Armored Shorelines

Travel along our coast, and you’ll see any number of engineered shoreline defenses from seawalls and groins to jetties and riprap. These manmade, hard barriers are designed to hold back the sea— slowing erosion, reducing storm surge, tidal and wave impacts, and protecting oceanfront property and infrastructure.

Armored structures may be necessary or work as a “quick fix” in the absence of natural shorelines, but they are environmentally—and economically—costly, and lack resiliency to climate impacts. They also can flood or fail along the North Shore’s 54.4 miles of armored oceanfront. Action must be taken now to transition towards more resilient options if our coastal communities are to be prepared for the challenges to come.

Climate Change Impacts

Climate change increases the damage to hard structures and intensifies their environmental impacts. Greater wave energy and water volume cause flooding by overtopping structures and scouring and undermining seawall banks. These natural forces also break and dislodge revetments, groins, and jetties. Hard barriers, meanwhile, accelerate erosion and flooding in adjacent areas, giving natural habitat nowhere to retreat.

Examples of potential impacts on hard barriers (and their effect on the coast) include:

Loss and Damage to Homes and Structures Most manmade barriers were not designed with climate change in mind. Shoreline rock armoring (riprap), for instance, has failed to protect portions of Plum Island, while an overtopped canal levee in Gloucester caused severe flooding.

Accelerated Erosion More intense storms and waves deflect off hard structures and erode neighboring shorelines. Hard barriers also block the flow of water, sand, and natural shoreline migration, starving areas of sand and sediments.

Loss of Recreational, Economic, and Public Safety Activities when hard barriers are damaged or deteriorate and impede critical public access to the coast. The Conomo Point seawall, for example, helps protect Essex properties and access to the primary boat launch used by emergency services and state Environmental Police.

Loss of Refuge, Feeding, and Breeding Areas, endangering migratory birds, fish, and shellfish. Studies show habitat near these structures may be suitable only for certain fish and crab species.

Greater Expense and Investment to maintain, repair or replace armored structures if properties, roads, and critical infrastructure are to be pre- served and public safety assured. The vast majority of structures statewide are at least 50 years old and have gone without any major repairs.

Current Coastal Strategies

The Trustees supports efforts to promote living shorelines and “green” over “gray” infrastructure, where possible. Communities on the North Shore recognize the need for:

Prioritizing the Assessment of Current Armored Structures for removal, repair, and redesign. Public safety and key economic centers may be at risk due to aging, deteriorating structures—some of which no longer serve their purpose.

Reducing the Impact of Armored Structures When possible, armored structures should be removed or adapted to allow floodwaters to recede and drain more easily.

Creating Living Shorelines that protect coastal communities while maintaining natural ecosystems with “soft” measures such as bank restoration, beach nourishment or salt marsh restoration, such as the project at Collins Cove in Salem.

FUTURE OPPORTUNITIES

Resiliency and effective adaption requires leadership and innovation when it comes to armored structures on the coast. Based on our latest findings, we propose:

Reducing Future Risks and Costs We must continue to weigh storm responses against more climate-adaptive approaches. We need forward- facing zoning and policies incorporating sea level rise scenarios, no-construction buffer zones, and setback lines to ensure buildings are not located in vulnerable areas.

Creating and Protecting Floodable, Resilient Open Space The Trustees, for example, is helping to create a climate-resilient Boston by working to build a series of waterfront parks that could serve as a model for North Shore communities.

Using Innovative Barrier Approaches to dissipate wave action and protect shorelines. The Alabama Nature Conservancy, for instance, is strengthening bulkheads with a stair-steps cage system containing marsh plants. Marblehead is part of an oyster restoration project, while Swampscott and Beverly are considering offshore “living reef” breakwaters and a portable floodwall/deployable barrier system, respectively, as part of their harbor and waterfront plans.

Redesigning Hard Barriers The Office of Coastal Zone Management’s StormSmart Coasts Program recommends the latest design practices for seawalls and revetments to reduce impacts, minimize maintenance costs, and improve structural longevity. For instance, seawalls can be built to better conform to the natural shoreline and provide habitat for marine animals.

Increasing Funding and Incentivizing New Coastal Resilience Measures Long-term capital budget planning is needed to support investments in “climate-smart” infrastructure and conservation efforts.