It’s home to 153 million people, or about 53% of the total US population. It generates tens of billions of dollars each year through industrial and business activities. It is the coast: the 95,331 miles of ocean and Great Lakes coastlines. And while the population continues to increase in coastal areas-3,600 people relocate to coastal areas each day, according to the Office of Coastal and Resource Management of the National Ocean and Atmospheric Administration (NOAA)-the land is also becoming increasingly eroded.
The erosion is due, in part, to human activity and to natural processes of sand erosion and deposition. Another potential cause for which many communities are now planning is that of rising sea levels due to climate change. Sea level rise exposes coastal communities to floods and increases their vulnerability to storm surges. It’s a topic of growing interest to academicians, politicians, and coastal residents and business owners. Questions abound: How severe will it get? Should construction still be allowed in erosion-prone areas? Should there be a buyout of homes or other structures in high-risk zones?
Long-Range Planning in Florida
The longest sea level records kept in the western hemisphere are those from measuring stations in Key West, FL, the southernmost tip of the United States. The records date to 1846 and, despite several multiyear gaps in information, show a long-term trend of sea level rise of about 2 millimeters per year in the area.
Professor George Maul, head of the Department of Marine and Environmental Systems in the College of Engineering at the Florida Institute of Technology, writes in a report that the sea level has been rising steadily for at least 160 years and will most likely continue that trajectory. He says it is not known from the data whether the rate of rise correlates with a changing climate. The Intergovernmental Panel on Climate Change (IPCC) in its 2007 report suggests that the global sea level between 1900 and 2000 has risen 16 centimeters.
Someone keeping a careful eye on the issue is James Murley, a land-use attorney and executive director of the South Florida Regional Planning Council. The council encompasses three densely populated counties: Broward, Miami-Dade, and Monroe, which incorporates the Florida Keys. Florida could well be a poster child for the issue of sea level rise. Other than Alaska, Florida has more coastline-8,436 miles including tidal areas, according to NOAA-than any other state.
The South Florida Regional Planning Council is one of several regional planning councils throughout Florida that work with the cities and counties within their respective jurisdictions. Examining the impact of erosion is one of the council’s many tasks. It may also take a coordinating or mediating role among local governments espousing different viewpoints with respect to beach nourishment programs, especially if they’re in conflict with a regional strategic plan. “Our planning document talks about the importance of beaches to our economy, so then we might have a reaction to [a] proposal,” Murley says.
The South Florida Regional Planning Council has combined efforts with the four-county Treasure Coast Regional Planning Council to the north along the state’s east coast to join other government, private, and not-for-profit groups in an organization called the Southeast Florida Regional Partnership.
The seven-county East Florida Coast partnership received a $4.25 million dollar grant-one of four nationally-from the US Department of Housing and Urban Development. Among the purposes of the three-year grant is to help the communities enhance community resiliency to the impacts of climate change as part of its “Regional Vision and Blueprint for Economic Prosperity.” The partnership will consider long-range development plans in a five-year time frame, then look at the region for the years 2030 and 2060.
“Those two years relate to one of our partners in this seven-county effort, the Southeast Florida Regional Climate Change Compact. They are using 2030 and 2060 as their scenario time frames for sea level rise,” says Murley. “We’re working with their information on scenarios for how sea level rise and other issues could be affecting erosion and other beach issues in those longer time frames.”
The evaluations could include such factors as planning and zoning, construction in the erosion-prone areas, and possible buyout of homes and other structures in high-risk areas. “Those kind of strategies and tactics are dependent on resources to execute them,” says Murley. “We will be talking about that, but we don’t have access to the kinds of significant financial resources that would be needed. We’re going to be providing to the counties and others, who today are spending money and evaluating those options, the context for knowing how the larger region looks at those issues.
“One of the outcomes the partnership hopes to generate at the end-in addition to the data, scenarios, and all of the good backup documents-is a relatively simple, consensus-driven list of the major infrastructure projects that the seven counties need to be thinking about long-term.”
