Trajectories of storm surges studied on Martha’s Vineyard

The Martha’s Vineyard Commission (MVC) and the Center for Coastal Studies (CCS) in Provincetown presented the results so far of the storm tide pathways study. According to the CSS website, storm tide pathways are pathways that running water would take in low-lying coastal areas.

VMC Special Projects Planner Dan Doyle said the study is being conducted to “identify the paths floodwaters will take on the island as sea levels rise and storm surges increase. “. The study and the mapping are carried out by CCS.

CCS coastal geologist Mark Borrelli said the study is a two-year project that began in September 2020 and will end in June 2022, when the results will be made public. The funding came from a grant from the Massachusetts Office of Coastal Zone Management, which the researchers were able to secure with help from the town of Oak Bluffs.

Borrelli said there were two aspects under consideration. The first is to map storm surge pathways for island cities, which will also be available for viewing on the National Weather Service’s Flood Threat and Coastal Flood Mapping website, as well as a standalone app for staff. of the town of Martha’s Vineyard and the public. The other is to compile an “island-wide inventory of low-lying roads and associated infrastructure.” Borrelli wants to ensure that the data collected is “useful and usable” for local and regional government entities so they can address current and future concerns. This means that the easier they make it easier to use data, the better it is for cities and the public. Borrelli said this is particularly important because many towns in Cape Town and the islands do not have their own staff to carry out geographic information system work.

“We do the mapping. We are there. We’re on the vineyard for three or four days in March doing all the island-wide mapping of these storm tidal paths,” Borrelli said. He said the National Weather Service was making real-time forecasts for the next two days of total water levels on the island, although there is no tide gauge yet.

Several communities in Massachusetts, such as Provincetown and Nantucket, have been studied for storm surge paths, according to Borrelli.

“People in Provincetown actually use this data when there’s a storm coming,” Borrelli said. “So they’ll see a storm one day, and they’ll go to those and figure out where the storm tide lanes are, based on the National Weather Service forecast — minor flooding, moderate flooding, that sort of thing — then they’ll look at our data to find out exactly where the water could flow in. They moved sandbags, they moved these portable flood walls to prevent flooding.

Although it takes a few years for the data to settle, Borrelli said the cities that hold the information “really love and use the data.”

Borrelli said there were three main numbers that were used to map storm tide pathways and water levels on Martha’s Vineyard: the highest high tide of the year, the “record storm,” and an addition of 8.5 feet to account for sea level rise and storms. The “record storm” for Martha’s Vineyard is the 1938 hurricane, which brought the water level to 9.42 feet at low tide. Borrelli said every half-foot rise in total water level can flood 360 acres of land.

According to Borrelli, there are a total of 717 storm tide lanes on Martha’s Vineyard. Of those trails, 57 of them are within 10 yards of roads “deemed critical infrastructure,” such as Lake Avenue in Oak Bluffs. These 57 trails are also within 100 yards of “critical facilities,” such as Martha’s Vineyard Hospital, police stations, and bridges, among others.

Borrelli also showed Provincetown examples of resources available online, such as the Breaking Seas Hazard Map and the National Weather Service’s Coastal Inundation and Flood Threat Map.

At the end of the presentation, a question and answer session took place in front of an audience of 53 people. People asked questions about how to use the data, what other parts of the island might be affected by the study, and how to involve the community.

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