Thames River ‘reef balls’ seem to be preventing erosion
Conn professor’s idea is protecting shoreline
New London — If you’re standing on the northern end of the Connecticut College waterfront with your back to the freight railroad tracks, the view is of 150 wiffleball-shaped concrete balls in rows running parallel to the shore, with an unusual shift in the low-tide mark partway up the rows.
They’re called reef balls and they range from 200 to 600 pounds, each more than a foot in diameter. Closer to the sailing dock, the rows of reef balls form a sort of barrier, separating the water from the sand. But as the rows move north along the shore, there’s a sudden point where the Thames River comes in a foot or two inland of the reef balls.
That’s the difference between reef balls placed in October 2021 and ones set this past July and September, and the line shows what the reef balls are trying to accomplish: preventing erosion.
These reef balls are the brainchild of biology professor Maria Rosa, who said the waterfront has lost four to five feet of shoreline since she started at Connecticut College in 2018.
She’s calling the project Camels Reef, for the school’s mascot.
As she talked about the reef balls Friday morning, she walked toward the invasive trees on a thin strip of land separating the railroad tracks from the river — land she said “is just going to collapse if nothing is done.” On the other side of the rail line are Pequot burial grounds and an athletic field.
“If nothing is done, we’re not just losing land; we’re losing infrastructure and culture,” Rosa said.
But, she explained, the reef balls slow down the waves, allowing for the deposition of sand. Rosa said the area in front of the first-placed reef balls used to all be gravel, but now the gravel is buried in 3 to 4 centimeters of sand.
As sand continues to accumulate, the reef balls will eventually be buried. Rosa initially forecasted this would take five to 10 years, but based on current sedimentation rates, she now thinks it will be more like three to five years.
If all goes well, she said, phase one of the project will include a total of about 400 reef balls extending north along the shore. She would then think about extending reef balls in the other direction, to the docks.
‘Plumbing and concrete pouring’
When Rosa started at the college, she was taking her students to the waterfront and said they noticed a “huge erosion problem.” She originally wanted to build an oyster reef but found out that permitting is difficult. Eel grass is good at reducing wave action, or the strength at which waves break on land, but swans ate all the eel grass she and students planted in 2019.
But she started learning about a project at the other end of the state. Sacred Heart University biology professor Jennifer Mattei — who Rosa called a “personal hero” — led a project to plant thousand-pound reef balls in Stratford, starting in 2014.
Reef balls have also been used in the Caribbean, but for coral restoration purposes.
Rosa wanted to show whether smaller reef balls than the ones in Stratford could also work. She had to get permits from the Connecticut Department of Energy and Environmental Protection and U.S. Army Corps of Engineers, and she needed clearance from fisheries.
She has gotten about $200,000 in funding from private foundations so far, which is funding reef balls and student interns. Rosa said she has had about 12 interns so far, either getting paid or receiving credit, and her forthcoming spring interns will learn about monitoring techniques and conservation.
Rosa used funds to purchase the largest reef balls from the nonprofit Reef Ball Foundation, but the others are ones she made with students and volunteers. She’s had volunteers from Mystic Aquarium, Boy Scouts and Girl Scouts, and depending on the day, they helped pour concrete or placed reef balls at water’s edge.
Rosa explained that the reef balls are made from Portland cement, pea gravel and sand, with silica used to properly adjust the pH balance. She has two cement mixers, and students and volunteers pour the mixture into a fiberglass mold. To make the holes in the reef balls, they used a few tetherballs — yes, the kind from school playgrounds.
“We joke with our students, a lot of ecology is plumbing and concrete pouring,” Rosa said.
More balls to put in place
In addition to slowing erosion, Rosa said the reef balls also create a “living shoreline” by re-creating a reef. She called the reef balls “massive crab condos” and has seen blackfish and menhaden, and she said oysters, mussels and barnacles will eventually settle on the reef balls.
But it’s been difficult to monitor wildlife, because the area was closed all summer due to construction; Connecticut College officially reopened the waterfront Oct. 21. But students in Rosa’s first-year marine science methods course, plus interns, will be doing monitoring in the spring semester. This will include using deposition traps to learn if sediment is coming in from the water or being lost from the land, taking photographs, measuring wave action, and doing more work around biodiversity.
And there are more reef balls to place.
Rosa said that can’t happen now, as the reef balls must be placed at low tide, when it’s not dark, when the water isn’t too cold, and when animals aren’t spawning. Her plan is to put more reef balls out in May, build more in June and July, and put out more in August and September. She also wants to put up a QR code in the area, so members of the public can get an explanation of the sight in front of them.
As she got ready to leave the waterfront Friday after excitedly talking about the project, she lovingly looked at the reef balls and murmured, “I’m so proud of these little balls. Look at them.”