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Proceedings of the U.S. Geological Survey (USGS) Sediment Workshop, February 4-7, 1997

SEDIMENT-TRANSPORT RESEARCH IN SAN FRANCISCO BAY

Schoellhamer, David H., U.S. Geological Survey, Placer Hall, 6000 J Street, Sacramento, CA 95819-6129
Cacchione, David A., U.S. Geological Survey, 345 Middlefield Road, MS 999, Menlo Park, CA 94025
Rubin, David M., U.S. Geological Survey, 345 Middlefield Road, MS 999, Menlo Park, CA 94025
Cheng, Ralph. T., U.S. Geological Survey, McKelvey Building, 345 Middlefield Road, Menlo Park, CA 94025
Dingler, John R., U.S. Geological Survey, 345 Middlefield Road, MS 999, Menlo Park, CA 94025
Jaffe, Bruce E., U.S. Geological Survey, 345 Middlefield Road, MS 999, Menlo Park, CA 94025
Stumpf, Richard P., U.S. Geological Survey, 600 4th Street South, St. Petersburg, FL 33701

San Francisco Bay is an urbanized estuary that has been affected by anthropogenic activities (Nichols and others, 1986). The U.S. Geological Survey began a broad program of scientific study in San Francisco Bay in 1968 (Cloern and others, 1994), and sediment chemistry and sediment transport have been and continue to be elements of this program. This abstract discusses present USGS sediment-transport research in the Bay, which includes analysis of time series of suspended-solids concentrations, remote sensing, particle-size analysis, bottom boundary layer processes, bedform migration, wetlands morphology, and changes in sedimentation rates. Another abstract in this volume discusses sediment chemistry research (Luoma, this volume).

Sediments are an important component of the San Francisco Bay estuarine system. Potentially toxic substances, such as metals and pesticides, adsorb to sediment particles (Kuwabara and others, 1989; Domagalski and Kuivila, 1993). The sediments on the bay bottom provide the habitat for benthic communities that can ingest these substances and introduce them into the food web (Luoma and others, 1985). Bottom sediments also are a reservoir of nutrients that contribute to the maintenance of estuarine productivity (Hammond and others, 1985). The transport and fate of suspended sediments are important factors in determining the transport and fate of constituents adsorbed on the sediments. In Suisun Bay, the maximum concentration of suspended solids usually marks the position of the turbidity maximum, which is a crucial ecological region in which suspended sediments, nutrients, phytoplankton, zooplankton, larvae, and juvenile fish accumulate (Peterson and others, 1975; Arthur and Ball, 1979, Jassby and Powell, 1994). Suspended sediments also limit light availability in the bay, which, in turn, limits photosynthesis and primary production (Cloern, 1987; Cole and Cloern, 1987), and deposit in ports and shipping channels, which must be dredged to maintain navigation (U.S. Environmental Protection Agency, 1992).

To determine the effects of wind waves, tidal currents, spring/neap cycle, watershed runoff, and other factors that affect suspended-solids concentration (SSC) in San Francisco Bay (Schoellhamer, 1996), a network of eight sites at which SSC is monitored has been established (Buchanan and Schoellhamer, 1996). Optical backscatterance sensors are deployed at two depths at each site, and measurements are automatically collected every 15 minutes. Water samples are collected periodically and analyzed for SSC, and the results of these analyses are used to calibrate the sensors. In addition to the continuous monitoring sites, which are located in relatively deep water (greater than 10 meters), instrument packages that measure current velocity, water depth, SSC, and wave properties have been deployed in relatively shallow waters (about 3 meters) of the Bay for periods of several weeks (Buchanan and others, 1996; Warner and others, in press).

The monitoring sites provide good temporal resolution but poor spatial resolution, so remote sensing techniques are being developed to map SSC distribution in the Bay. Satellite images for San Francisco Bay during 1994-96 were selected on the basis of hydrologic and meteorologic conditions and processed. The images show where SSC in the Bay and adjacent coastal waters was increased by floods in 1995. SSC data from the monitoring stations in the Bay and a semi-analytic method (Stumpf and Pennock, 1989) were used to relate satellite-observed reflectance to SSC.

Instrumentation is being developed and tested to measure the in-situ size distribution of suspended particles in the Bay, which are typically fine grained and flocculated (Krank and Milligan, 1992). A Laser In-situ Sediment Scattering Transmissometer (LISST, Agrawal and Pottsmith, 1994) from the Navy that is designed to record time series of particle-size distribution has been deployed once in San Francisco Bay and twice in San Diego Bay. During these deployments, independent measurements of SSC were made. Ralph Cheng has worked very closely with the manufacturer to process the LISST data. Thus far, only qualitative agreement between the LISST and independent measurements of SSC has been achieved. The LISST has potential for in-situ determination of sediment particle-size distribution, but it requires additional development. A LISST is being purchased to continue developing this capability and it will be tested initially in the lab.

