Influence of Harbor Construction on Downcoast Morphological Evolution: Santa Barbara, California

Sand impoundment caused by construction of the Santa Barbara Harbor in the 1920s, created an erosion wave that impacted downcoast Carpinteria Beach. Historic beach and shoreline changes were analyzed to understand continuing erosion using a combination of historic air photos, lidar, and physical measurements. The long-term analyses show a clockwise rotation with erosion of –0.35 m/yr at the updrift end and accretion downdrift of 0.3 m/yr. Storm impacts measured before and after the 1982–83 and 1997–98 El Niño events show similar rotation patterns, providing evidence that El Niños may be driving coastal evolution. Differences in shoreline responses between El Niño events show that the erosion hotspot migrated downdrift following construction of a revetment after the 1982–83 storms. Seasonal field measurements in the winter show beach narrowing while sediment coarsen variably alongshore. The coarsest materials and erosion hotspot are co-located at the end of the revetment on the city beach.