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 Depositing in or eroding from the Bay

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

Accounting rules Where: SF Bay from Mallard Island to Golden Gate When: Water years , , and a normal water year Lifeline: Conservation of mass: inflow-outflow=change in storage Uncertainty: varies by term, Not THE answer – Steve Ritchie

Odgen Beeman and Krone

New information for TermOBKNew information Supply from DeltaNo deposition in Delta Delta sediment outflow 1/3 of inflow Bathymetric change Data from navigation charts Data from actual surveys Sand miningAssumed zeroRough estimate

Revised annual budget Units are mass in millions of metric tons per year (~1.5 Mcy)

Revised annual budget Assume Krone Central Bay deposition is ocean sand

Revised annual budget Suspended sediment outflow from conservation of mass (lifeline)

Revised annual budget Sand mining is a very rough estimate

annual budget

Box model used to get change in storage and outflow

annual budget Assume no change in supply of ocean sand

was all wet

Normal annual budget Remove water years 1995 and 1998 where possible

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

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

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