The size of a dune that East Hampton Town is considering building at Ditch Plain may ultimately be dictated by a Federal Emergency Management Agency calculation that would make it nearly 20 feet high.
“The dune will be designed to maintain public access points and will be designed so those access points can be plugged up in a storm event,” said Councilwoman Cate Rogers, who supports moving forward on the project.
Like so much, it comes down to funding. If the dune is built too small, the town would not be eligible to receive federal funding to rebuild it in a declared disaster.
“In the event of a declared disaster, you can apply for FEMA reimbursement, so the town doesn’t have to come out of pocket every time this happens,” Patrick Barrineau, a project manager for Coastal Science and Engineering, said at Tuesday’s East Hampton Town Board work session.
The board is trying to get out of a cycle of smaller projects that are ineligible for federal funds and must be funded by the state, county, and town.
“I am supportive,” said Councilman David Lys, while noting that a 20-foot dune could change the nature of the beach. “It could be startling to some,” he allowed. “It’s going to be a very high peak with a very high slope.”
Mr. Barrineau said that to qualify for FEMA money, “Their rule is you need 540 square feet in the profile of the dune above the stormwater level in a one-in-100 storm, or a 1 percent probability event on the oceanfront. In the vicinity of Montauk at Ditch Plains, the Army Corps of Engineers has determined this at nine feet.”
So, in theory, the ocean rises nine feet in such a storm and there would still be plenty of dune above it to protect the Ditch Plain neighborhood on the other side of the dune.
To get to that level, 54,000 cubic yards of sand would be placed between the so-called “dirt lot” on the east end and Seaview Avenue on the west — 2,700 linear feet. Those two points link two major bluff points. To put it in perspective, 5,500 cubic feet of sand was used to replenish the beaches before the season began this year. That sand has mostly been washed away.
“That recreational beach is down to hardpan once again,” said Councilman Lys, “After the town put in nearly $300,000 worth of sand to make sure we had a summertime recreational beach.” While it is impossible to predict how long a new dune might last, in a phone call after the meeting, Mr. Barrineau said that with beach replenishment projects there tend to be increasing returns. “The bigger the project, the longer it will last.” It matters less that the sand will be placed farther upland, he said, and more that roughly 10 times the amount placed in June will be positioned.
“I would estimate that you won’t be rebuilding every year or two. This should be a longer-term project.”
The problem is placing that volume of sand in a tight area, and he said that was the focus of his work this week. It’s a tradeoff between the height and width of the dune. “We’re trying to not just put up a wall of sand.”
“I do have concerns about the slope of the dune and what it would do to the recreational beach,” Councilman Lys said at the meeting.
Ditch Plain is a popular beach. Too much dune and the bathing area would shrink. Perhaps even more important, in keeping with the history of the beach, was ensuring the surf break isn’t affected. “You don’t want to mess with that surf break,” Mr. Barrineau told the board.
He showed cross sections of the dune from before and after last year’s winter storms. The storms took five feet from the dune crest, which stood at 15 feet before the storms. While that was bad, equally troubling was that the crest also migrated landward 10 feet. So, the dune got shorter and closer to the houses behind it. The majority of the neighborhood sits only five feet above sea level. “Flood hazard is enhanced with the dune gone,” he said.
Once a FEMA-compliant dune is built, the town would need to monitor it annually and maintain it. Mr. Barrineau pointed out that it wasn’t just about flood prevention. Repairing the dune could help the entire dune ecosystem and the species that are dependent on it for their survival.
There are bound to be tradeoffs for the human species too. For those on adjacent parcels, “There will be viewshed impact,” he said. Councilwoman Rogers indicated that she would be meeting with the homeowners on Tuesday evening after the board’s work session. The town will need easements from them to build the dune and will also need a permit from the New York State Department of Environmental Conservation once the final volume of sand is calculated. Mr. Barrineau said that could be done by this week.
Sand would come from UpIsland sand pits that have been preapproved by the state for beach replenishment, but Mr. Barrineau said he would have to ensure they had enough volume. Once that is done, a construction protocol will be developed. After the dune is sculpted, a drone will survey to make sure it is FEMA compliant.
“I have multiple concerns,” said Councilman Lys. “Yes, the protection of the neighborhood. Yes the protection of an iconic surfing area, but also the recreation and enjoyment of residents and visitors to the beach. These are all questions that the town board has to understand before we make a final decision. It is moving forward, but this type of design is going to change that beach area pretty dramatically. There are positives and negatives.”
“When we look at the reality of sea level rise, the storm surges, the intensity of storms, the frequency of storms, we are going to have to take a hard look at what we value,” said Councilwoman Rogers. “Keeping what it was historically, which is absolutely impossible, or changing with the reality that we’re faced with.” Cost was not addressed at the meeting.
