Life along the shoreline is going to change. Scientists predict sea levels could rise by 3 feet or more in the short time span of the next 50 to 100 years. Of course, to some extent you’ll have choices if you’re part of human society living on the coasts-we can relocate, adapt, or build barriers or pumps to control the water. But what about communities that don’t happen to be human that depend on the shoreline and its various ecological niches for survival? Entire ecosystems don’t have the ability to plan ahead for disaster; they can’t pack up and move to avoid being inundated, damaged, or destroyed. Putting an even tighter squeeze on the limited coastal habitat from the other end, pressures from development and other human activities have turned the coastline more toward the needs of people rather than the needs of nature. Whether nature brings a wave or a landowner owner decides to pave, the result is the same for nature’s coastal communities: They lose precious irreplaceable ground.
And the squeeze is already under way.
March of the Bulkheads
Bret Webb, assistant professor and specialist in coastal engineering at the University of South Alabama, says the natural coastal habitat of Mobile Bay has been dwindling away “for a number of years,” in part as an ironic result of the very efforts made by citizens to preserve the shoreline. He explains: “Starting in the 1950s, the common and preferred way to stabilize a shoreline was to use a concrete bulkhead or a sea wall. People really didn’t give any thought to doing anything differently because it was easy, relatively inexpensive, and the design was straightforward, as well as the construction.”
However, he notes, “When one person installed a bulkhead, the adjacent properties started to feel some accelerated erosion at their end, so their response would be to build a bulkhead and tie it into the neighbor’s structure, and thus began the march of bulkheads around the shoreline.”
For a period of five or six decades, Webb says, there’s been “a proliferation of bulkheads” around Mobile Bay with “absolute loss of intertidal habitat and sandy shoreline” behind each one. “Today, between 40 and 60% of all of the bay’s shorelines are armored with something that prevents all habitat or sandy beach value,” he says.
Webb believes living shorelines can help turn that trend around, with the caveat that we first agree on the terminology. According to Webb, the term living shoreline has become so popular that people are now using it to describe several different things. “The name has sort of been usurped by a number of different groups that really have no interest in protecting a sandy shoreline or vegetated shorelines. Now, the term living shoreline is being used to describe habitat projects that have little to do with shoreline processes whatsoever.” Webb defines living shorelines as “any shoreline stabilization methodology or technique that has some incorporation of natural-and maybe some synthetic-materials, with a focus on allowing shoreline processes to occur with habitat benefits.”
Along similar lines, he notes, the National Oceanic and Atmospheric Administration (NOAA) definition also includes “shoreline management practices that provide erosion control benefits; protect, restore, or enhance natural shoreline habitat; and maintain coastal processes through strategic placement of plants, stones, sand-fill, or other structural organic material.”
Putting Theory and People to Work
Jeff DeQuattro of The Nature Conservancy appreciates the importance of finding sustainable new ways to stabilize Alabama’s shoreline. He says living shorelines offer an alternative to fighting fire with something worse. He managed installation of a $2.9 million living shoreline project for The Nature Conservancy to create new habitat at two sites on Alabama’s coastline: Portersville Bay and Alabama Point. The project, funded by the American Reinvestment and Recovery Act of 2009, installed more than 1.5 miles of oyster reef to test out a variety of techniques that could potentially protect major stretches of the state’s shoreline from accelerated erosion.
DeQuattro, who is coastal projects manager for The Nature Conservancy in Alabama, the lead nongovernmental organization heading up the effort, says the project had several goals: one, to increase biodiversity; two, to reduce erosion; and three, to create jobs by putting displaced employees from the fishing industry back to work.
The project also included an experimental angle to study the efficacy of three different technologies for building artificial reefs. DeQuattro says ongoing monitoring efforts along the 1.9 miles of constructed reefs will compare the performance of reef-balls made of concrete, cubes of steel rebar constructed to attract oyster spat, and oyster shell bagged in wire mesh, each for its ability to recruit oyster spat and provide sustainable habitat.
