Risk assessment of soil erosion with RUSLE using geographic information system and organic carbon and total nitrogen loadings of suspended sediment in Sogutlu Stream Watershed of Trabzon, Turkey

Erosion is a global problem that negatively affects the land structure, soil and crop productivity, water quality, and socio-economic stability of watersheds. Assessing the amount of soil loss and sediment delivery ratio (SDR) in a watershed is important for planning soil and water conservation efforts, as this information assists in evaluating erosion risk. In this study, soil loss and SDR values were determined in the Söğütlü Stream Watershed, and an erosion risk map was created. Using the RUSLE method in the ArcGIS program, the transported soil amount and SDR were calculated. Soil samples from the top 0–30 cm layer were collected from 123 points to calculate RUSLE-K. Annual suspended sediment (SS), organic carbon (C), and total nitrogen (TN) in SS were directly measured. Monthly water samples were collected from August 2019 to July 2020. The results showed an average soil loss of 1.91 tonsha⁻¹ year⁻¹,annual soil loss of 52,209.01 tonsyear⁻¹, an SDR of 0.43, and a sediment yield of 0.82. The estimated sediment reaching the streams was 22,449.87 tonsyear⁻¹, with C and TN calculated at 312.95 and 41.936 tonsyear⁻¹. The measured sediment was lower at 12,549.82 tonsyear⁻¹, with C and TN at 174.96 and 23.44 tonsyear⁻¹. The findings of this study hold significant suggestions for future studies on soil and water conservation using ARCGIS, offering guidance to reduce soil erosion and improve water quality.