Coastal Design Criteria in Southern California

Southern California was subjected to a series of severe winter storms in 198 3 that caused record damages to the coast. In the aftermath of the storms, emergency repairs were made and new designs were developed that responded to the severe conditions. These designs were often considerably more conservative than those previously undertaken. Agencies, owners, and engineers were compelled to use both higher design criteria and longer recurrence intervals to account for the wave characteristics and water levels that caused damages along the coast. This paper briefly discusses the unusual circumstances of the storm conditions and the associated damages. The primary purpose of the paper is to present new data that incorporates the effects of the 1983 winter storms to estimate the change in perception of what the wave climate and design criteria may be in this highly developed coastline. The results indicate that the design wave height for a given recurrence interval has increased approximately 26 percent, the wave periods are longer than previously used, and the severe storms tend to coincide with the extreme water levels. The engineer should consider the impacts of the 1983 winter storms in future designs. Despite the record damages, many structures survived. Merely using the highest water elevations and most severe waves of record may not be the most prudent design criteria. The concept of project life and economics must be employed to develop a design.