Nearshore and Surf-Zone Morphodynamics: A Global Environmental Model for Predicting Hazards and Changes. Appendix 5. Morphodynamics of a Bar-Trough Surf Zone

摘要

A field study was made of the distinguishing morphodynamic operating in a surf zone which perennially exhibits accentuated bar-trough topography. Characteristic morphological features include a shallow bar with a steep shoreward face, a deep torugh, and a steep beach face. This morphology, which is favored by moderate breaker heights and small tidal ranges, strongly controls the coupled suite of hydrodynamic processes. In contrast to fully dissipative surf zones, the bar-trough surf zone is not at all saturated and oscillations at incident wave frequency remain dominant from the break point to the subaerial beach. The degree of incident wave groupiness does not change appreciably across the surf zone. Infragravity standing waves which, in dissipative surf zones, dominate the inshore energy, remain energetically secondary and occur at higher frequencies in the bar trough surf zone. Whereas the bar is highly mobile in terms of onshore offshore migration rates, the beach face and inner regions of the trough are remarkably stable over time.