Nearshore Reef: Flood Adaptation Measure


Oyster Reef in the Gulf Coast, Texas ©Jerod Foster

ECOLOGICAL INFRASTRUCTURE
WATER LEVEL RANGE: Intertidal to subtidal

SHORELINE LOCATION: In Water



DESIGN LIFE
ADAPTABILITY
IMPACT ON THE WATERFRONT
CONSTRUCTION COST
N/A
Low
Minor Intervention
TBD


COASTAL FLOOD HAZARDS MITIGATED:
Enhancements can provide flood protection when combined with other physical infrastructure
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:
Nearshore reefs are made of bags or baskets of oyster shells, concrete structures (ex: Reef Balls™, Oyster Castles™, cement oyster rings), rip-rap, or concrete blocks. They are best suited to shallow waters with low wave energy. Reefs with subtidal or intertidal crests dissipate wave energy and reduce wave transmission. Depending on location and layout, reefs can also trap sediment on their lee side and stabilize the bottom. Nearshore reefs provide habitats for a variety of marine species, and promote the growth of rock dwelling mollusks and aquatic vegetation.


CONSIDERATIONS:
ADVANTAGES:
DISADVANTAGES:
  • Nearshore reefs can augment subtidal and intertidal habitat. They perform best when wave environments, water levels, and geotechnical and seismic conditions are carefully considered in the design.
  • Target habitats should be consistent with environmental conditions (wave energy, water circulation, contaminant inputs, water levels, existing flora and fauna) at the site.
  • Habitat creation.
  • Local shoreline erosion protection.
  • Low visual impact.
  • Shellfish reefs can improve water quality by filtering out pollutants.
  • Can provide educational opportunities.
  • Compatible with seismic mitigation measures. Seismic performance depends on foundation and type of construction.
  • Shallow water depths only.
  • Low wave energy environments only.
  • Potential shoreline changes in vicinity of project site due to altered wave environment.
  • Potential navigation hazard.


CONSTRUCTION IMPACTS TO THE PUBLIC:
SEA LEVEL RISE ADAPTATION OPPORTUNITIES:
CASE STUDIES:
  • Installation can be completed from the water. Possible marine traffic disruption.
  • Can be designed for a range of water levels, however once constructed, adjustments to mitigate for long term sea level rise would be difficult and costly.
  • Increased water levels can result in less wave attenuation, however there is some potential for the reef to grow due to natural processes with time which could mitigate for the effects of sea level rise.
  • None cited


DESIGN OPPORTUNITIES:
Ecological Enhancements
Urban Design
Form
  • Provides and protects nearshore habitat, and enhances biodiversity and food supply for wildlife.
  • Though predominantly underwater, intertidal reef crests can pose educational opportunities to visually engage people with the water.
  • Form is maximized to provide shelter to marine organisms.


DESIGN CONSIDERATIONS:

  • Environmental conditions (water levels, waves, currents, water quality, sedimentation potential) should be well defined for each site considered.
  • Bottom conditions should be such that they will support the placement of shells or artificial reef structures.

SITE-SPECIFIC CONSIDERATIONS:

  • Conditions at the site must be compatible with the target habitat.
  • For shellfish reefs, the presence of live oysters on hard substrate at the site or historical knowledge of areas where the target shellfish existed can give an indication of the potential for success.
  • The site should have adequate circulation to deliver food and oxygenated water to the reef as well as carry away waste products.
  • Sites with point sources of pollution (sediment, stormwater), and/or high or persistent wave activity are not appropriate.

INSTALLATION AND CONSTRUCTABILITY CONSIDERATIONS:

  • Requires the placement of reef material on the bottom. Placement can be challenging depending on reef size, materials, and site conditions, and will require a marine contractor. Construction would need to consider marine weather time windows to minimize downtime and potential marine traffic disruption. Improper timing of construction relative to growing or spawning seasons of the target habitats may delay recruitment.

OPERATIONS AND MAINTENANCE CONSIDERATIONS:

  • Periodic inspections should be performed to check for settlement and wave damage.

