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Simulated Small-Channel Bed Scour and Head Cut Erosion Rates Compared

Dep. of Soil and Atmospheric Sciences

R. L. Peyton

Dep. of Civil Engineering, Univ. of Missouri, Columbia, MO 65211

E. E. Alberts

USDA-ARS Cropping Systems and Water Quality Research Unit, Columbia, MO 65211

* Corresponding author ( snrzhu{at}mizzoul.missouri.edu).

ABSTRACT

Concentrated-flow erosion is often a major part of cropland erosion. The concentrated-flow processes of bed scour and head cut need improved characterization to better predict and prevent erosion. This study was conducted to compare the erosion rates due to simulated small-scale bed-scour (D_b) and head-cut (D_h) processes. A 6.4-m-long by 0.15-m-wide hydraulic flume was used to simulate concentrated-flow erosion on five Midwestern soils: Barnes (fine-loamy, mixed Udic Haploboroll), Forman (fine-loamy, mixed Udic Argiboroll), Mexico (fine, montmorillonitic, mesic Udollic Ochraqualf), Sharpsburg (fine, montmorillonitic, mesic Typic Argiudoll), and Sverdrup (sandy, mixed Udic Haploboroll). For slopes of 1.5, 3.5, and 5.0%, flow rates of 3.78, 5.67, 7.65, 11.34, and 15.12 L min^–1 were used to provide a range from low (0.5 Pa) to moderate (2.5 Pa) shear stresses (). Soil detachment rates are functions of slope, flow rate, and shear stress. Slope, flow, their squares, and the slope x flow interaction were highly significant predictors of D_b. Only flow, its square, and its interaction with slope were significant predictors of D_b. Nonlinear power regressions using as an independent variable were better predictors of detachment than simple linear regressions. Erodibility for the soils from this study does not relate well with soil erodibility calculated using the Universal Soil Loss Equation. Differences in the slope and intercept of detachment vs. exist among soils. The value of D_b was at least four times greater than D_b for all soils at equal slope and flow rate, indicating that head cutting is the main process of detachment for the conditions tested.

This work was conducted as a part of the Missouri Agric. Exp. Stn. Project 396 and the Missouri Engineering Exp. Stn. with partial financial support from a Missouri Dep. of Natural Resources grant (no. 88-2) and with additional support from the USDA-ARS. Submitted as no. 11931 in the Journal Series of the Missouri Agric. Exp. Stn.

Received for publication October 12, 1993.