, insitu measurements (particle size analyses, permeability tests), and advanced spatial processing, to model the five RUSLE factors: rainfall erosivity (R), soil erodibility (K), topography (LS), land cover (C), and conservation practices (P). Results indicate an average annual soil loss of 50.20 t/ha/year—five times the tolerable threshold—and a total estimated loss of 132,286 tonnes/year. Erosion is exacerbated by high climatic erosivity (R: 950 - 1055 MJ·mm·ha？1·h？1·year？1), locally fragile soils (K up to 0.452), steep slopes (LS > 8), and dense urbanization (66.77% of the watershed). Critical erosion zones (>359 t/ha/year), concentrated in the southern and eastern sectors, result from the combined effects of steep terrain, highly erodible soils, and impervious surfaces. These findings highlight the effectiveness of the RUSLE-GEE approach for rapid, accurate, and reproducible erosion assessment in tropical urban environments.
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