Assessment of erosion risk in the Porsuk River basin using remote sensing and GIS-based RUSLE method

The Porsuk River Basin, located in Northwestern Anatolia, is one of the most significant subbasins of the Sakarya Basin. This study aims to quantitatively determine soil erosion and analyze the spatial distribution of erosion-driving factors in the Porsuk River Basin using the RUSLE model integrated with Geographic Information Systems (GIS). According to the results, the basin experiences an average annual soil loss of 2.35 t ha⁻¹ yr⁻¹, corresponding to a total annual soil loss of 2,538,269.32 tons. Particularly in steeply sloped areas such as the Sündiken and Karlık Mountains, local erosion risk is considerably high. While the proportion of "Very Slight" and "Slight" erosion classes is 85.69% across the Sakarya Basin, this ratio decreases to 48.12% in the Porsuk Basin, indicating a greater erosion threat in comparison. The findings demonstrate that erosion risk at the basin scale is shaped not only by climate and topography but also by geological lithology, land use, and anthropogenic influences. Accordingly, the study provides a scientific basis for sustainable land management and erosion control strategies in the Porsuk River Basin, while also revealing that the integration of the RUSLE model with up-to-date satellite data is an effective approach for watershed-based environmental planning. By employing CHIRPS precipitation data, the ALOS PALSAR digital elevation model, and Sentinel-2 satellite imagery, erosion risk factors were calculated using recent and high-resolution datasets. Furthermore, unlike previous studies conducted at sub-basin levels, this research evaluates the entire Porsuk Basin from a holistic perspective. In this respect, it fills a critical gap in the literature and serves as a strong reference for both academic research and applied watershed management practices.