Wetland and Prairie Restoration

Sept. 1, 2007

Perhaps no events more closely drew attention to wetland loss and the need for wetland restoration than the recent wave of hurricanes that have hit the Gulf Coast.

Coastal wetlands play an important role in reducing the height of storm surge when a major storm makes landfall.

Some 40% of the coastal wetlands of the contiguous United States are located in Louisiana. Over the past several decades, the state has lost up to 40 square miles of marsh per year, comprising nearly 80% of the nation’s annual coastal wetland loss. If this current loss is not stemmed, it is estimated that by 2040, Louisiana shoreline will advance inland as much as 33 miles in some areas due to an additional loss of 800,000 acres of wetlands.

Additionally, of those wetlands still in existence, some 90% are at or below sea-level elevation.

In 1990, Congress passed the Coastal Wetlands Planning, Protection and Restoration Act (CWPPRA), funding wetland enhancement projects throughout the United States, with some $60 million designated for work in Louisiana.

And with wetlands in general (beyond coastal), there also are concerns about their disappearance. Florida’s St. Petersburg Times in 2005 reported that in 15 years, 84,000 acres of Florida’s wetlands had disappeared despite “no net loss” federal policies that mandate the replacement of lost wetlands.

According to the University of Florida, the continental United States has lost 53% of its wetland acreage since an accounting was made in 1780. Florida has lost the most acreage cover at 9.3 million acres; California has lost the largest percentage of its original wetlands at 91%. Some 22 states have lost more than half of their original wetlands; only Alaska, Hawaii, and New Hampshire have retained more than 80% of their original wetlands.

And while federal wetland management plans emerged during the 1980s, resulting in a rise in wetland restoration efforts, hundreds of thousands of wetland areas are drained each year.

The prevailing theory with Louisiana coastal wetlands is that the hard-armoring of the Mississippi River—including much of the levee system around New Orleans and the shipping and navigation channels along the river—has been preventing the natural deposition of silt in the coastal wetlands, accounting for their gradual disappearance.

In Louisiana, several initiatives are in place to address this state’s critical concerns. According to Louisiana Sea Grant, they include some 149 projects benefiting more than 135,000 acres of coastal wetlands through the CWPPRA, authorized by Congress to respond to national wetland loss with special attention paid to Louisiana.

In another program, Coast 2050: Toward a Sustainable Coastal Louisiana, the state developed the strategy in 1998 in conjunction with several federal agencies, outlining 77 ecosystem restoration efforts needed to protect and sustain the state’s remaining coastal wetlands.

Additionally, research is being conducted and funded by such agencies as Louisiana Sea Grant to address the challenges of wetland loss.

Current research includes Louisiana State University’s (LSU’s) Coastal Ecology Institute’s study on “Nutrient Dynamics and Primary Productivity at the Caernarvon Freshwater Diversion.” The study will look at the impact of freshwater diversions on estuarine water quality and determine the effectiveness of coastal wetlands in processing Mississippi River water before it enters the Gulf of Mexico. Introducing freshwater diversions into deteriorating coastal wetlands is viewed as a sound strategy to obtain needed nutrients and sediment, but if the introduced water contains more nutrients than the wetlands can use for plant growth, it may add to a hypoxic condition that causes the northern Gulf of Mexico “dead zone,” researchers say.

Another LSU study looks at “Coastal Wetland Restoration: The Development of Functional Criteria to Predict the Sustainability of Restored Wetlands.” The study delves into sediment and will look at such factors as the degree of sediment enrichment required to achieve wetland sustainability.

LSU’s AgCenter’s Rice Research Station is examining “Development of Seed-Based Spartina alterniflora (Smooth Cordgrass) Propagation Technology for Coastal Wetlands Restoration and Remediation” as an effort to develop quick and successful plant science technology in vegetative restoration.

While Louisiana is a standout because of its status in the wetlands system, it is one of many areas throughout the United States where restoration efforts are taking place. Restoration efforts take many forms, from protecting human life and property on coastal areas to re-establishing habit for wildlife displaced during construction activity. And there are many tools utilized in those projects, including dredging, the promotion of the growth of aquatic and marsh plants (and the use of chemicals to discourage the growth of non-native plants), and structures to encourage silt and sediment deposition.

Dredge America has been involved in several restoration efforts. Among them, a US Navy base in Puerto Rico had been closed down and part of the environmental cleanup in turning it back over to the Puerto Rican government involved restoring a large mangrove forest on part of the base. The aim was to get a flushing action of the tides in order to promote the health of the mangroves.

“We’re dredging a channel through the middle of it so there is more water coming in and going out, and there are a couple of culverts there that separate the ocean from the mangrove area. They are making that much bigger and dredging this channel to get more of a flushing action,” says Dan McDougal, president of Dredge America.

By opening up that area, aquatic life is expected to pick up the pace in the vicinity. The project, initiated earlier this year, was expected to take two to three months.

