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Summary of my Suspended Sediment Transport Research in San Francisco Bay David Schoellhamer U.S. Geological Survey.

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Presentation on theme: "Summary of my Suspended Sediment Transport Research in San Francisco Bay David Schoellhamer U.S. Geological Survey."— Presentation transcript:

1 Summary of my Suspended Sediment Transport Research in San Francisco Bay David Schoellhamer U.S. Geological Survey

2 Acknowledgements Greg Brewster, Paul Buchanan, Jay Davis, Judy Drexler, Amber Forest, Neil Ganju, Bruce Jaffe, Megan Lionberger, Michael MacWilliams, Andy Manning, Lester McKee, Tara Morgan, Cathy Ruhl, Rob Sheipline, Greg Shellenbarger, Brad Sullivan, Kathleen Swanson, John Takekawa, John Warner, Scott Wright, and more Funding: U.S. Army Corps of Engineers, SF Regional Water Quality Control Board, Interagency Ecological Program, California Coastal Conservancy, US Fish and Wildlife Service, USGS programs, and more

3 “Regional sediment management recognizes sediment as a resource.” 1)Erosion and deposition processes: is sediment suspended? 2)Fluxes: How much is sediment is moving? 3)Sources and sinks: Where is it coming from and going to? 4)Surplus and deficits: Is there too much or too little? 5)Information gaps: What are the greatest uncertainties?

4 Continuous monitoring of SSC present Processes

5

6 Erosion and deposition processes Point San Pablo, mid-depth Processes

7 Erosion and deposition processes Point San Pablo, mid-depth Semidiurnal tides Spring/neap cycle Lunar month Solstice/equinox Processes

8 Erosion and deposition processes Point San Pablo, mid-depth Flood Processes

9 Erosion and deposition processes Point San Pablo, mid-depth Wind wave resuspension Processes

10 Delta Outflow and SSC Processes

11 Connectivity of Central Bay to Delta Processes Bay Bridge Thank you CASCaDE colleagues

12 Connectivity of Central Bay to Delta Processes Bay Bridge Thank you CASCaDE colleagues

13 Naturally occurring maxima of suspended- sediment concentration Generally caused by convergent sediment transport or trapping Vary with spring/neap cycle and seasonally Estuarine Turbidity Maxima Processes

14 Freshwater sediment is flocculated Floc settling velocities Processes Andy Manning

15 Freshwater sediment is flocculated No concentration effect observed Floc settling velocities Processes

16 Freshwater sediment is flocculated No concentration effect observed Larger flocs settled at slack tide, sand in flocs Floc settling velocities Processes Slack tide

17 Freshwater sediment is flocculated No concentration effect observed Larger flocs settled at slack tide, sand in flocs Settling velocity correlates with 66 minute lagged tidal velocity (courtesy Michael MacWilliams) Floc settling velocities Processes

18 “Regional sediment management recognizes sediment as a resource.” 1)Erosion and deposition processes: is sediment suspended? 2)Fluxes: How much is sediment is moving? 3)Sources and sinks: Where is it coming from and going to? 4)Surplus and deficits: Is there too much or too little? 5)Information gaps: What are the greatest uncertainties?

19 Aquadopp ADCP DTS-12 Turbidity Probe with wiper Flux

20

21 Dumbarton Cumulative Sediment Flux Negative is flood tide direction (into far south SFB) Uncertainty analysis not completed, previously ±30-40% Flux

22 South Bay source and restoration sink Suspended-sediment flux into far SFB –Tributary input: 20,000 m 3 /yr –Past Dumbarton: 617,000 m 3 /yr Approximate time to fill subsided volume (32 Mm 3 ) –Tributaries input: 1,600 yrs –Past Dumbarton: 50 yrs Sources/sinks

23 Suspended Sediment Flux Measurements Flux, Sources/sinks

24 Sacramento River annual sediment yield >99% probability (p<0.01) of decreasing trends, both discharge bins Sources/sinks

25 Tidal creeks are a sediment sink Sources/sinks Relief map of the Corte Madera Creek watershed by Dewey Livingston Friends of Corte Madera Creek Watershed Corte Madera Creek gages

26 Normal annual budget Pacific Ocean is a large poorly quantified sediment sink Sources/sinks

27 “Regional sediment management recognizes sediment as a resource.” 1)Erosion and deposition processes: is sediment suspended? 2)Fluxes: How much is sediment is moving? 3)Sources and sinks: Where is it coming from and going to? 4)Surplus and deficits: Is there too much or too little? 5)Information gaps: What are the greatest uncertainties?

28 Point San Pablo, mid-depth, USGS WY1999: 36% step decrease in Bay SSC Surplus/deficit

29 Transport regulation Surplus/deficit

30 Supply regulation Surplus/deficit

31 Wetland sustainability and sea level rise Surplus/deficit Organic input Initial pore space Organic matter Pore space Surface cohort Buried cohort Processes: Decomposition Compaction Root growth Mineral input Inorganic material Revising Callaway model

32 Mudflat and marsh sustainability Where deposition does not keep up with sea level rise Mudflats lost, wave energy on shoreline increases, shoreline erodes Surplus/deficit 0.06 m SLR, CASCaDE

33 “Regional sediment management recognizes sediment as a resource.” 1)Erosion and deposition processes: is sediment suspended? 2)Fluxes: How much is sediment is moving? 3)Sources and sinks: Where is it coming from and going to? 4)Surplus and deficits: Is there too much or too little? 5)Information gaps: What are the greatest uncertainties?

34 Information gaps For a numerical model of San Francisco Bay sediment: Delta supply: direct measurement, future trend Local watershed supply considering tidal reaches Ocean exchange: Golden Gate flux Bottom sediment and variability Quantify erosion and settling Bed sediment dynamics Calibration/validation: flux more robust than concentration Vegetation: tidal marsh accretion, shoreline erosion Watersheds model, including Central Valley Describe connectivity of watersheds, estuary, and ocean Linkage to ecology and contaminants


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