Beaches have value in protecting coastal areas, providing an economic benefit and providing natural systems values, Murley points out. “Beaches are, in fact, regional,” he says. “They are defined as such: This is Boynton Beach’s beach, but it’s on a stretch of beach that starts at one inlet and ends at another. Each local government jealously wants that beach to be there because it’s so important to their tax base, but they literally can’t go about doing projects without working with their neighbors.”
While coastal development and restoration projects may take place in one jurisdiction, they affect the surrounding communities, Murley points out. “We think the region’s ability to [carry out projects] is going to be strengthened by having that consensus list and having both regions working together to try to get it accomplished,” he says. “Typically, you’re not doing projects in an independent way-you’re doing it with state and federal government.”
Still, political considerations intervene. Murley points to Everglades restoration efforts as a case in point. “Some of the original projects that were in the 2000 plan have ended up not to be the ones that are the most feasible,” he says. “We couldn’t get funding for other parts, so they’re reassessing or redoing parts of the project. That’s an example of the kind of process we’re envisioning-there will be some initial proposals based on the best information we have, and we’ll go forward with them in an initial project. If that demonstrates politically or otherwise it is not going to be able to proceed, we’ll step back and try to figure out how to fix it and what we might be able to do to move forward.”
Some vulnerable areas, however, can’t be put on hold. “Ultimately, you’re going to find areas that have recurring damage from erosion or storm events and they will become obviously areas that have to be addressed sooner than later,” Murley points out. “We’ve got hypotheticals around the sea level rise issue,” he says, “but we get high-tide events, which we think will be much like what happens with sea level rise.”
He cites particular lunar tides in Southeast Florida during October, when on a sunny day with no rain and no storm occurring, water-because of the tides-backs up into the storm-drain system and into the roads and adjoining yards. “Property owners and public officials are saying, “˜What’s going on here?’ Unlike a storm event where the water recedes fairly quickly, this water usually sits there for a couple of days,” Murley says. “We’re talking to the officials about it in the context of sea level rise, in that this could be closer to the phenomena of what’s going to happen.”
Such factors as tides, drainage, and historical storm events along with a gravity-driven system give modelers an idea of what they think may happen, “but until it happens, to some degree you can’t do your final calibrations,” says Murley. “It’s been an advantage to be able to show people in real time something that might be comparable to sea level rise,” he says. “These tides can’t be accurately termed sea level rise in a sense, but certainly they’re being exacerbated by a long-term rise in sea levels.”
Sea level rise projections vary with each study. Glacier melts and other factors are cited as causes. “The real question is whether there is an acceleration in some of these models we’re looking at today or not,” Murley says. “That’s why it’s so important to monitor this very carefully and see if some of these projections in the long range are headed in the direction we thought-or maybe they’re not, in which case you can recalibrate.”
That calls for the long-range plans to be based on a common set of indicators used to measure data, Murley says, adding that the data will be available on a website so people can monitor it as it is collected and form independent judgments about what’s happening.
Defining a Framework
Heidi Moritz, a coastal engineer with the Portland (Oregon) District of the US Army Corps of Engineers, is currently working with the corps’ Institute for Water Resources to produce an Engineering Civil Works Technical Letter that addresses incorporating sea level change adaptation at Corps of Engineers projects. “We have a national team with some international members who are trying to come up with a reasonable and implementable approach for corps projects with respect to sea level change that will fit all coasts,” Moritz says.
The letter is expected to undergo a review and complete approval process by mid- to late summer 2012. Rather than “getting hung up on predicting a specific number for future sea level change or storm conditions,” it’s more useful to define a framework for the analysis that allows informed decision-making and helps define the residual risk potential, Moritz says.
Key elements of the technical letter include the following:
- Establishing a strategic decision context for the project area, including an assessment of the potential for significant or catastrophic consequences in the near and far term. This would include awareness of strategic development investments that have the potential to shape future and long-term community development.
- Using a variety of planning options-anticipatory, adaptive, and reactive-depending on the cost and the risk of getting the answer wrong.
- Creating an awareness of critical thresholds, system connectivity, and cumulative system effects.
- Framing and guiding the discussion “so that all involved can feel comfortable that we have adequately and realistically assessed the risks,” notes Moritz-from low risk to high risk-over the adaptation horizon of 100 years.
