Wind and waves can be powerful, beautiful enemies. Magnificent to experience, they pose a threat to a shoreline’s longevity.
Whether you’re protecting property, preserving habitat, or restoring an area to its natural state, the methods of shoreline erosion control available to select from can be as colorful as the shells that lie scattered across the sand. The key to a successful shoreline restoration or protection project lies in pairing the right method with your project’s budget and aesthetic needs.
Stopping Traffic on the Jersey Shore
Ocean waves not only erode the shoreline but can also flood roadways, bringing traffic to a snarling halt. On the east side of a roadway connecting south Avalon, NJ, with the northern section of the city, a sea wall borders the Atlantic Ocean.
“On the west side of the road, they had a berm along the side of the road,” says David Faust of Bethlehem Precast Inc., based in Bethlehem, PA. “Every time a storm would come, the wave water would overtop the seawall and stop traffic completely.”
Cable Concrete erosion mats-invented by patent holder International Erosion Control Systems-based in Ontario, Canada, and fabricated, manufactured, and distributed in the Northeast by Bethlehem Precast-were installed to protect the roadway in January 2008. The mats were placed on the west side of the roadway by South State Inc. contractors of Bridgeton, NJ, who then “dug out through the berms to the wetlands on the other side of the berms so the standing water on the road would drain into the wetland,” explains Faust. The 25,856 square feet of trapezoid-shaped Cable Concrete mats were placed right up to the road’s surface.
“It’s articulated concrete block that’s held together with stainless steel aircraft cable. It’s bisected through each block, and geotextile fabric is attached to each 4- by 16-foot or 8- by 16-foot mat,” says Faust. “The geotextile fabric allows for infiltration and drainage while, at the same time, eliminates erosion and washout. It’s a stormwater BMP [best management practice] and erosion control BMP for the DEP [Department of Environmental Protection]. The design was changed to tie it right in with the roadway so the mat would not be undermined and no water would get under the system.
“This is the Cable Concrete 20 mat: 20 pounds per square foot of concrete that’s connected by cables with the geotextile fabric attached to it,” he adds. “That’s our smallest mat.”
The site is located in Cape May County, NJ, a hotbed of East Coast tourism during the warm weather months. Timing could have proved challenging for the project, which had to be completed before the spring and summer tourist season, but Bethlehem Precast typically keeps 100 mats of each of its designs in stock at all times, according to Faust.“What’s nice about the Cable Concrete is it’s an articulated concrete block. There’s a 20% opening at the top of the block, which allows for the municipality to fill it with topsoil and seed it,” says Faust, who recommends seeding the blocks with native species. “That also helps to stabilize the mats to prevent erosion.”
The Jersey shore is also the setting for another ongoing project in which Bethlehem Precast is working with Woodstown, NJ-based contractor R.E. Pierson Construction Company and the Army Corps of Engineers; it is a residential site located in North Wildwood, NJ.
“There are some beach houses where the footers are starting to be washed out from underneath by the amount of water that is getting underneath the sand. They are using the Cable Concrete mat along with Tensar geogrid and our geotextile fabric, which is attached to the mat,” describes Faust. “They are lining the embankment of the inlet waterway. It’s stabilizing the embankment, so no sand can wash out from underneath.”
In the project’s first phase, 53,760 square feet of custom-made 8-foot by 64-foot mats were installed at the site. Battling the shifting sands and relentless waves in this environment, however, is not unexpected.
“Anywhere along the shoreline, the sand is always moving continuously: daily, weekly, monthly. If you don’t stabilize the shoreline, the water can encroach on houses,” says Faust. “They are always having to replace sand on the beaches, especially for beachfront property. Even in Florida, after hurricane season, they bring in millions of tons of sand and replace it every year.”
An Unlikely Source of Shoreline Erosion
Wind, water, and fire are elements typically associated with erosion. But developers in the Williamsburg section of Lincoln, NE, discovered another source of lakefront erosion: muskrats.
“Muskrats would tunnel into the shoreline,” says Mark Ewalt, landscape supervisor of Hampton Enterprises in Lincoln. “When they tunneled, the banks would collapse.”
The small, unnamed lake is located at the center of the commercial section of a 320-acre site, which has been in development for the past 15 years. The tributary is used primarily for rainwater collection.
Hampton Enterprises researched a variety of erosion control methods for the site, including “driving metal shoring into the banks,” according to Ewalt. Company members had seen the Stone Strong System used on other lakes, and selected the 6-foot-wide by 3-foot-tall blocks to prevent further shoreline erosion approximately five years ago.
“We have a single course set on a bed of gravel. Stone Strong has its niche because it’s such a large block. The mass of these things alone makes a lot of sense-the weight of them,” says Ewalt. “It takes bigger equipment to set them, but obviously it doesn’t take very many blocks.”
The system features interlocking blocks with rebar lifting loops. Each block has a center void where gravel fill is added during installation. Twenty-four-foot, dual face, 45-degree, and 90-degree blocks are also available as part of the Stone Strong system.
Concrete color blocks were used at the Williamsburg site.
