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Coast Guard - Summer 2009
Leaving coastline in its natural state is key to protection
by Melissa Gaskill
After Hurricane Katrina, Russ Marane, president of the St. Simons Land Trust in Georgia, viewed aerial photographs of a two-mile-wide barrier island off the Mississippi coast. On the island’s seaward side, the storm completely flattened trees for about a quarter-mile inland. Trees in the next quarter-mile lost their tops, but on the backside of the island trees remained fully intact. Behind that island, and in contrast to the rest of the coast, “Not a single structure was damaged,” Marane says. “It’s one of the best examples I’ve seen of why you don’t touch barrier islands.”
Coastal landscapes – barrier islands, dunes, wetlands, grassy marshes, woodlands and mangroves – provide protection from the winds, waves and storm surges. This protection is worth an estimated $23.2 billion per year, according to Robert Costanza, Ph.D., professor at The University of Vermont. “Coastal wetlands reduce the damaging effects of hurricanes by absorbing storm energy in ways that neither solid land nor open water can,” he says. “Coastal vegetation also decreases surges and waves and maintains shallow water depths, which has the same effect.”
Wetlands also serve as filters, cleaning rainwater before sending it out to the ocean or aquifer. By contrast, water quickly runs off pavement and other impervious surfaces, carrying with it fertilizers, pesticides, oil, heavy metals and other chemicals. This pollution is directly related to the amount of impervious cover and is the leading threat to water quality nationwide.
A natural coastline is also more durable than an altered one. Wetland systems and mangroves reduce shoreline erosion by retaining sediment, a function especially critical where dams and levees reduce the flow of sediment from rivers. Beach dunes serve as reservoirs of sand, slowing erosion and replenishing beaches. Artificial seawalls, ironically, contribute to further erosion. In response, communities often rebuild beaches with sand dredged from the ocean floor. This sand is different from what occurs on the beach naturally, thus disrupting vegetation and wildlife. This approach also damages the marine environment and is very expensive. “It would be more sensible and economical to leave dune systems intact,” says David Godfrey, executive director of the Caribbean Conservation Corporation, “and keep development far enough behind them to account for normal and storm-wrought changes on the beach.”
It is far too late, of course, to leave much of the U.S. coastline in its natural state. However, better development practices can preserve many benefits of those natural systems. Three key practices, according to Texas SeaGrant and the Gulf Coast Institute, are creating compact development, controlling stormwater run-off, and preserving as much open or natural space as possible.
“The one thing that does the most by far is compact development,” says John Jacob, associate professor, Texas A&M University, and director of the Texas Coastal Watershed Program. “Nothing else comes close.” Compact development may create more impervious cover on a few acres, but it results in less overall. For example, a typical suburban layout of four units per acre for 1,000 houses would cover 250 acres. At 10 units per acre, those same 1,000 homes occupy 100 acres. A 20-house-per-acre development, such as townhomes, occupies only 50 acres. “Fifty is a big difference from 250,” Jacob says. “And you get a more interesting neighborhood, with the benefits you get from bringing people together and the natural environment around you. It’s the best of both worlds.”
Palmetto Bluff in South Carolina is a development of Crescent Resources, and it clusters development in three villages on 20,000 acres. Patty Kennedy, executive director of the non-profit Palmetto Bluff Conservancy, says, “We are developing in areas where settlement had historically occurred.” Much of the rest of the land is left undisturbed.
Building more compact communities allows developers to protect dunes, wetlands and open space – and to enjoy their benefits – says John Kuriawa, a coastal management specialist with the National Oceanic and Atmospheric Administration’s Ocean and Coastal Resource Management Office on the Chesapeake Bay. “Sprawl clearly results in degradation of water.”
Kuriawa explains that people can take action at every level. Individuals can leave trees and reduce the size of driveways. Subdivisions can put in narrower roads, permeable pavement and swales. The city or regional level offers the opportunity to protect large areas of natural landscape. “One of the best things is to convert existing impervious cover to accommodate growth, rather than allowing it to spread and cause death by a million cuts,” Kuriawa says. “An abandoned mall can be redeveloped into mixed use with open space.”
One of the most important tools, he adds, is for communities to protect and encourage the use of native plants and trees.