While many project analyses are focused on a particular project and the impact on its immediate area, “in some cases, there is connectivity with other factors in the community,” Moritz points out. “There are potential negative impacts if you do something in one place versus another,” she adds. “We are trying to be aware of the system and cumulative effects of what any particular action could have. Additionally, we’re trying to be aware of critical thresholds or tipping points beyond which an alternative is not sustainable.”
The technical letter, while directed at sea-level change, will be followed by a larger climate-focused approach that includes storm intensity and frequency, addressed in a “step process, so that we build a foundation and deal with one issue before we move onto another,” Moritz says.
The draft explores strategic frontline considerations before embarking on a project:
- Is this a small or a large project? Existing or new project?
- What are the business line and mission areas affected?
- How might these change under the high sea level curve?
- Are there system or cumulative effects possible?
- Is there potential for negative or maladaptation impacts?
- What is the potential for significant or catastrophic consequences (life safety, property, critical infrastructure, or ecosystems)?
- Does the project encourage public and private investment that will influence future risk?
- Who should be involved in the evaluation of input and potential impacts?
Moving from that point, a project is evaluated according to its vulnerability to sea level change. The density of critical resources is considered. Critical resources include structures, infrastructures, recreation, environment and habitat, emergency facilities, and evacuation routes. Alternative development strategies are considered.
“We’re trying to move people away from getting hung up on the prediction of what the exact sea level change might be,” Moritz says. “That blurs what we need to be thinking about, which is really an assessment of potential risk.
“When you’re dealing with environmental loading or climate change or any type of a natural process, there’s always variability, there’s always uncertainty,” she notes. “In the case of sea-level change, there is a certain amount of discussion out there as to which number is correct. There is no way we can tell which future number is correct at this point in time.”
Rather than focusing on a specific number, the corps is instead considering a range of possibilities, defining the project to understand the potential risks and the consequences of taking one action over another, Moritz says.
A small project such as a localized revetment may not present significant consequences but merely require an occasional repair, “whereas a much larger project that involves a long seawall protecting a highly developed area will have a different level of consequences as well as connectivity with other coastal components,” Moritz says. “We’re trying to make sure that we find the strategic context as well as potential range of what could happen so that everybody is comfortable with the risk identified.”
Planning for Emergency Response
Coastal erosion mitigation is more reactive than proactive, says Dennis Barkemeyer, senior technical representative for Hesco Bastion USA. Hesco manufactures the Concertainer, a multicellular wall system that can be used for coastal or flood protection. The units can be delivered to a site flat, then assembled and filled with sand or other material to act as a barrier.
Barkemeyer, whose background is in construction management, says he tries to promote the benefits of being proactive as is called for by FEMA’s predisaster mitigation.
“Many times, we respond in what we call an emergency alert,” he says. “We have a contract with the Army Corps of Engineers; if they call, I need to be on a plane on my way to a job site if they activate our contract within 24 hours.
“The problem with that is, if you haven’t educated the emergency manager or the engineer of that city, you’re starting from scratch-and time is of the essence. Every hour that you have is valuable because with one crew of five people and a piece of equipment, I can erect 150 linear feet of Hesco wall per hour. If you have 1,000 volunteers with sand bags, you couldn’t do half of that per hour because it takes so many more sand bags.”
In a flood event, many city engineers worry about wastewater, clean potable water, and the water treatment facility. “We can go in there and train these guys ahead of time,” Barkemeyer says. “We’re going to predetermine you have X amount of miles. We’re going to have everything labeled. It’s going to go in within 48 hours. The whole town is protected.”
Barkemeyer says when he and his colleagues tour states to speak with municipal officials, they are sometimes met with the response “We don’t flood.”
“Do you know how many people I’ve dealt with who say that, and I’ve wound up working side by side with their emergency manager telling me they should have looked into this three years ago. It’s preplanning. You’ve got to have a game plan. Hesco’s good, but if you have a plan for Hesco, you can do some very extraordinary things.”
Barkemeyer had an “a-ha” moment in the days following Hurricane Katrina. Among the many sites devastated by the hurricane were nine miles of beachfront property where Barkemeyer had spent weekends with his aunt and uncle. It also was a site where Hesco units had been placed in a pilot project to rebuild marshlands at Lake Catherine.
