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Coastal Morphology Group • Scripps Institution of Oceanography

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Sediment Budget

Dropcap The existence of a sandy beach depends on the balance between the power in waves and currents and the sediment available for transport. This balance or budget is calculated from the sediment flux contributions and losses to the cell.

Much like a bank account, there are deposits (sediment flux from streams), withdrawals (loss to shelf and submarine canyons), and the balance (sand in transport along the beach).

The boundaries of the littoral cell delineate the geographical area within which the budget of sediment is balanced.

Developing this inventory requires knowledge of the sources, transport mechanisms, and deposition rates for the region.

One of the most studied littoral cells in the world is the Oceanside Littoral Cell here in the San Diego region.

Transport rates in the Oceanside Littoral Cell vary with the wave climate. During dry La Niña periods, the average rate is 200,000 m3 (260,000 yd3) per year to the south. With El Niño conditions, a southerly shift in wave direction causes a reversal in transport, and net rates may range between 50,000-100,000 m3 (65,000-130,000 yd3) per year.

Streamflow and sediment flux data for streams entering the sea off the Oceanside Littoral Cell can be found in the interactive Watershed Map. These data for sediment supply to the cell are used in calculating the budget of sediment.

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Coastal Morphology Group • Scripps Institution of Oceanography

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