Bay Sediment Budgets:

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

• Entering the Bay
• Leaving the Bay
• Depositing in or eroding from the Bay

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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

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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-outflowchange in storage

• Uncertainty varies by term,
  Not THE answer Steve Ritchie

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Odgen Beeman and Krone 1955-1990
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New information for 1955-1990
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Revised 1955-1990 annual budget
Units are mass in millions of metric tons per
year (1.5 Mcy)
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Revised 1955-1990 annual budget
Assume Krone Central Bay deposition is ocean
sand
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Revised 1955-1990 annual budget
Suspended sediment outflow from conservation of
mass (lifeline)
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Revised 1955-1990 annual budget
Sand mining is a very rough estimate
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1995-2002 annual budget

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1995-2002 annual budget
Box model used to get change in storage and
outflow
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1995-2002 annual budget
Assume no change in supply of ocean sand
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1995-2002 was all wet
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Normal 1995-2002 annual budget
Remove water years 1995 and 1998 where possible
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1955-1990
1995-2002
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1955-1990
1995-2002
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1955-1990
1995-2002
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1955-1990
1995-2002
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1955-1990
1995-2002
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1955-1990
1995-2002
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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

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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)

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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