As Barkemeyer drove to the site to check on the Hesco units, he saw 20 feet of timber on either side of the road. “That used to be people’s houses,” he says. “I got to my aunt and uncle’s place, and it was overwhelming because I couldn’t find it. All of the landmarks were gone. I saw that their house was gone, with some of their belongings still sitting on the slab.
“I made my way to the back and came across Hesco units that were unscathed. That’s when I knew we had something to work with. You have to show something before the government can justify looking into it. We’ve proved that it can work.”
Hesco products were originally created for streambank stabilization and erosion control 25 years ago and then adopted for military use to replace sandbags as a means of protection for soldiers in battle.
The Corps of Engineers realized the product was better than sandbags in erosion control efforts, Barkemeyer says, adding it has become the corps’ go-to product for elevating levies, protecting towns and critical infrastructure, and protecting coasts and wetlands. The units are also used to preserve, maintain, and rehabilitate coastal sand dunes.
Five products are part of the Hesco system. The Concertainer is designed as a cellular structure, using a welded mesh framework and geotextile lining. After it is joined and filled, the system is used to create walls designed to provide strength and structural integrity. The products are pre-assembled and delivered flat, with joining pins for unit connection.
The Floodline unit is a specialized flood-protection unit designed at the request of the Army Corps of Engineers. When filled, the unit’s permeability is reduced. The units are designed for easy removal and are suitable for filling with earth, sand, or well-graded gravel.
Rockface is the company’s geotextile-lined unit with a 1-inch-wide unlined front section. The geotextile-lined rear section allows the use of more economical indigenous fill, such as earth, sand, or gravel. Joining pins and ties also are supplied. “It’s the same concept as a gabion, but using about one-fifth or one-sixth the amount of rock,” says Barkemeyer. That’s useful in such areas as Louisiana. “We don’t have rock, and it’s very expensive,” he notes.
Rockbox is an unlined Concertainer unit for general use as a welded wire fabric gabion. “Gabions are put together in the field for the most part,” says Barkemeyer. “Contractors don’t care for that work because it’s so tedious. This is like every other product, but it’s prefabricated. All you do is connect a five-basket section to another five-basket section.”
For use in wetland restoration projects, the Delta unit has unlined front compartments, alternately rectangular and triangular. The geotextile-lined rear section accommodates more economical fill, such as earth or sand, to allow planting, and unlined sections for retaining organic material. “We put old oyster shells into the front faces to create habitat for new oysters to grow,” says Barkemeyer. “Hesco is protecting the shoreline but also providing a habitat for oyster spat, which is larvae. Oysters will grow on the bottom of a boat, rock, bottles-anything. We are introducing this friendly environment for new oysters to come and attach themselves.” After five years, the Hesco units will rust away and the oyster reef has become more established.
Oyster reefs are the second line of defense, says Barkemeyer. “The first one is the barrier islands, but they’re going away. Eventually these reefs on the outer banks of the coastal lines will be the first line of defense. You can’t stop storm surge, but you can deter it,” he says.
Hesco has funded several pilot projects with its units that have withstood numerous hurricanes and survived everyday wave fetch for years. The Hesco units provide an alternative to “dredging sand, sticking plants in it, and saying you’ve created an island, because the first big storm that comes through is going to take that away,” says Barkemeyer. “It doesn’t even take a big storm. Everyday wave fetch takes it little by little and it’s not noticeable unless you look at it over a long period of time and survey the area. We can create the land that was lost. We can protect what we still have.”
One project demonstrating the Delta unit’s effectiveness was built at the University of New Orleans Coastal Research Facility along the Chef Menteur Pass in New Orleans. Partnering with the University of South Florida and coastal geologists, Hesco funded a study on a Florida barrier island owned by Eglin Air Force Base. The units placed there contain sand and act as a planter to jump-start the growth of a new dune. When built in particular configurations, Hesco can take advantage of aeolian processes that typically cause erosion and serve as a buffer and tidal break in a surge event.
