| Sand moves along the coast of California, under the influence of waves, feeding California's intensively used beaches. The consequences of interrupting the "river of sand", or littoral drift, traveling along the coast are often adverse and detrimental to the adjacent shoreline.; The construction of coastal armoring structures has reduced the total sand supply to the Santa Barbara and Oceanside littoral cells by an estimated 20 percent (12,300 cubic yards per year) and 18 percent (2,750 cubic yards per year), respectively. Seacliff erosion plays an insignificant role as a source of sand for the Santa Barbara littoral cell in particular, both now and before armoring. The total amount of sand supplied to the beaches by seacliff erosion, whether under natural or actual conditions, is less than 1.0% of the total littoral budget. Seacliff erosion is, however, a significant contributor of sand to the Oceanside Cell. The erosion of the seacliffs and terrace erosion and gully enlargement provide 11.6 and 60.6 percent respectively of the overall sand supplied to this cell.; Sand budgets were developed for three of California's major littoral cells, the Santa Barbara, Oceanside, and Eureka cells. The Santa Barbara Cell is an ideal cell for using harbor dredging as a proxy for littoral drift and as a calibration or check point when developing a sand budget because of the four harbors placed throughout the cell. Littoral drift volumes for this cell are ∼300,000, ∼600,000, and ∼1,000,000 cubic yards annually at the Santa Barbara, Ventura, and Channel Islands/Port Hueneme harbors respectively.; The sand budget developed for the Oceanside Littoral Cell indicates that the majority of sand on the beaches emanates from local rivers, gullies and terrace degradation, and to a lesser extent, seacliff erosion. Net littoral drift at Oceanside Harbor is ∼220,000 cubic yards per year in a southerly direction.; Dredging of Humboldt Bay's bar and entrance channel indicate a littoral drift of ∼465,000 cubic yards per year for the Eureka Littoral Cell. This sand is dredged and deposited offshore effectively removing it from the littoral system. Most of the sand discharged by the Eel River, over 2 million cubic yards annually, is lost offshore to the continental margin or travels south around False Cape and Cape Mendocino eventually ending up on the Mattole and Mendocino submarine canyons. (Abstract shortened by UMI.)... |
