Suspended sediment transport and nearshore bar formation on a shallow intermediate-state beach

Estimates of cross-shore suspended sediment flux were obtained during a 3-day storm event on the North Sea coast of Denmark. The suspended sediment flux estimates were correlated with volumetric beach change as registered at 28 permanently deployed survey rods crossing the intertidal beach and inner surf zones. During this storm, a nearshore bar initially migrated onshore and welded to the beach face at its updrift end; subsequently a new bar formed on the seaward slope of the former. Suspended sediment transport, recorded using optical backscatter sensors and electromagnetic current meters, corresponded well qualitatively with the morphological evolution; indications are that such measurements may account for a significant fraction of the actual cross-shore sediment transport. The onshore migration of the nearshore bar was the result of onshore directed mean currents associated with a cell circulation. Renewed bar formation took place when this circulation was (locally) replaced by an offshore-directed mean current (undertow). Suspended sediment transport due to oscillatory waves at incident and infragravity frequencies was generally subordinate to the mean transport. (C) 1998 Elsevier Science B.V. All rights reserved.