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. Storm tide pathways are routes flowing water would take in low-lying coastal areas, according to the CSS website.
MVC special projects planner Dan Doyle said the study is being conducted to “to identify paths that flood water will take on the Island as sea level rises and storm surges increase.” The study and mapping are being done by CCS.
Mark Borrelli, CCS coastal geologist, said this study is a two-year project that began in September 2020 and will be completed in June 2022, which is when the results will be publicly available. The funding came from a grant from the Massachusetts Office of Coastal Zone Management, which the researchers were able to attain through the help of the town of Oak Bluffs.
Borrelli said there were two aspects to the study. The first is mapping the storm tide pathways of the Island towns, which will also be available for viewing on the National Weather Service’s Coastal Flood Threat and Inundation Mapping website, alongside a standalone app for Martha’s Vineyard town staff and the public. The other is making an “Island-wide inventory of low-lying roads and associated infrastructure.” Borrelli wants to make sure the data gathered are “useful and usable” to local and regional governmental entities so that they can address current and future concerns. That means the easier they make the data’s usability, the better it is for the towns and the public. Borrelli said this is particularly important because many towns on the Cape and Islands do not have their own personnel to do geographic information system work.
“We do the mapping. We’re out there. We’re on the Vineyard for three or four days in March to do all the mapping Island-wide of these storm tide pathways,” Borrelli said. He said the National Weather Service does real-time predictions for the next two days of what the total water levels will be on the Island, although there is no tide gauge as of yet.
Several Massachusetts communities, such as Provincetown and Nantucket, have been studied for storm tide paths, according to Borrelli.
“The folks in Provincetown actually use this data when there is a coming storm,” Borrelli said. “So, they’ll see a storm a day out, and they’ll go to these and figure out where the storm tide pathways are, based on the predictions from the National Weather Service — minor flooding, moderate flooding, that kind of thing — then they’ll go to our data to find out exactly where the water could be flowing in. They’ve moved sandbags, they’ve moved those portable flood walls to prevent flooding.”
Although it takes a couple of years for the data to settle in, Borrelli said the towns who have the information “really like and use the data.”
Borrelli said there are three main numbers that were used to map out the storm tide pathways and water levels on Martha’s Vineyard: the highest high tide of the year, the “storm of record,” and an addition of 8.5 feet to take into account sea level rise and storms. The “storm of record” for Martha’s Vineyard is the hurricane of 1938, which brought the water level up to 9.42 feet during low tide. Borrelli said every half-foot increase of total water level can flood 360 acres of land.
According to Borrelli, there are a total of 717 storm tide pathways on Martha’s Vineyard. Among these pathways, 57 of them are within 10 meters of roads “considered critical infrastructure,” such as Lake Avenue in Oak Bluffs. These 57 pathways are also within 100 meters of “critical facilities,” such as Martha’s Vineyard Hospital, police stations, and bridges, among others.
Borrelli also showed the Provincetown examples of what resources are available online, such as the Surging Seas Risk Zone Map and National Weather Service’s Coastal Flood Threat and Inundation Mapping.
At the end of the presentation, a question and answer session was held for the audience of 53 people. People asked questions about how to go about using the data, other parts of the Island that can be impacted by the study, and how to get the community involved.
