The control of resuspension over megaripples on the continental shelf

The simultaneous measurement of suspended sand concentration profiles (by acoustic backscatter) and the evolution of the bed forms (using fan-beam and pencil-beam sonars) on the continental shelf during a tropical storm has offered a opportunity to investigate the influence of bedforms on the suspension process. The reference concentration, C-0, during the storm increased rapidly for the first 20 hours but then remained approximately constant although wave heights continued to increase (for a further 30 hours). The time at which C-0 stopped increasing corresponded to the beginning of the reconfiguration of the sea bed suggesting that the bed form (orbital megaripples) changes may acting to reduce the suspension process. If generally true, then the suspension (and transport?) over sea beds in equilibrium with the waves (the orbital ripple condition) maybe be significantly less than that over non-equilibrium ripples, under the same wave conditions. The suspension profiles over the bedforms were also observed to depend on the position of measurement, with the higher concentration associated with the ripple troughs.