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ARS Home » Midwest Area » West Lafayette, Indiana » National Soil Erosion Research Laboratory » Research » Publications at this Location » Publication #80694
Title: LANDSCAPE POSITION, SURFACE HYDRAULIC GRADIENTS AND EROSION PROCESSES

Author
item GABBARD, DANIEL - PURDUE UNIV., W. LAF, IN
item HUANG, CHI-HUA - PURDUE UNIV., W. LAF, IN
item Norton, Lloyd
item STEINHARDT, G - PURDUE UNIV., W.LAF,IN

Submitted to: Earth Surface Processes and Landforms
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/21/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Soil surface condition, especially how water flows in and out of the soil, at different locations of a hillslope may have a profound effect on the dominant erosion processes. A laboratory study was designed to recreate the hillslope hydrologic condition and quantify its effects on erosion for a Glynwood clay loam soil. A 5-m long, 1.2-m wide soil pan was constructed for this study. Different combinations of slope steepness with seepage or drainage gradients were used to simulate the hydrologic conditions on a 5-m segment of a hillslope profile. Results showed that, under drainage conditions, interrill processes dominated and rilling was limited. After the run, the surface contained scattered crescent-shaped pits. Under seepage conditions, rilling processes dominated and caused severe erosion. Erosion rates increased by as much as 60 times under seepage conditions representative of the lower backslope when compared to drainage conditions that generally occur at the upper backslope. This indicated that rills and gullies on backslopes and footslopes may be catalyzed or enhanced by seepage conditions. This study improved our understanding of erosion processes at the landscape. This knowledge may lead to different management practices on hillslopes where seepage occur frequently.

Technical Abstract: Different hydraulic gradients, especially due to seepage or drainage, at different locations on a hillslope profile may have a profound effect on the dominant erosion processes. A laboratory study was designed to simulate hillslope processes and quantify effects of surface hydraulic gradients on erosion for a Glynwood clay loam soil (fine, illitic, mesic Aquic Hapludalf). A 5-m long, 1.2-m wide soil pan was used at 5 and 10 percent slopes with an external watering tube to vary the soil bed¿s hydrological conditions. Different combinations of slope steepness with seepage or drainage gradients were used to simulate the hydrologic conditions on a 5-m segment of a hillslope profile. Runoff samples were taken during rainfall-only and rainfall with added inflow. Results showed that, under drainage conditions, interrill processes dominated and rilling was limited. The surface contained scattered crescent-shaped pits after the run. Under seepage conditions, rilling processes dominated and the inflow introduced at the top of the soil pan further accelerated the headward erosion of the rills. Erosion rates increased by as much as 60 times under seepage conditions representative of the lower backslope when compared to drainage conditions that generally occur at the upper backslope. This indicated that rills and gullies on backslopes and footslopes may be catalyzed or enhanced by seepage conditions rather than form from flow hydraulic shear stress alone. An understanding of spatial and temporal changes that affect both hillslope hydrology and erosional processes is needed to develop accurate process- based erosion prediction models. This knowledge may lead to different management practices on landscape positions where seepage occurs.