Coastal Circulation and Beach Pollution

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Coastal Circulation and Beach Pollution

• John Largier1
• Keith D Stolzenbach2
• John Oram2,3

1- UC Davis, Bodega Marine Labs 2- UCLA Civil and
Environmental Engineering 3- San Francisco
Estuary Institute
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IntroductionThe story of the S and the three Ts
Source Transport Transformation Target
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Management issues Public health or
conservation, fisheries, mariculture
Dischargers - point source - non-point source
Where does it come from?
Where does it go to?
i.e., fate transport
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Outline

• Studies of transport idea that pollutant
  distributions primarily determined by currents.
• Open coast beaches - wastewater outfalls -
  creek runoff
• Enclosed beaches - water residence - the
  unresolved problem
• Semi-Enclosed Beaches
• Similarities to both open and enclosed beaches

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Transport at Multiple Scales
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Zone of Impact - partitioning.
Some entrained into surf zone - move W with
waves. Some moves offshore - advected by tides
currents.

• How does runoff partition between surfzone
  offshore?

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Zone of Impact - partitioning.

• Matching surfzone tidal ZoI -- reduces dilution
  and enhances beach pollution, e.g., Santa Ana,
  Tijuana.

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Zone of Impact - Santa Ana River
Jan Svejkovsky

• Dry weather studies off Huntington Beach
• Dye plumes from
• Talbert Marsh and Santa Ana River.

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Creek (or bay) Outflow

• Transport fate of land runoff (steady or
  tidal).
• tidal outflow- creek outflow - surfzone impact

Tidal outflow from Bodega Harbor (turbidity
pattern zone of impact)
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Wastewater Outfalls.
Offshore discharge at depth - strong initial
mixing trapped beneath thermocline.
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Wastewater Outfalls.

• Plume survey of OCSD sewage plume off Huntington
  Beach.

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Wastewater Internal Tide.
Marlene Noble,USGS

• Internal tide swash transports cold water upslope
  into nearshore
• (Huntington Beach)

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Hyperion Wastewater Outfall
UCLA ROMS
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Also, what about sticky water?
Campbell Cove
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SM Bay SAR Image
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Stormwater Plume Simulations in San Pedro Bay

• 4 sets of 9 floats released at 6 hour intervals
  over 1 day to represent a typical stormwater
  discharge event
• Center of mass is indicated by the red line
• Spread around the center of mass is an indicator
  of the dilution by horizontal mixing

From Eileen Deng (UCLA)
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Categorizing Center of Mass Trajectories
71 Trajectories
36 (51) stagnant
35 (49) not stagnant
8 (23) offshore
27 (77) alongshore
11 (41) upcoast
16 (59) downcoast
From Eileen Deng (UCLA)
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Movement of Center of Mass
Typical coastal currents

From Eileen Deng (UCLA)
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Effective Dilution
From Eileen Deng (UCLA)
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often contaminated
Heal the Bay
Enclosed Beaches
Exceedance Days, 1999 - 2004
Sheltered beaches low energy in bay, estuary,
harbor, or lagoon.
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