SOIL DETACHMENT BY SHALLOW FLOW AT LOW SLOPES

Detachment of soil particles by shallow surface flow is influenced by soil cohesion, soil aggregate properties, and hydraulic flow characteristics. This study was conducted to evaluate relationships between soil detachment rates, soil aggregate size, soil tensile strength, flow shear stress, and flow stream power. Detachment rates were measured in a hydraulic flume on three aggregate size classes of two soils. Tensile strength and wet aggregate stability were measured to characterize each aggregate class. Flow depths ranged from 0.5 to 2.0 cm and slopes ranged from 0.5 to 2%. Detachment rates increased with both increasing flow depth and increasing bed slope. Multiple linear regression analyses indicated that the logarithm of detachment rate vs. flow depth, slope, and either mean weight diameter or tensile strength were good models (R2 = 0.94 and 0.91, respectively) for predicting detachment rates. Detachment rate for a given soil material was not a function of either shear stress or streampower of the flow. The largest size class of aggregates were detached at a faster rate than the smaller two aggregate size classes.