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Title: HYDROLOGICALLY DRIVEN MECHANISMS OF HEADCUT DEVELOPMENT

Author
item Romkens, Mathias
item PRASAD, S. N. - UNIV. OF MISSISSIPPI

Submitted to: International Journal of Sediment Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/30/2005
Publication Date: 9/30/2005
Citation: Romkens, M.J., Prasad, S. 2005. Hydrologically driven mechanisms of headcut development. International Journal of Sediment Research. 20(3):176-184.

Interpretive Summary: Overland flow erosion is a major cause of soil loss from field size areas. Most of the soil detached and transported down-slope from these areas originated from a succession of small headcuts that migrate up-slope. This article presents an analysis of headut growth as affected by overland and subsurface flow regimes for conditions when surface seals have formed during rainstorms. The analysis indicated that surface seal strength and hydraulic thrust primarily control headcut growth, but that the subsurface hydrology of the substrate for both the infiltration case through the vertical headcut as well as exfoliation (seepage) case are significant contributing factors. The analysis also indicated the need for improving our capability of analytically quantifying seepage flow.

Technical Abstract: This study concerns an analytic investigation of the effect of surface seal mechanical properties, overland flow, and subsurface hydrology on headcut development. It has often been observed that headcut growth rates on upland areas are quite small (less than 0.00015 meter per second) and that they occur in increments in which chips break off at points where cracks have developed in surface seals. The substrate soil under the seal collapses and is removed by the flow. This mode of headcut development is the result of a strong interaction between the surface and the subsurface processes. The surface process is energetically controlled by the mechanical features of the seal whereas the subsurface process is hydrologically controlled. The analysis yields estimates of the temporal scale of headcut velocities. In cases of infiltration from the vertical gully wall into the substrate, it was found that the flexural wave velocity (seismic sound velocity) inversely affects headcut velocity.