san francisco district coastal activities

San Francisco District

San Francisco District Coastal Activities

Frank WuCERB MeetingJune 4, 2009


• Open Coast– Ocean Beach– Humboldt Bay– Santa Cruz Harbor

• In-Bay– Sacramento DWSC– SF Bay to Stockton

DWSC– South SF Bay

Shoreline


• 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


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)


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

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d D

ata

: H

eig

ht

ab

ov

e M

LL

W (

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t)R

es

idu

al D

ata

: D

iffe

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(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)


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

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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

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North Reach, Accretion: + 0 ~ 6 m/yrSouth Reach, Erosion: -1 ~ 2 m/yr


Erosion Spot


• Available sediment distribution

• Beach sand (~ >0.25 mm)


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


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


Pre-Project Shoreline Changes


Comparisons / Shoreline Changes


Comparisons / Elevation Changes


Monitoring Results / Sediment Movement


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)


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)


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


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)


Beach Erosion

• USACE aerial photo (1992-2005)

• Erosion of North Spit• Accretion of South Spit


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)


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)


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)


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)


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


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


Acknowledgements

• USACE-SPN PDT

• USGS / M&N

• USACE-SPD

Thank You

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