Submitted to: International Soil Science Congress Proceedings
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/30/1998
Publication Date: N/A
Interpretive Summary: Soil erosion on upland areas is a complex phenomenon involving detachment and transport of soil particles, storage and runoff of rainwater, and infiltration. The relative magnitude of these processes depends on the antecedent conditions and scale of operations. A series of experiments was conducted to determine the soil loss and runoff response on a small upland area of 0.6 m by 3.75 m to different rainstorm regimes, overland flows, slope steepnesses, subsurface water pressures, and surface roughness under controlled laboratory conditions using a flume and rainfall simulator as water applications and a laser microreliefmeter and tensiometric system as soil response measuring devices. The soil chosen was a Glossic Fragiudalf, a highly erodible silt loam. The results show: 1) a sequence of rainstorms of decreasing intensity cause more soil loss than a sequence of similar storms of increasing; 2) for situations with high flow rates soil loss is not necessarily positively related to slope steepness; 3) subsurface soil water pressure substantially affects sediment concentration in runoff but impacts only marginally the runoff amounts; 4) smooth, uniform surfaces yield less soil loss than rough surfaces; 5) interrill runoff occurs as spatially varying flow which flow patterns determine the locations of rills.
Technical Abstract: Soil erosion on upland areas is a highly complex phenomenon impacted by a multitude of conditions and factors. Under field conditions many of these factors are operative at the same time and the relative significance of each one of them is difficult to assess. With the ever higher standards and demands for more effective erosion and runoff control, it is necessary to obtain a better insight concerning the relative importance of each one of these factors. This information would allow the selection of more effective control measures. Three important factors were considered in this highly controlled laboratory study: the nature of the rainfall intensity regime, the degree of surface roughness, and the effect of subsurface soil water pressures on sediment production. The results indicate that all three factors appreciably affect soil loss. A sequence of four 45 mm rainstorms of decreasing intensity causes appreciable more soil loss than a sequence of rainstorms of increasing storm intensity. Secondly and contrary to expectations, uniform smooth surfaces yielded less soil loss than the rough surfaces. Thirdly, negative soil water pressures substantially affect sediment concentration in runoff. These results will be very helpful in improving soil loss prediction and control technologies.