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Fri April 25, 2014
Protecting shorelines with natural, vegetative barriers is not only better for the ecosystem, it’s a more effective means of slowing shoreline erosion. We speak to a local researcher about her work with “living shorelines.”
A new way of keeping water at bay is taking hold not only in eastern North Carolina but up and down the East Coast and local research is helping spread the word on living shorelines. In high wave action areas, manmade bulkheads make the most sense, but for low to medium wave areas, such as rivers, estuaries, and soundside properties, living shorelines can be more cost effective and better for the environment. Bulkheads are a common sight along waterways in eastern North Carolina. The wood or concrete structures protect the shoreline from erosion and keep water from encroaching on homes and businesses. But bulkheads can have negative impacts to the ecosystem. A more environmentally beneficial way of stabilization is living shorelines, whereby stone, gravel or oyster shell filled bags are placed one on top of the other creating a sill.
“These structures, the bags and the rocks serve to protect the shoreline from erosion.”
North Carolina Coastal Federation Scientist Dr. Lexia Weaver supports living shoreline erosion management.
“They help to reduce wave energy that affects the shoreline. And the area landward of that structure is planted with thousands of plugs of marsh grass. So it not only looks very aesthetic and appealing but it also functions really well in preventing erosion, protection from storms, and creating good oyster and salt marsh wetland habitat.”
There are approximately 45 permitted living shorelines today in eastern North Carolina. Examples include an oyster shell sill along Taylor’s Creek near Beaufort. In Morehead City, Atlantic Beach and Beaufort, there are living shorelines made of granite. And several private properties in Emerald Isle have stone sills. In the White Oak River, Weaver says there are multiple living shorelines around Jones Island.
“Since 2007, we’ve been working out at Jones Island to prevent erosion of the island. The island has some really high bluffs that have been eroding through the years through tropical storms and hurricanes and also from boat wakes.”
Weaver says 1,200 feet of oyster shell sills and over 60,000 plugs of marsh grass have been placed at Jones Island over the past seven years. In 2009, a team of 65 Public Radio East volunteers and Marines built a 150 foot oyster shell bag sill to celebrate PRE’s 25th anniversary. Weaver says that sill is holding up.
“They have built up a little bit of land behind them, the marsh grass is doing great. We were actually just out there this week, they’re full of mussels, full of crabs. We have stone crabs, mud crabs, there’s a lot of fish that like to use the sills for habitat. So it’s been a very successful project both in terms of reducing erosion on the island but also creating that valuable habitat for species that live in the White Oak River.”
One local researcher is making a name for herself in the Marine Science community. Rachel Gittman, a doctoral student at the University of Chapel Hill’s Institute of Marine Science in Morehead City has been studying living shorelines since 2010. While her research focused on the ecology of salt marshes, she also studied the impact bulkheads have on the environment.
“Bulkheads, particularly when they lack any type of vegetation tend to support lower abundance and diversity of fish and crustaceans, also of benthic infauna, so invertebrate that fish are feeding on. They tend to induce a type of scour or deepening of the shallow sub-tidal habitat which can actually reduce the amount of suitable habitat for juvenile fish and crustaceans.”
As part of Gittman’s dissertation research, she evaluated different shoreline stabilization approaches, and their effectiveness during storms.
“I did find during one storm event in particular, Hurricane Irene back in 2011, that marshes with these stone sill structures seaward of the marsh actually did perform better in some instances in terms of no changes in sediment, surface elevation, or vegetation density when compared to bulk heads along the same shoreline that often times and actually collapsed or suffered some kind of damage that would require the homeowner to do some form of maintenance or repair.”
Another part of her research looked at the ability of living shorelines to offer habitat for fish and crustaceans.
“It’s really providing a refuge for juvenile fish, crustaceans. So it’s a nursery for both commercial and recreationally valuable species and also the species that those fish feed upon. Blue crabs love the shallow structured habitat, you’ll find juvenile red drum, you’ll find juvenile speckled trout, lots of pig fish and pin fish, lots of shrimp also use this structured habitat.”
Gittman recently won a University of North Carolina’s Graduate Education Advancement Board Impact Award for her research. Both state and federal policymakers and managers are using her findings as they address coastal management challenges.
“I’ve taken the results of my research and I’ve presented it to the Division of Coastal Management and also to the Coastal Resources Commission and basically tried to help them decide whether or not the current permitting process for living shorelines are adequate, whether or not they need to make changes to the condition of their general permit they have in place for marsh sills which is a type of living shoreline that includes this offshore structure with the marsh plantings.”
Gittman says the Division of Coastal Management is still working with the Army Corp of Engineers to decide what changes could potentially be made to the permitting process. Before living shorelines become the accepted approach for erosion control, there are challenges to overcome. For instance, the permitting process for building a living shoreline is more arduous than for the construction of a traditional bulkhead.
“The other major issue is availability of materials. Oyster shell would be a preferred option for doing living shoreline work but it’s not necessarily available to every homeowner here and granite and other structures can be expensive. Contractors are not as familiar with constructing living shorelines and so they can often be hesitant to recommend that to a private property owner.”
If you live along the water and are interested in constructing a living shoreline, the North Carolina Coastal Federation assists property owners in site assessment, submitting permits, ordering marsh grasses and selecting a contractor to building the living shoreline.
Building a living shoreline can be less expensive than constructing a sea wall or bulk head. However, the cost depends on the types of materials used and the size of the project.
“Some of the local nurseries we work with charge about $.65 cents per individual plant and depending on how long your shoreline is and how wide, you may plant between 500 to maybe a few thousand plants. So that’s going to be substantially less expensive than say putting in a bulkhead. If you want to put in a stone structure, granite can often be fairly expensive and so it’s probably on par with the construction of a bulkhead. It just really depends on where you’re located along the coastline and what contractor you use.”
Preliminary research shows living shorelines are as effective in low wave situations as bulkheads. But Gittman says decades of study needs to be conducted to determine if living shorelines offer the same amount of protection as a bulkhead or sea wall over time. For more information on living shorelines and to see pictures of sills around eastern North Carolina, visit our website, publicradioeast.org.