July 15, 2014 11:44

Beach Erosion

What can be done?

EVERYBODY LOVES THE BEACH. A long, white-sand strand, framed by a rocky shoreline, cooled by coastal breezes, with crashing, pounding waves providing a soundtrack, is our notion of paradise.

But those pounding waves exact a price. Slowly, they eat away at the shoreline, taking bigger and bigger bites, encroaching on homes and businesses. Every day erosion nibbles at coastlines; big storms, such as hurricanes, swallow huge gulps.

Coastal erosion is a global problem; it’s estimated that at least 70 percent of sandy beaches around the world experience it. In the U.S., around 86 percent of East Coast beaches have significantly eroded in the past 100 years. There’s plenty of erosion on the West Coast and the Gulf of Mexico as well.

According to NOAA’s Office of Ocean and Coastal Resource Management, coastal erosion causes approximately $500 million per year in property loss, including damage to structures and loss of land. According to at least one study, one out of four houses that lie within 500 feet of the U.S. shoreline may disappear by 2050.

The causes

What causes beach erosion? Climate change and rising sea levels play a part. But for the biggest cause, look in the mirror. To quote Pogo, “We have met the enemy and he is us.” The most important factor in beach erosion—by far—is human interference.

“Beach erosion is a natural process; it’s something that happens on all coastlines, all over the world,” said Katie Arkema, PhD, senior scientist at the Natural Capital Project.

“It’s part of nature. It grows and retreats to adapt and respond to the forces of nature,” Arkema continues. “It shouldn’t be a problem, except that we’ve built infrastructure on the coasts.”

“Beach erosion’s not a ‘problem,’ it’s the response of the shoreline to something,” said Greg Guannel, PhD, a coastal engineer at the Natural Capital Project.

Guannel explains that beaches erode, but they also accrete, or build back up. However, that process could take years, even decades. “The beach will come back—eventually. The problem is the timeline.

People say, ‘Well, I can’t wait, because in the meantime, my property will fall into the water.’” So what can we do about it? Fortunately, there are a number of soft, hard, and hybrid soft/hard solutions that can be applied.

Making it worse?

Unfortunately, some of the things we do to prevent beach erosion can actually exacerbate the problem. “We build structures along the shoreline to ‘protect’ our property,” says Guannel. “But at the same time, we’re cutting off the supply of sediment to the beach next to us. And we transform the wave processes next to the structure, so there’s more erosion on the non-structured shoreline.”

“The second thing we do is build dams on rivers. Rivers bring water to a coast. They also bring sediment. When we build a dam near a coast, we starve the beach, slowly but surely. That’s what’s happening on the coasts of Oregon and Washington, from damming the Columbia River.”

Billy Mack, co-owner of First Coastal Corporation, an erosion control contracting firm in Westhampton Beach, Long Island, New York, recalls a project that caused more harm than it prevented. “There was a federal project back in the late ’60s, early ’70s. It allowed shore-perpendicular structures, jetties and groins (structures that are intended to impede the flow of sand) to be built along Eastern Long Island. Wherever the downdrift locations were, you’d find accelerated erosion. That impacted quite a few beachfront homes over the decades.”

“Back in the ’60s and ’70s, groins tended to be pretty high, so the response on the downdrift side was pretty pronounced,” explains Doug Gaffney, P.E., D.C.E. (diplomate in coastal engineering), marine regional sales manager for Tensar Corporation in Alpharetta, Georgia.

“Since then, people have figured that out, and now, generally speaking, they’re lower in elevation. Lowprofile groins work quite well.”

Replacing vegetation

“When people first settled here, there were very few beaches that looked like the New Jersey coastline does now,” said John Ravert, director of technical services for Bernville, Pennsylvania-based East Coast Erosion Blankets, LLC. “In those undisturbed beach areas, you’d find dune grasses and shrubs, natural vegetation that kept the sand in place.”

