Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 26, 2001
Publication Date: N/A
Interpretive Summary: This study was designed to better understand the basic physics of soil erosion by water. The objective was to determine how various factors such as energy and forces associated with flowing water cause soil particles to become detached. We measured the flow depth, velocity, slope, and quantity, and along with these factors we also measured the amount of soil eroded. The results showed that flow energy and flow velocity appear to be the critical factors that determine the rates of soil detachment by flow. These results will provide scientists information to build better technologies for assessing erosion rates, which in turn will help land managers make better decisions to help conserve America's soils. The impact will be an improved soil resource base for the country necessary for sustainable food production into the future.
Technical Abstract: Soil detachment is a fundamental soil erosion process. A precise understanding of soil detachment rate is necessary to establish a basic understanding of soil erosion and to the development of a truly 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 in a 5-m long and 0.4-m wide hydraulic flume with constant, artificial roughness upstream of and surrounding the sample area. Flow discharge ranged from 0.25 to 2.0 l s-1 and slope gradient ranged from 3.5% to 46.6%. The experimental results indicated that detachment rates increased with both the increase of flow discharge and slope gradient. Detachment rate was more sensitive to discharge than to slope gradient. The influence of slope gradient 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 well predicted by a power function of discharge and slope gradient (R2 =0.97). Substituting flow depth for discharge gave a poorer prediction (R2 =0.92). Mean flow velocity was more significantly correlated to detachment than was any other hydraulic parameter (r2 =0.90). Flow detachment rates were better correlated to a power function of stream power (r2 = 0.89) than to functions of either shear stress or unit stream power. The results of this study suggest that soil detachment by flow is more closely related to flow energy than to flow stress.