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ARS Home » Southeast Area » Tifton, Georgia » Southeast Watershed Research » Research » Publications at this Location » Publication #151689
Title: Variable Rainfall Intensity Effects on Runoff and Interrill Erosion From Two Coastal Plain Ultisols in Georgia

Author
item FRAUENFELD, BERND - UNIV.AG.SCI.,VIENNA,AUSTR
item Truman, Clinton

Submitted to: Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/11/2003
Publication Date: 2/1/2004
Citation: Frauenfeld, B., Truman, C.C. 2004. Variable rainfall intensity effects on runoff and interrill erosion from two coastal plain ultisols in Georgia. Soil Science. 169:143-154.

Interpretive Summary: Predictions of runoff and soil losses could be improved if the effect of variable rainfall intensity during a storm was quantified. We quantified and compared effects of constant (Ic) and variable (Iv) rainfall intensity patterns on infiltration, runoff, and soil losses from a Tifton loamy sand and Greenville sandy clay loam. Each soil was placed in a 1-m x 1-m stainless steel erosion pan (Tifton=4% slope; Greenville=7% slope). Simulated rainfall was applied at a constant (2 in/h) and variable rainfall intensity pattern for 70 min. Maximum runoff for Ic and Iv events ranged from 45-49 mm h-1 and 83-99 mm h-1, respectively, and peak runoff for Iv events occurred 35-37 min before that of Ic events. Total and maximum soil loss values for Iv events were 20% to 2-fold and 16% to 3-fold greater than that for Ic events, respectively. Greenville was 75-97% more erodible than the Tifton.

Technical Abstract: Predictions of runoff and soil losses could be improved if the effect of variable rainfall intensity during a storm was quantified. We quantified and compared effects of constant (Ic) and variable (Iv) rainfall intensity patterns on infiltration, runoff, and soil losses from a Tifton loamy sand and Greenville sandy clay loam. Each soil was air-dried, sieved (19-mm), then placed in a 1-m x 1-m stainless steel erosion pan (Tifton=4% slope; Greenville=7% slope). Simulated rainfall was applied at a constant (57 mm/h) and variable rainfall intensity pattern for 70 min. Maximum runoff for Ic and Iv events ranged from 45-49 mm h-1 and 83-99 mm h-1, respectively, and peak runoff for Iv events occurred 35-37 min before that of Ic events. Total and maximum soil loss values for Iv events were 20% to 2-fold and 16% to 3-fold greater than that for Ic events, respectively. The Greenville was 75-97% more erodible than the Tifton. Variable rainfall intensity causes problems, conceptually and mathematically, when calculating interrill erodibility (Ki). With Iv events, Ki values were not solely a property of the soil, were not constant, and did not increase as soil loss increased. Maximum soil loss for both soils was up to 13 times greater than for steady-state soil loss values, yet Ki values for steady-state conditions were 3-5 times greater than those for maximum loss conditions. If Ki represents the susceptibility of a soil to erosional forces and given the fact that rainfall intensity distributions, runoff, and soil loss within a rainfall event vary, then, according to our results, Ki distributions within the same event should also vary.