Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/20/1997
Publication Date: N/A
Interpretive Summary: Soil erosion by water not only decreases land productivity in the eroding areas but also causes enormous economic damages in the downstream areas by silting up waterways and reservoirs which can lead to further flood damage. To control soil erosion and preserve our lands, predictive tools or models which can be used to lay out the best conservation plans must be developed. This study evaluated the effects of rainfall intensity, slope steepness, water runoff rate, and soil properties on soil loss from areas between furrows or rills. Results showed rainfall intensity, water runoff rate, slope steepness, and soil type had significant impacts on soil loss. A mathematical model or equation was developed from this study to describe the effects of rainfall intensity, water runoff rate, slope, and soil type on soil loss. Comparison between measured and model-predicted soil losses showed the model worked well in estimating soil loss. This result will provide useful information to model developers. With this information, they can develop better tools which can be used by land planners and soil conservationists to help farmers to lay out the best conservation plans.
Technical Abstract: The inclusion of a runoff parameter in interrill erosion models is important and useful because it reduces or eliminates the dependence of the interrill soil erodibility K sub i on the soil infiltration characteristics. The purposes of this study were to evaluate the effects of rainfall, runoff, slope, and their interactions on interrill erosion, and to develop a general model to better predict interrill sediment delivery. A complete factorial experiment with two soils (Cecil sandy loam and Dyke clay), four intensities (I = 42, 62, 78, and 90 mm h**-1), four slopes (S = 9, 18, 27, and 36 percent), and two replicates was conducted with runoff pans (0.4 by 0.2 m) under pre-wetted conditions. Results showed rainfall intensity I, unit discharge q, slope S, soil type, and their interactions had significant impacts on sediment delivery per unit area D sub i. Unit discharge provided the highest correlation coefficient with sediment delivery among these factors; however, neither discharge nor rainfall alone could adequately simulate sediment delivery. The equation D sub i = K sub i×I×q**1/2 × S**2/3 was proposed. The linear intensity term represents detachment of soil materials by raindrop impacts and enhancement of transport capacity of sheet flow, while the product of q**1/2 S**2/3 simulates sediment transport of the flow. Validation with an independent data set showed that the model-predicted soil erodibilities were closer to their intrinsic values, indicating that interrill erosion processes are adequately described with the proposed model.