Floating Wave Attenuator

Measure under the Breakwater measures related to physical infrastructure opportunities to address flood risk

Looking for more? Head back to the Measures Explorer to check out other flood and seismic measures.


West Harbor Breakwater, San Francisco, CA ©Marinetek
DESCRIPTION:
Floating wave attenuators reduce wave energy on the shore side of the structure through a combination of reflection of incoming waves off the side of the structure or dissipation as the wave passes over and under the structure. Floating wave attenuators have traditionally been used to reduce wave energy inside of harbors. However can be used to reduce waves at the shoreline and, therefore, reduce wave runup and overtopping and erosion during a storm event.



PHYSICAL INFRASTRUCTURE:
SHORELINE LOCATION: In Water





DESIGN LIFE:
ADAPTABILITY:
IMPACT ON THE WATERFRONT:
CONSTRUCTION COST:
25 Years
Varies
Living with Water
TBD




COASTAL FLOOD HAZARDS MITIGATED:





Sea Level Rise
Storm Surge
Groundwater
Waves
Erosion




MEASURES COMPATIBILITY:
ECOSYSTEM SERVICES: Measure may affect these shoreline values
Flood
Seismic
All
All
Aquatic Habitat
Terrestrial Habitat
Water Quality
Carbon Storage




CONSIDERATIONS:

ADVANTAGES:

DISADVANTAGES:





  • Placement and function is dependent on the location and aspect to wave action.

  • Retain their functionality at varying water levels.
  • Cost effective for areas with deep water or poor foundation material.
  • Minimal impact to water circulation and fish migration.
  • Low visual impact. Low profile, regardless of tide elevation.
  • Potential for multiple uses such as walkways and docks.
  • Can be moved or relocated relatively easily.

  • Limited wave attenuation compared with fixed, bottom-supported structures.
  • Not suitable for areas with moderate to long period waves.
  • Fatigue can lead to failure of system components.
  • Likely to be attractive to seals and sea lions for habitat.




CONSTRUCTION IMPACTS TO THE PUBLIC:

SEA LEVEL RISE ADAPTATION OPPORTUNITIES:

CASE STUDIES:





  • Minimal as construction is in the water and parts are mostly modules that are built off site and transported in.

  • Wave attenuators float so can be adjusted to changing water levels over time, however since these measures do not influence tidal water levels sea level rise could still be an issue.

  • Small Boat Marina, Gibraltar
  • Taqah Fishing Marina, Taqah, Oman
  • West Harbor Breakwater, San Francisco, CA




DESIGN OPPORTUNITIES:





Ecological Enhancements

Urban Design

Form
  • Can be designed to incorporate habitat for nesting shore birds.

  • Can be designed to incorporate public uses such as walkways and docks.

  • TBD




DESIGN CONSIDERATIONS:

  • Floating wave attenuators must be designed for the local wave conditions.
  • Floating wave attenuators and their moorings must be designed for extreme wave loads.
  • Because they move with the waves, fatigue can also be an issue, particularly at connections between units and with mooring components.


SITE-SPECIFIC CONSIDERATIONS:

  • Design for local wave conditions and depth.
  • Sites exposed to ocean swell on the northern reach of the waterfront should be considered poor candidates for floating wave attenuators due to longer wavelengths of incident waves.
  • Sites along the eastern/southern shoreline with extreme wave periods on the order of 5 seconds or lower should be considered as candidate sites for floating wave attenuators.
  • Sufficient water depth should be available to prevent the attenuators from bottoming out during low tides.


INSTALLATION AND CONSTRUCTABILITY CONSIDERATIONS:

  • Wave attenuators are typically constructed offsite in modules and these transported to the site by road and/or water. Modules are towed into place and connected to each other and to the mooring system. Offshore construction to be performed from a barge by a competent marine contractor.


HISTORICAL RESOURCE CONSIDERATIONS:

  • In-Bay construction would need to consider potential buried archeological resources.


OPERATION AND MAINTENANCE CONSIDERATIONS:

  • Periodic inspection and maintenance as required, particularly connections and moorings.


Other Types of Breakwaters:

Click the images and links below to check out other types of Breakwaters.


Wave BarrierArtificial Reef



Head back to the Measures Explorer to check out other flood and seismic measures.