According to a report in the Alabama newspaper Lagniappe earlier this spring, within a day of reefs being placed in Alabama Point and Portersville Bay, “sea life was attracted to it.” The report continues: “Two years later . . . one reef has far exceeded the project’s target oyster count, while the other is slightly behind but still outpacing the productivity of commercial reefs further offshore.”
With a target density for oysters on the reef of around 100 per square meter, Quattro told reporters that within two years he was able to count up to 60 oysters per meter, far outstripping commercial reefs, which average only 14 oysters per meter.
DeQuattro says, however, that it’s too early to draw comparisons among the three technologies; nonetheless, the data show that along the shorelines where The Nature Conservancy placed the new artificial reef structures, they have successfully “cut erosion rates by half.”
Doing these experiments makes sense, DeQuattro says, because there is no one-size-fits-all solution when it comes to finding effective living shoreline technologies. In low-energy environments, such as rivers and canals where waters are relatively calm, coir logs might provide the optimum stabilization technique for homeowners looking to install a highly economical living shoreline without the need for a boat. Oyster shell, on the other hand, might be appropriate material for a living shoreline in areas of deeper water, where oysters are found in nature and that can be accessed by boat. The key to success is to carefully match solutions with local site conditions.
One Thousand Volunteers
The big news from Alabama, DeQuattro says, is the way in which living shorelines have captured the public imagination.
In the aftermath of the tragic Deepwater Horizon oil spill and the devastation it brought to Alabama’s coasts, the state responded with a project called “100-1,000: Restore Coastal Alabama.” Tapping into a share of the oil spill disaster recovery funding, the project aims to build 100 miles of oyster reefs and protect and promote growth of 1,000 acres of marshland habitat to help ecological health return to the state’s coastline and tidal wetlands. Volunteers from the community have been showing up by the hundreds to take part in building massive artificial oyster reefs and other living shoreline structures. In May 2013, 900 volunteers placed almost 25,000 “oyster castles,” weighing 35 pounds each, to construct 224 feet of living shoreline at Pelican Point. Before that, in January 2011, more than 500 volunteers built a quarter-mile of reef at Helen Wood Park in Mobile. To date, The Nature Conservancy, 100-1,000: Restore Coastal Alabama, and volunteers have installed close to 2 miles of living shoreline.
DeQuattro says volunteering has given hundreds of people a chance to see how living shorelines work, and that is starting to create demand from homeowners. Having already installed living shorelines in front of five different homes (although he said finding funding for homeowner projects is always an issue), he now has a list of several dozen more residents who would like living shorelines at their homes.
Caught in the Middle
The Mid-Atlantic’s Delaware Bay Estuary represents a delicate resource caught between the pincers of development and sea level rise. Considered the world’s largest freshwater tidal estuary, a highly productive fishery, and vacation haven, the bay region is also home to 9 million residents.
Danielle Kreeger says, however, that the estuary’s natural ecology is losing ground. A wetlands ecologist, associate research professor at Drexel University, and a senior research scientist with the Academy of Natural Sciences of Drexel University with more than 25 years of experience working as a research scientist and educator, Kreeger also serves as science director for the Partnership for the Delaware Estuary. That organization focuses on the science, management, and restoration needs in the estuary.
“We are seeing the marshes already collapse. We’re losing an acre a day-so it’s not something in the future; it’s happening now,” she says.
Pointing out the potential troubles the bay is facing, Kreeger says, “I don’t want to sound alarmist, but there is a lot at stake. With the population expected to increase by 80%, jobs that depend on a healthy estuary become an issue. The population increase could also put a strain on drinking water supplies.” Adding urgency, Kreeger says, the water that is available could become less palatable over time. “With sea level rise we’re expecting salinity rise, and we take our drinking water from the bay’s tidal freshwater prism.”
Healthy Kidneys
According to Kreeger, wetlands formerly fringed the whole shoreline of both sides of the Delaware Bay. “They are the kidneys of the estuary, helping to maintain water quality, protecting coastal communities, and growing lots of fish, shellfish, and other wildlife.”
