Equilibrium Characteristics of Sand Beaches

Abstract

Theoretical developments utilize the equation of wave-induced motion of a discrete bed particle to develop a criterion for classifying sand beaches according to their tendency to aggrade or degrade under a given incident wave. Laboratory experiments show this criterion to be more dependable than the conventional separation of summer and winter profiles solely according to deep water wave steepness. The experiments also show the theory to provide reasonable quantitative equilibrium profiles in the zone offshore of appreciable breaker influence and to predict, with considerable assurance, the offshore limit of profile modification. The extent of the agreement between experiment and a theory based solely on bed load considerations indicates the importance of bed load mechanics in the determination of equilibrium beach characteristics at least in the offshore zone of profile modification. Bed load movement probably plays a relatively small role in the net sediment transport causing the profile modification.