SUSPENDED SEDIMENT TRANSPORT AND NEARSHORE BAR FORMATION ON A SHALLOWINTERMEDIATE-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 s ediment flux estimates were correlated with volumetric beach change as registered at 28 permanently deployed survey rods crossing the intert idal beach and inner surf zones. During this storm, a nearshore bar in itially migrated onshore and welded to the beach face at its updrift e nd; subsequently a new bar formed on the seaward slope of the former. Suspended sediment transport, recorded using optical backscatter senso rs and electromagnetic current meters, corresponded well qualitatively with the morphological evolution; indications are that such measureme nts may account for a significant fraction of the actual cross-shore s ediment transport. The onshore migration of the nearshore bar was the result of onshore directed mean currents associated with a cell circul ation. Renewed bar formation took place when this circulation was (loc ally) replaced by an offshore-directed mean current (undertow). Suspen ded sediment transport due to oscillatory waves at incident and infrag ravity frequencies was generally subordinate to the mean transport. (C ) 1998 Elsevier Science B.V. All rights reserved.