Developed Coastlines

The wild beauty and vital resources of the ocean are what draw so many of us to its shores to live, work, and play. And yet, as the impacts of climate change intensify, it is this very proximity to water, wind, and wave energy which presents the developed coastlines of Martha’s Vineyard and Nantucket with their greatest risks. 

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TWO MAIN ISSUES EXIST FOR ISLAND COMMUNITIES The first is an urgent need to protect the critical supply chain infrastructure located at vulnerable waterfront and port areas and to safeguard (or rapidly restore) transportation, communication, and medical services that face disruption during severe storms and weather-related emergencies. The second issue is about shifting where we live and work so that we stay out of harm’s way. 

Accelerating forces of melting ice, warming oceans, and higher seas may not impact us as gradually as we once thought. In some areas, today’s flood zones are forecast to be tomorrow’s high tide zones, threatening road access to harbors, hospitals, airports, and downtown commercial areas. 

Fishing vessels and ferries, providing vital connections to and from the mainland and between island outposts, may face inundated and/ or storm-damaged docks. Utility and communication infrastructure may be damaged or interrupted. And residents who rely on private wells may lose access to clean water due to saltwater intrusion. 

And then there are the year-round homes and vacation retreats, from the low-lying campground cottages of Oak Bluffs to the shingled beach houses of Madaket. Many people have lived here for generations. Others return season after season. As a strategy, retreat inland is not always a viable option for them. 

WHAT THE DATA SHOWS 

VULNERABILITY IS WIDESPREAD, especially on the Islands’ ocean-facing southern tiers. The latest data shows: 

  • Erosion threatens an estimated $2 billion worth of coastal parcels on Martha’s Vineyard and $2.6 billion in Nantucket, not including structures, FEMA (Massachusetts Coastal Erosion Hazard Map) data shows. 

  • Overall, more than 3,500 structures on the Islands may be flooded during a 10-year storm in 2050 [CIT. 3] while almost 800 structures may be threatened by erosion, FEMA data [CIT. 10] shows. 

  • Nantucket may experience daily tide flooding of 25 miles of roads (5%) by 2050 [CIT. 3]. 

  • About 95 miles of roadway are projected to flood on Martha’s Vineyard during a 10-year storm event [CIT. 3], including 49 miles in Edgartown — nearly twice as many miles as the Boston Marathon. 

  • Even Gosnold, which is relatively undeveloped with more high ground, could see nearly 8 miles of roads flooded in a 10-year storm in 2050 [CIT. 3]. 

LOOKING AHEAD 

Our projections indicate Islanders must make hard choices now about how to avoid or reduce flood risk. It’s not just a matter of looking at local infrastructure, site by site. To buy time and increase the odds of success, discussions and initiatives should focus on the best opportunities to collaborate and improve resiliency. 

Based on our latest findings, we propose: 

ELEVATING AND ADAPTING INFRASTRUCTURE It’s urgent that buildings in current and projected flood zones are designed for adaptive reuse, with features such as breakaway walls. And while individual structures can be raised, a more comprehensive approach is also necessary to develop consistent solutions over time that respect historic character. We can look at: 

  • Boston’s Planning & Development Agency (BPDA) has plans for a Coastal Flood Resilience Overlay District that will require new development and retrofits to limit damage and displacement due to coastal storm and sea level rise impacts. 

  • Amphibious buildings are designed to avoid damage when water levels rise. They range from foam-based flotation systems to sophisticated designs with terraced landscapes acting as early flood warning systems. 

ENGINEERING TO ABSORB WATER “Sunny day” flooding already occurs in some downtown areas, so it’s imperative to channel or redirect water away from homes, businesses, and critical infrastructure or find ways to live with it. Together, we can think outside the box and find ways to adapt urban models like “sponge cities” to the Islands, transforming hardscapes into permeable areas for water to be naturally absorbed, retained, and filtered. 

WEIGHING RETREAT AGAINST OTHER PRIORITIES For some residents and business owners, retreat may be the only viable option when retrofitting or relocation to another inland area are not possible or realistic. With significant impacts forecast to occur within the lifetime of most mortgages, property owners need the Islands to determine viable retreat areas and weigh those against land conservation plans. 

MITIGATING VULNERABLE TRANSPORTATION ROUTES Choices need to be made about whether to relocate piers and ports offshore as floating networks or further inland, as the shoreline recedes. We need to ask whether low-lying areas should be adapted for port areas and causeways and if harbors should be transformed into more open resilient spaces. With many places at high risk of flooding, it’s also time to plan for strengthening inland routes, raising roads, and using new technology such as floating roads and bridges.