The shoreline is constantly changing, with some areas gaining and some losing ground. “In a natural equilibrium state, the erosion of those marshes is balanced by marsh accretion,” she says. “But right now we’re losing on balance about an acre a day in the Delaware Estuary. Erosion, or marsh drowning, is occurring in excess of new marsh being created-the system is out of balance.”
Reviewing existing data, Kreeger says that over an 11-year period ending in 2006 the bay lost about 2.5% of its coastal wetlands. “That might not sound like a lot, but when you have 150,000 acres and they are so crucial as a hallmark feature of the system, that turns out to be more than 3,000 acres.” And more worrisome, she says, “Sea level is rising faster and it’s going to continue to rise faster still, into the future-and that pushes a lot of our wetlands past their threshold, to a point where they can no longer keep pace.”
An economic analysis by the University of Delaware showed the state benefits from a $20 billion economy connected to the water resources, providing around 600,000 jobs. “Probably half of those jobs are connected to the wetlands in one way or another,” Kreeger notes. “What happens when we lose 90% of the wetlands in the Delaware Estuary, which is what we’re projecting by 2100? If you lose 150,000 acres of marsh, that’s going to have catastrophic impacts, not just on the ecology, but on jobs and livelihoods.
“I don’t think we can afford to let things go the way nature is taking them with the projections we’re looking at, because so much of our economy hinges on not losing that large amount of wetlands and other natural resources connected to the shoreline.”
Kreeger’s prescription for New Jersey’s shore: Use nature to heal nature. She says living shorelines should be a key ingredient.
Goals and Nature
Drawing upon techniques that restore or encourage the natural ecology of intertidal areas, Kreeger envisions living shorelines that can continue growing and strengthening themselves long after the initial installation is completed. Her living shoreline design concepts emphasize materials, organisms, and structures that slow down and trap fine suspended material that is already in the water, enabling “a natural biological community such as marsh vegetation to establish on those structures.”
Energy from waves and currents are the two main forces driving erosion along the seaward edge of marshlands. These two factors are the main cause of rapid retreat of the edge. Living shorelines mitigate those effects by providing a vegetative organic buffer that can absorb and dissipate these forces in areas protected from ocean surf.
Like DeQuattro in Alabama, Kreeger says it’s critical to match designs, materials, goals, and flora and fauna to local conditions. “Every living shoreline is different, and the goals are different,” she notes.
Kreeger is particularly impressed with a living shoreline tactic that employs the assistance of ribbed mussels. The straightforward reason: In her location, it works.
Musseling In
The salt marshes of the Delaware estuary are dominated by two species, one plant and one animal, Kreeger says. The key plant is a grass called Spartina alterniflora, or cordgrass, and the primary animal species is the bivalve mollusk known as the ribbed mussel (Geukensia demissa).
She explains: “In a natural salt marsh, ribbed mussels outweigh all the other fiddler crabs and fish combined. Throughout the salt marshes of the Mid-Atlantic, the ribbed mussel and Spartina alterniflora live in mutualism together. Ribbed mussels attach by byssal threads to any hard substrate, like oyster shells and cordgrass stems, and protrude above the surface. Typically, one can find ribbed mussels embedded in and amongst salt marsh sediments, attached by byssal threads to each other or to Spartina stalks.” And it is this symbiosis that shapes the contour of natural intertidal marshlands.
The mussels put out hairlike thistle threads that Kreeger characterizes as “the strongest glue on earth.” These threads “attach very tightly to the roots and ligands of the plants. The plants help the mussels by providing a carbon source and a place for the mussel to attach. Together, the plants and the mussels naturally trap sediments-the mussels through their filtration of water, and by depositing the particles on the bottom, and the plants by providing a denser canopy to allow passive particle settling.”
Awed by the humble creatures’ many positive attributes, Kreeger says, “I actually call them super mussels because there are so many cool things about them. They are one of the few bivalve shellfish in the world-maybe the only ones-that can air-breathe, so they can be exposed to a lot of air during the day.” As a result, “They can live in the very high intertidal zones.” In addition, they can survive freezing temperatures and keep chugging on at temperatures up to 130°F.
