PREDICTING SOIL DETACHMENT FROM HIGH-DISCHARGE CONCENTRATED FLOW

Abstract

Field experiments were conducted on a loam and a silt loam soil to determine the effect of tillage on soildetachment in concentrated flow channels carrying high discharge rates. Soil detachment rates from tilled channels werean order of magnitude greater than rates from no-till channels. Based on a linear constant-parameter soil detachmentmodel, soil erodibility was seven times greater for tilled soil than for no-till, while critical shear values for no-till wereabout twice that for tilled soil. The coefficient of determination for the soil detachment models improved when soilerodibility and critical shear were related to field measurements of a soil strength index, measured by a fall conepenetrometer and a vane shear device. The fall cone index resulted in better model fits (greater R2) than the vane shearindex for modeling soil erodibility and critical shear. Both linear and exponential equations were used to model soildetachment rates. An exponential equation with detachment related to excess shear, which has both soil erodibility andcritical shear as linear functions of soil strength, is the recommended form for modeling soil detachment from highdischarge concentrated flow.