Sie befinden Sich nicht im Netzwerk der Universität Paderborn. Der Zugriff auf elektronische Ressourcen ist gegebenenfalls nur via VPN oder Shibboleth (DFN-AAI) möglich. mehr Informationen...
Form drag is a major component of bed shear stress associated with tidal flow in the vicinity of an isolated sand bank, Torres Strait, northern Australia
Tidal current and elevation data were collected from five oceanographic moorings during October 2004 in Torres Strait, northern Australia, to assess the effects of large bedforms (i.e., sand banks) on the drag coefficient (
C
D
) used for estimating bed shear stress in complex shallow shelf environments. Ten minute averages of tidal current speed and elevation data were collected for 18 days at an on-bank site (<7
m water depth) and an off-bank site (<10
m). These data were compared to data collected simultaneously from two shelf locations (<11
m) occupied to measure regional tidal behaviour. Overall
C
D
estimates at the on- and off-bank sites attained 7.0±0.1×10
−3 and 6.6±0.1×10
−3, respectively. On-bank
C
D
estimates also differed between the predominant east–west tidal streams, with easterly directed flows experiencing
C
D
=7.8±0.18×10
−3 and westerly directed flows
C
D
=6.4±0.12×10
−3. Statistically significant differences between the off-bank and on-bank sites are attributed to the large form drag exerted by the sand banks on the regional tidal currents, and statistically significant differences between the westward and eastward flows is ascribed to bedform asymmetry. Form drag from the large bedforms in Torres Strait comprises up to 65% of the total drag coefficient. When constructing sediment transport models, different
C
D
estimates must therefore be applied to shelf regions containing steep bedforms compared to regions that do not. Our results extend the limited inventory of seabed drag coefficients for shallow shelf environments, and can be used to improve existing regional seabed mobilisation models, which have direct application to environmental management in Torres Strait.