Nearshore and Surf-Zone Morphodynamics: A Global Environmental Model for Predicting Hazards and Changes. Appendix 3. Beach and Surf Zone Equilibria and Response Times

摘要

Analyses were performed on a 6 1/2 year time series of daily wave data, daily beach state data and monthly beach and surf zone profile data. Beach state changes, which involve the relatively rapid redistribution of sediment already stored locally, are predictable in terms of Dean's simple parameter omega = H sub b/(w sub s T) where H sub b is breaker height, w sub s is sediment fall velocity and T is wave period. Each of the six beach states has a different equilibrium range of omega values and the direction of change (erosion or accretion) depends on the departure from the equilibrium association. Empirical eigenvector analyses performed on the profile data permitted separation of different response components. We infer that the fast response, and more predictable, components of beach and surf zone change largely involve smaller scale sediment exchanges between the beach and surf zone whereas the slower responses are related to larger scale exchanges between the surf zone and the inner continental shelf. (Reprints)