Experiments on sediment deposition by overland flow

Experiments were conducted to evaluate the influence of sediment concentration, slope and discharge on sediment deposition rates and patterns associated with a reduction in bed slope. Analysis of the data shows that up to a certain unit discharge a simple settling equation without a transport term gives a good prediction of the sediment delivery ratio and the grain-size distribution of the deposited and the exported material. Only when this critical unit discharge is exceeded do properties of the overland flow influence the sediment delivery outcomes. The presently available data do not allow the best model for predicting deposition rates in this domain to be identified, but clearly indicate the necessity of a threshold value in any transport or re-entrainment function which is used to model deposition.