Effect of sediment characteristics on erosion and deposition in ephemeral-stream channels / Влияние характеристик донных отложений на эрозию и отложение осадков в руслах временных потоков

This study of five semiarid valleys emphasizes the importance of physical properties of sediment in determining streamchannel shape and differences in the mechanics of erosion and deposition between areas. Prerequisites for selection of the five areas were a progressive decrease in the percent silt-clay in stream channels and banks, active aggradation or erosion within a reach of the stream channel, and nearly uniform lithology within each drainage basin. A comparison of the data obtained from each area demonstrates that in a drainage channel composed of fine-grained, highly cohesive sediment, deposition occurs on the sides of the channel as well as on the channel floor. The result is a reduction in the channel width-depth ratio across an aggrading reach. Vegetation seems to aid deposition by its rapid growth on recently deposited fine alluvium, but it is not the initial cause of aggradation. Bank caving yields only small amounts of sediment and, caved blocks are often nuclei for deposition along channel sides because of their resistance to disintegration. Degradation in the finer sediments is generally by upstream headeut migration. 
In contrast, those channels containing only small amounts of silt-clay are aggraded from bottom to top. No plastering of fine sediments on the banks occurs. Less vegetation grows on these poorly cohesive, highly mobile sediments. Headcutting occurs only where the coarser sediments are capped by a layer of fine material. In general, a break in the longitudinal profile of this type channel is quickly removed by channel degradation. Bank caving seems to supply more sediment to the stream load, for the blocks of poorly cohesive alluvium disintegrate upon impact. <...>