One way to fix beach erosion is simply to put the missing plants back. That’s what Griff Evans does, as a vice president and partner in Ecological Restoration and Management, a commercial landscape and ecological restoration contracting firm in Cockeyesville, Maryland.

“Our biggest thing is the revegetation of dunes. Here in the northern Mid-Atlantic area, we mostly plant two species; further south, there’s more diversity in what you can use. Generally, it’s Atlantic Coastal panicgrass or one of several cultivars of American beachgrass, called Cape American.”

Erosion, like rust, never sleeps. What do you do while you’re waiting for that vegetation to grow?

Fortunately, there are other natural things that can protect it while it’s growing, such as biodegradable coconut fiber (coir) mats and logs. “Coir mats are also very successful in holding sand in place,” says Revert. “You can plant through them, and they’re tolerant of briny situations. They can last up to five years in that environment.”

What about the relentless pounding of the waves? Is there something that can blunt that tremendous energy? Once again, coir can come to the rescue. “Putting coir logs down where the waves break knocks the energy out before it gets to the beach,” said Revert.

But vegetation has its limitations. “There are a couple of caveats here,” said Jenna Phillips, EI, MS, a coastal engineer and technical manager at Williamsport, Marylandbased Maccaferri, USA. “Yes, vegetation can help stabilize a dune or a beach, but only up to a certain degree. A vegetation-reinforced dune can’t withstand the force of a Category 3, 4, or 5 hurricane.”

“You have to consider what’s behind that dune. Is it a multimillion-dollar building? Are people living or working back there, whose lives could be lost? If so, what level of protection are you really going to need?”

Hybrid solutions and beach renourishment

Hybrid solutions, a blend of the soft and the hard, seem to be the cutting edge of beach erosion remediation. Such an approach was employed on the coast of Virginia.

The city of Virginia Beach kept losing its boardwalk. It was constantly battered by tropical storm surges and nor’easters that hit the Commonwealth’s coastline at least a dozen times.

The Norfolk District of the U.S. Army Corp of Engineers (USACE) was enlisted to design and help construct the Virginia Beach Hurricane Protection System, a $13.7 million project begun in 2001. The most recent phase, completed in 2013, widened the beach from 150 feet to as much as 300 feet in places.

“There was a need to reevaluate the measures that could protect this oceanfront area, about a six-mile stretch of beach,” said Jennifer Armstrong, a product manager for the USACE Norfolk District’s Environmental Analysis Section. “We looked at everything, including doing nothing.”

“We considered a variety of different things: pump stations, seawalls, and the renourishment option. We decided that the greatest amount of damage prevention would be provided by an integration of all three approaches, working together as a system.”

Creating a sacrificial sand-dune buffer was part of that plan. To do that, 1.5 million cubic yards of sand was dredged from a federal navigation channel and brought to the beach.

To get the sand to the beach, a 30- inch diameter pipeline in 800-foot segments was laid. This was connected to a floating rubber hose, through which the slurry was discharged up onto the beach.

“In 2002, we completed the initial construction,” says Armstrong. “That consisted of a new concrete seawall, integrated into the boardwalk, for about four miles of the beach. North of that seawall, extending for two miles, is an enhanced dune system, planted with beach-friendly vegetation.”

The next vital component was a stormwater runoff system, consisting of two pump stations. “This discharges internal drainage from rainfall. The pump stations discharge through a series of pipes about a thousand miles offshore.”

“All of these work together to provide protection,” Armstrong continues. “The beach berm is the first line of defense. It absorbs the energy from the waves pounding the beach before it gets to the seawall. That way, any water that does get to the seawall, or to the enhanced dune system, is not nearly as intense. Then the pump stations deal with the interior drainage.”

Beach renourishment is pretty simple, as a concept. It’s just putting sand back that’s been lost; it seems logical. However, not everyone is a fan.

“The Army Corps really likes beach renourishment,” says Guannel. “Unfortunately, it doesn’t discourage people from building near the beach. They’ll keep coming, because they know that the Corps will keep replenishing the beach.”