“You build these dunes in a strategic formation, because this island is overtopped by storms and it takes out the roadway and depletes the sand dunes,” Barkemeyer says. “We created an obstacle course for the water to have to travel through to reach the other side. The sand is going to drop at a certain point, almost like a pinball game. It’s not going to take all the sand, but build sand.”
Hesco often partners with educational institutions to test its units under various circumstances. One such project was growing and protecting “living shorelines.” The grant-funded project was done in partnership with the University of New Orleans, the city of New Orleans Environmental Affairs Department, and the Natural Resources Conservation Service.
Hesco units were used to repair an eroded canal bank and recreate lost wetlands. The project also entailed spot-planting of cord grass, providing a “living wall structure” method of protection as a riprap alternative.
Dunes and bluffs along the Gulf Coast act to protect property and often need rebuilding after a serious erosion event, such as destructive hurricanes. In one project in Sandestin, FL, Hesco units were used to fortify property while giving a rebuilt dune a core of integrity and strength. The units were covered with sand and planted with vegetation such as sea oats.
“I went into Sandestin after Hurricane Dennis in 2005 and two major storms wiped out the Panhandle,” Barkemeyer says. “There were condos that were condemned. People couldn’t get into their own condos because they were missing 12 feet of foundation underneath.”
Every time a storm hit the area, the residents would have to pay $26 to $30 per yard for a certain grade of sand that had to be approved by the Florida Department of Environmental Protection. “These people get tired of paying for their sand year after year,” says Barkemeyer. “They’ve been spared for the last five years. These people have to pay their assessments; they’re still paying their mortgage; they can’t rent out their condo; so they’re losing money.”
Barkemeyer spoke with the residents about Hesco: “When a storm comes, you may lose the swimming pool again and you may lose the front face and the covering of the Hesco baskets, but you’re not going to lose the sand that’s in or behind the basket,” he explains.
Flexible Systems That Adapt
Using “intelligent” methods is a potentially effective way to address coastal erosion issues and sea level rise, says David Roman, senior staff engineer for Geosyntec Consultants.
To that end, Geosyntec Consultants developed a regulated tide gate (RTG) that is able to manage tidal flows using real-time monitoring and control technology. “Intelligent operation of flood control measures can ultimately protect infrastructure and also maintain, enhance, and protect existing coastal resources by artificially attenuating or otherwise modifying the tidal cycle upstream of flood barriers as global sea level potentially increases,” says Roman.
“The RTG system shifts critical design decisions from being embedded in concrete during project development to being embedded in software. These flexible systems are therefore able to quickly adapt to changing boundary conditions and environmental factors as well as feedback on past performance. The applications of intelligent tidal control are readily applicable to meet a wide range of needs and constraints at low-lying coastal areas throughout the world.”
The National Oceanic and Atmospheric Administration (NOAA) and the University of New Hampshire Cooperative Institute for Coastal Estuarine Environmental Technology provided partial funding to Geosyntec Consultants for the RTG system’s development.
Roman says when the research on the RTG system originally began, it predominantly focused on salt marsh restoration. “There are a lot of approaches out there that are unable to universally meet site-specific restoration needs,” says Roman. “The funding was to create a modern, innovative, and versatile method for salt water marsh restoration. In the past year, we realized this could also be really useful for meeting the competing needs of restoration, resource protection, and flood control.”
According to a literature review by Roman and Marcus Quigley of Geosyntec, salt marshes have disappeared at an “alarming rate” along all coasts of the United States. Up to 90% salt marsh losses have been reported in Oregon and Washington, especially in areas adjacent to seaports and urban areas. Based on historical maps dating back to 1777, New England has lost some 37% of its salt marshes, with 80% of the salt marshes in the Boston area destroyed.
In the early 20th century, people didn’t realize that salt marshes were among the most productive ecosystems in the world, Roman says. “They were diked, dredged, and filled for land development and other human needs. But now we realize that salt marshes can act as a barrier for storm surges and floods in addition to providing habitat for fish, birds, and other wildlife.
“There were productive salt marshes all over New England during the Colonial era, but over time roads and other manmade structures such as earthen dikes were built across the marshes that restrict the amount of water that enters the marsh at high tide,” Roman says. “Tidal restrictions can lead to decreased transport of sediment and nutrients to upstream marsh areas. Consequently, marsh areas upstream of tidal restrictions can be impacted by severe subsidence.”
