Some beaches in southern Maine lost up to 30 feet of dunes from the twin storms that wreaked havoc on the coast last week, according to early estimates.
The two storms that hit Maine on Wednesday and Saturday caused massive flooding to low-lying areas that damaged homes, docks, roads and boats. The storms also dramatically eroded some of the natural and human-made barriers that protect those areas from the ocean, leaving them more vulnerable to the second of the two storms on Saturday and to future weather events.
Sand dunes, which make up about 2 percent of Maine’s coast, act as natural barriers between communities and the ocean, and throughout the year, it’s normal for them to undergo some amount of erosion and rebuilding, according to Peter Slovinsky with the Maine Geological Survey. Larger waves carry sand out to sea during winter, then calmer waves deposit it back on the beach in summer to rebuild the dunes.
But the back-to-back storms last week inflicted more extensive damage, Slovinsky said, and it could now take two years for some of the dunes to naturally repair themselves.
While authorities are still assessing the damage, Slovinsky said that each storm took about 10 to 15 feet of sand off the dunes in some southern Maine communities. And while it’s normal for a single storm to erode dunes that much, it’s unusual for such storms to hit in quick succession, eroding up to 30 feet of sand.
“Some locations took a big hit in the first storm, and then the dune kind of got flattened,” Slovinsky said.
In the York County city of Biddeford, Mayor Martin Grohman said that some local dunes were completely washed out by the pair of storms. With the community’s monetary damages estimated in the millions, Grohman said he doesn’t yet know if the city will rebuild the dunes or let them repair themselves naturally.
There were also reports of serious dune loss on Willard Beach in South Portland and at some of Maine’s state parks.
As sea levels rise, big storms typically push dunes towards land, Slovinsky said. As waves wash over the dunes, they bring sand with them, eating away at the ocean side and depositing sand on the land side. Over time, this causes dunes to continually move landward along with the waves.
But Slovinsky warned that there’s a challenge for beachside communities that have gotten too developed, as human structures can prevent this natural creep of sand, keeping the beach from adapting to rising seas brought on by climate change.
“I think with a storm like this, it’s an eye-opener for coastal communities,” Slovinsky said. “What we’ve had along our coastline in the past isn’t necessarily what’s going to stand up to the conditions we have now or the conditions we are going to have in the future.”
That means when communities inevitably rebuild their coastal barriers and infrastructure, they’ll need to raise them even higher than in the past, for example by placing houses on stilts, or rebuilding seawalls or dunes to a greater height, Slovinsky said, as storms this intense will only become more frequent.
Rebuilding dunes isn’t as expensive as repairing seawalls or other infrastructure, Slovinsky said. After a storm on Patriot’s Day in 2007, Camp Ellis trucked in sand and used volunteers to repair the dunes on Ferry Beach for $20,000, he said. State officials are also restoring the dunes at Popham Beach, using old Christmas trees to help with the process.
Some towns have opted for artificial dunes. In the 1970s, after the town of Ogunquit noticed erosion to its dunes, it constructed a dike made of sand that replaced the natural dunes, creating a barrier to protect the inland. Old Orchard Beach also has some artificial dunes, Slovinsky said, that cover a sewer line running across the beach.
Slovinsky said the best way Mainers can protect the dunes in their everyday lives is to stay off of them. During the summer, most beaches have ropes and signs to keep beachgoers from trampling the dunes. Slovinsky said if someone has to go onto a dune to retrieve something, they should make sure to stay off of the fragile dune grass.
“Stay out of the dunes. It’s not a place we really need to go to do things,” Slovinsky said. “The beach is where we go to do things and the dunes are there to protect the adjacent uplands and the adjacent marsh habitats.”
