Preliminary Restoration Design

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Expected Long Term Site Evolution of Alameda
Creek and former Salt Ponds following Tidal Marsh
Restoration
Matt Wickland m.wickland_at_pwa-ltd.com Philip
Williams Associates
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Presentation Summary
Development of future channel and marsh plain
conditions to better inform flood modeling of
Alameda Creek and Old Alameda Creek using
geomorphic design tools from similar tidal marsh
restoration sites
- Project overview- Development of long term
site conditions - Hydrodynamic modeling
application
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Overview Setting
Downstream reach of the creekfrom Ardenwood Blvd
to the BayMajor flood control facility
designedby USACEConveyance capacity reduced by
sedimentation
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Overview Project Goals
Work with Alameda County to develop conceptual
alternatives for the Eden Landing area that 1
- Maintain or increase flood protection on
Alameda Creek Flood Control Channel and Old
Alameda Creek2 - Integrate with South Bay Salt
Ponds restoration alternatives3 - Examine long
term conditions ( 50 years )

• Channel evolution
• Marsh plain sedimentation
• Sea Level Rise

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Overview SBSP Project Description

• Each SBSP programmatic alternative integrates
• - habitat restoration
• flood management
• public access

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Overview SBSP Alternatives
The SBSP programmatic alternatives are
Alternative A No Project Alternative
Alternative B Mix of Tidal Habitat (50) and
Managed Pond (50) Alternative C Mix of
Tidal Habitat (90) and Managed Pond (10)
Alternatives B and C are the same for the E2
pond complex
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Supplemental Alternatives
Short Term (development)- Breaches (internal
and external levees) will maximize channel
scour are based on the historic channel
networkLong Term (evolution)- Cross section
and breach dimensions were estimated
using hydraulic geometry relationships-
Restored marsh areas were assumed to increase
in elevation to MHHW (w/ sea level rise)
develop channels based on historic channel
network
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Supplemental Alternatives
Short Term (development)- Breaches (internal
and external levees) will maximize channel
scour are based on the historic channel
networkLong Term (evolution)- Cross section
and breach dimensions were estimated
using hydraulic geometry relationships-
Restored marsh areas were assumed to increase
in elevation to MHHW (w/ sea level rise)
develop channels based on historic channel
network
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Tidal Scour and Fluvial Flooding

• Levees separate channels from adjacent salt ponds
• Channels fill in with sediment and salt ponds
  subside
• Levee lowering/ removal causes channel scour and
  marsh sedimentation
• Salt pond restoration can reduce fluvial flood
  hazards through increased conveyance

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Tidal Scour
Sonoma Baylands Main Channel
1996 Tidal prism 1 million ft3
2004 Tidal prism 26 million ft3
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Levee Breach Locations
Historic channels were used to locate breaches
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Levee Breach Locations
Supplemental Alternative 1
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Levee Breach Locations
Supplemental Alternative 2
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Levee Breach Locations
Supplemental Alternative 3
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Supplemental Alternatives
Short Term (development)- Breaches (internal
and external levees) will maximize channel
scour are based on the historic channel
networkLong Term (evolution)- Cross section
and breach dimensions were estimated
using hydraulic geometry relationships-
Restored marsh areas were assumed to increase
in elevation to MHHW (w/ sea level rise)
develop channels based on historic channel
network
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Cross Section Development
What is hydraulic geometry?
A set of empirical geomorphic relationships that
predict tidal channel cross section dimensions as
a function of contributing marsh area or tidal
prism

• Developed for SF Bay - Marshes from 2 to 5,700
  ha- Design tool for restoration projects

Williams, Orr, Garrity (2002)
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Cross Section Development
Breach sizes were based on anticipated drainage
areas (estimated from historic network and
interior levee layout)
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Cross Section Development
Cross section example
width
MHHW
depth
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Restored Marsh Areas

• Former salt ponds will eventually fill with
  sediment to the elevation MHHW (including
  sea level rise)- Sediment supply in South Bay is
  sufficient to fill former ponds

PWA, 2006. South Bay Geomorphic Assessment.
Prepared for California State Coastal
Conservancy, US Fish Wildlife Service,
California Dept. of Fish and Game.
Assumed sea level rise of 0.15 meters over 50
years
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Restored Marsh Areas
Long term bathymetry includes sedimentation, sea
level rise, and estimated channel network (based
on historic channels)
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Hydrodynamic Modeling
MIKE Flood 1-D (MIKE 11) and 2-D (MIKE 21)
models Connected through lateral and standard
links
880
Ardenwood Blvd
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Modeling Description
Model runs - Short term, post breach
conditions - no scour, no sedimentation -
Long term, worst case conditions - no scour,
with sedimentation sea level rise - Long
term, most likely conditions - with scour,
sedimentation, sea level rise - Long term, no
action conditions - with levee failures - with
scour, sedimentation, sea level rise
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Model Results
Reduction in peak water levels at Ardenwood Blvd
- Larger channel dimensions - Reduction in flow
(routed through salt ponds)
Water surface and levee crest elevations
DRAFT
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Conclusion

• Long term conditions should be considered in any
  design - Long term site geometry (channels and
  marshes) can be predicted from analogous
  tidal marsh restoration sites- Tidal marsh
  restoration can be beneficial to flood
  management and flood control

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Questions?Thanks to Alameda County Flood
Control and Water Conservation District