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The impact of mobile disarticulated shells of Cerastoderma edulis on the abrasion of a cohesive substrate

The impact of mobile disarticulated shells of Cerastoderma edulis on the abrasion of a cohesive substrate
The impact of mobile disarticulated shells of Cerastoderma edulis on the abrasion of a cohesive substrate
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 transport pattern of the cockles was monitored. The release of bed material to the water column was monitored and compared to releases in the absence of shells (due only to the flow). The shells moved in traction; firstly as surface load (dragging) and then by rolling. The motion of the shells was found to be directly related to their motion settling rate in still water. The fluid induced stresses were unable to cause any detectable erosion of the bed. The addition of even single shells induced significant erosion. The erosion was found to be the result of abrasion rather than corrosion, 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 presence of large numbers of cockle shells in areas such as Southampton water and Lymington have suggested that the processes investigated here may be responsible for the erosion regimes in these areas.
corrasion, cohesive sediment, erosion
0160-8347
204-214
Thompson, C.E.L.
2a304aa6-761e-4d99-b227-cedb67129bfb
Amos, C.L.
d0a18a13-bccd-4fdc-8901-aea595d4ed5c
Thompson, C.E.L.
2a304aa6-761e-4d99-b227-cedb67129bfb
Amos, C.L.
d0a18a13-bccd-4fdc-8901-aea595d4ed5c

Thompson, C.E.L. and Amos, C.L. (2002) The impact of mobile disarticulated shells of Cerastoderma edulis on the abrasion of a cohesive substrate. Estuaries, 25 (2), 204-214.

Record type: Article

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 transport pattern of the cockles was monitored. The release of bed material to the water column was monitored and compared to releases in the absence of shells (due only to the flow). The shells moved in traction; firstly as surface load (dragging) and then by rolling. The motion of the shells was found to be directly related to their motion settling rate in still water. The fluid induced stresses were unable to cause any detectable erosion of the bed. The addition of even single shells induced significant erosion. The erosion was found to be the result of abrasion rather than corrosion, 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 presence of large numbers of cockle shells in areas such as Southampton water and Lymington have suggested that the processes investigated here may be responsible for the erosion regimes in these areas.

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Published date: 2002
Keywords: corrasion, cohesive sediment, erosion

Identifiers

Local EPrints ID: 12470
URI: http://eprints.soton.ac.uk/id/eprint/12470
ISSN: 0160-8347
PURE UUID: e7395dcf-1780-494a-bb98-b38aa354c7e4
ORCID for C.E.L. Thompson: ORCID iD orcid.org/0000-0003-1105-6838

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Date deposited: 18 Nov 2004
Last modified: 16 Mar 2024 03:14

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