New Project Hoped To Help Save The Popponesset Spit
By: Brian Kehrl
The shrinking of the long, narrow sandbar that protects the property along and ecology of Popponesset Bay has for years been a major concern for representatives of Save Popponesset Bay, a local nonprofit that owns about two-thirds of the spit. It has led to a new project this year, aiming to stabilize the spit and rebuild the lowest areas of the dunes, the areas at the greatest risk for breaching.
The installation of wooden “sand drift” fencing and planting thousands of shoots of dune grass in three areas along the spit began late last week, two weeks after a dredging project pumped 5,000 cubic yards of sand from the entrance of the bay over to the spit.
Four decades ago, the dunes along the Popponesset spit reached upward of 15 feet above the water line, a high wall of sand and grass that could withstand the surge of even heavy storms. By the 1990s, some parts of the spit had eroded down to less than six feet high, a far less formidable barrier from the elements. In an illustration of the consequences of that erosion, seven different sections of the spit breached in the storms last month, according to a coastal engineer who has closely studied the spit. The fence will be a conspicuous new feature of the spit this spring and summer, as residents and visitors head out on their annual migration to the beach. Its visibility, a sharp contrast to building up the beach with dredged sand, will be part of an education campaign meant to inform the public about the delicacy and importance of the landscape, said Richard J. Bailey, executive director of Save Popponesset Bay.
The project, and the extensive review that Save Popponesset Bay had to work through in order to permit it, illustrates the competing interests for use of the beach, a phenomenon seen across Cape Cod. Property owners want to protect their land, residents want to use the beaches for recreation, and environmental advocates want to preserve the shore for wildlife habitat and other ecological functions. In other Cape towns, the situation has evolved into bitter struggles for use of the beaches.
But in the case of the Popponesset spit, in part due to a measure of good fortune, in part due to dogged pursuit, the groups involved were able to work together for a sort of compromise.
“It is a balance. That is the decision that is up to the permitting agencies, they have to make these difficult decisions. I think it is just going to become harder and harder with sea level rise and fewer and fewer sites for nesting,” said Rebecca Harris, director of the Massachusetts Audubon Society Coastal Waterbirds Program.
Sacrificial Drift Fencing
The fence and revegetation are part of a three-pronged approach by Save Popponesset Bay to protect and preserve the spit, Mr. Bailey said. First, the dredged spoils are used to add sand to the spit, both at the base, from where wave action will push the sand along the shore, and for the first time this year, directly to the low-lying, “overwash” areas. Then the fencing and dune grass will be used to hold the sand in place, to prevent it from washing back out to sea and from eroding over into the channel between the spit and Popponesset Island. And finally, the public education campaign, which Mr. Bailey called “behavior modification” of the people that use the spit.
The wooden fencing is about two-and-a-half feet high, built into a zigzag formation in two areas near the tip of Popponesset Island and another area about 1,000 feet down the spit.
The fence is “sacrificial,” designed to break apart during a strong storm, according to Norman Hayes, an engineer contracted for Save the Bay from the firm BSC Group.
“It isn’t permanent. It is a drift fence. It is envisioned to try to keep dogs and the public out of the most critical areas,” Mr. Hayes said. The fenced areas will feature narrow walkways allowing passage from one side of the spit to the other, he said.
The fences are designed to trap blowing sand to rebuild the dune and to break up the energy from waves, Mr. Hayes said. When wind carrying sand hits the fence, the wind loses velocity and drops the suspended sand, he said. The zigzags are meant to capture wind blowing from all directions, unlike the more common “snow fencing” which only works for wind blowing from one main direction, he said.
“We are talking about 12 inches or maybe 14 inches of sand over a year. But that is huge, because of the area we are talking about,” Mr. Hayes said. The 2,500 shoots of dune grass, which he said he hopes will spread out from the plantings behind the fenced areas, will also trap the sand and stabilize the sand and the dune.
The fencing will be built with gaps between the slats, so that birds can move through it, he said.
Because of strict state and local regulations governing barrier beaches, permits for “hard” or permanent structures are rare, Mashpee Conservation Agent Andrew McManus said in an interview last week. The fencing has been used with some success at locations on the outer Cape, but this is the first project of its kind in Mashpee, he said.
