The impact of mobile disarticulated shells ofCerastoderma edulis on the abrasion of a cohesive substrate |
| |
| Authors: | C E L Thompson C L Amos |
| |
| Institution: | (1) Environment Canada, 867 Lakeshore Rd., P.O. Box 5050, Burlington, ON L7R 4A6, USA |
| |
| Abstract: | An annular laboratory flume was used to investigate the effect of mobile cockle shells on the erosion of a cohesive sediment bed. A standard clay bed was created and shells of differing sizes placed upon it. Flow in the flume was increased in increments and the onset of motion and the transport patterns of the cockles were monitored. The release of bed material to the water column was monitored and compared to controls made in the absence of shells (due only to the flow). The shells moved as bedload; first as surface creep (sliding) and then by rolling. The onset velocity of motion (Uc) of the shells was found to be directly related to the settling rate (Ws) in still water. The fluid-induced stresses did not cause any detectable erosion of the bed. The addition of even a single shell induced significant erosion rates (E). The erosion was found to be the result of abrasion rather than corrasion, as the shells never entered into saltation. There was a linear increase in erosion rate with increasing shell size, and an exponential increase in the suspended sediment concentration with time. The drag coefficients (Cd) for settling in traction were calculated. The ratio of the drag forces acting on the shells when settling and moving as traction was found to equal to 1/tan(ф) where ф is the friction angle. |
| |
| Keywords: | |
| 本文献已被 SpringerLink 等数据库收录！ |
|
