Floating Wave Attenuator: Flood Adaptation Measure


NEED CAPTION/CREDIT

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


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.


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.
  • None cited


DESIGN OPPORTUNITIES:
Ecological Enhancements
Urban Design
Form
  • N/A
  • Can be designed to incorporate public uses such as walkways and docks.
  • N/A


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.


Download the Floating Wave Attenuator Factsheet.

Learn about other types of measures from our Measures Explorer page.


NEED CAPTION/CREDIT

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


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.


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.
  • None cited


DESIGN OPPORTUNITIES:
Ecological Enhancements
Urban Design
Form
  • N/A
  • Can be designed to incorporate public uses such as walkways and docks.
  • N/A


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.


Download the Floating Wave Attenuator Factsheet.

Learn about other types of measures from our Measures Explorer page.