Posted on May 25, 2020
Rhode Island’s inaugural “living shoreline” project passed its first test before it was even finished.
Built over the last three weeks on a stretch of beach below Rose Larisa Memorial Park that opens onto Narragansett Bay, the stone-and-sand structure was designed to stop the steep bluffs behind it from eroding any further.
When winds churned up the Bay on a recent afternoon, the gusts drove foamy waves onto the narrow beach toward the tree-lined slopes that rise 20 to 30 feet above. But where the new structure was installed, the waves broke harmlessly onto a rock shelf, their force dissipated before the water could go much higher.
“It was blowing pretty strong and you could already see wave attenuation taking place,” said John O’Brien, policy specialist with The Nature Conservancy. “That was clearly evident.”
The waves were admittedly small, well short of the powerful surges pushed forward by coastal storms that are responsible for much of the erosion here in the Riverside section of East Providence and elsewhere along the Rhode Island shoreline, which is creeping back by nearly two feet a year on average.
But it was still an encouraging moment for the conservancy and its partners, the Rhode Island Coastal Resources Management Council and the City of East Providence, not least because what will arguably be the key component of their test project — the part that will make it “living” — was not yet in place.
That piece is the planting of water-tolerant grasses in the sand that was filled in behind the stone shelf, or sill. There, 2,000 plugs of smooth cordgrass and spikegrass in the sand that will hopefully form another line of defense in front of the bluffs.
If the plants get rooted and spread — a scenario that will to some extent depend on how well they can withstand the grazing of geese in the area — they will begin to form a salt marsh, an ecologically-rich habitat that can also act as a natural buffer to storm surges by absorbing much of their energy.
The man-made marsh along with a hillside stabilization structure just to the north are the first living shoreline projects to be tried in Rhode Island that are aimed at preventing coastal erosion. The only precursor in the state is at Save The Bay’s center at Fields Point in Providence, where a small marsh was built for the exclusive purpose of creating wildlife habitat.
The state coastal council and the conservancy are experimenting with living shoreline techniques as alternatives to traditional concrete or rock structures, such as bulkheads, breakwaters or revetments. These hard structures deflect wave energy, often exacerbating erosion elsewhere along the shore. They also interfere with the natural movement of sand in front of them, leading to the narrowing of beaches and, in time, the loss of public access along the shoreline.
Nature-based projects have seen some success in southern and mid-Atlantic states, but they’re less common in the Northeast. The projects in Riverside are part of a regional program being funded in large part by the National Oceanic and Atmospheric Administration that also include new rounds of work in Maine and more rigorous evaluations of previous construction in Connecticut, New Hampshire and Massachusetts.
Groups are taking a closer look at erosion-control techniques that preserve habitat in part because of sea level rise, which is occurring in the Northeast at a rate that is among the highest in the world. As seas rise, surges will become higher and reach further inland, making more places vulnerable to their erosive power.
The hope is that the projects in Riverside can serve as models for coastal property owners who are looking to enhance protections. They come as the state coastal council has amended its so-called “Red Book” — rules that regulate all coastal development in Rhode Island — to more strongly discourage hardening the shoreline in favor of nonstructural methods, such as planting vegetation or adding sand to beaches.
“We’re trying to look at alternatives to just putting in a wall,” said Janet Freedman, geologist with the coastal council. “We’re hoping to show that you can create habitat and still protect your property.”
Here, at the site of the former Crescent Park, waves have carved out the base of the bluffs, undermining the slope in places and toppling trees. Previous efforts to protect the area by building seawalls or piling up riprap have failed. Scattered stones and slabs of broken concrete are all that remain of those earlier attempts.
Crews from SumCo Eco-Contracting, of Salem, Massachusetts, were supposed to start the living shoreline work in the late fall, but the projects were delayed while the partners tied up funding. Most of the money to cover the $232,000 cost came from a $142,000 NOAA grant. 11th Hour Racing donated $50,000, and the remaining $40,000 came from a state habitat-restoration fund overseen by the coastal council.
SumCo’s workers were classified as essential, so they’ve been able to work during the coronavirus pandemic.
They removed about 50 tons of rubble from the shoreline to make way for the new marsh. The rock shelf they installed is divided by channels to allow water to flow in and out of the area. About half of the site is covered by a coconut-fiber mat to protect the plantings from waterfowl while the other half is bare to see if the grasses can survive without that shield.
Whether a true marsh can be created is not clear. The marsh at the Save The Bay Center used a similar design as the project in Riverside. It took years to get established after it was built in 2003. Horseshoe crabs spawn on the small beach there now and sandpipers feed within the marsh, but it took a lot of work to make it a success.
“Now, it is a fringe marsh and it has built up elevation, but getting these salt marshes established is very challenging,” said Wenley Ferguson, director of habitat restoration for Save The Bay.
The second project in Rose Larisa Memorial Park is just north of the marsh site, on another section of hillside that had started to give way. Workers re-graded it with 200 cubic yards of fill, installed a stone toe to stabilize the slope, added coconut-fiber logs, then covered the whole thing with sand and planted it with 3,200 stems of American beachgrass, a native plant that forms underground networks of tough rhizomes that are perfect for preventing erosion.
The coconut fiber logs will break down over five or 10 years, giving the beachgrass time to spread.
“It’s like a crutch,” said Annie Procaccini, senior project coordinator with SumCo. “That’s the idea with biodegradable material. It allows the vegetation to take over.”
The conservancy and the coastal council will closely monitor the projects to judge how they’re faring. They’re doing drone surveys and photo comparisons and will eventually do plant counts to get a better sense of what’s working and what’s not.
The results will go some way to determining whether similar projects are tried along Rhode Island’s fragile coast.
“We’re hoping this works,” said Freedman. “We expect it to stop the erosion.”
Source: Providence Journal