“I don’t think it is an unusual application. I think it makes a lot of sense, a lot more sense than doing nothing,” Mr. McManus said. “The idea is to enhance the natural capacity of the area to rebuild itself, to work with nature.”
Seeking The Proper Balance
The use of the spit by protected shorebirds like piping plovers and least terns drives some of the most stringent regulations. Save the Bay has been working to permit the project for the past six years, Mr. Hayes said, since a study was done on the feasibility of different approaches to preserving the spit.
Ms. Harris said barrier beaches like the spit are critical for piping plovers because the birds like to have both the ocean and a bay nearby. Studies have shown that chicks that have access to bayside habitat as well as ocean habitat grow faster and have a better chance of survival than those that don’t, she said.
MassAudubon owns the land at the end of the spit, making the two nonprofits joint landowners.
“It has been a good collaboration with Save Popponesset Bay, of doing what is best for the birds and maintaining the beach for public use and for property protection,” she said, a relationship that is often not the case. “Some people don’t even want us on their property to monitor the birds. They don’t even want to know that they are there. So our relationship with them is one of the best.”
In other cases, there can be a bit of a conundrum between protecting habitat and protecting property. Piping plovers and other shorebirds are often drawn to the overwash areas, Ms. Harris said. They like the open space for nests and foraging. But it is those overwash areas that those interested in property protection dislike the most, because they tend to be the most at risk of a major breach. So, often the areas that property owners want to armor are the very same areas that wildlife advocates want to be left alone. “When you deposit dredge spoils, the birds will be attracted. You often end up with nests right in the middle of dredged material,” Ms. Harris said. On the spit, though, a bit of good fortune allowed a compromise. Whereas the overwash across from the island is the greatest concern for breaching, it has not been home to plover nests in recent years according to nesting activity information provided by Mr. Bailey. The plovers predominantly nest out on the far end of the spit, including in some overwash areas that will be left alone.
That focus on areas where plover nests have not been found lately led to MassAudubon’s support of the project.
The Catch-22 between habitat and property protection also extends deeper as well. Just as MassAudubon wants to maintain shorebird habitat by limiting human impact on the shoreline, they also recognize that if nothing is done to protect the shore, there is a risk of losing the habitat completely. “Just in terms of maintaining the beach, and because the sand will eventually move down to where the birds tend to nest, it is beneficial to them, we think,” Ms. Harris said. “This beach can’t be taken over by the birds. There has to be space for people as well, so we don’t want to fence off the whole thing. It is sort of a balance.
“There is no easy answer, that’s for sure...It is hard to know what works. Dredge spoils can wash away so quickly, just after the first spring storm, so all that work and money can be for nothing. It is hard because we have armored the beach so much already. It would be more stable overall without the groins and jetties and seawalls that we’ve built. It would allow for more movement in some areas, which is natural, so there would be changes in the microscale, but more stable overall. With armoring, we end up with big losers and big winners,” she said.
A ‘Gift,’ Not A ‘Right’
And just as piping plovers like the overwash areas, so, too, do people. They are a natural place to cross over from one side of the spit to the other, so they are some of the most heavily trafficked areas for the thousands of beachgoers that frequent the spit every summer.
It is that traffic that Save Popponesset Bay is hoping to control with the fencing. “The traffic is wearing down the dune,” Mr. Hayes said. With a more visible structure out there, and a new explanatory sign to accompany it, Mr. Bailey said Save Popponesset Bay is hoping to use the opportunity to inform the public about the risks to the spit and what they can do to help. He compared the effort to working to inform residents about nutrient loading, fertilizers, and septic systems.
“The single greatest predator out there is people and their dogs,” he said. “What it amounts to is we are trying to minimize the impacts that humans have on the spit.”
Mr. Hayes said many of the beachgoers do not seem to recognize the consequences of their actions, but many of the issues are from innocent behavior, like children flying kites during plover nesting season. The plovers see the kites and think they are predator birds, so will not go out to eat if kites are flying overhead, he said.
Dogs, too, can scare the birds, disturb nests, and take time away from important food gathering, he said. Dogs and people walking through beach grass can kill the plants, which help hold the dune in place, he said. “Hopefully this will be the first step of a new education about the critical nature of the stability of the spit and the wildlife habitat,” Mr. Hayes said. “The use of the spit is not a right. It is kind of a gift, temporary and fleeting.”