ABSTRACT

Many sandy shorelines along open coasts have relatively permanent configurations which often are the result of an equilibrium adjustment between the predominant swell waves, the predominant conditions of littoral sand movement and the rate of sand supply.

The sand movement along several stretches of equilibrium shoreline near Point Reyes was studied using two methods: (1) common techniques of tracing heavy minerals and (2) theoretical predictions based on swell data and diagrams of wave travel in shallow water. Patterns of heavy mineral distribution in the beach and offshore sands established that negligible net movement of sand occurs along the beaches and that no significant supply of sand is being added to the beaches at present. Analysis of the predominant littoral and offshore waves showed that the sand transportation which was anticipated on the basis of predicted currents generated by the predominant swell coincides with that indicated by the heavy mineral patterns.