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The Effects of Saltmarsh Vegetation on Drag Forces and Shear Stresses

Author(s): R. Malki; C. A. M. E. Wilson; J. Aberle

Linked Author(s): Jochen Aberle

Keywords: No Keywords

Abstract: Flow velocities through and over a common saltmarsh species; Spartina anglica (common cordgrass) were studied in a series of flume experiments. Three stem densities; 714, 1039 and 1624 stems m-2, two bed gradients; 1 in 300 and 1 in 1000, and a range of vegetation emergence levels ranging between 0. 3 3 and 1. 50 were selected. The se values were chosen within the ranges observed on the Llanelli saltmarsh (S. Wales, UK). The velocity profiles clearly illustrate the vegetation’s ability to reduce flow velocities within the canopy. A reduction was seen in drag coefficients with increasing projected areas of obstruction, regardless of the stem density, and this is attributed to higher cylinder wake interference effects. Turbulent shear stresses were also considered: form- induced stresses were relatively negligible over the flow depth for both submerged and emergent conditions, Reynolds stresses were considerably greater, particularly within the surface flow layer.


Year: 2007

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