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United States Department of Agriculture

Agricultural Research Service

Title: Soil Detachment of Natural Undisturbed Soil by Shallow Flow

Authors
item Zhang, G - BEIJING NORMAL UNIV
item Liu, B - BEIJING NORMAL UNIV
item Nearing, Mark
item Liu, G - BEIJING NORMAL UNIV
item He, X - BEIJING NORMAL UNIV

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 5, 2002
Publication Date: N/A

Interpretive Summary: Soil erosion models are used to help land managers choose conservation practices and as engineering tools for designing dams, reservoirs, channels, and other engineering structures. Recently, more work has been done to develop process-based soil erosion prediction tools, primarily because they provide us with much more information than do older, statistically based models of erosion. Whereas older models, such as the Universal Soil Loss Equation (USLE), provided only information on soil loss, process based models such as the Water Erosion Prediction Project (WEPP) model provide detailed information on exactly where and when the soil erosion occurs, how much surface water runs off the land during storms, and where the sediment ends up after a storm. However, in order to use such models we must have basic information on how soils erode. This study was undertaken to evaluate the difference in basic rates of soil erosion for soil in the undisturbed state relative to disturbed condition. The purpose is to find out what happens to the susceptibility of soil to erode if it is left in a natural state as opposed to a state of frequent disruption, such as occurs during many farming operations. The results have significant implications for using process-based soil erosion models, and in particular relative to US conservation programs that are based in part on returning land to an undisturbed or natural condition.

Technical Abstract: 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 evaluate the influence of flow discharge, slope gradient, flow velocity on detachment rate and to investigate the relationship between detachment rate, shear stress, stream power, and unit stream power using natural undisturbed loess soil. Flow rate ranged from 0.25 to 2.0 l/s and slope gradient ranged from 8.8% to 46.6%. The literature data sets were selected to analysis the necessity of using natural undisturbed soil to simulate detachment process. The results indicated that randomness existed in the results of detachment rate by using disturbed soil. Some soil physical properties were destroyed during the process of soil sample preparation, thus increase the detachment rate for 1 to 23 times. Therefore, natural undisturbed soil sample was necessary for real detachment rate measurement. Detachment rate increased with both increasing of flow rate and slope gradient. Detachment rate increased as simple linear function as flow rate increasing, however, relationship between detachment rate and slope gradient was depended upon flow rate. The influence of flow rate and slope gradient on detachment rate was not the same. Stepwise variable selection analysis indicated that detachment rate could be well predicted by a power function of flow rate and slope gradient (R2=0.96). Mean flow velocity was close correlated to detachment rate (R2=0.91). Flow detachment rate was better correlated to a power function of stream power (r2=0.95) than to functions of either shear stress or unit stream power.

Last Modified: 11/26/2014
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