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ARS Home » Pacific West Area » Tucson, Arizona » SWRC » Research » Publications at this Location » Publication #161948
Title: RUNOFF AND SEDIMENT LOSSES FROM ROUGH AND SMOOTH SOIL SURFACES IN A LABORATORY EXPERIMENT 1591

Author
item GOMEZ, J. - INSTITUTO DE AGRICULTURE
item Nearing, Mark

Submitted to: Catena
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/21/2004
Publication Date: 12/1/2004
Citation: Gomez, J.A., Nearing, M.A. 2004. Runoff and sediment losses from rough and smooth soil surfaces in a laboratory experiment. Catena 59:253-266.

Interpretive Summary: Soil surface roughness may significantly impact runoff and erosion under rainfall. A common perception is that runoff and erosion are decreased as a function of roughness because of surface ponding and increased hydraulic roughness that reduces effective flow shear stress. The objective of this study was to measure the effects of initial surface roughness on runoff and erosion under controlled laboratory conditions. Initially rough and smooth surfaces were exposed to 5 simulated rainfall applications at 5% and 20% slopes. In all cases, runoff was delayed for the case of the initially rough surface, however, this effect was temporary. Overall, no statistical differences in either total runoff or erosion were measured on the 20% slope. At 5% slope, runoff was less on the rough surface for the first rainfall application, but greater on the final three, probably due to formation of a depositional seal in that case. This resulted in an overall insignificant difference in runoff for the sum of the five rainfall applications. Erosion was greater on the rougher slope at 5% steepness, probably due to concentration of flow as it moved around the roughness elements on the rougher slope. These results contradict commonly held perceptions of the impact of soil surface roughness on runoff and erosion.

Technical Abstract: Soil surface roughness may significantly impact runoff and erosion under rainfall. A common perception is that runoff and erosion are decreased as a function of roughness because of surface ponding and increased hydraulic roughness that reduces effective flow shear stress. The objective of this study was to measure the effects of initial surface roughness on runoff and erosion under controlled laboratory conditions. Initially rough and smooth surfaces were exposed to 5 simulated rainfall applications at 5% and 20% slopes. In all cases, runoff was delayed for the case of the initially rough surface, however, this effect was temporary. Overall, no statistical differences in either total runoff or erosion were measured on the 20% slope. At 5% slope, runoff was less on the rough surface for the first rainfall application, but greater on the final three, probably due to formation of a depositional seal in that case. This resulted in an overall insignificant difference in runoff for the sum of the five rainfall applications. Erosion was greater on the rougher slope at 5% steepness, probably due to concentration of flow as it moved around the roughness elements on the rougher slope. These results contradict commonly held perceptions of the impact of soil surface roughness on runoff and erosion.