Comparative impacts of the 1982-83 and 1997-98 El Nino winters on the central California coast

Although most indices suggest the 1997-98 El Nino-Southern Oscillation (ENS O) was more intense than the 1982-83 ENSO event, the coastline of central C alifornia sustained approximately $14 million in damages during the 1982-83 winter, more than double the economic impact experienced during the 1997-9 8 winter. We attribute the difference in coastal response to a combination of oceanographic and anthropogenic factors. During 1982-83, the large wave events tended to coincide with more southerly and higher velocity winds, in creasing set-up along the shoreline and beach erosion due to offshore-direc ted flow. These large wave events also occurred during very high tides, cau sing the waves to break closer to shore and to strike the coast with more e nergy, increasing their impact on coastal structures and property. During t he 1997-98 winter, however, the largest waves arrived during lower tides an d coincided with lower wind velocities. The northwesterly winds reduced set -up along the shoreline and caused net onshore flow, decreasing wave impact . Another important factor contributing to the disproportionate damage betw een the winters was the higher percentage of shoreline that had been armore d by 1997. Most areas significantly damaged in 1982-83 winter were protecte d by more substantial seawalls or revetments during the 1997-98 ENSO event. improving the understanding of variations in coastal response to extreme s torm events is essential to bolstering the resiliency of our coastal commun ities.