Measure under the Breakwater measures related to physical infrastructure opportunities to address flood risk

Looking for more? Head back to the Measures Explorer to check out other flood and seismic measures.


West Harbor Breakwater, San Francisco, CA ©Marinetek
DESCRIPTION:
Floating wave attenuators reduce wave energy on the shore side of the structure through a combination of reflection of incoming waves off the side of the structure or dissipation as the wave passes over and under the structure. Floating wave attenuators have traditionally been used to reduce wave energy inside of harbors. However can be used to reduce waves at the shoreline and, therefore, reduce wave runup and overtopping and erosion during a storm event.



PHYSICAL INFRASTRUCTURE:
SHORELINE LOCATION: In Water





DESIGN LIFE:
ADAPTABILITY:
IMPACT ON THE WATERFRONT:
CONSTRUCTION COST:
25 Years
Varies
Living with Water
TBD




COASTAL FLOOD HAZARDS MITIGATED:





Sea Level Rise
Storm Surge
Groundwater
Waves
Erosion




MEASURES COMPATIBILITY:
ECOSYSTEM SERVICES: Measure may affect these shoreline values
Flood
Seismic
All
All
Aquatic Habitat
Terrestrial Habitat
Water Quality
Carbon Storage




CONSIDERATIONS:

ADVANTAGES:

DISADVANTAGES:





  • Placement and function is dependent on the location and aspect to wave action.

  • Retain their functionality at varying water levels.
  • Cost effective for areas with deep water or poor foundation material.
  • Minimal impact to water circulation and fish migration.
  • Low visual impact. Low profile, regardless of tide elevation.
  • Potential for multiple uses such as walkways and docks.
  • Can be moved or relocated relatively easily.

  • Limited wave attenuation compared with fixed, bottom-supported structures.
  • Not suitable for areas with moderate to long period waves.
  • Fatigue can lead to failure of system components.
  • Likely to be attractive to seals and sea lions for habitat.




CONSTRUCTION IMPACTS TO THE PUBLIC:

SEA LEVEL RISE ADAPTATION OPPORTUNITIES:

CASE STUDIES:





  • Minimal as construction is in the water and parts are mostly modules that are built off site and transported in.

  • Wave attenuators float so can be adjusted to changing water levels over time, however since these measures do not influence tidal water levels sea level rise could still be an issue.

  • Small Boat Marina, Gibraltar
  • Taqah Fishing Marina, Taqah, Oman
  • West Harbor Breakwater, San Francisco, CA




DESIGN OPPORTUNITIES:





Ecological Enhancements

Urban Design

Form
  • Can be designed to incorporate habitat for nesting shore birds.

  • Can be designed to incorporate public uses such as walkways and docks.

  • TBD




DESIGN CONSIDERATIONS:

  • Floating wave attenuators must be designed for the local wave conditions.
  • Floating wave attenuators and their moorings must be designed for extreme wave loads.
  • Because they move with the waves, fatigue can also be an issue, particularly at connections between units and with mooring components.


SITE-SPECIFIC CONSIDERATIONS:

  • Design for local wave conditions and depth.
  • Sites exposed to ocean swell on the northern reach of the waterfront should be considered poor candidates for floating wave attenuators due to longer wavelengths of incident waves.
  • Sites along the eastern/southern shoreline with extreme wave periods on the order of 5 seconds or lower should be considered as candidate sites for floating wave attenuators.
  • Sufficient water depth should be available to prevent the attenuators from bottoming out during low tides.


INSTALLATION AND CONSTRUCTABILITY CONSIDERATIONS:

  • Wave attenuators are typically constructed offsite in modules and these transported to the site by road and/or water. Modules are towed into place and connected to each other and to the mooring system. Offshore construction to be performed from a barge by a competent marine contractor.


HISTORICAL RESOURCE CONSIDERATIONS:

  • In-Bay construction would need to consider potential buried archeological resources.


OPERATION AND MAINTENANCE CONSIDERATIONS:

  • Periodic inspection and maintenance as required, particularly connections and moorings.


Other Types of Breakwaters:

Click the images and links below to check out other types of Breakwaters.


Wave BarrierArtificial Reef



Head back to the Measures Explorer to check out other flood and seismic measures.


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Page last updated: 04 September 2020, 13:15