“Natural landscapes need little maintenance. You don’t have to mow, edge, fertilize or water once they are established,” says Meg Whitmer, landscape architect and director of the Land to Sea Initiative at the Ocean Research and Conservation Association. “The best thing is to gently place your home among what is there naturally.”
That was the approach the Episcopal Diocese of West Texas took in building Mustang Island Conference Center, a dining hall and two dorms connected by boardwalks. “We looked at the buildings more as a ship at sea, parting the waters and leaving no evidence behind,” says David Richter, FAIA, LEED AP, of Richter Architects in Corpus Christi. “One of the most beautiful plants that grows on the island is a vine. We designed the buildings the way that vine meanders across the ground.” In the space underneath the elevated buildings, where it is too shady for native plants to grow, he put permeable surface for parking with a moveable perimeter.
“Outside of that perimeter, we didn’t do anything. We didn’t bring in one plant or do any kind of landscaping,” Richter says. “In my opinion that is not done enough on barrier islands.”
Native plants help minimize runoff by mimicking natural hydrologic processes, says Darla Inglis, Ph.D., lead for the central coast office of The Low Impact Development Center, especially when combined with measures such as rain barrels, cisterns, rain gardens, green roofs and permeable pavement.
In the Florida panhandle, St. Joe Company uses native plants in developed areas and prohibits grass lawns for individual homes, according to wildlife biologist Jim Moyers, community development naturalist for WaterSound and WaterColor communities. This reduces run-off; what remains is collected in ponds. “All the run-off from WaterSound Beach goes to five large ponds, which takes energy out of the run-off, decreases erosion and settles out the crud from the streets,” Moyers says. “These are also landscaped with native wetland plants to mimic a natural wetland, so they also have wildlife enhancement value.”
Palmetto Bluffs requires residential rainwater harvesting. It also actively preserves natural space by requiring a 100-foot setback along the riverfront and by prohibiting clearing. In addition, on a 500-acre parcel approved for 100 homes, the company planned only 10 lots and placed about half of the acres under conservation easement.
St. Joe Company has set aside coastal dune areas, explains Moyers, in some cases to conserve federally listed endangered species. “But we treat this area as a community amenity. It has value as a visual amenity and in some cases protection for development behind it. We get a lot of benefits from keeping the dunes – the plant and animal species that inhabit those systems, a great vista from the developed area and that protection from Mother Nature.” Hurricanes Ivan in 2004 and Dennis in 2005 proved that the approach works. “All we lost was the front half of tall dunes, the natural landscape – which regenerates – and boardwalks over the dunes, which are easily replaced. We didn’t lose any real property – houses or hardened structures.”
At Asilomar Conference Center, on 107 acres of state park land near Pacific Grove, California, structures built in the 1920s were situated behind the dunes. Those dunes, however, suffered from decades of heavy use. Beginning in the 1990s, a restoration project removed non-native plants, planted natives and installed boardwalks.
“Asilomar is a classic example of coastal development with dune restoration, buildings set back from the ocean and a boardwalk through the dunes,” says Travis Longcore, science director of The Urban Wildlands Group. “Current developments could learn from this.”
One lesson – the importance of preserving or restoring native vegetation – applies even in urban areas. San Francisco Bay, the largest and most ecologically important estuary on the U.S. Pacific Coast, could hardly be called a natural system after more than a century of drainage, pollution and alteration. Fortunately, intense efforts by an alliance of public agencies, nonprofit organizations and citizen groups have restored hundreds of acres of native habitat, including native flowering eelgrass, Zostera marina. The grass provides nursery habitat for fin fish and crabs, as well as keystone habitat for bay scallops, and it contributes to improved water quality.
An even larger eelgrass restoration project in The Nature Conservancy’s 38,000-acre Virginia Coast Reserve began more than a decade ago. The effort is a joint partnership between The Nature Conservancy and the Virginia Institute of Marine Sciences and relies heavily on volunteers to collect seeds in the spring for planting in the fall. The project has planted more than 200 acres, and the grass has spread on its own to cover roughly 1,450 acres, says Barry Truitt, chief scientist for the Virginia Coast Reserve.
The health of this underwater prairie, like that of all coastal systems, depends on water quality. Water quality is affected by everything that happens on the land, and that, of course, depends on us.