“We have a solid, stable shoreline. It looks really nice; it really touched off the area,” says Ewalt, adding that the installation achieved the desired effect: “It eliminated the muskrat problem.”
Making the Most of Geosynthetics
A waterfront property in Lusby, MD, on the picturesque Chesapeake Bay was facing serious erosion challenges posed by wave action in 2006. The waves would undermine cliffs on the property, eroding them as much as 15 inches per year. Edwin Lange of Tri-State Stone and Building Supply Inc. based in Bethesda, MD, was the consulting engineer on the project. He says that after the landscape was graded, Typar 3401G geotextile from Old Hickory, TN-based Fiberweb was used on site for erosion protection.
“It met all the criteria for shoreline [use],” says Lange, noting that the geotextile was tied into an existing revetment. “We’ve been using them since the seventies. We used about 1,000 feet lengthwise and [the textiles] were about 12 feet wide.” Carderock Stone, quarried by Tri-State Stone and Building Supply Inc., was used for the revetment.
The Typar 3401G is made from 100% polypropylene. It works well in shoreline applications because of its uniformity. “It passes water readily; it’s very permeable. And has a high modulus, which means it doesn’t stretch very easily,” explains Bill Hawkins, a retired business manager for Fiberweb. He explains that the product also doesn’t rupture easily.
The surface of the site where the geotextile is to be placed should be prepared to be as smooth as possible. “It’s best to have a very uniform surface. Then you just roll the fabric out as you would on a sloped roof, so that the upper section overlaps the lower section-kind of as a shingle, but they are 100-yard long rolls,” describes Hawkins. “Normally, you can either put stone or rock at different points to hold them in place, or use sod pins; you just punch them through it into the ground. It depends on the surface.”
The manufacturer considered various soil particle sizes during the material’s design.
“It does have a very good opening size to match up with most soils so the soil won’t wash through it,” says Hawkins. “You’re trying to hold the soil in place so that the mechanical energy from the water doesn’t move it around.”
After the material is pinned in place, 2 or 3 inches of bedding stones should be placed over the site, explains Hawkins, noting that larger stones are then placed over the bedding stones to absorb most of the water’s wave action.
Geosynthetic materials were also a vital part of a shoreline reconstruction project on the Chedoke River in Hamilton, ON, Canada. The shore’s slope had eroded over time in an area where no erosion control methods had been used in the past. Layfield Geosynthetics’ Aqua Dam was installed as part of the reconstruction process.
“The protection was to reinforce the embankment with a mechanically stabilized earth wall, which was to protect the access road from eroding into the river,” explains Cameron Martin of Layfield Geosynthetics, based in Richmond, BC. “The Aqua Dam was dual purpose, as it enabled the contractor to dewater a work area and it provided sediment control for the river.”
Lightweight, portable, and designed to provide rapid deployment, the Aqua Dam is filled with water and can be installed to change the flow of water or contain it to a particular area.
Geotextiles were used to stabilize residential property in South Haven, MI, bordering Lake Michigan. The site battled wind erosion from the Great Lake, had soil that tended to seep when it was saturated, and was experiencing runoff pouring down the length of a slope, according to Jill Pack of North American Green, based in Evansville, IN.
“They wanted to keep it natural-looking,” says Pack. “They wanted it to be vegetated. It sloped down to the Lake Michigan beach area.”
Begun in May 2007, the project incorporated C350 turf reinforcement mats from North American Green. The C350 mat is a coconut-fiber blend combined with three-dimensional polypropylene nettings.
Slopes on the site were primarily graded by hand. The area was seeded with a temporary seed mix that included bluestem switchgrass and native species before the mats were rolled on the site. The mats are held in place with wooden stakes, explains Pack, who adds that a variety of fasteners may be used in conjunction with this type of mat. In spring 2008, more permanent native shrubs were planted on the site, including sandbar willow and red austere dogwood.
Maintaining a Natural Aesthetic
Ships moving in and out of port and prevailing winds caused wave energy to wear away a section of Apollo Beach on Florida’s Tampa Bay, according to Steve Spencer, a licensed architect with the Living Shores division of Seagrass Recovery, based on Indian Rocks Beach in Florida.
Living Shores chose Envirolok, a vegetated living wall system from Madison, WI-based Agrecol, to combat the shoreline erosion.
“We came in and tied our wall into the boulders,” says Spencer, explaining that his company completed a 142-linear-foot section that is about 7 feet high just before the natural shore. “The natural shoreline has receded another 5 feet already. When we did [the work], our wall was flush with the face of the natural shore. Now, in just a few months, the natural shore has receded.”
Spencer, who explains his company relocates, restores, and recovers sea grass beds, appreciated the green attributes of the wall system, which is filled with organic material, allowing plants to grow through and strengthen the soil with their roots.
“We grow our own sea grasses,” he says. “It was a natural fit for us.”
The wall at Apollo Beach, which is a preserve, was planted with Paspalan, a hearty, salt-tolerant grass that’s a species native to the region. Hillsboro County officials who contracted the fall 2007 project were pleased with the results.
