4_S03C_Veirs

sveirs
Noise impacts in the Salish Sea under commercial shipping growth scenarios
Scott Veirs*, Beam Reach Marine Science
Val Veirs, Colorado College
Jason Wood, Sea Mammal Research Unit

* scott@beamreach.org
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Ships dominate the Salish Sea soundscape
Bulk carrier
China Steel Entrepreneur
300m x 50m
203,512 metric tons
Bulk carrier
Ocean Prometheus
300m x 50m
203,300 metric tons
Oil Tanker
Voyager
272m x 46m
150,000 metric tons
Click  each  image  for  sound  samples  from  some  of  the  largest  vessels  in  their  class
What are the potential acoustic impacts of increasing fossil fuel transport by ship in the Salish Sea, particularly for the endangered Southern Resident killer whales?
    Motivation
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    Study Site
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    • Lime Kiln State Park

    • Mar 2011 - Oct 2013

    • Calibrated sound pressure level of ~1500 unique, isolated ships

    • 14.5+/-4 kts avg speed

    • ~20 ships/day transit Haro Strait

    • 1 or more ships are present
      40% of the time
    Received levels: all ships vs backgroud
    • At Lime Kiln, ships increase noise above background at
      all       frequencies, not just below 1 kHz

    • 95% of ships have receive levels (blue) above the
      75% quantile of
      background noise (lower black curves)

    • Median increases are +15 dB at orca call frequencies & +6 dB at click frequencies
    Orca
    Clicks
    Orca   Calls
    Source levels: all ships
    • Computed using near-spherical spreading with & without absorption

    • Per Hz, 1/12-, and 1/3-octave band levels

    • We focus on 12-octave bands for comparison with killer whale auditory response curve
    Source levels: by ship class
    • Median 1/12-octave band levels, without absorption

    • Bulk carriers & tanks have similar spectra
      • <200 Hz: in +15dB group
      • 0.2-20 kHz: ~5dB below containers, cargo, & vehicle carriers
      • >20 kHz: all ships similar
    More  details:  Veirs et al., in Prep
    Signals & noise in a spectral masking model
    12th-octave spectra (broadband levels):

    Orca click (~205 dB re 1uPa@1m)

    Orca call (~155 dB re 1uPa@1m)

    Ship noise (~172 dB re 1uPa @ 1m; 110 dB received)

    Background noise (~90 dB re 1uPa)

    Orca hearing threshold
    Model details  :     Veirs et al., 2011
    Growth Scenarios

    (tankers  &  bulk carriers   only)
    1) Current vessel traffic levels
        400 tankers + 2600 bulk carriers
        =3000 vessels per year

    2) Double current levels
        Added vessels from proposed projects
    • +796 tanker transits (3x current)
    • +1614 bulk carriers (1.5x current)
    • =2410 added vessels (~2x current levels)
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    Vessel  Traffic  projections  from :  Protectwhatcom.org/table/
    % of Day with ships 
    Range reduction
    Missed  Calls
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     Current
    36% (40)
    scenario
    2x current
    68%
    Modeled impact on communication space
    43%
    68%
    44%
    37%
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    Assumptions:
    • 1/2 hr per ship
    • random timing
    % of Day with ships 
    Range reduction
    Fish reduction
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     Current
    36%
    scenario
    2x current
    29%
    Modeled impact on foraging space
    43%
    29%
    58%
    49%
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    Main shipping noise source is cavitation
    CAUSES:

    • Propeller design

    • Blade rate (tip velocity)

    • Wake flow (hull design)

    • Propeller depth

    • Propeller maintenance
    1. Reduce noise by slowing down
    • tanker & bulk carrier speeds:
        13.6+/-1.5 and 13.7+/-1.6 kts

    • -1 dB/knot

    • Varies by class

    • Less cavitation means less high-frequency noise
    2. Other mitigation strategies

    • Re-schedule
    • Re-route
    • Maintain

    • Shift ship population
      • New vessels below 10% quantile
      • Change size?
      • Add quieting technology
    The pace of growth in the region, coupled with associated increases in impervious surfaces, alteration and loss of habitat, and pollutants in the air and water, continue to drive a silent crisis. While the Sound appears beautiful, its web of life is at risk. 


    -- 2007 State of the Sound report
    A not so silent crisis?
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