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Bay Sediment Budgets: Sediment Accounting 101

Bay Sediment Budgets: Sediment Accounting 101. David Schoellhamer Megan Lionberger Bruce Jaffe Neil Ganju Scott Wright Greg Shellenbarger U.S. Geological Survey. NASA. A sediment budget describes the quantity of sediment. Entering the Bay Leaving the Bay

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Bay Sediment Budgets: Sediment Accounting 101

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  1. Bay Sediment Budgets: Sediment Accounting 101 David Schoellhamer Megan Lionberger Bruce Jaffe Neil Ganju Scott Wright Greg Shellenbarger U.S. Geological Survey NASA

  2. A sediment budget describes the quantity of sediment • Entering the Bay • Leaving the Bay • Depositing in or eroding from the Bay

  3. Who cares? • Dredgers: disposal of deposition in ports and channels • Regulators and dischargers: sediment associated contaminants and TMDLs • Restoration managers: deposition needed for restoration without eroding existing habitat

  4. Accounting rules • Where: SF Bay from Mallard Island to Golden Gate • When: Water years 1955-1990, 1995-2002, and a normal water year 1995-2002 • Lifeline: Conservation of mass: inflow-outflow=changein storage • Uncertainty: varies by term, “Not THE answer” – Steve Ritchie

  5. Odgen Beeman and Krone 1955-1990

  6. New information for 1955-1990

  7. Revised 1955-1990 annual budget Units are mass in millions of metric tons per year (~1.5 Mcy)

  8. Revised 1955-1990 annual budget Assume Krone Central Bay deposition is ocean sand

  9. Revised 1955-1990 annual budget Suspended sediment outflow from conservation of mass (lifeline)

  10. Revised 1955-1990 annual budget Sand mining is a very rough estimate

  11. 1995-2002 annual budget

  12. 1995-2002 annual budget Box model used to get change in storage and outflow

  13. 1995-2002 annual budget Assume no change in supply of ocean sand

  14. 1995-2002 was all wet

  15. Normal 1995-2002 annual budget Remove water years 1995 and 1998 where possible

  16. 1955-1990 1995-2002

  17. 1955-1990 1995-2002

  18. 1955-1990 1995-2002

  19. 1955-1990 1995-2002

  20. 1955-1990 1995-2002

  21. 1955-1990 1995-2002

  22. Implications • Sediments disposed of in the ocean may be needed to maintain and restore Bay habitats • The Bay bottom will continue to erode and supply legacy contaminants • Restoration sites will be depositional and may increase erosion elsewhere • Dredging, restoration, and water quality are connected by the sediment budget

  23. Most important and most uncertain terms • Golden Gate fine suspended sediment outflow (model because difficult to measure) • Golden Gate sand supply, 1.2-2.9 MMT/yr (Central Bay bathymetric change) • Eroded mass (new surveys, measure bed density) • Sediment supply from watershed (±25%)

  24. Acknowledgements • U.S. Army Corps of Engineers • SF Regional Water Quality Control Board • California State Coastal Conservancy • USGS Priority Ecosystem Science Program • USGS Federal/State Cooperative Program • Lester McKee • Patricia Chambers and Linda Wanczyk

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