Vinyl Innovations in Illinois
Located northwest of Chicago, in Schaumburg, IL, Lake Schaumburg borders a park area, a residential area, and a roadway. In August 2007, the area’s park district workers knew they had to take action to protect
“They had an existing steel seawall that corroded completely through,” says Tim Cederlund, vice president of Reil Construction based in Union, IL. “They wanted to replace it before it became a hazard.”
Reil Construction removed the steel wall and selected a sea wall from Riverwalls Ltd., based in Fox River Grove, IL, to replace it.
“We knew we had to go to a vinyl wall,” says Cederlund, noting that because of its location beside a major road, salt from the roadway might corrode the steel. One of Cederlund’s concerns was that many vinyl sea walls in today’s market could only be installed in straight sections.
“We wanted curved [sections],” he says. “This is the only product that allowed us to do that. [It has] the functionality of vinyl with the aesthetics of steel. It’s 2,000 lineal feet total.”
While the wall itself is vinyl, the fastening mechanism is vinyl-covered steel. Darryl Burkett, CEO of Riverwalls, which served as a subcontractor on the Schaumburg site, invented this fastener. “Previously, all vinyl sheet pile that goes into the ground was used with posts of wood in straight lines at the top of the sheeting and at the water line-all in straight lines,” says Burkett. He notes that his system, which can easily adapt to curving shorelines, has become popular on Nicklaus Signature golf courses around the country as well as in sensitive habitats.
“So far, it’s been exceptional. It was really easy to install,” says Cedarlund. “It’s easier than the typical vinyl would have been and about the same as steel time-wise and in level of difficulty.”
Rescuing a Maryland Habitat
The Severn River was designated as a Maryland Scenic River in 1971, according to Fred Kelly, the Severn Riverkeeper, based in Annapolis, MD. He says that with that designation, however, came no special protection.
“It’s a dying waterway,” says Kelly, explaining that the nonprofit Severn Riverkeeper program has 15 monitoring stations that have determined that dissolved oxygen levels are dropping. “We’re getting increasing dead zones, with little or no oxygen, in which nothing can live. Your oysters can’t move, so they die. Your fisheries crash. The yellow perch fishery has really been destroyed in the Severn River. It was once a major fishery.”Wave action, particularly due to the increasingly large number of boats on the river, is the main form of natural slow shoreline erosion, says Kelly. In 2003, the Severn River Living Shoreline Project at Drevar Park began as an attempt to protect the waterway, which is a major tributary of the ecologically sensitive Chesapeake Bay. The park is located beside the Epping Forest residential community near Annapolis, MD, part of the Severn’s southwest shore. The site’s beach is not used for swimming and had been neglected.
The Severn Riverkeeper Program worked with contractor Underwood & Associates of Annapolis to install what it described as a “living shoreline.” The project was funded by a grant the Severn Riverkeeper Program received from the Chesapeake Bay Trust.
“We put large stones, riprap, 10 or 15 feet into the water. Instead of regular riprap, we actually have breaks in the riprap-holes so the water can flow through,” says Kelly, noting that the riprap protects the marsh from wave action. “It worked-the marsh has grown nicely. It’s added a good environmental ecological value to the area. It provides a habitat for the fish to hide in.”
The riprap is installed to protect the marshland, and sand is added at the shoreline if it’s deemed necessary. At this site, which covered approximately 100 feet of shoreline, about 100 volunteers of all ages came in to take part in constructing the living shoreline, including teachers and children from 10 specially selected public school science classrooms. The students helped plant marsh grass that traps sediment and creates a feeding area for small native crabs, shrimp, and fish. Spartina alternaflora was planted primarily, with spartina patens grass added where “the flow is a super-high tide,” explains Kelly. “Spartina alternaflora is the classic marsh grass,” he says, adding there are also cattails at the site.
Uncontrolled stormwater runoff into the waterway has caused an abundance of algae growth, sucking the oxygen out of the water, says Kelly. There was no previous shoreline protection at the site. Kelly explains that while newer subdivisions along the waterway are required to infiltrate stormwater onsite as much as possible, some older, established subdivisions in the area had allowed stormwater runoff into the nearest waterway, with few controls or protection.
“With that kind of uncontrolled development, the amount of nutrients coming off the land is destroying water,” says Kelly. “Water is directed into a ravine, moving sediment, including nitrates and phosphates, into the waterway.”
The living shoreline not only protects the land from eroding, “but at the same time reestablishes those productive marshes,” he explains. “The marsh is really the incubator of life in the waterway. The marsh itself purifies the runoff from the land.”
The grassroots, educational conservation organization is pleased with the Devar Park project’s results.
“It’s a very successful living shoreline,” says Kelly. “We now have a very much alive habitat adding tremendous ecological value to the waterway.”Protecting the integrity of a shoreline project can mean the difference between a temporary and a lasting solution. Play to the site’s strengths: using materials that work with nature will bolster not only the growth of the shoreline itself, but also the long-term effectiveness of a shoreline protection plan.