Study On Flow Erosivity Indicators for Predicting Soil Detachment Rate at Low Slopes

Soil detachment is known as an important process in soil erosion and its quantification is necessary to establish a basic understanding of erosion. This study was carried out to find the best flow erosivity indicator(s) for predicting detachment rate at low slopes. For this purpose, 12 experiments including 6 flow discharges (75, 100, 125, 150, 175 and 200 ml/s) and 2 slope gradients (1.5 and 2%) were performed. Accordingly, different stream powers less than 0.175 W m-2 were simulated. Soil detachment rate was related to flow depth, flow velocity, unit flow discharge, shear stress, unit stream power and stream power as erosivity indicators. The results showed that the relationship was more significant at slope 2% (R2 > 0.94) than slope 1.5% (R2 > 0.84). Among different indicators, flow velocity and unit stream power exhibited unlinear relationships as exponential, while the others showed linear ones. Considering flow depth, unit flow discharge and unit stream power a range of critical values were obtained at different slopes. It was found that for shallow surface flows, measurement of flow depth is difficult while, unit flow discharge can be measured, accurately. Finally, the finding of this research reveals that stream power is the best indicator for predicting soil detachment rate.