Impact of soil aggregates on the size selectivity of the sediment depositio- n process

Experiments were conducted to evaluate the impact of sediment concentration- , slope and discharge on sediment deposition rates, patterns and sediment sorting using well-aggregated sediment. Comparison of data from aggregated sediment with experimental data obtained using completely dispersed sediment shows that the aggregated sediment has an important influence on both sediment delivery ratio and deposition pattern. Large aggregates of low density are easily transported by rolling over the bed of the flume. These aggregates have a dispersed size distribution closely resembling the source soil material. This results in limited sediment sorting during transport over an area of net deposition. Furthermore, considerable quantities of organic matter, incorporated within soil aggregates, are deposited. Therefore, one may conclude that soil aggregates have an important impact on the transport of nutrients and contaminants by overland flow.