TIME SCALES OF NEARSHORE PROFILE CHANGES

William A. Birkemeier

Abstract


Time scales of nearshore profile change are examined using a unique set of highly accurate surveys collected over a 3% year period at CERC's Field Research Facility. The data are analyzed in terms of the formation and movement of the nearshore bars and with empirical eigenfunctions. The largest and most rapid changes in the profiles occurred during storms. The inner bar (depth of -0.6 to 1.5 m, 1.6 to 4.5 ft) moved offshore during even minor storms and recovered relatively quickly. The outer bar (depth of 3 to 4 m, 9 to 13 ft) formed during the largest storms and recovery was considerably slower, requiring six months or longer. The eigenvector analysis confirmed the importance of storms but identified a seasonal shift of material from the beach and inner bar to the offshore.

Keywords


profile change; time scale; nearshore profile

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