“At the same time,” Guannel concedes, “it’s necessary to do things like this, to prevent loss of lives and property.”

Armstrong defends the Corps’ strategy. “I see a lot of benefit in going the renourishment route,” she says. “Let’s say you were just going to put a seawall in place; no sand berm. You’d need a very high seawall to absorb that amount of wave energy, because you no longer have that first line of defense.”

“The investment in this project so far has been about $100 million,” Armstrong points out. “To date, it’s prevented more than $443 million in damages that would have occurred had we not had the system in place. The costs have already recovered themselves.”

Artificial islands

An interesting “soft” solution was implemented by the city of Fort Pierce, Florida, whose municipal marina was completely annihilated by Hurricane Frances back in 2004. The Category 2 hurricane caused almost $15 million in damages to boats and $13 million in damages to the marina facilities.

“The city marina anchored the whole downtown area,” explains Phillips. “It’s where City Hall was, plus several parks, shops and restaurants. The marina generated revenue for the city.”

An ingenious breakwater system was designed, consisting of twelve small artificial islands and a long peninsula. These don’t lie along the open coast, but in the Intercoastal Waterway, separated from the ocean by Tern Island, a natural barrier isle. In addition to providing storm protection, it also creates almost 15 acres of habitat for shorebirds and oysters.

The system is designed to withstand waves up to six-and-a-half feet high, with a storm surge elevation of 10.5 NAVD (North Atlantic Vertical Datum), coming every seven seconds. To create the system, two different sand-filled geotextile tube products, along with polymeric marine mattresses, were used.

The state of Florida has recognized this project for its sustainable, environmentally-friendly elements. It may be a model for future beach erosion and storm protection projects, as an alternative to harder solutions.

Hard and semi-hard armor

Geosynthetic tubes, such as those used on the Fort Pierce project, are also used extensively by First Coastal. “We can build a seawall with those,” says Mack. They use heavy-duty geosynthetic bags filled with as much as one ton of sand. The bags are strapped together with other one-ton bags, “kind of like Legos.”

“You end up with a semi-hard structure that can dissipate wave energy without the use of wood, stone, or steel,” says Mack. “This way, we’re able to satisfy the desire to have a softer solution, yet still have a more predictable level of erosion protection than sand berms, beach grass, or other vegetation can give you.”

There are times, though, when the sheer force of crashing waves requires hard armor, sturdy steel or rock. First Coastal builds quite a few of those structures, too.

“On certain parts of the shoreline, in high-energy areas, permanent steel bulkheads are appropriate, and the preferred method,” says Mack. “For those, we use 25- to 35- foot steel sheeting driven or vibrated into the ground. To support the walls, we’ll build a tieback system— or a cantilever—behind it.”

Maintenance, not ‘magic bullets’

When it comes to beach erosion, there’s no such thing as ‘one and done.’ “We work with a lot of clients who are looking for that ‘magic bullet’ solution,” says Phillips. “That just doesn’t exist when you’re working with something as dynamic as the ocean.”

“The old mindset was, build a rock revetment, or a concrete seawall, then all our problems are solved; we can just go off and leave it,” Phillips continues. “Those days are gone. We know we have to adapt to everchanging conditions, and constantly maintain those systems.”

“Most of the work we do requires a level of maintenance, especially after storm activity,” says Mack. “It’s very hard to find a coastal project that’s not going to require some level of maintenance. Parts of rock walls may require re-chinking, for instance, after getting damaged by high-energy waves.”

“When we planned the Virginia Beach project,” says Armstrong, “we anticipated that about every three years, 765,000 cubic yards of sand would have to be replaced.”

One thing is certain, there’s going to be plenty of work for beach erosion contractors in the decades to come. In an ideal world, everyone moves away from the beach, and we let nature take its course. That just isn’t going to happen. We humans crave the water, and we’re not going to leave it. Entire economies depend on beach tourism. What happens at the beach affects everything, even national defense.

In that sense, we all live at the beach.

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