The South Coastal area of California includes all basins draining into the sea between Rincon Creek (Ventura County) on the north and the American part of Tia Juana Basin on the south, about 28,500 square kilometers. Annual runoff over the past three decades, and suspended load of the 1961-1962 season were determined for the Los Angeles, San Gabriel, and Santa Ana basins, 10,000 square kilometers constituting 35 per cent of the South Coastal area. Extrapolation suggests that 700,000,000 cubic meters of water with a suspended and dissolved load of 2,760,000 metric tons (2,760, 000,000 kilograms) is supplied annually to the ocean by southern California. Approximately 580,000 tons coarser than 64 microns forms beach and nearshore sediment. Estimated 1,640,000 tons, coarser t an 1 micron, are dispersed widely over the continental shelf and beyond. The remaining 540,000 tons finer than 1 micron could not be analyzed by existing techniques. Centrifuge concentration of marine waters and optical counts of mineral particles reveal fairly uniform suspension values of several milligrams per liter close to shore, decreasing to several tenths of a milligram at the shelf edge 70 miles offshore. Suspension grain sizes parallel this trend, grading from coarse silt nearshore to fine silt and clay at the shelf edge.

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