Dredge America also has been engaged in some larger restoration efforts such as one along the Texas coast a few years ago in which the company installed 2.5 miles of geotextile tubes, which were filled with a dredge, creating a wetland behind that.

“It was all planted and that protected the area from wave action over time, when the wetlands are being washed away,” says McDougal. “This created a barrier to the wave breaker so the wetlands could be re-established behind the geotextile tubes.”

A recently completed project in the Florida Panhandle close to Mobile, AL, entailed the installation of geotextile tubes in a circular pattern along a dredge spoil island. “In the future, when the main channel is dredged, they’re going to let the fines be released out of the dredge spoil island, which will fill inside this geotextile tube and create a large wetland,” McDougal says.

It’s a sign of the times that more attention is being paid to wetlands and the environment in general, says McDougal, noting that dredging is playing an increasing role in restoring such areas. “It used to be dredging was considered very negative in a lot of circles, but now a lot of the things that we create are getting attention, such as these islands, for example,” he says. “We did a job a few years ago off the Texas coast where we extended an island, putting in geotextile tubes and filling inside of them for the sake of the brown pelican; it was strictly a bird island.

“A lot of what used to be called dredge spoil islands are actually fabulous habitat for all kinds of species along the coastal areas.”

Aer-Flo Inc. manufactures floating and staked turbidity barriers for working in and near water. Staked barriers keep the spread of sediment that’s stirred up and are used in water up to 18 inches deep in a non-active waterway. A new type of staked barrier has come onto the market that will not require an installed trench below grade but will use a chain ballast at the base.

“It’s similar to the floating barrier, so you do not need to trench, which would reduce the amount of disturbing the bottom anyway,” says Bill Henning, Aer-Flo president. “The chain allows the barrier to sink in and anchor to its own.”

Aer-Flo floating turbidity barriers are playing a key role in restoration work at Lake Charles in Louisiana. The barriers are being used along more than 3 miles of lake shoreline as a pipeline damaged during Hurricane Katrina is restored.

Floating turbidity barriers are constructed as such: The top is a floating boom with a curtain of impervious vinyl-coated polyester, and a chain ballast runs the full length of the bottom. The barriers typically come in 50- to 100-foot-long sections.

“In this case, these barriers were down to 10 feet deep. They are attached together into a strength that keeps waterborne sediments from spreading out in the waterway,” says Henning. “It’s really the only BMP [best management practice] that can be used in the pre-construction and construction phases of a job site, whether it be for reconstruction or construction.”

Generally, barriers are used to address the damage that can be done by sediment that can flow with stormwater off of a construction site. Uncontained corroded sediment stirred up or added to waterways spreads out and causes extensive damage.

“Turbidity barriers contain waterborne sediment, allowing it to settle out in an area so it doesn’t spread and cause more damage,” Henning says. “In this case, any damage done by a hurricane is done. Barriers contain the sediments from spreading out while you are fixing the problem.

“These are used everywhere from a section of a small stream or pond to large projects, such as one a few years ago in Florida where we put in 120,000 linear feet just for reconstruction projects after a hurricane.”

Seeding plays a large role in site remediation projects. Many consulting firms and contractors in California have turned to S&S Seeds in Carpinteria, CA, for help.

Melissa Howe is an associate principal with the habit restoration group for BonTerra Consulting, an environmental consulting firm in Temecula, CA. Among the company’s habitat restoration efforts is wetlands restoration done as part of mitigation programs.

Outlining the steps her company undertakes to create a riparian habitat project, Howe says that site preparation to create the conditions necessary for riparian species begins with grading. Any weed problems still apparent are removed by hand or through the use of an approved herbicide for wetland areas. Surface soil preparation is done to create suitable plant establishment conditions. Following that, a site ready for plants is either hand-seeded or hydroseeded depending on the access and the size. Other options include the use of planting containers and cuttings.

Seed mixes and plants chosen depend on site conditions, the habitat being established, and plants typical for the area. Willow, for example, is typical for riparian use.

A prairie restoration in Ohio has helped remediate a former refinery landfill site by increasing the biological activity in the soil, enhancing treatment, and making the area look attractive. North American Wetland Engineering did the remediation after former efforts failed, says Shane Sparks, a company hydrogeologist.

The former refinery in Lima, OH, consisted of two sections: a pond used to store the refinery’s wastewater and a landfill for sludge and construction material. The site was shut down in the early 1980s because it was contaminated.

It had been determined that the soil still was contaminated and was leaking the contaminants into the nearby river. The landfill was capped and a company was brought in to do prairie restoration. But the initial prairie restoration failed for lack of proper preparation.

North American Wetland Engineering was later called in to do the prairie restoration on the 20-acre site. The company planted native prairie grasses, such as prairie clovers and Indian grasses. The company has returned to the site to do maintenance by reseeding as necessary and to mow areas to control weeds that cannot be controlled through herbicides.

Nature’s Image in Lake Forest, CA, runs the gamut in habitat restoration projects. The company does mitigation work for developers by creating a nature preserve or enhancing or creating a habitat that has been displaced through construction projects. A lot of that is driven through state regulations.