And they build a hardy bulwark against erosion.
Kreeger observes that along the edge of a marsh, the mussels “are very, very dense,” forming a “carpet of mussels in some areas.” Although they tend to die back at a rate of about one meter per year because they are ripped from their purchase by winter ice rams, Kreeger says the mussels naturally recruit at an equivalent rate when things warm up and the larvae begin to disperse along the edge of the marshes during the spring, thus maintaining their line in a state of equilibrium.
“What we found was that where these mussels are very dense, erosion was very slow. On the other hand, the areas that were eroding quickly did not have dense mussels,” Kreeger says.
Taking these observations of nature as her cue, Kreeger decided to experiment with using the mussels to build a first-of-its-kind living shoreline using ribbed mussels at Matts Landing, on the New Jersey shore of the Delaware Estuary.
Prepared for Landing
Kreeger describes the initial conditions at Matts Landing as rather unappealing, made so by misdirected efforts to hold back erosion. “Basically, it was a riprap area where they were just dumping everything that they could over the side,” she says. Although both commercial and sport fishermen embark from the site to fish the rich waters of the bay, some of the boat launch’s outstanding features prior to her project included “concrete rubble, big pieces of cinderblock and glass, and rebar. It was just a mess and had virtually no ecological value. In fact, it was probably impaired.”
Nonetheless, the landing was still considered a valued asset by local fishermen, who customarily slung their minnow pots over the edges of the improvised bulwarks to capture bait for their expeditions. At the outset of the project, the fishermen, accustomed to the degraded shoreline, jokingly admonished Kreeger’s research team of scientists and technicians that, whatever it was they thought they were doing to fix up the rundown shoreline, it was “not going to work.”
Despite the teasing, Kreeger and her team persevered. “Our goal there was not to protect marsh; we were trying to protect their buildings and trying to green up this really icky shoreline.”
It was a bad scene from top to bottom. “What would happen is waves would come in from passing boats and they’d hit these bulkheads and riprap walls and either bounce back-or reflect-or the waves would burst vertically up, releasing a lot of energy. When you get the wave bouncing back and hitting an incoming wave, you get what’s called standing waves-there’s just a lot of energy in that.” The disturbances from these reflected waves eventually scour the river bottom, denuding submerged vegetation and ruining fish habitat, she explains.
Technicians installed coir fiber logs to get things started, later planting them with Spartina communities once they had trapped enough sediment to provide a root zone.
“We basically created a fringe marsh in front of the shore that grew up over top of the riprap, which also had the benefit of helping to abate flooding,” she says.
The waves began to smooth out.
Shortly after that, the fishermen began changing their tune. “They quickly stopped making fun of us and started putting the minnow traps in front of our living shoreline. We have monitoring data showing that the richness of fish and blue crabs all really responded positively to this installation,” Kreeger says.
The calming effect was potent. To illustrate, Kreeger recounts an incident that took place during Hurricane Sandy. On the eve of the storm, a number of floating docks that fishermen used to tied up their boats when idle had been left moored in their usual positions, bobbing around in the water near the bulkhead. However, after the storm had passed, they were found thrown ashore, “stacked like pancakes on top of the bulkhead, which itself took a beating.” Although no one has come forward as a witness to the storm’s raucous behavior on the landing, Kreeger surmises that “all that wave energy that was hitting the bulkhead was tossing the docks high into the air, and they basically pancaked on top of each other.” However, in spite of the havoc created by wave action in front of the bulkhead, Kreeger says, “there was no damage to the grass-fringed edges” where the living shoreline had recently established itself.
“That was good evidence that the natural shoreline was able to not only tolerate, but dissipate the waves-less erosion, less damage.”
She adds, “Now the fishermen are our biggest supporters. They tell their friends about it. Private landowners and others come to us and say, “˜Hey, can we do this on our property?'”
Shores That Rise With the Tides
Kreeger says living shorelines are ultimately resilient because they are highly adaptable. “They can raise their elevation by their biological processes and their ability to pull out sediment. They can act as natural levee builders, whereas rock does not build itself up. You have a greater chance of armored installations keeping pace with sea level rise if you use biological material.”
