|Gordon, Lee - UNIVERSITY OF BUFFALO|
|Bennett, Sean - UNIVERSITY OF BUFFALO|
Submitted to: International Symposium on Gully Erosion
Publication Type: Proceedings
Publication Acceptance Date: April 10, 2007
Publication Date: September 17, 2007
Citation: Gordon, L.M., Bennett, S.J., Wells, R.R., Alonso, C.V. 2007. Ephemeral Gully Headcut Development and Migration in Stratified Soils. Proceedings of the IV International Symposium on Gully Erosion. September 17-19, 2007, Pamplona, Spain, J. Casali and R. Gimenez (eds.). Public University of Navarre. p. 52-53. Interpretive Summary: Soil erosion and sedimentation by water are major problems that reduce cropland productivity, degrade water quality, and clog water conveyance structures. The present investigation sought to examine the effect of soil layering on the development and migration of headcut scour holes typical of agricultural fields. Laboratory experiments were performed to understand the role of erosion resistant layers at depth within the soil profile. When an erosion resistant layer was incorporated into the packed soil bed at a depth that exceeded an expected scour depth, the erosion and hydraulic processes of the migrating headcuts remained unchanged. When the erosion resistant layer was placed so as to intersect the potential headcut scour depth, the erosivity of the water was unable to erode this layer, and the depth of scour, the entry angle of the water, and sediment discharge all were reduced inversely proportional to the relative depth of the resistant layer.
Technical Abstract: Experiments were conducted to examine the effect of vertical stratification in soil erodibility on the development and migration of steady-state headcut scour holes in upland concentrated flows typical of agricultural fields. Packed soil beds with a pre-formed step were subjected to identical simulated rainstorms and clear-water overland flow rates, which resulted in predictable, actively migrating headcut scour holes with nearly identical characteristics. When an erosion resistant layer was incorporated into the packed soil bed at a depth that exceeded this expected plunge pool scour depth, the erosion and hydraulic processes of the migrating headcuts remained unchanged. When the erosion resistant layer was placed so as to intersect this potential headcut scour depth, the erosivity of the reattached wall jet was unable to erode this layer, and the depth of scour, the nappe entry angle, and sediment efflux all were reduced inversely proportional to the relative depth of the resistant layer. These data were successfully predicted using modified jet impingement theory for headcut scour holes, and demonstrate further the effects of soil management and tillage practices on total soil losses from agricultural fields.