Hydrodynamics is an important factor in determining the resuspension and transport of sediments in the Bay, so concurrent measurement of water velocity, water depth, and wave properties are often collected with SSC time-series data. Acoustic Doppler Current Profilers (ADCP) are used to collect velocity profiles either in the bottom boundary layer (Gartner and Cheng, 1996; Cheng and others, in press; Gartner and others, in press) or throughout the water column (Burau and others, 1993; Cheng and others, 1996). Point velocity meters are deployed (Cheng and Gartner, 1984; Buchanan and others, 1996) and also can be used to measure properties of wind waves in shallow water (Schoellhamer, 1995). The Geoprobe instrument tripod (Cacchione and Drake, 1979) contains several point velocity meters that are used to measure velocity profiles in the bottom boundary layer (Sternberg and others, 1986, Cacchione and others, 1996). Velocity and water-depth measurements are used to calculate horizontal, residual (tidally averaged) fluxes of suspended solids (Tobin and others, 1995; Lacy and others, 1996; Warner and others, in press), and bottom boundary layer measurements provide a better understanding of sediment resuspension and deposition (Cacchione and others, 1996; Gartner and others, in press). In addition, a numerical model of sediment transport in the Bay has been developed (McDonald and Cheng, in press).

Bedform migration is being studied in Central San Francisco Bay, initially with field surveys using side-scan sonar and sub-bottom profiler mapping. On the basis of side-scan sonar records (Rubin and McCulloch, 1979), the Geoprobe tripod (Cacchione and Drake 1979) with rotating side-scan sonar (Rubin and others, 1983) and an upward-looking ADCP will be deployed in a well-defined field of large sand waves off Tiburon in Central San Francisco Bay during summer 1997. The repeated side-scan sonar images will reveal the movement of sand ripples and sand waves, while the Geoprobe system will provide simultaneous measurements of water levels, currents, and suspended sediments. Bedform migration models of Rubin and Hunter (1987) will be tested with these data, and transport estimates for the region will be made.

In an attempt to recover some of the 95 percent of the San Francisco Bay tidal wetlands that have been converted to other land types since 1850 (Dingler, 1994), various Federal and State agencies have banded together to restore 350 acres of farm land to tidal wetland. Morphodynamic processes will be monitored to improve the design of future restoration sites. This information is provided by measuring sedimentation patterns and rates of change, geotechnical characteristics, and tidal-channel development within the restoration site and in the existing tidal wetland bayward of the site.

To study sedimentation processes at the decadal time scale, bathymetric surveys have been analyzed to determine spatial and temporal sedimentation patterns (Jaffe and others, in press). Bathymetric surveys of San Pablo Bay, a subembayment of San Francisco Bay, indicate that a reduction in riverine sediment supply (Oltmann, 1996) is reflected by a decrease in sediment volume (increasing water depth) during the latter half of the 20th century. In addition, the surface area of mudflats in San Pablo Bay is decreasing. Mudflats are shallow-water areas adjacent to wetlands that probably contribute sediments to wetlands.

Although the studies mentioned in this extended abstract pertain to San Francisco Bay, the techniques and findings of the studies are applicable to other sediment studies conducted by the USGS. Sediment erosion, transport, and deposition are of critical importance to a broad range of environmental and economic issues, many of which are addressed by the USGS: coastal erosion, reservoir sedimentation, pollutant transport, and the origin of sedimentary deposits, such as petroleum reservoirs. In addition to diverse projects in the USGS, industry, academia, and other federal and state government agencies are confronted with problems associated with sediment transport. Despite the importance of such projects, their success is often severely handicapped by a lack of ability to accurately measure and predict the rate and direction of sediment transport as a function of flow conditions, particularly where flow varies through time or spatially. Studies of sediment chemistry and of the effect of sediments and sediment chemistry on biological resources require knowledge of how sediments move in the environment.

References cited

Agrawal, Y.C., and Pottsmith, H.C., 1994, Laser diffraction particle sizing in STRESS: Continental Shelf Research, v. 14, no. 10/11, p. 1101-1121.

Arthur, J.F., and Ball, M.D., 1979, Factors influencing the entrapment of suspended material in the San Francisco Bay-Delta Estuary, in Conomos, T.J., ed., San Francisco Bay: The urbanized estuary: San Francisco, American Association for the Advancement of Science, Pacific Division, p. 143-174.

