The Roles of Rainfall and Runoff in the Sediment Transport Capacity of Interrill Flow

Abstract

ABSTRACT Alaboratory study was conducted to examine the transport capacity of interrill flow. Experiments were performed in flows with and without rainfall to isolate the contributions to transport capacity from surface runoff and raindrop impact. Theory and measurement indicated that the runoff contribution was determined by discharge and bedslope. The transport capacity was greatly enhanced by raindrop impact, and the enhancement depended on rainfall intensity and bedslope. Rainfall momentum and kinetic energy fluxes were also significant in explaining the transport enhancement. Interrill transport capacity equations based on the separate runoff and raindrop impact contributions were developed. Simpler equations, with the two contributions lumped, were also investigated. Rainfall-disturbed flows were better able to transport the larger particles of the sediment mixture. However, observations of restricted flow competence suggested that the transport capacity of interrill flow is dependent on soil, as well as on hydraulic and rainfall properties.