Session6: Water-related Disaster Risk Reduction
Title: HYDRAULIC CONDITIONS FOR RILL INITIATION ON STEEP SLOPES
Seung Sook Shin, Sim Young Ju, Park Sang Deog
Rill erosion occurs frequently on steep slopes of development sites with disturbed surface soil. In other to understand the characteristics of the rill initiation, rainfall simulation was conducted in soil box where the inflow water is supplied at the top of the slope. The location and shape of the rill initiation were influenced by rainfall intensity, inflow rate, surface runoff rate, slope, hydraulic characteristics of surface runoff. When rainfall and inflow water generate simultaneously into soil, surface soil was formed newly as it undergoes a constant transport and deposit process. The rill initiation began when the shear velocity of the surface runoff exceed the critical shear velocity. As the slope steepness increased, the location of the rill initiation moved to the upslope, and the formation of rill deepened and widened. Sediment yield including rill erosion increased remarkably with increase of surface runoff and flow velocity.