Sand Level Changes on Torrey Pines Beach, California.

摘要

Three parallel range lines were established along a straight beach at Torrey Pines, California, and were surveyed at monthly intervals during June 1972 to May 1974. Offshore sand level changes were measured using reference rods placed in the bottom at selected stations on each range line. Beach profile measurements indicate that the beach underwent seasonal changes in configuration which are related to changes in the wave regime. During the summer months the beach profile progressively changed with the seaward progradation of the berm crest by sand accretion. This change was caused by onshore transport of sand from immediately offshore depths of less than -20 feet (-6.1 meters) relative to MSL. The transition from the summer to the winter beach profile was abrupt with the coincident occurrence of high waves and tides. Periods of high waves during high tides resulted in wave swash overtopping the berm crest and quickly eroding the beach. The rapid shoreward retreat of the berm crest caused by the offshore transport of sand was accompanied by a corresponding deposition of sand offshore at depths less than -30 feet (-9 meters) relative to MSL.