For example, Roman has seen marsh beds upstream of tidal restrictions that are a full meter lower than on the unrestricted ocean side. “That can be a real issue for flooding in the future,” he points out. “Subsidence increases upstream flood potential in the event of sea level rise or if a restriction such as a road is breached during a storm.”
Passive self-regulating tide gates (SRTGs) and controlled RTGs have been developed for salt marsh restoration and flood control, and although they are commercially available and effective in some areas, they are not universally suitable for all site locations, Roman and Quigley maintain. “They can be complicated and expensive to install, maintain, and operate,” says Roman. “These traditional tide-gate systems typically cannot be installed without heavy machinery, which can be cost-prohibitive or not feasible for remote or inaccessible sites.
“Traditional tide gates may not be an option for sites without readily available power or sites where there is a need for flood control to protect nearby infrastructure,” he adds.
In contrast with traditional gates, the RTG system can be installed with minimal labor and no heavy equipment, has low capital and expected maintenance costs, and can be used in new installations and retrofit situations without major infrastructure modifications, says Roman.
The RTG includes three major components: a valve or gate subsystem, a compressor subassembly, and the real-time control platform.
The bidirectional controlled valve system consists of a high-density polyethylene (HDPE) pipe fit with a rectangular, full-circumference industrial rubber bladder. The bladder serves as an inflatable pinch valve and can inflate or deflate according to flow needs. A standard mechanical compressor sub-assembly is used to inflate and deflate the bladder. It operates on a 24-V DC power source with a 20-gallon tank capacity and is compatible with off-the-shelf solar power components for independent power.
The RTG system uses a real-time control platform developed by Geosyntec called OptiRTC that interfaces with in-the-field measurement devices and Internet data feeds, such as weather forecasts. In particular, real-time data are collected from pressure transducers installed on the upstream and downstream sides of the valve. These data are logged to Internet-connected servers. An algorithm determines when to activate the compressor subassembly and inflate or deflate the valve to achieve intended water surface elevation goals. The controller is equipped with fail-safe mechanisms for control when power is lost or to override the system in an emergency.
The benefit of an RTG over a passive flood protection measure such as a self-regulating tide gate or floodwall is that it enables real-time monitoring and can be programmed to meet changing or unanticipated environmental conditions, Roman says.
“Let’s say you install a flood barrier, but 20 years down the road, sea level rise is higher than anticipated during the design phase, or storms become more intense. The flood barrier might not work as it was designed,” he says. “If the RTG system is used instead, relevant variables can be changed on the fly to adapt to unforeseen changes. Cycling between inundation goals, low-level goals, and flood control goals, one can achieve a variety of complex, predictable, and precise synthetic inundation patterns and frequencies.”
For example, the RTG system can be deployed in restoration mode by leaving the valve open as the tide comes in. When the tide begins to ebb, the valve is closed, detaining water in the upstream system. When the tide turns again and begins its flood stage, the valve is opened to allow additional water into the system. As a result, the water level of the degraded upstream salt marsh can be incrementally increased over multiple tidal cycles, allowing nutrient rich ocean water to inundate the system and foster restoration.
Another advantage is that the system is monitored remotely, Roman adds. “We can monitor any number of variables such as valve status, current and past water levels in the system, and whether any storms are forecast,” Roman says.
Data are streamed to any Internet-enabled device such as a computer or cell phone. “Real-time data streaming enables end-users to assess and react to information in the field on a continuous basis,” Roman says. “As a result, the system can even be adapted to serve as a flood-alert system based on measured and predicted water levels.”
Roman says any measure must work in concert with the concerns of environmental groups regarding the welfare of upstream resources. “I think the real issue is that if a landowner were to try to implement a standard flood protection measure such as a flap gate to protect upstream infrastructure from sea level rise, it would be difficult to get the environmental groups or local and state permitting authorities to sign on for that because it would end up degrading upstream resource areas. With the RTG system, we can enable both groups to meet in the middle by providing flood protection in concert with resource protection and restoration.”
