Con Com study says sea level rise portends problems for Oak Bluffs

Results of a new vulnerability study will be presented at a conservation commission public meeting Thursday

As sea levels rise, scenes like this will be a more commonplace in Oak Bluffs. — Martha's Vineyard Times file pho

Thursday night Oak Bluffs residents will have the opportunity to hear the results of the Oak Bluffs Coastal Climate Change Vulnerability Assessment, at the library meeting room at 6 pm. The extensive study with the extensive name was commissioned last year by the Oak Bluffs Conservation Commission to determine just how vulnerable Oak Bluffs is to sea level rise and storm surge, and what can be done to mitigate the potential damage.

Not surprisingly, the low-lying, eastward-facing seaside town has some glaring weak spots.

“The harbor region, the Crystal Lake area, Beach Road, especially near Farm Pond, and all the roads in the hospital area are the most problematic,” Andre Martecchini, principal engineer for Kleinfelder, a Cambridge-based consulting firm, told The Times. “To some degree, they are already having problems. You could have tremendous flooding in the downtown area today. Luckily, the hospital itself looks somewhat high and dry.”

Overall, Mr. Martecchini said, the town’s vulnerability to sea level rise is “slightly above average,” because main roads and the business district will be increasingly susceptible to flooding. “Also, being that Oak Bluffs is an Island community, recovery from major flooding can be expected to be more difficult than for most communities,” he said.

Not much time

The study 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.

“2030 sounds like a long way off, but it’s only 15 years out,” Mr. Martecchini said. “When you’re talking about municipal planning, that’s not much time, especially when big money is involved.”

Mr. Martecchini said the computer models used in the study 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. The calculus of the WHG includes projected sea level rise and worst-case scenarios from hurricanes and nor’easters.

“No surprise to anyone, the forecast gets worse as time goes on,” Mr. Martecchini said. The study is focused on town-owned property and infrastructure; however, effective sea level mitigation policy will ultimately require cooperation between the public and private sectors. “When you look at the harbor, you have quite a bit of town-owned land, but then as you head to East Chop, you have a long line of private homes,” he said. “The town can raise its seawalls, but if private homeowners don’t raise theirs, it does no good. You need participation by everybody to make it work.”

Mr. Martecchini said Oak Bluffs is particularly vulnerable because the eastern-facing coastline takes the full brunt of nor’easters. “Nor’easters are longer-duration events than a hurricane, so you can have a higher storm surge because it stretches over several tide cycles. You don’t get that with a hurricane,” he said. “Nor’easters are also much more common than hurricanes. There have only been two Category 3 hurricanes in the area in the last 100-plus years.”

Nature vs. nature

In addition to manmade infrastructure, the study will show how sea level rise will affect the natural resources on the Island. “The natural resources are more your wetlands and beaches,” he said. “We use a different modeling system to look at the impact on natural resources. The impact on the wetlands is the day-to-day tides. As the sea level rises, if the growth of the wetlands can’t keep up with it, your wetlands die off and become mud flats,” he said.

Mr. Martecchini said the study will recommend that the town adjust some bylaws to better prepare for the inevitable. As an example, he said, a current town bylaw that restricts a residential building to 32 feet in height hamstrings effective flood mitigation. “Increasingly, coastal towns are encouraging homeowners to raise their houses, but in Oak Bluffs, any house at or near 32 feet won’t be able to do that under the current laws on the books,” he said. According to the FEMA guidelines, homeowners could also also benefit from a bylaw change, because raising their homes could considerably reduce their flood insurance premiums.

“The town is basically trying to proactively understand its vulnerabilities and start that long-term thinking,” Mr. Martecchini said. “Part of it may be that you do nothing. Many communities are taking that approach. At the same time, Sandy took a lot of people by surprise, and we have not had a major storm for quite a while. [The Massachusetts coast] lucked out in Sandy, because it hit us at low tide. If it hit during high tide, it would have been devastating.”