Planted marshes are generally considered to be one of the most cost-effective and environmentally desirable erosion-control approaches. In contrast to wide “meadow” marshes, fringing marshes are narrow areas of marsh plants lining the shoreline of rivers and bays. Like meadow marshes, fringing marshes protect adjacent uplands by gradually dissipating wave energy, absorbing the force of breaking waves, and stabilizing the soft, underlying soil. Marshes can be created or restored by increasing tidal flow. Additionally, planting marsh grass can be a particularly effective restoration strategy where previous marshes were destroyed by dredging and filling. Planting is also cost-effective, as you may be able to do it yourself.
Marsh planting is most effective in areas that are sheltered from the wind and where waves and boat wakes are not a major problem. A fringing marsh at least 10 feet wide is necessary for erosion control, but 20 feet or more is preferred. If the marsh is not established continuously along the shoreline, erosion can continue on the unprotected areas. In some cases, two or more planting attempts may be required for the marsh to take hold. From a regulatory standpoint, marsh creation or restoration will likely require permitting from state and federal regulatory agencies.
North Carolina's Shoreline Erosion Control Using Marsh Vegetation and Low-Cost Structures provides a good outline for how to plant and create a new coastal wetland. Similarly, the North Carolina Coastal Federation Erosion Control: Non-Structural Alternatives, A Shorefront Property Owner’s Guide provides some good guidance for marsh plantings. The techniques and species discussed in these guides are applicable to Maine’s marsh systems. Tidal bank protection using vegetative plantings is also outlined by the Maine DEP under their Maine Erosion and Sediment Control Best Management Practices.
Commonly used grasses include species native to Maine salt marshes, such as saltmeadow hay (Spartina patens) and smooth cordgrass (Spartina alterniflora). Planting elevations can vary but can be determined by observing the elevations of healthy native marshes nearby. Marsh grasses may be purchased from specialized commercial nurseries (such as Pierson Nurseries in Biddeford), or possibly can be transplanted from existing marshes with a permit.
Be aware of the threat posed by invasive species. Phragmites australis, also known as common reed, is considered an invasive plant by the State of Maine and should not be planted or allowed to spread.
Increasing tidal flow into marsh areas by removing or replacing inadequately functioning road culverts can help facilitate the natural proliferation of marsh plants. Adequate tidal flushing is required for marsh growth, and also helps eliminate invasive species that are not salt-tolerant. Increasing tidal flow also helps dissipate floodwaters by allowing water to drain naturally to the ocean, while restricting the flow will often increase flooding. Note that permits are likely required from Maine DEP and the US Army Corps of Engineers for work associated with road culverts.
The above marsh restoration information was adapted from Managing Erosion on Estuarine Shorelines, which was prepared for estuarine shorelines in North Carolina. However, much of the information and techniques outlined transfer to Maine’s marshes. Additional online resources regarding techniques that provide good guidance for marsh restoration and creation include Maine Salt Marshes: Their Function, Values, and Restoration and Salt Marshes in the Gulf of Maine, Human Impacts, Habitat Restoration and Long-Term Change Analysis.
Follow the steps below to gain the environmental and regulatory information needed for decision making. The steps are listed in general order although some steps may be conducted concurrently.
1) Contact local, state and/or federal regulatory officials. Individuals experienced with coastal regulations may not need to consult officials in all cases; however, if in doubt seek regulatory advice before proceeding with a project.
2) Obtain an environmental assessment from a certified engineer, landscape architect, or other qualified professional. In most cases local, state, and/or federal regulators can help direct you to the best professional discipline to assist with your specific project. Sometimes it is helpful to have the consultant completing the environmental assessment and the construction contractor present at regulatory consultation meetings.
3) Evaluate your risk. Check your insurance coverage to make sure you have adequate liability coverage related to loss due to shoreline erosion or flooding, as well as flood insurance through the National Flood Insurance Program.
4) Develop a mitigation plan if implementation of one or more “best management practices” is recommended. The plan does not need to be prepared by a professional in all cases; however, the quality and clarity of the plan will generally improve the efficiency and timeliness of any subsequent permitting that may be required. Good plans will also benefit the construction contractor and can help prevent costly mistakes.
5) Be Neighborly. If the plan involves work at or near a property boundary, or activity that may affect an abutter’s “viewshed,” consider sharing the plan with the abutter(s) to make sure they fully understand the work to be performed and the potential impact to their property. This consultation is a courtesy at this stage, and not a regulatory mandate; however, obtaining “buy in” from abutter(s) can potentially avoid neighbor disputes that may lead to costly permitting and/or construction delays.
6) Need a local permit? Share plans with local code enforcement in order to determine what, if any, town ordinances may need to be followed. Local shoreland zoning ordinances generally contain requirements for vegetation removal and re-planting.
7) Need a state permit? If the plan involves alterations within 75 feet of highest annual tide (HAT), within or adjacent to another protected natural resource as defined by the Maine Natural Resources Protection Act, or within a development permitted by the Site Location of Development Act, a state permit will likely be required. When possible, plan to meet standards of a permit-by-rule to simplify the state regulatory review process. Typically work within 25 feet of the highest annual tide line is not allowed under permit-by-rule, however there is some exception for disturbances associated with establishing vegetation. An individual permit will be required for any plan that does not qualify for permit-by-rule. Alterations to a development or a lot within a development permitted under the Site Location of Development Act may require the revision or amendment of the development’s permit.
8) Need a federal permit? If the plan involves work below the highest annual tide (HAT) and/or in a freshwater wetland or habitat for endangered or threatened species, a federal permit(s) under the Federal Clean Water Act and Rivers and Harbors Act may be required. Share the plan with all applicable federal authorities in order to determine what permits may be necessary.
9) Hire qualified contractors who are experienced with coastal stabilization projects and the implementation of “best management practices.”