“The sea level is rising, folks, there’s no doubt about it,” Andre Martecchini, project engineer for Cambridge-based consulting firm Kleinfelder, told an overflow crowd at the Oak Bluffs library meeting room last Thursday night.
Mr. Martecchini was on hand to share the results of the “Coastal Vulnerability Assessment and Adaptation Plan,” commissioned last year by the Oak Bluffs Conservation Commission to determine just how vulnerable Oak Bluffs is to sea level rise and to storm surge, and what can be done to mitigate the potential damage.
“We’re not going to get into whether it’s manmade or not; that’s a political conversation. We’re only dealing with science tonight. It is occurring. It is a fact. The tide gauge in Boston tells us the tide has risen eight inches since 1920,” he said. “Our models tell us the tide will rise another eight inches by 2030. What took 95 years before will take 15 years. Fifteen years is not a lot of time.”
Not surprisingly, Oak Bluffs, a low-lying, eastward-facing, seaside town, is extremely vulnerable today, and will only become more so as sea level rise (SLR) increases. Mr. Martecchini suggested a paradigm shift will be required to defend against the inevitable. “Some of the ideas are going to be very controversial, and expensive,” he said. “Think of the Dutch. They control the ocean to survive.”
The assessment was conducted over the winter by Kleinfelder and the Woods Hole Group (WHG), using the most current computer models to determine the town’s vulnerability at present, and for the years 2030 and 2070. Mr. Martecchini said the computer models used were developed by the Woods Hole Group as part of a recent Department of Transportation (DOT) Boston Harbor study that included the entire Massachusetts coast, using the highest global sea level rise curve as published by U.S. National Climate Assessment in 2012.
The calculus of the WHG includes projected sea level rise and worst-case scenarios from hurricanes and nor’easters. The study evaluated the town’s susceptibility in a 100-year storm, the strongest storm that is projected to hit the Island once every century. According to calculations, a 100-year storm in 2030, with current town infrastructure, would leave Circuit Avenue Extension, the harbor area and large parts of Seaview Avenue under roughly five feet of water.
“The roads around the hospital are also very vulnerable,” Mr. Martecchini said. “Fortunately, the hospital will be high and dry, but not by much. Beach Road will be gone, which leaves only one access road to the hospital during a natural disaster, assuming it hasn’t been blocked off.”
Mr. Martecchini said the projected flood levels did not take into account storm precipitation and “washover,” water that tops the seawalls. Tides were also not incorporated into projections. “Massachusetts really dodged a bullet in Hurricane Sandy because it hit at low tide,” he said. “If it had been high tide, it could have been catastrophic.”
Problem areas
The data rated the top 20 most vulnerable “assets” in town. The harbor and vicinity; the Eastville area and roads surrounding the hospital; Seaview Avenue, particularly near Farm Pond; and the Crystal Lake area on East Chop topped the list. Mr. Martecchini said there are a variety of “infrastructure adaptation strategies” the town can take. “All of them are costly,” he said.
Mr. Martecchini said the seawall on Seaview Avenue could be raised in stages, in a modular fashion, until reaching 9.7 feet, the height projected to buffer a 100-year storm in 2070, which models say is almost a 100 percent certainty. Schematics showed that a wider culvert between Farm Pond and Nantucket Sound with a floodgate, a project which has been in the works for over a decade and is finally close to being fully funded, could also buffer against storm surge. The plan also calls for raising Seaview Avenue five feet. Since Seaview Avenue is a state road, current regulations would require going through a permitting gauntlet. “There’s no question permitting challenges will present big challenges in many of these solutions,” Mr. Martecchini said.
To hold back storm surge in the harbor, passive flood barriers that are stored in the sidewalk and raised during storm surge, along with permanent glass flood barriers around the bulkhead, approximately 9 feet tall, were shown as containment options. Mr. Martecchini said fortifying the existing jetties and installing a hurricane barrier at the harbor mouth, as was done in New Bedford, could significantly restrict the size of the surge.
Beach restoration and “sacrificial dunes” along East Chop, and virtually the length of Seaview Avenue, were suggested, although Mr. Martecchini said these would be an impractical solution for the town until state regulations allow for offshore sand mining. An added complication in Oak Bluffs is a town bylaw that prohibits “manmade alteration to dunes” that would need to be amended.
Raising the roads that lead to the hospital was considered crucial. “When you have one road open and a tree falls over the road, you’re stuck,” he said. “Our models show the new bridge will be fine, but the roads leading to it will be well underwater.”
Natural resources that are at risk due to SLR were also addressed. Mr. Martecchini pointed to Sunset Lake, an area which already floods with regularity, as a good candidate for a marsh restoration project and enhanced tidal flow, i.e. a larger culvert with a floodgate, similar to the planned replacement culvert at Farm Pond.
When it comes to the Crystal Lake area on East Chop, Mr. Martecchini suggested it may be time to raise the white flag. “To be honest, I don’t see a good solution here,” he said. “This may be an area where the town looks to buy out the properties and let it go. If I was a homeowner there, I’d definitely look into raising my home.”
As he mentioned in a previous interview with The Times, Mr. Martecchini said the town needed to look at zoning changes, so at-risk homes built to the current height maximum can be raised. “If you’re not going to encourage them to retreat, encourage them to raise,” he said, adding that this applies to commercial buildings and roadways as well.
Mr. Martecchini said Oak Bluffs is in better shape than many towns when it comes to planning for flooding and SLR. “You have an excellent floodplain overlay district in Oak Bluffs,” he said. “Other towns often use it as a model.”
Mr. Martecchini said that the study focused on town-owned property and infrastructure; however, effective sea level mitigation policy will ultimately require cooperation between the public and private sectors. It will also require cooperation among Island towns — a notion that elicited a wave of sardonic laughter from many attendees.
“There are millions of dollars of grant money out there; they are looking for regional projects,” he said. “I strongly suggest a multi-town project, for instance on Beach Road,” he said. “If one town does it and another doesn’t, what’s the point?”
Oak Bluffs is the only town that has commissioned such a study to date. The final version will be done in about a month. “This study will help us get funding in the future,” conservation agent Liz Durkee said. “We’re hoping other towns do this as well, maybe through the MVC.”
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