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Pacific Coastal and Marine Science Center

Coastal Processes

Fine Sediment Transport

Color-shaded bathymetry maps of San Pablo Bay for 1856-1983; click to visit the source.
Color-shaded bathymetry maps of San Pablo Bay for 1856-1983.

These scientific papers describe the movement of fine sediments (particles smaller than sand: mud, silt, and clay) in San Francisco Bay.

Comparison of sediment supply to San Francisco Bay from watersheds draining the Bay Area and the Central Valley of California, McKee, L.J., Lewicki, M., Schoellhamer, D.H., Ganju, N.K., Marine Geology, 2013,

  • Fluvial suspended sediment loads to the tidal zone of San Francisco Bay
  • Suspended sediment loads in Central Valley Rivers vary 21-fold between years
  • Suspended sediment loads in small tributaries vary 53-fold between years
  • Step-changes in sediment loads between wet and dry periods were observed
  • Small tributaries covering 5% of the watershed area, supply 61% of the sediment.

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,

  • A conceptual model of the effects of increasing then decreasing sediment supply
  • Adjustment to decreasing sediment supply propagated downstream in the 20th century
  • Rivers and upper estuary adjusted to increasing supply quicker than decreasing supply
  • Adjustment to increasing supply was slower in the lower estuary than upstream
  • Step adjustments throughout the system may occur now only during greater floods

Simulating sediment transport processes in San Pablo Bay using coupled hydrodynamic, wave, and sediment transport models, Bever, A.J., MacWilliams, M.L., Marine Geology, 2013,

  • Coupled 3D hydrodynamic, wind wave and sediment model applied to San Francisco Bay
  • Model accurately predicts hydrodynamics, waves, and suspended sediment concentration
  • Sediment fluxes in the system result from a complex interaction of tides and waves
  • Including effect of wind waves on bed shear stress increased erosion rate on shoals
  • Wave height more sensitive than orbital velocity to water level during large waves

Does centennial morphodynamic evolution lead to higher channel efficiency in San Pablo Bay, California?, van der Wegen, M., Jaffe, B.E., Marine Geology, 2013,

  • The main channel in San Pablo Bay has narrowed over the past 150 years
  • We investigate the impact on channel efficiency by means of a 3D hydrodynamic model
  • Energy dissipation levels and sediment throughput have increased over 150 years
  • Estuarine, morphodynamic adaptation time scales may be in the order of centuries

Factors controlling floc settling velocity along a longitudinal estuarine transect, Manning, A.J., Schoellhamer, D.H., Marine Geology, 2013,

  • Presents new observations of floc properties throughout San Francisco Bay
  • Individual floc sizes & settling rates measured by a high resolution video system
  • Mass-weighted population mean settling velocity ranged from 0.5 to 10 mm/s
  • Macrofloc dynamics dominated San Pablo Bay; microfloc mass dominant in Central Bay

A sediment budget for the southern reach in San Francisco Bay, CA: implications for habitat restoration, Shellenbarger, G.G., Wright, S.A., Schoellhamer, D.H., Marine Geology, 2013,

  • Measurement of estuarine suspended-sediment fluxes in a tidal subembayment
  • High sediment concentrations at Dumbarton Narrows are decoupled from tributary inflow
  • The salinity field in the spring is a key control on sediment flux
  • Flux through the Dumbarton Narrows controls the sediment budget for this reach
  • Monte Carlo simulations are effective for quantifying uncertainty of flux estimates

Influence of history and environment on the sediment dynamics of intertidal flats, Jones, C.A., Jaffe, B.E., Marine Geology, 2013,

  • Three intertidal environments were studied with measurement and analysis tools
  • In the lowest energy environment, the critical shear stress prevents net erosion
  • Sediment properties have a strong relationship to morphologic trends and history

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,

  • In 1983 total suspended solids underwent a significant step decrease
  • After the step, TSS had a significant declining trend despite more high-flow events
  • The step decrease coincided with record discharge events following 1982-83 El Niño
  • The erodible sediment pool was flushed through the estuary in discontinuous pulses
  • It is likely that the upper estuary erodible sediment pool is currently depleted

Seasonal variations in suspended-sediment dynamics in the tidal reach of an estuarine tributary, Downing-Kunz, M.A., Schoellhamer, D.H., Marine Geology, 2013,

  • Measurement of suspended-sediment flux in the tidal reach of an estuarine tributary
  • During wet periods, this estuarine tributary is a net source of suspended sediment
  • During dry periods, this estuarine tributary becomes a suspended-sediment sink
  • Existing estimates of sediment supply are likely overestimates in this estuary
  • A quadrant analysis was developed to characterize sediment transport events


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