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Living Shoreline Planning and Implementation
When planning a living shorelines project, there are several factors that restoration practitioners need to consider, including the permits and approval involved and the appropriate type of restoration for the habitat type. Here, we list the steps involved in planning and implantation.
- Site analysis: Practitioners must determine whether living shoreline stabilization is appropriate in a particular area; this analysis includes an evaluation of the bank erosion rate and elevation, wave energy, prevailing wind and wave direction, vegetation, and soil type. Design of restoration activities is done after the site analysis.
- Permit approval and legal compliance: Compliance with all federal, state, and local laws, regulations, and permits for proposed restoration activities must be done prior to implementation.
- Site preparation: This begins after appropriate permits are obtained from regulatory agencies. The site is cleared of debris and unstable trees, and failing seawalls and bulkheads can be removed. Any runoff issues should also be identified and addressed prior to material installation.
- Installation: Typical living shoreline treatments include planting riparian, marsh, and submerged aquatic vegetation; installing organic materials such as bio-logs and organic fiber mats; and constructing oyster reefs or “living breakwaters” that dissipate wave energy before it reaches the shore.
- Post-construction monitoring and maintenance: This includes scientific monitoring of restored habitat to gather information on the success of the project for the purpose of improving the construction and implementation of future efforts. Maintenance activities include debris removal, replanting vegetation, adding additional sand fill, and ensuring that the organic and structural materials remain in place and continue to stabilize the shoreline.
Habitat Zones and Living Shoreline Treatments
Living shorelines use a variety of stabilization and habitat restoration techniques that span several habitat zones and use a variety of materials. View the picture to the left to find suggested living shoreline techniques suitable for various habitat zones.
1. Upland Buffer / Bankface Zones
Sand fill and clean dredge material is typically used to create a gentle bank slope that dissipates wave energy and provides a surface on which to plant vegetation. Sites without a bulkhead can be regraded, filled, and replanted with native vegetation. Bulkheads can be removed and the shoreline then regraded, filled, and replanted. Another option is to leave the structure in place, add sand fill in front of the bulkhead, and then regrade and replant the shoreline and embankment with native vegetation.
Tree and grass roots stabilize the riparian zone above high tide by holding on to the soil, which minimizes bank erosion while filtering upland runoff and providing wildlife habitat. Common riparian vegetation used at each site differs depending on the species native to that area, but typically includes a combination of native woody trees, shrubs, and grasses.
2. Coastal Wetlands and Beach Strand Zone
Marsh grasses dissipate wave energy, filter upland runoff, and improve habitat for fish and wildlife. Native grasses are planted in the water and at the mean high tide mark in the intertidal zone. Marsh grasses may be more successful if they are planted in the spring in areas where there is evidence of existing marsh, where there is less than 3 miles of open water, and where the prevailing winds will not cause destruction of the newly planted grasses.
Mangroves are woody plant communities that play an important role in stabilizing the shoreline. Through their extensive root system, mangroves trap sediment and nutrients and dissipate wave energy. Mangroves are found in estuarine tropical and subtropical environments and could significantly decrease coastal erosion if used at living shoreline sites. These plant communities typically grow in the Caribbean, southern Florida, and portions of south Louisiana.
Natural fiber logs (or bio-logs) made of biodegradable coconut fiber and netting are commonly used to stabilize slopes and minimize bank erosion. These logs are placed at the foot of bank slopes or in the water, molded to fit the bank line, and then anchored in place. They trap and retain sediment, retain moisture for plant growth, and provide bank stability while new vegetation takes root and increases in density.
Natural fiber matting is made of coir fiber, wood, straw, jute, or a combination of organic, biodegradable materials. The matting is laid over eroding steep slopes or coastal areas to minimize the loss of sediment from the land and trap wave-transported sediment. Organic matting can also be planted with marsh grasses or riparian vegetation to enhance shore stabilization.
Rock footers are small amounts of rock or boulder material used to anchor and support bio-logs and stabilize the restored shoreline. The rock footer supports the structural integrity of the bio-log and prevents it from sloughing off into deeper waters of the bank slope.
Low-crested segmented rock sills are freestanding rock structures placed in the water parallel to shore to dissipate wave energy and protect eroding marshes and shorelines. Sills are generally segmented and stand no more than 6 to 12 inches above mean high water. This allows boats and wind-induced waves to pass over the structure and provides wildlife access to both the water and the shoreline habitat.
Living breakwaters are structures placed parallel to the shore in medium- to high-energy open-water environments for the purpose of dissipating wave energy while providing habitat and erosion control. These breakwaters are constructed rock that is seeded with oyster spat. Living breakwaters create calm areas near the shoreline, which can be replanted with submerged aquatic vegetation and marsh grasses to create intertidal and marsh habitat for aquatic organisms.
Rubble and recycled concrete breakwaters can be used at living shoreline sites as material for offshore breakwaters to reduce wave energy. To provide maximum benefit to the ecosystem, these rubble and concrete breakwaters should be seeded with oyster spat to improve water quality and provide habitat while reducing wave energy.
Sediment-filled geotextile material tubes are placed parallel to shore to dissipate waves in high-energy environments. The tubes, which measure approximately 12 feet in diameter, create new avenues for dredge material disposal, and produce a hard surface on which the eastern oyster can construct reefs.
Filter fabric is a porous layer of geotextile material placed beneath rock sills and breakwaters to prevent sand movement into or through the rock or concrete structure at hybrid living shoreline sites.
3. Subtidal Water Zone
Seagrass beds dampen wave energy, stabilize sediments, improve water quality, and provide food and shelter for marine organisms. When used in conjunction with other living shoreline components such as marsh grasses, a natural shoreline buffer is created that reduces coastal erosion and stabilizes sediments via root growth.
Native reef-building oysters play an important role in aquatic ecosystems. Oyster reefs can be enhanced or created at living shoreline sites as natural shoreline protective structures to dissipate wave energy, decrease coastal erosion, increase habitat for fish species, improve water quality, and provide protection for newly planted marsh grasses and submerged aquatic vegetation.
Small concrete oyster balls can be used at living shoreline sites to decrease wave energy while enhancing fish and oyster habitat. These hollow concrete structures provide a surface on which oysters colonize and form small living reefs, thus providing habitat and food for fish and other aquatic species. These structures also dissipate waves, decreasing coastal erosion and providing an area in which newly planted vegetation can grow.