Author(s): Sean J. Bennett; Carlos V. Alonso

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Keywords: Headcuts; jets; scour; soil erosion; turbulence; wall pressure

Abstract: Soil erosion remains the principle cause of soil degradation worldwide, and the development and migration of headcuts in rills, crop furrows, and gullies can significantly increase soil losses on hillslopes, upland areas, and agricultural fields. Experiments were conducted to define the time-mean turbulent flow characteristics within fixed headcut scour holes typical of upland concentrated flows and to assess the distribution of these flow and pressure parameters for discrete areas of the scour hole domain. These data show that: (1) flow within headcut scour holes is analogous to plane turbulent reattached wall jets; (2) turbulence maxima are associated with the jet entry, recirculation eddies, and flow reattachment; (3) turbulent velocities are distributed asymmetrically about the free jet axis within the scour hole; (4) turbulent velocities associated with the reattached wall jet display good similarity collapse when scaled with the jet entry velocity; and (5) distributions of wall pressure near reattachment agree well with a similarity argument derived for impinging jets. This study supports the use and application of a jet impingement approach for modeling flow and soil erosion in upland concentrated flows due to headcut development and migration. Moreover, it is suggested that velocity-gradient shear, turbulent shear, and near-bed pressure gradients all are involved in soil erosion within headcut scour holes.

DOI: https://doi.org/10.1080/00221686.2006.9521702

Year: 2006