However, she concedes that because living shorelines like the one at Matts Landing are composed of biological material, including coir fiber mats and logs, they are also susceptible to decay at a faster rate than rock or a bulkhead. In some circumstances, she says, a living shoreline’s structural biological components might require replacement or maintenance within a year or two. “But, that’s not always the case: We’ve had some out there for six years and they look fine,” she notes.
“With this tactic, the whole goal is to slow the rate of erosion enough so these natural communities can get established. Then, maybe every five to 10 years you might need to augment your living shoreline treatment and adaptively manage it to ensure that the community doesn’t have any breaks in it.”
Like Webb, Kreeger says it’s important to provide a definition whenever discussing the living shoreline as a practice. “It’s a joke, but someone who just puts potted plants on top of a bulkhead might say, “˜Hey it’s a living shoreline,’ but it’s not by our criteria. It needs to meet some sort of design criteria and outcomes that are the main goals that managers want. It should not deteriorate the environment-it should enhance the environment.”
She adds, “We should not confuse a living shoreline with a natural shoreline. Some people might think “˜Oh, you’ve restored the natural shoreline by using plants and animals’-but it’s not the same. Typically, a living shoreline is an engineered structure designed to meet certain criteria. If it was simply restoring things to natural shoreline, and if that shoreline is eroding, there is no reason to expect that it would not keep eroding.”
In the Delaware Bay, in addition to projects designed to preserve coastal amenities, living shorelines have been proposed for a range of uses that coincide with the region’s industrial backstory.
“Your outcomes are going to depend on the goals. Here in the Wilmington area, there’s a lot of interest in living shorelines not to protect big expanses of wetlands, not to try to green things up, but to try to cap and contain old legacy pollutants that are in the brownfields along the river here. So how you measure performance really depends on what you’re trying to do,” Kreeger says.
Good Business
Kreeger says living shorelines can be very “cost effective if done in the right places and tailored to local conditions.” Chris Boyd, associate extension professor of coastal ecology at Mississippi University, agrees: “If you just have to put down marsh plants, it will be a lot less cost than a bulkhead. You could do a bulkhead for $150 per foot, but for plants-you can put those down for $10 or less per foot using a contractor.”
As a member of Mobile Bay’s Resilience Team, Bret Webb says, “This is something that a homeowner can do at an appropriate scale, and at a cost that is commensurate with other forms of shoreline protection. That’s going to give some natural shoreline value and also function.”
The US Army Corps of Engineers has implemented a new general permit for living shorelines on the Gulf Coast that will streamline the approval process for homeowners hoping to use more sustainable methods to forestall erosion along shorefront properties.
Since the simplified permit went into effect in Alabama, Webb says, “We’re seeing small contractors, locally, that are getting more interested in getting into the field, so every time we have workshops, we also have an invitation to local contractors to come get some education on how these things work, the types of materials that are used, and the types of proprietary devices that are out there. And more and more show up for the training and are getting interested in it.”
Jeff DeQuattro says he has already identified a number of contractors and builders in the Mobile Bay area who have the experience and training, as part of The Nature Conservancy’s restoration projects, who are ready to put their living shoreline knowledge and expertise to work for homeowners and businesses in the region.
“It really is a cottage industry for the homeowner-scale projects, but the larger, more comprehensive projects really still need expertise at the coastal engineering level to make sure to, at least, do an assessment of the impact on shoreline processes to make sure there aren’t negative impacts, and if there are, to find a way to mitigate them,” Webb says.
Looking at the big picture, Boyd says, “You might not be able to stop erosion, but you might slow the rate of erosion.” In addition, with living shorelines, he says, “You’re increasing the marine habitat and other habitats that help maintain the coastal wetlands and maintain access to the water. Engineers can do a lot with rock and other things, but we want to make sure we maintain those coastal processes and to be aesthetically pleasing-to make sure not to put some large amount of structure out on the water creating the same problems they had on the shore.” He adds, “When the shore can be protected in an environmentally sensitive way, it’s a great option.”
