The relationship of sediment transport rates and paths to sandbanks in a tidally dominated area off the coast of East Anglia, U.K.

Sand transport measurements of bedload and suspended load in the Sizewell-Dunwich Banks area, East Anglia have shown that the suspended mode is dominant The depth-integrated spring tidal residual is 5.66 g cm-1 sec-1 although the neap rate is only one of fifth of this. The calculated bedload transport rates also vary, from 0. 012 to 0.040 g cm-1 sec-1, correlating with changing meteorological conditions. In order to predict the bedload sediment circulation pattern from midwater current meter measurements, five sediment transport equations were calibrated, using fluorescent dyed sand Yalin's relationship gave the best estimates The bed shear stress was determined by extrapolating the velocity profile as a power law relationship, with an exponent equal to 0.1, from midwater down to 2 m and as a lognormal profile from 2 m to the sea-bed. Roughness length values appropriate to the substrate were used. Although bedload transport residuals are mainly to the south, the banks trend northwards from the coast and have also elongated in this direction. This is thought to be in response to the dominance of the suspended sediment transport it is suggested that a tidal residual eddy mechanism is responsible for the banks' maintenance, similar to the process operating in Start Bay, Devon. The well-documented westward movement of the banks is likely to be related to wave processes. [ABSTRACT FROM AUTHOR]