San Francisco Bay “Its All About the Sediment” Brenda Goeden San Francisco Bay Conservation and...
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Transcript of San Francisco Bay “Its All About the Sediment” Brenda Goeden San Francisco Bay Conservation and...
San Francisco Bay
“Its All About the Sediment”
Brenda GoedenSan Francisco Bay Conservation and Development Commission
San Francisco Bay
Approximately 54 Square Miles Today
• Two Major Fresh Water Rivers to the East:
Sacramento and San Joaquin
• Drain 40% of the state
1849 2100
Area subject to high tide with 16 inches of sea level rise
Current 100-year flood plain
Changed Situation
The New World: Sea Level Rise
Floods
Storm Surge
Shoreline and Beach ErosionShoreline and Beach Erosion
The New World: Sediment Deficit
Changed Situation
0
200
400
600
800
1000
1200
1400
1600
SS
C, m
g/L
1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
Point San Pablo, mid-depth, Dave Schoellhamer, USGS
Why Do We Care?
Shorelines LeveesHabitatSea Level Rise
What’s Changed?
The System?
Our Understanding of the System?
Sediment Rich Sediment Poor
1990/2011 San Francisco Bay
Historic marshes diked off
Historic beaches no longer connected
Watersheds channelized
Watersheds clogged with fine grain sediment
Sediment trapped behind dams
Shoreline developed
Water from Delta controlled
Oakland Museum Creek Guide
Sediment Supply Shift: from the Delta to local tributaries
Changed Situation
A Large Water A Large Water and Sediment-and Sediment-shedshed
Clemson University
Local Tributaries are Becoming Increasingly Important
Embayments: Erosional & Depositional
Fregoso, Jaffe, Foxgrover, USGS
South Bay - Depositional
San Pablo Bay - Erosional
Central Bay - Erosional
Ebb-Tide Delta Erosion
Dallas & Barnard, USGS
• Sediment Removal from system
• Changed wave refraction
• Erosion along outer coast
Sand mining removing sand
Patrick Barnard & Rikk Kvitek
Sand appears slow to replenish
Dredging Projects
✳ Federal Channels
✳ Ports
✳ Refineries
✳ Marinas
In-Bay Disposal Sites
In-Bay Disposal Sites✳ Alcatraz✳ San Pablo Bay✳ Carquinez Strait✳ Suisun Channel
Ocean Disposal Site
Dispersive In Bay sites
LTMS EIS/EIR
Carquinez San Pablo
Alcatraz
Ocean Disposal Removes Sediment from the System
Per
cen
t of
all
Dis
posa
l
FINAL EIS/EIRLTMS MANAGEMENT STRATEGY FOR THE
PLACEMENT OF DREDGED SEDIMENT IN THE BAY AREA
MONTEZUMAWETLANDS
MONTEZUMAWETLANDS
HAMILTON WETLANDS WITH BEL MARIN KEYS
PARCEL V ADDITION
SONOMA BAYLANDS
In An Ever Changing World “New” Issues to Contend With…
Habitat Restoration
and Maintenance
Dredging and Aggregate
Mining
Sediment Supply and
Demand
Regional Sediment Management Is…
The integrated management of littoral, estuarine, and riverine sediments to achieve balanced and sustainable solutions to sediment related needs.”
Regional sediment management recognizes sediment as a resource.
Sediment processes are important components of coastal and riverine systems that are integral to environmental and economic vitality.
NeedShorelines, Marshes and Beaches need sediment to keep up with sea level rise
PWA & PRBO in review
Walnut Creek
Ballona Creek
Flood Protection is a Key
Component in Regional Sediment
Management
Need to Find New Ways to Protect From Flooding and Support
Sediment Supply to Wetlands
and the Bay
To Respond to a Changing Bay, A New Approach and Much Coordination is Needed
New Areas to Consider Sediment Sources and
Sinks Flood Protection
Aggregate Mining
Dredging
Wetland Restoration
Beach Nourishment
Shoreline Protection
Local Tributaries Sediment Flow Analysis
Quantify local tributaries contribution to Bay sediment budget
Corte Madera & Alameda Creeks Sediment gauges at head of tide and creek
mouth Sediment flow and flux between creek and
Bay Short term study – need funding to
continue First step in developing a predictive
numerical model for local tributaries Working with SFEI and USGS
Corte Madera Creek Study Wetland wave attenuation study
Resilience of tidal marsh to sea level rise and coastal flooding
Improve analytical tools for assessing flood risk
Improve guidance for local decision makers Use data to build and calibrate 2D and 3D
models Collect and analyze sediment cores for
sedimentation rates and peat accumulation
Working with USGS and Marin County Flood Control & Water Conservation District
Modeling Can Help
Tidal Hydrology
Watersheds
Sediment Transport
Flood Districts and Watersheds
Need