SOIL DETACHMENT BY SHALLOW FLOW

摘要

A precise understanding of soil detachment rates is necessary to establish a basic understanding of soil erosion and to develop a fundamentally based erosion model. This study was conducted to investigate the relationships between soil detachment rates and flow discharge, slope gradient, flow depth, mean flow velocity, shear stress, unit stream power, and stream power. A 5-m long × 0.4-m wide hydraulic flume with constant artificial roughness upstream of and surrounding the sample area was used. Flow discharge ranged from 0.25 to 2.0 L s -1 and slope gradient varied from 3.5% to 46.6%. The experimental results indicated that detachment rates increased with both greater flow discharge and slope gradient. Detachment rate was affected more by discharge than by slope gradient. The influence of slope gradient on detachment rate was greater at high slopes. The effect of flow depth on soil detachment rate was also dependent on slope gradient. Stepwise variable selection analyses indicated that detachment rate could be predicted by a power function of discharge and slope gradient (R 2 = 0.97). Substituting flow depth for discharge gave a poorer prediction (R 2 = 0.92). Mean flow velocity was more closely correlated to detachment than was any other hydraulic parameter (r 2 = 0.90). Flow detachment rates were better correlated to a power function of stream power (r 2 = 0.89) than to functions of either shear stress or unit stream power. The results of this study suggest that soil detachment by shallow flow is more closely related to flow energy than to shear stress