Effect of soil texture, tailwater height, and pore-water pressure on the morphodynamics of migrating headcuts in upland concentrated flows

Rill and gully erosion in upland and agricultural areas can result in significant soil degradation worldwide, and headcuts are the primary mechanism by which this landscape dissection occurs. Experiments were conducted to further examine the morphodynamic behavior of actively migrating headcuts in upland concentrated flows with varying boundary conditions. The effect of soil texture greatly modified the erodibility of the select soils, and headcut migration rates, scour depths, and sediment discharges were correlated to the critical shear stress and erodibility of the select soils. The effect of increasing tailwater height greatly reduced the nappe entry angle at the brink of the headcut, completely arresting the soil erosion processes. Altering subsurface pore-water pressures markedly changed the erodibility coefficients of the select soil, which caused greater headcut migration rates and sediment discharges, yet shallower scour holes, in the presence of a subsurface water table. Current analytic formulations based on jet impingement theory successfully predicted these experimental observations, further demonstrating the utility of such analytic formulations in advancing watershed management technology.