|Franti, T - UNIV. OF NEBRASKA|
|Watson, D - FOX ENGR. ASSOCIATES|
Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 22, 1998
Publication Date: N/A
Interpretive Summary: Erosion that occurs in small gullies, called ephemeral gullies, has a major effect on our nations lands. Presently, we lack good soil erodibility information for predicting ephemeral gully erosion. This study was conducted to evaluate the feasibility of using field soil strength measurements to estimate erodibility of soils for estimating ephemeral gully erosion. If field measurements of soil strength could be used to estimate soil erodibility, estimates of ephemeral gully erosion could be made quickly and easily by field technicians, assisting farmers and ranchers in selecting practices to reduce soil erosion, and in targeting field areas for land treatment. In this study, soil erodibility was measured under controlled conditions at very high flow rates-near those that might be encountered under field conditions. Two devices were used-a fall cone device and a vane shear device. Treatments included conventional and chisel plowing and no till, the study was conducted on two soils in Iowa. An equation was developed to predict rill erodibility and critical shear based on measured soil strength by these two methods. These equations can be used in conjunction with field measurements of soil strength to estimate ephemeral gully erosion. These results are most important to federal agency personnel, and to other scientists evaluating techniques for estimating soil erosion.
Technical Abstract: Field experiments were conducted on two soils to determine the effect of tillage on soil detachment in concentrated flow channels having high discharge rates. Soil detachment rates from tilled soil were an order of magnitude greater than from notill. Based on a linear, constant parameter soil detachment model soil erodibility was seven times greater for tilled soil than for no-till, while critical shear values for no-till were about twice that for tilled soil. Soil erodibility and critical shear were related to field measurements of soil strength measured by a fall cone penetrometer and a vane shear device. The fall cone proved superior to the vane shear device for modeling soil erodibility and critical shear. Both linear and exponential functions to predict soil detachment rates were evaluated. An exponential function of excess shear, with soil both erodibility and critical shear as a linear function of soil strength is the recommended soil detachment model for high discharge concentrated flow.