Friday, April 19, 2024

A softer approach, living shorelines as an alternative to a hardened coast

Dubbed "living shorelines," alternative shore stabilization methods are slowly gaining traction in North Carolina

SOUTHEASTERN, N.C.—Research over the last decade points toward the pursuit of living shorelines for coastal landowners seeking erosion control.

But, with regulatory lag and miles of shoreline lost each year to harsh structures, it’s not always easy.

Read Parts one and two:

What does it mean that our shoreline is ‘hardening?’ It’s not good

3 days vs. 3 months? Regulatory structure makes it tougher protect wetlands

Though a permit to obtain a bulkhead can be returned in just days, the turnaround time for a marsh sill is three months. Research produced by UNC-Chapel Hill Institute of Marine Sciences in 2012 found that over a third of surveyed bulkheads were damaged after a storm, while no damage was observed in marsh sills.

Two years later, some of the same researchers produced an additional study that revealed even more damage to bulkheads in a post-storm environment. After Hurricane Irene, the UNC-Chapel Hill team observed damage to 76 percent of bulkheads surveyed.

“Less intrusive alternatives, specifically marsh plantings with and without sills, have the potential to better sustain marsh habitat and support its ecosystem services,” the study states.

Salt marsh plugs

While the hurricane temporarily reduced the marsh’s vegetation density, the study found vegetation recovered within a year. One approach to erosion control is to just let the coastline be.

“If you can, there is the option to leave your shoreline in a vegetative state as it already exists,” Daniel Govoni, Federal Consistency Coordinator for the NCDEQ, said.

When accepting erosion is not an option, National Oceanic and Atmospheric Administration (NOAA) and other environmental agencies encourage coastal property owners to start with the softest approach first.

This graphic represents National Oceanic and Atmospheric Administration's continuum of shoreline stabilization methods. (Port City Daily/Courtesy NOAA)
This graphic represents National Oceanic and Atmospheric Administration’s continuum of shoreline stabilization methods. (Port City Daily/Courtesy NOAA)

There is no permitting process to plant salt marsh plugs, a practice that is embraced by the North Carolina Aquarium at Fort Fisher’s Teen Ocean Stewards and North Carolina Coastal Federation.

Each plug costs anywhere from $0.50 to $1.25 according to Ted Wilgis, a biologist with North Carolina Coastal Federation. Wilgis’ group will plant 3,000 marsh plugs on a day dedicated to stabilizing a particular shoreline. All that’s needed is a dibbler, a metal tool with a wedged end.

“It’s not hard to do,” Wilgis said. “You take that dibbler, jam it into the mud and shove the plug down.” 

Still, there are cases when denser wetland environment is not enough to fight erosion.

“We are trying to promote wetland plantings by themselves, where appropriate,” Govoni said. “There may be situations where wetland plantings aren’t going to work.”

Marsh sills

Marsh sills function as a speed bump for erosion. Often made of oysters, rock, wood, or oyster-concrete domes, sills placed parallel to the shore allow a wetland habitat to grow behind it.

Though riprap—think, piled up rocks—is sometimes made from the same material as marsh sills, its placement is what categorizes it as a technique that can “harden” the shoreline.

When situated on the shoreline, these rock structures can fail to give natural plantlings the opportunity to flourish.

“Riprap on your normal high waterline is not allowing your waterline to grow,” Govoni said.

Fourteen years ago, Tracy Skrabal led one of the first living shoreline projects in the state. A scientist for North Carolina Coastal Federation, Skrabal successfully transitioned a failing bulkhead into a marsh sill. Though the site took a few years to fully stabilize it showed promise of reversing a hardened shoreline.

According to Katherine Brogan, a spokesperson for NOAA, communities are embracing living shorelines at their own pace.

“Living shorelines, or shoreline stabilization made of mostly native material, are being discussed nationally,” Brogan wrote in an email. “Some regions have more practice and others are newer to considering different living shorelines and natural shoreline stabilization techniques.”

With recent research supporting the efficacy of marsh sills compared to bulkheads, it will take the coordination of those most plugged in with the coast to soften the shore.

Softer approach

In high-wave energy environments like the Intracoastal Waterway, living shorelines are not always feasible.

“We encourage waterfront property owners to utilize the technique recommended for their shoreline type,” Anne Deaton, a habitat assessment coordinator for the Division of Marine Fisheries, said.

Deaton said that through targeting people who install bulkheads and riprap as well as those who pay to install it, the shoreline could shift.

“We try to talk to the guys that put in stabilization structures to try to get them to be more willing to put them in,” Deaton said. “A lot of the contractors, they’ve just been putting in bulkheads.”


Johanna Ferebee can be reached at johanna@localvoicemedia.com or @j__ferebee on Twitter

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