BIOGEOCHEMICAL PROCESSES AND SOIL MANAGEMENT IMPACTS ON SOIL EROSION, SOIL/AIR/WATER QUALITY, AND GREENHOUSE GAS EMISSIONS
Location: National Soil Erosion Research Lab
Title: Raindrop and flow interactions for interrill erosion with wind-driven rain
Submitted to: Journal of Hydraulic Research IAHR
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 18, 2013
Publication Date: April 24, 2013
Citation: Erpul, G., Gabriels, D., Norton, L.D., Flanagan, D.C., Huang, C., Visser, S. 2013. Raindrop and flow interactions for interrill erosion with wind-driven rain. Journal of Hydraulic Research. DOI: 10.1080/00221686.2013.778339.
Interpretive Summary: Soil erosion by water is a major environmental problem in the World. Many rainstorms that cause water erosion also have strong winds that can blow the raindrops causing them to hit the ground at an angle. This angular impact can cause the detached soil particles to move either up or down a slope. We conducted a study in a wind tunnel equipped with a rainfall simulator and looked at slopes facing the wind and pointed away from it, and measured the amount of erosion coming off small soil pans during a simulated rain and wind storm. Using data from these experiments we were able to include wind velocity and slope direction in mathematical equations to improve a predictive model of soil erosion from rain and wind impacted slopes. The model gave much better results when these factors were added, compared to the normal way of just assuming that the raindrops hit the soil surface straight on. This research affects other scientists, university faculty, extension personnel, and soil conservation agency staff who use predictive models to estimate the amount of soil erosion from storms. The impact of this research is that we can provide decision makers more accurate modeling tools to predict water erosion from rainstorms that are influenced by wind.
Wind-driven rain (WDR) experiments were conducted to evaluate interrill component of the Water Erosion Prediction Project (WEPP) model with two-dimensional experimental set-up in wind tunnel. Synchronized wind and rain simulations were applied to soil surfaces on windward and leeward slopes of 7, 15 and 20%. Since WDR fall trajectory varied with differences in horizontal wind velocity, both magnitude of raindrop normal and lateral stresses on flow changed and a vector field was established at impact-flow boundary and differentially directed lateral jets of raindrop splashes with respect to downward flows occurred. To account for these differences, a vector approach with kinetic energy fluxes of raindrop splashes and flow were used instead of vector-free parameters of intensity and interrill runoff. When compared with original WEPP approach, these replacements resulted in greater correlations when predicting sediment rates, and using all experimental data the model coefficients of determination (r2) were 0.63 and 0.96, respectively.