The RTG system will have more flexibility in areas with large tide ranges, Roman says. While the Northeast has been the focus of Geosyntec’s efforts, he envisions the RTG system can be used in other coastal scenarios. To date, the RTG system has not been used on a wide scale.
“We’d like to test it out at low-risk locations prior to widespread use to optimize system operation and ensure that the system fail-safes are working as designed to prevent unnecessary flooding,” Roman says.
Battling Erosion in Maine
With 3,478 miles of coastline, Maine’s exposure to sea level changes and increased storm activity creates significant erosion issues. On April 16, 2007, the Patriot’s Day storm brought high tidal flooding during the late morning hours, putting it on the books as the seventh biggest tide on record for Portland at 13.28 feet. Waves 30 feet high ripped at buoys and damaged personal property at such locations as Chabeague Island in Casco Bay off the coast of Portland.
Seven residential property owners on the island with exposure to the north and west hired Baker Design Consultants to engineer a solution to resulting erosion. The area also includes a town right of way to the beach.
Baker Design Consultants is a civil engineering consulting firm in Yarmouth, ME, specializing in waterfront projects such as piers, docks, bulkheads, boat ramps, coastal walkways, and coastal erosion solutions. The firm had 750 feet of the shoreline surveyed and calculated the erosion that’s occurred over the last 100 years. Some of the property markers that once used to be at the top of the bank are now on the beach.
Barney Baker, P.E., says his firm determined a loss of some 40 feet of beach frontage in a span of 100 years.
The soil formation at the site created a soft clay, with water coming through the bank, creating what Baker calls “a real nightmare in terms of embankment stabilization.”
The site presented challenges prompting Baker Design Consultants to consider several options.
“It’s an island that has no quarries, no rock supply,” Baker says. “Everything—even loam—has to come from the mainland. We looked at using a natural stone, which meant a riprap solution. We looked at a sheet pile wall.”
Ultimately, Baker’s firm chose Tensar’s Triton Marine Mattresses, designed to be uniform, porous, and flexible, and to conform to uneven topography. “We eventually came to these mattresses because they have the unique ability to reinforce the slope and be planted, so you have a green solution when you’re finished,” Baker says. “They also are used in areas of unstable slopes because they’re anchored at the top—they are essentially hung onto the slope—so we felt they would be resilient to continued wave attack, but also allow the bank to recover from and support water.”
Baker also used several types of rolled erosion control products, such as Tensar/North American Green P550 and SC250 turf reinforcement mats (TRMs). P550 is a permanent TRM designed to provide long-term, prevegetated erosion protection and permanent turf reinforcement in severe applications including steep slopes and extreme, high-flow channels and shorelines. The Vmax3 SC250 TRM is constructed of a permanent, high-strength, three-dimensional matting incorporating a straw/coconut fiber matrix to enhance the matting’s initial mulching and erosion control performance for up to 24 months.
Because there had been a lot of water coming through the bank, Baker’s firm designed a natural surface drain and added other drains as well.
“The mattresses seem to be very successful in dealing with this type of slope,” Baker says.
Baker Design Consultants went through a lengthy permitting process, with two criteria influencing the design. The first was the need to create a stable bank. To do that, the firm stabilized the toe of the bank with stone to combat direct wave action and also to stabilize the base of the slope mattresses, which are placed perpendicular to the slope.
The mattresses extend up to the base flood elevation and down to the high-tide mark. The stone at the base extends into the beach and protects the toe of the slope. A pneumatic drill was used to install 10-foot anchors to hold the mattress units into the slope.
Another factor influencing the design was the property owners’ desire to have a “green planted finish” to the solution, Baker says, adding that they did not want to look at a “band of stone.”
The slope was cut back. Geotextile was placed on the slope, and the mattresses were placed atop the geotextile and anchored at the top of the slope. After toe stone was placed at the base, the mattress units were planted with salt-tolerant species.
“The P550 was used above the mattresses for additional soil reinforcement because we’re dealing with relatively steep slope,” says Baker. “That was to engineer a steeper slope above the mattresses out of the wave window based on elevation.”
Baker agrees with others that the sea level “is certainly changing,” but how rapidly that is occurring is an unknown.
