San Francisco District San Francisco District Coastal Activities Frank Wu CERB Meeting June 4, 2009.
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Transcript of San Francisco District San Francisco District Coastal Activities Frank Wu CERB Meeting June 4, 2009.
San Francisco District
San Francisco District Coastal Activities
Frank WuCERB MeetingJune 4, 2009
San Francisco District
• Open Coast– Ocean Beach– Humboldt Bay– Santa Cruz Harbor
• In-Bay– Sacramento DWSC– SF Bay to Stockton
DWSC– South SF Bay
Shoreline
San Francisco District
• Beneficial reuse of dredged material for beach nourishment at Ocean Beach and Humboldt Bay
• Background info / controlling parameters / beach erosion• O&M dredge disposal activities / available sediment• Nearshore placement demo projects• Monitoring programs• Future nearshore/onshore placement layout
development• Proposed numerical approaches• Conclusions and recommendations
San Francisco District
Ocean Beach Onshore Placement Demo Project
• Tidal range (4’ ~ 6’)
• El Niño and storm surge (1.5’ ~ 2.5’)
• Tidal currents (0.1 ~ 1 m/s)
• NW and SW waves (1 ~ 3 m)
• Sea level rise (0.2 m/100 yr)
San Francisco District
1983-01-26 to 1983-01-28, SF gage (hourly data)
-4
-2
0
2
4
6
8
10
1/24/830:00
1/25/830:00
1/26/830:00
1/27/830:00
1/28/830:00
1/29/830:00
1/30/830:00
1/31/830:00
Time
Ve
rifi
ed
an
d P
red
icte
d D
ata
: H
eig
ht
ab
ov
e M
LL
W (
fee
t)R
es
idu
al D
ata
: D
iffe
ren
ce
(fe
et)
Pred (ft)
Vrfy (ft)
Vrfy - Pred (ft)
1983-12-03, SF gage (hourly data)
-2
0
2
4
6
8
10
12/1/8312:00
12/2/830:00
12/2/8312:00
12/3/830:00
12/3/8312:00
12/4/830:00
12/4/8312:00
12/5/830:00
12/5/8312:00
Time
Ver
ifie
d a
nd
Pre
dic
ted
Dat
a: H
eig
ht
abo
ve M
LL
W (
feet
)R
esid
ual
Dat
a: D
iffe
ren
ce (
feet
)
Pred (ft)
Vrfy (ft)
Vrfy - Pred (ft)
San Francisco District
Weibull Distribution of Annual Peak Hourly Predicted Data, SF Gage (1901-2005, 105 years)
0
1
2
3
4
5
6
6.85 6.9 6.95 7 7.05 7.1 7.15 7.2 7.25 7.3
Height above MLLW (feet)
Pro
ba
bili
ty D
en
sit
y
Weibull Distribution of Annual Peak Hourly Residual Data, SF Gage (1901-2005, 105 years)
0
0.2
0.4
0.6
0.8
1
0 0.5 1 1.5 2 2.5 3 3.5 4
Difference (feet)
Pro
ba
bili
ty D
en
sit
y
San Francisco District
North Reach, Accretion: + 0 ~ 6 m/yrSouth Reach, Erosion: -1 ~ 2 m/yr
San Francisco District
Erosion Spot
San Francisco District
• Available sediment distribution
• Beach sand (~ >0.25 mm)
San Francisco District
USACE Nearshore Placement Demo Project
• 2005, 2006, 2007 (May)
• 300,000 cy x 3
• 750 m offshore, 9 ~ 14 m depth
• Expect sediment onshore movement
• Protect beach and outfall
San Francisco District
USGS Monitoring Results
• Pre and post sediment placement• 2005, 2006, 2007 (summer and winter)• Bathymetry, beach profile, wave, current• 50% sediment remained at disposal site• Confirm sediment onshore movement• Recommend future placement depth < 5 m,
including nearshore and onshore placements
San Francisco District
Pre-Project Shoreline Changes
San Francisco District
Comparisons / Shoreline Changes
San Francisco District
Comparisons / Elevation Changes
San Francisco District
Monitoring Results / Sediment Movement
San Francisco District
Conceptual Beach Nourishment Layout Development
• 300,000 ~ 1,000,000 cy onshore placement
• 3,000’ length, 30’ height, 150’ ~ 250’ width
• Fine sand dune (1:3 slope)
• Coarse sand berm (water front slope 1:25)
San Francisco District
Conclusions and Recommendations for Ocean Beach
• Plan onshore placement demo project
• Prepare a draft report (9/30/09)
• Target construction timeline (summer 2011)
• Numerical modeling (ERDC, CMS-FLOW & CMS-WAVE, tide, wave, longshore and onshore-offshore sediment transport, 2D/3D), (USGS)
San Francisco District
Humboldt Bay Nearshore Placement Demo Project
• Develop nearshore placement site
• Lessons learned from Ocean Beach
• Beneficial reuse of dredged material
• Establish monitoring plan• Proposed numerical
approaches
San Francisco District
High Energy System
• Swell (NW, winter and summer)
• Wind wave (SW, winter; N summer) (H: 3 ~ 13 ft; T: 12 ~ 16 s)
• Tidal range (5’ ~ 7’)• Tidal current
(1.5 ~ 2.5 ft/s)
San Francisco District
Beach Erosion
• USACE aerial photo (1992-2005)
• Erosion of North Spit• Accretion of South Spit
San Francisco District
Entrance Channel Maintenance
• USACE Maintained 1881• Northern, CA
– 225 mi. N of SF Bay
– 156 mi. S of Coos Bay, OR
• Deep draft harbor (-48 ft MLLW)
• Annually 1,000,000 cy (>95% sand)
San Francisco District
Dredge Disposal Sites Map
• SF-3 1940 ~ 1988 60’ ~ 90’ depth
• NDS 1988 and 1989 50’ ~ 60’ depth
• HOODS > 1989 160~ 180’ depth non-dispersive 50 x 106 cy capacity (60% left)
San Francisco District
Nearshore Project Benefits
• Nourish north spit
• Increase wave protection
• Reduce dredge disposal at HOODS– Maintain littoral cell– Reduce maintenance costs
• Improve recreation (surf, beach)
• Restore Habitat (snowy plover)
San Francisco District
Proposed Nearshore Demo Project
• Preliminary development (800,000 ~ 1,000,000 cy placement)
• Area: 3 mi x ¼ mi• Sediment deposition:
~ 1.0 ft• 2 control cells (N & S)• Hopper dredge Essayons
(USACE)
San Francisco District
Demo Project Monitoring/Modeling• Control Cells
– Sediment samples pre and post placement– Biological Survey (crabs)
• Bathymetric Survey
Suggested Future Activities• Field monitoring program (USGS / local university)
– Beach response and sediment transport
• Numerical modeling (ERDC)– CMS-FLOW and CMS-WAVE
San Francisco District
Conclusions and Recommendations for Humboldt Bay
• Lessons learned from Ocean Beach
• Develop field measurement programs / bathymetry survey / monitoring
• Perform numerical analysis / simulation
• Design nearshore placement scheme
San Francisco District
Acknowledgements
• USACE-SPN PDT
• USGS / M&N
• USACE-SPD
Thank You