Beach changes in the Oceanside Littoral Cell

The Oceanside Littoral Cell, extending about 80 km southward from Dana Point in Southern California to Point La Jolla, is one of the most extensively studied coastal regions in the world and among the first to be investigated regionally. It is clearly defined by prominent rocky headlands at either boundary with evidence that there is little sediment exchange with neighboring cells. It is maintained by episodic river borne sediment inputs and erosion from the bluffs that back the majority of the beaches. It also suffers episodic losses of sand from the flushing of a submarine canyon near its southern boundary. The cell contains several coastal lagoons, some with jettied entrances and some connected to the sea episodically, hi addition to these jetties, a system of jetties and breakwater extensions was constructed to protect an artificial harbor at the city of Oceanside, roughly in the middle of the cell. With the exception of these entrances, the cell consists of continuous beaches throughout its length. The paper describes the Oceanside cell geography, the near-coast geology that impacts the beach and the physical forces that result in beach changes. It then discusses the background variability of beach volumes and the positive and negative impacts of human activities on the variations. To accomplish this analysis, the cell is divided into a small number of subregions with similar characteristics and histories. There is limited use of conventional profiles in the discussion. Emphasis is placed on changes to the recreational beach asset, that which is exposed at low tide. Seasonal, long-term and human-induced changes are separated to the extent possible for each of the subregions. Maps and aerial photography are utilized to illustrate the significant attributes.