EXTREME SEA LEVELS ON THE COAST OF CALIFORNIA

Abstract

During the winter of 1982-1983, a combination of high tides, higher than normal sea level and storm-induced waves were devastating to the coast of California. Damage estimates for public and private property destruction in the coastal counties of California total over $100,000,000. Much higher than average sea levels played a very important contributory role in the flooding damage. This report describes and examines the oceanographic and meteorological conditions prevailing during winter 1982-1983, and attempts to put them into perspective using historical information at San Diego. Emphasis is placed on the processes and forces that contribute to extreme sea levels in the hope that better understanding of these and more complete information on historical extremes will help the engineer in design and in assessment of risk. The unusually high sea levels were due to a combination of higher than normal mixed layer temperature associated with a strong, 2-year El Nino, storm surge due to low atmospheric pressure and persistent onshore winds, and the cumulative effect of steady, "global" rise in relative sea level. Higher than average high tides coincided to an unusual extent with the peak sea levels reached during the numerous storms between November 1982 and March 1983. Important cyclical variations occur in California's tide regime and the consequences of these on extreme tides have not been considered previously.