“Another factor that has affected the coastal projects significantly is the fact that we have more violent weather,” he adds. “When we had our big storm event in April 2007, we had significant tides, and when we have a surge tide with a storm on top of that, that’s when we get all of our big damage. We had storms consecutively from 2005 to 2007 that have not given the coast much time to recover. So we are experiencing significant erosion.”
While being proactive might be ideal, “it’s certainly very expensive,” Baker points out.
“We have to be smart, we have to educate property owners on how to maintain the vegetation on their slopes, and we need to design structures on the coast in a responsible manner so we don’t encourage erosion to follow the structures that we put there. We engineer these structures to last through any storm cycle that they’d see in their lifetime.”
Restoring Coastlines
Jimmy McDaniel finds himself busy these days mitigating the effects of coastal erosion. “People are losing their land due to the erosion, and they’re looking for methods that are not only effective, but cost-effective as well,” he says, adding that in the area in which his company is located, he is noting “serious issues” with beach erosion.
His company, Mac Marine Erosion Control in Palm City, FL, uses geotextile tubes manufactured by Midwest Construction Products. “They sew up the material to whatever desired width or circumference I need for the job for coastal and water protection in general,” says McDaniel.
“The normal price of a seawall around a lake would be astronomical,” he says. “You may not really need something that bulky and expensive.”
Mac Marine pulls material from the bottom of a lake to use as fill for the geotextile tubes, depending on the project. “A lot of times, it ends up rejuvenating the lake, cleaning out some of the nasty stuff that spills out on the bottom over the years, such as pesticides and fertilizers,” he says. “We check with environmental agencies to see if we’re allowed to do it. If not, we’ll usually bring in sand” to use as fill.
The geotextile tubes may not be the best approach for areas with fast-moving currents, McDaniel says. Much of his work is focused on lakes, canals, and other bodies of water without heavy current and winds. One such project was in Palm Beach, FL, adjacent to the Atlantic Intracoastal Waterway, which runs the length of the East Coast and, in most cases, is separated from the Atlantic Ocean by a small width of land.
The exclusive Everglades Club in Palm Beach is adjacent to the Intracoastal Waterway and was experiencing erosion, McDaniel says. “When they’d get a heavy rain, it would flood the ponds up and they’d drain to the Intracoastal,” he says. “With years of lawn mowers and weed eaters cutting through there, they ended up with a nasty-looking shoreline.”
In May 2011, he installed about 1,800 lineal feet of geotextile tubes on the property. “The man I bought the company from four years ago did a job on one of their other lakes,” says McDaniel. “They gave it a few years to see if it would hold up well, and it did, so they called me to do the rest of their lakes. It gave it an unbelievable look and it stopped all of the erosion.”
McDaniel also works for Aquatic Plants of Florida, which provides wholesale customers in the southeastern United States and the Caribbean with plants for use in mitigation projects, such as freshwater herbaceous and salt-tolerant plants, native grasses, shrubs, ferns, trees, and wildflowers to restore, rebuild, and replenish beach dunes, wetlands, marshes, and retention ponds. In spring 2011, McDaniel helped Aquatic Plants of Florida on an Army Corps of Engineers restoration project at Pascagoula Beach, MS, as part of the Mississippi Coastal Improvements Program.
The project entailed beach toe protection to minimize erosion caused by high-wave energy from the Mississippi Sound. There was potential for lost sediment migrating into areas of shipping traffic and increasing the frequency of future dredging intervals.
The project initially involved the repair of a concave seawall, replacement and extension of existing drainage structures, fill and placement of 7,700 feet of geotubes, excavation of almost 290,000 cubic yards of sand, and extensive sand placement on the Pascagoula waterfront in the Mississippi Sound. “A giant geotube was installed along the beach, and we planted marsh hay cord grass,” says McDaniel. “The tube itself is only as strong as what’s holding it together on top. You’ve got to have some kind of protection on top, like a sod. The materials were pumped from 7 miles inland. It really is an effective method. The best part is, it’s very environmentally friendly. It’s using the same materials in your environment, so there’s less impact on the environment bringing in heavy machinery.”