Buchanan, P.A., and Schoellhamer, D.H., 1996, Summary of suspended-solids concentration data, San Francisco Bay, California, water year 1995: U.S. Geological Survey Open-File Report 96-591, 40 p.

Buchanan, P.A., Schoellhamer, D.H., and Sheipline, R.C., 1996, Summary of suspended-solids concentration data, San Francisco Bay, California, water year 1994: U.S. Geological Survey Open-File Report 95-776, 48 p.

Burau, J.R., Simpson, M.R., and Cheng, R.T., 1993, Tidal and residual currents measured by an acoustic Doppler current profiler at the west end of Carquinez Strait, San Francisco Bay, California, March to November 1988: U.S. Geological Survey Water-Resources Investigations Report 92-4064, 79 p.

Cacchione, D.A. and Drake, D.E., 1990, Shelf sediment transport: An overview with applications to the northern California continental shelf, in LeMehaute, B., and Hanes, D., eds., The sea: New York, Wiley & Sons, Ocean Engineering Science, v. 9, p. 729-773.

Cacchione, D.A., Tate, G.B., Ferreira, J.T., Cheng, R.T., and Gartner, J.W., 1996, Measurements of flow and suspended particulate transport in a tidal boundary layer, San Francisco Bay, California: Eos, v. 76, no. 3, p. 32-33.

Cheng, R.T., and Gartner, J.W., 1984, Tides, tidal and residual currents in San Francisco Bay, California--results of measurements, 1979-1980: U.S. Geological Survey Water-Resources Investigations Report 84-4339.

Cheng, R. T., Gartner, J.W., Cacchione, D.A., Tate, G.B., 1996, An Observed Unusual Estuarine Flow Condition in South San Francisco Bay, California: Eos, v. 76, no. 3, p 33.

Cheng, R.T., Gartner, J.W., and Smith, R.E., in press, Bottom boundary layer in South San Francisco Bay, California: Journal of Coastal Research.

Cloern, J.E., 1987, Turbidity as a control on phytoplankton biomass and productivity in estuaries: Continental Shelf Research, v. 7, no. 11/12, p. 1367-1381.

Cloern, J.E., Luoma, S.N., and Nichols, F.H., 1994, United States Geological Survey San Francisco Bay program: Lessons learned for managing coastal water resources: U.S. Geological Survey Fact Sheet FS-053-95, 3 p.

Cole, B.E., and Cloern, J.E., 1987, An empirical model for estimating phytoplankton productivity in estuaries: Marine Ecology Progress Series, v. 36, p. 299-305.

Dingler, J.R., 1994, Coastal wetlands and sediments of the San Francisco Bay system: U.S. Geological Survey Fact Sheet.

Domagalski, J.L., and Kuivila, K.M., 1993, Distributions of pesticides and organic contaminants between water and suspended sediment, San Francisco Bay, California: Estuaries, v. 16, no. 3A, p. 416-426.

Gartner, J.W., and Cheng, R.T., 1996, Near bottom velocity measurements in San Francisco Bay, California: Proceedings of the Oceans 96 Marine Technology Society, IEEE meeting, Septembe 23-16, 1996, Ft. Lauderdale, Florida, p. 457-462.

Gartner, J.W., Cheng, R.T., Cacchione, D.A., and Tate, G.B., in press, Near bottom velocity and suspended solids measurements in San Francisco Bay, California: Proceedings of the XXVII International Association of Hydraulic Research Congress, San Francisco, California, August 10-15, 1997.

Hammond, D.E., Fuller, C., Harmon, D., Hartman, B., Korosec, M., Miller, L.G., Rea, R., Warren, S., Berelson, W., and Hager, S.W., 1985, Benthic fluxes in San Francisco Bay: Hydrobiologia, v. 129, p. 69-90.

Jaffe, B.E., Smith, R.E., and Zink, L., in press, Historical sedimentation and bathymetric change in San Pablo Bay: 1856-1983: US Geological Survey Open-File Report, 1 sheet.

Jassby, A.D., and Powell, T.M., 1994, Hydrodynamic influences on interannual chlorophyll variability in an estuary: Upper San Francisco Bay-Delta (California, U.S.A.): Estuarine, Coastal and Shelf Science, v. 39, p. 595-618.

Krank, K., and Milligan, T.G., 1992, Characteristics of suspended particles at an 11-hour anchor station in San Francisco Bay, California: Journal of Geophysical Research, v. 97, no. C7, p. 11373-11382.