Download the Nearshore Reef Factsheet.

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



Oyster Reef in the Gulf Coast, Texas ©Jerod Foster

ECOLOGICAL INFRASTRUCTURE
WATER LEVEL RANGE: Intertidal to subtidal

SHORELINE LOCATION: In Water



DESIGN LIFE
ADAPTABILITY
IMPACT ON THE WATERFRONT
CONSTRUCTION COST
N/A
Low
Minor Intervention
TBD


COASTAL FLOOD HAZARDS MITIGATED:
Enhancements can provide flood protection when combined with other physical infrastructure
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:
Nearshore reefs are made of bags or baskets of oyster shells, concrete structures (ex: Reef Balls™, Oyster Castles™, cement oyster rings), rip-rap, or concrete blocks. They are best suited to shallow waters with low wave energy. Reefs with subtidal or intertidal crests dissipate wave energy and reduce wave transmission. Depending on location and layout, reefs can also trap sediment on their lee side and stabilize the bottom. Nearshore reefs provide habitats for a variety of marine species, and promote the growth of rock dwelling mollusks and aquatic vegetation.


CONSIDERATIONS:
ADVANTAGES:
DISADVANTAGES:
  • Nearshore reefs can augment subtidal and intertidal habitat. They perform best when wave environments, water levels, and geotechnical and seismic conditions are carefully considered in the design.
  • Target habitats should be consistent with environmental conditions (wave energy, water circulation, contaminant inputs, water levels, existing flora and fauna) at the site.
  • Habitat creation.
  • Local shoreline erosion protection.
  • Low visual impact.
  • Shellfish reefs can improve water quality by filtering out pollutants.
  • Can provide educational opportunities.
  • Compatible with seismic mitigation measures. Seismic performance depends on foundation and type of construction.
  • Shallow water depths only.
  • Low wave energy environments only.
  • Potential shoreline changes in vicinity of project site due to altered wave environment.
  • Potential navigation hazard.


CONSTRUCTION IMPACTS TO THE PUBLIC:
SEA LEVEL RISE ADAPTATION OPPORTUNITIES:
CASE STUDIES:
  • Installation can be completed from the water. Possible marine traffic disruption.
  • Can be designed for a range of water levels, however once constructed, adjustments to mitigate for long term sea level rise would be difficult and costly.
  • Increased water levels can result in less wave attenuation, however there is some potential for the reef to grow due to natural processes with time which could mitigate for the effects of sea level rise.
  • None cited


DESIGN OPPORTUNITIES:
Ecological Enhancements
Urban Design
Form
  • Provides and protects nearshore habitat, and enhances biodiversity and food supply for wildlife.
  • Though predominantly underwater, intertidal reef crests can pose educational opportunities to visually engage people with the water.
  • Form is maximized to provide shelter to marine organisms.


DESIGN CONSIDERATIONS:

  • Environmental conditions (water levels, waves, currents, water quality, sedimentation potential) should be well defined for each site considered.
  • Bottom conditions should be such that they will support the placement of shells or artificial reef structures.

SITE-SPECIFIC CONSIDERATIONS:

  • Conditions at the site must be compatible with the target habitat.
  • For shellfish reefs, the presence of live oysters on hard substrate at the site or historical knowledge of areas where the target shellfish existed can give an indication of the potential for success.
  • The site should have adequate circulation to deliver food and oxygenated water to the reef as well as carry away waste products.
  • Sites with point sources of pollution (sediment, stormwater), and/or high or persistent wave activity are not appropriate.

INSTALLATION AND CONSTRUCTABILITY CONSIDERATIONS:

  • Requires the placement of reef material on the bottom. Placement can be challenging depending on reef size, materials, and site conditions, and will require a marine contractor. Construction would need to consider marine weather time windows to minimize downtime and potential marine traffic disruption. Improper timing of construction relative to growing or spawning seasons of the target habitats may delay recruitment.

OPERATIONS AND MAINTENANCE CONSIDERATIONS:

  • Periodic inspections should be performed to check for settlement and wave damage.

Download the Nearshore Reef Factsheet.

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