Effects of the Santa Cruz harbor on coastal processes of northern Monterey Bay,California

An average of 230,000 cubic meters of sand is provided to the beaches of northern Monterey Bay each year by littoral transport from upcoast and from local river input. Two jetties constructed as part of a small craft harbor interrupted the littoral flow of sand and significantly altered the area's natural coastal processes. A wide protective beach immediately formed upcoast against a formerly retreating beach cliff. Sand now filling the harbor mouth each winter has led to expensive yearly dredging as well as seasonally or permanently depleted downcoast beaches. Seacliff retreat, always a problem in the area, is caused primarily by surf attack of weaker stratigraphic units and erosion along joint sets and faults, causing collapse of the bluffs. The seasonal loss of protective beaches has led to a two- to three-fold increase in the rate of downcoast cliff retreat following harbor construction except where protective rip-rap has been emplaced by property owners.