Kuwabara, J.S., Chang, C.C.Y., Cloern, J.E., Fries, T.L., Davis, J.A., and Luoma, S.N., 1989, Trace metal associations in the water column of South San Francisco Bay, California: Estuarine, Coastal and Shelf Science, v. 28, p. 307-325.

Lacy, J.R., Schoellhamer, D.H., and Burau, J.R., 1996, Suspended-solids flux at a shallow-water site in South San Francisco Bay, California: Proceedings of the North American Water and Environment Congress, Anaheim, California, June 24-28, 1996.

Luoma, S.N., Cain, D., and Johansson, C., 1985, Temporal fluctuations of silver, copper, and zinc in the bivalve Macoma balthica at five stations in South San Francisco Bay: Hydrobiologia, v. 129, p. 109-120. McDonald, E.T., and Cheng, R.T., in press, A numerical model of sediment transport applied to San Francisco Bay, California: Journal of Marine Environmental Engineering.

Nichols, F.H., Cloern, J.E., Luoma, S.N., and Peterson, D.H., 1986, The modification of an estuary: Science, v. 231, p. 567-573.

Oltmann, R.N., 1996, Sediment inflow to the Delta from the Sacramento and San Joaquin Rivers: Newsletter of the Interagency Ecological Program for the Sacramento-San Joaquin Estuary, v. 8, no. 2, p. 22-23.

Peterson, D.H., Conomos, T.J., Broenkow, W.W., and Doherty, P.C., 1975, Location of the non-tidal current null zone in northern San Francisco Bay: Estuarine and Coastal Marine Science, v. 3, p. 1-11.

Powell, T.M., Cloern, J.E., and Huzzey, L.M., 1989, Spatial and temporal variability in South San Francisco Bay (U.S.A.). I. Horizontal distributions of salinity, suspended sediments, and phytoplankton biomass and productivity: Estuarine, Coastal and Shelf Science, v. 28, p. 583-597.

Rubin, D.M., and Hunter, R.E., 1987, Bedform alignment in directionally varying flows: Science, v. 237, p. 276-278.

Rubin, D.M., and McCulloch, D.S., 1979, The movement and equilibrium of bedforms in central San Francisco Bay: in Conomos, T.J., ed., San Francisco Bay: The urbanized estuary: American Association for the Advancement of Science, Pacific Division, p. 97-113.

Rubin, D.M., McCulloch, D.S., and Hill, H.R., 1983, Sea-floor-mounted rotating side-scan sonar for making time-lapse sonographs: Continental Shelf Research, v. 1, p. 295-301.

Schoellhamer, D.H., 1995, Sediment resuspension mechanisms in Old Tampa Bay, Florida: Estuarine, Coastal and Shelf Science, v. 40, p. 603-620.

Schoellhamer, D.H., 1996, Factors affecting suspended-solids concentrations in South San Francisco Bay, California: Journal of Geophysical Research, v. 101, no. C5, p. 12087-12095.

Sternberg, R.W., Cacchione, D.A., Drake, D.E., and Krank, K., 1986, Suspended sediment transport in an estuarine tidal channel within San Francisco Bay, California: Marine Geology, v. 71, p. 237-258.

Stumpf, R.P, and Pennock, J.R., 1989, Calibration of a general optical equation for remote sensing of suspended sediments in a moderately turbid estuary: Journal of Geophysical Research, v. 94, no. C10, p. 14,363-14,371.

Tobin, A., Schoellhamer, D.H., and Burau, J.R., 1995, Suspended-solids flux in Suisun Bay, California: Proceedings of the First International Conference on Water Resources Engineering, San Antonio, Texas, August 14-18, 1995, v. 2, p. 1511-1515.

U.S. Environmental Protection Agency, 1992, State of the estuary: Dredging and waterway modification: U.S. Environmental Protection Agency San Francisco Estuary Project, chap. 8, p. 191-215.

Warner, J.C., Schoellhamer, D.H., and Burau, J.R., in press, A sediment transport pathway in the back of a nearly semienclosed subembayment of San Francisco Bay, California: Proceedings of the XXVII International Association of Hydraulic Research Congress, San Francisco, California, August 10-15, 1997.

Autobiography for David Schoellhamer

I was a civil engineer with the WRD National Research Program 2/84 to 5/87, and I transferred to the Tampa subdistrict 6/87. I studied Coastal and Oceanographic Engineering at the University of Florida under the Graduate School Training Program 8/88 to 8/89. I was chief of Tampa Bay sediment resuspension and light attenuation project from 10/87 to 4/93. I transferred to the Califdornia district 4/93 where I am presently chief of San Francisco Bay suspended-sediment transport processess project.

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