Hydrophysical Approach to Soil Detachment and Sediment Transport by Overland Flows

摘要

The new equation of soil particles detachment based on hydrophysical approach is suggested. Soil detachment is proportional to the cubed flow velocity if it exceeds the critical value more than 1.6 times. In the field where flow velocity is close to critical value the detachment rate attains stochastic nature and is determined by the probability that instantaneous velocity create the shear stress which exceeds the resistance of soil particles protruded into water. Using a number of detachment tests for adjusting and verification of the model showed a satisfactory results. Coefficients of determination for different sets of data ranged from 0.98 to 0.99. In the field where flow velocity are much less than the critical value the extremely slow detachment of soil particles takes place too. It is probably due to decreasing of cohesion forces under ions exchange between water and soil. It was shown that hydrophysical approach is applicable to modelling of sediment transportation by water flow. The model was justified and verified on the sets of sediment transport data received under the wide range of slope (0.5%-35%) flow depth (0.5 cm - 4 cm) and sediment grain size (0.16 mm - 2.0 mm). The result of verification is good (coefficient of determination equals 0.98-0.99).