RATES, PATTERNS, AND PROCESSES OF SEACLIFF EROSION IN SANTA BARBARA, CALIFORNIA

We use a time series of terrestrial LiDAR scans, wave pressure sensors, and sand level measurements over a two year period (2015-17) to gain a better understanding of short term erosion rates, patterns, and processes of seacliff erosion near Santa Barbara, Ca. Scans were taken following several El Nino storms to assess the impact of individual storms on coastal erosion. We find that where beaches are narrow and have lower elevations, the base of the seacliff is eroded uniformly along its length during high energy storms in the winter months, whereas the top of the cliff undergoes spatially variable failures in the following spring and summer months. At these sites, erosion rates of each the top, middle, and base of the cliff converged over the course of a year and ranged from 13-24 cm. At sites where beaches are wide and have higher elevations, wave energy was dissipated before it reached the cliff and no change occurred along the base of the cliff. At these sites, erosion rates at the top of the cliff are correlative with higher than average rainfall and range from 1-5 cm. Erosion rates are positively correlated with wave impact hours, significant wave height, and wave energy flux. However, significant variability exists between sites, suggesting that erosion at the base of the cliff is also dependent on the particle size distribution at the base of the cliff, fracture spacing and density, and the degree of weathering. This study implies that elevated water levels and narrower beaches from sea level rise will increase erosion rates at the base of seacliffs, which will subsequently induce more frequent cliff top failures along this section of the Californian coast.