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Pacific Coastal & Marine Science Center

Coastal Processes

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Giant sand waves on the sea floor west of the Golden Gate, click for details
Giant sand waves on the sea floor west of the Golden Gate

Interesting facts from scientific papers in a special volume of the journal Marine Geology.

San Francisco Bay is the largest estuary on the California coast. (source)

Most of the sand in San Francisco Bay came from the Sierra Nevada. (source)

Hydraulic mining for gold in the Sierra Nevada from 1850 to 1900 added lots of sand and mud to San Francisco Bay. (source)

Local streams and rivers now supply over half the sand and mud entering San Francisco Bay. (source)

Sand moves from the Sierra Nevada, through the Delta, Suisun Bay, San Pablo Bay, Central San Francisco Bay, and Golden Gate, to the South Coast and offshore. (source)

Just outside the Golden Gate is one of the largest underwater sand wave fields in the world. (source)

Sand waves and dunes are common on the floor of Central San Francisco Bay. (source)

Sand moves from northern Ocean Beach, east through Baker Beach, through the Golden Gate to Crissy Field. (source)

Sand moves from offshore of Hunters Point in southeast San Francisco, north and west around San Francisco, to the Golden Gate and beyond. (source)

Sand moves from local rivers and creeks to South San Francisco Bay — and no farther. (source)

Sand moves from the Russian River south, around Point Reyes and offshore. (source)

Over 40% of California drains through San Francisco Bay. (source)

About 8 billion cubic meters (2 trillion gallons) of water move through the Golden Gate every day. (source)

Peak water flow through the Golden Gate is about 60,000 cubic meters per second (16 million gallons per second). (source)

On average, less than 1% of the water going through the Golden Gate is fresh water; 99% is from tides. (source)

90% of fresh water entering San Francisco Bay comes from the Delta. (source)

In dry months, salty ocean water can reach as far east as Suisun Bay, but in wet months only reaches San Pablo Bay. (source)

A major reduction in sand and mud from the Sierra Nevada is causing major erosion in San Francisco Bay, the South Coast, and offshore. (source)

The 1982-1983 El Niño floods permanently decreased the sand and mud entering San Francisco Bay. (source)

Sand and mud entering San Francisco Bay from the Delta will slowly decline. (source)

The highest shoreline erosion rates in California are just south of San Francisco. (source)

Since the 1980s, shoreline erosion has increased 50% between Ocean Beach and Point San Pedro. (source)

Over 200 million cubic meters (260 million cubic yards) of sand and mud were dredged or mined from San Francisco Bay in the 20th century. (source)

Mining and dredging remove more sand and mud than is coming into San Francisco Bay. (source)

During large storms, waves break on the sandbanks outside the Golden Gate and move lots of sand and mud offshore. (source)

Erosion of the sandbanks outside the Golden Gate changed ocean currents, affecting Ocean Beach erosion and accumulation. (source)

By 2050, 100-year storms could occur every year in the San Francisco Bay area due to climate change. (source)

By 2100, San Francisco Bay sea level could rise 1.66 meters (5.4 feet). (source)

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Adapted from:

Sediment transport in the San Francisco Bay Coastal System: an overview, Barnard, P.L., Schoellhamer, D.H., Jaffe, B.E., McKee, L.J., Marine Geology, 2013, http://dx.doi.org/10.1016/j.margeo.2013.04.005

Bedrock geology of the San Francisco Bay area: a local sediment source for bay and coastal systems, Elder, W.P., Marine Geology, 2013, http://dx.doi.org/10.1016/j.margeo.2013.02.006

Sub-tidal benthic habitats of central San Francisco Bay and offshore Golden Gate area - a review, Greene, H.G., Endris, C., Vallier, T., Golden, N., Cross, J., Ryan, H., Dieter, B., Niven, E., Marine Geology, 2013, http://dx.doi.org/10.1016/j.margeo.2013.05.001

Adjustment of the San Francisco estuary and watershed to reducing sediment supply in the 20th century, Schoellhamer, D.H, Wright, S.A., Drexler, J.Z., Marine Geology, 2013, http://dx.doi.org/10.1016/j.margeo.2013.04.007

Cross-validation of bedform asymmetry and modeled residual sediment flux to determine sediment transport patterns in the San Francisco Bay Coastal System, Barnard, P.L., Erikson, L.H., Elias, E., Dartnell, P., Marine Geology, 2013, http://dx.doi.org/10.1016/j.margeo.2012.10.011

Heavy mineral analysis for assessing the provenance of sandy sediment in the San Francisco Bay Coastal System, Wong, F.L., Woodrow, D.L., McGann, M., Marine Geology, 2013, http://dx.doi.org/10.1016/j.margeo.2013.05.012

Integration of bed characteristics, geochemical tracers, current measurements, and numerical modeling for assessing provenance of beach sand in the San Francisco Bay Coastal System, Barnard, P.L., Foxgrover, A.C., Elias, E.P.L., Erikson, L.H., Hein, J.R., McGann, M., Mizell, K., Rosenbauer, R.J., Swarzenski, P.W., Takesue, R.K., Wong, F.L., Woodrow, D.L., Marine Geology, 2013, http://dx.doi.org/10.1016/j.margeo.2012.11.008

Understanding processes controlling sediment transports at the mouth of a high-energetic inlet system (San Francisco Bay, CA), Elias, E.P.L., Hansen, J.E., Marine Geology, 2013, http://dx.doi.org/10.1016/j.margeo.2012.07.003

Changes in surf zone morphodynamics driven by multi-decadal contraction of a large ebb-tidal delta, Hansen, J.E., Elias, E., Barnard, P.L., Marine Geology, 2013, http://dx.doi.org/10.1016/j.margeo.2013.07.005

A step decrease in sediment concentration in a highly modified tidal river delta following the 1983 El Niño floods, Hestir, E.L, Schoellhamer, D.H., Morgan-King, T., Ustin, S.L., Marine Geology, 2013, http://dx.doi.org/10.1016/j.margeo.2013.05.008

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