Grady Banister of Nature’s Image explains that California requires one-to-one to one-to-five mitigations. “If a company disturbs or destroys 1 acre of habitat, they need to replace it with 1 acre or up to 5 acres to replace that particular acre, depending on the quality of the habitat and what type of species they’ve impacted,” Banister says.

His company does a great deal of exotic-weed-removal work as well as erosion control work. The company also helps biologists determine population counts on animals being affected through development by setting up trap arrays.

The company also does imprinting and hydroseeding. Banister says the imprinting is done through a machine that looks like a large drum with cleats on it, and the machine is drawn behind a tractor, dropping seed into the ground and leaving a waffle pattern in the ground, which protects the seed that already has soil contact.

“You don’t need to get the seed wet to put it down,” Banister says. “In areas where there is intermittent rainfall or no irrigation, that’s an effective way to seed.”

His company has the ability to imprint on steep slopes using a machine that is mounted on a bulldozer.

Nature’s Image also does native plant salvage and relocation. The inherent challenge in such efforts is that success in germination rates is not necessarily noted immediately if it’s a dry rain year.

“You are not sure if you are successful until a couple of years go by and you’ve gotten some good rainfall, so you may not know if you are successful to the point where you’ve met the requirements for a couple of years,” says Banister.

“We’ve helped with projects where they have relocated animals like the threatened southwestern pond turtle or helped build environments for those that were away from an area being disturbed, where they are held there temporarily and then put back into the original areas. We’ve built small ponds for them and it is a holding/breeding pool for them until they can get moved back to the area that was being disturbed by the development.”

The company also does wetlands work. “Typically, we do detention basin or riparian corridor work,” says Banister. “The stream beds and detention basins are anything from ones that are intermittently dry to ones that always have water in them. We also have worked on several marshes in San Diego County and have helped create wetlands, where a grading company will grade out wetlands by lowering the soil level so the water table will affect that area. Sometimes they expand on an existing stream or a wetlands area by making the area larger to provide more habitat for desired plants or species.”

Nature’s Image will do plantings in those areas and install irrigation systems as needed. “A lot of times, there are irrigation systems on the outer boundaries of the wetlands where they’re trying to establish riparian plants and get some cover,” Banister adds.

The company also has done work on salt marshes. “Sometimes there is very little irrigation on those areas except maybe in the upland areas,” says Banister. “You’re planting down in salt water, so you have to wait for low tide.”

Some of the wetlands projects Banister’s company is helping create are coastal marshes. A number of those projects are natural marshes, where a little bit of grading is done to lower the soil level and get closer to the water table before planting and irrigation systems are added. The primary purpose of those projects is to enlarge the wetlands and thus increase the habitat for the various species that utilize the wetlands.

“Most of these wetlands we’re working on are within a mile or two of the coast, but not too influenced by tidal,” says Banister.

Salix Applied Earthcare in Redding, CA, was involved in Phase III of the Sulphur Creek Restoration Project—Middle Reach Erosion Control and Habitat Enhancement Project. Salix’s John McCullah served as a geomorphologist on the project.

A restoration plan was designed by the Sacramento Watersheds Action Group to address erosion, stream function, and flooding problems as documented by the Sulphur Creek Watershed Analysis and Action Plan. As part of the project, stream reaches were realigned and restored. Sewer access roads were improved and proper drainage and road base were established to address erosion challenges. Sewer and water main crossings are protected by a “low water crossing” for an access road.

The first part of the job entailed establishing equipment access to the stream by removing debris such as car bodies and other objects. Excavators were used to clear the brush and remove noxious plans.

Loamy-silt sediment deposits had been discovered in the channel, which was believed to have originated from the nearby railroad and recent land developments. Because it posed a detriment to the aquatic stream system, it was removed from the channel to an area where it could be stabilized from erosion.

Fish passage structures were created. A Union Pacific Railroad culvert acted as a velocity barrier downstream, but fish needed to jump vertically more than 2 feet. An alternative modified step-pool approach was constructed. Rock cross vanes were chosen for two controls. Three- to 4-ton stones were tightly fitted together for the apex and footer rocks and “sealed” with fines. They also were modified with riffles downstream to help fish pass during low-flow periods.

A large rock vane—a transverse tapered rock structure jutting out one-third of the bank width and angled 30 degrees upstream—was built at the culvert. This redirected flows from the culvert so they no longer erode the bank; the redirected flow was focused to maintain the scour pool, and the flow was narrowed across the apron to deepen the water and permit better fish migration.

The project also included several habitats, and biotechnical enhancements were made downstream of the culvert and apron. All disturbed areas above bank full discharge were revegetated with native grasses.

The primary erosion and sediment control BMP was to “wash fines” for the in-stream work areas at elevations below bank full discharge, or annual high water. To wash fines, a water truck is used to clean the gravel and cobbles from equipment work that brings the matter to the surface. Washing fines effectively mimics first flush on seasonal streams so when the actual first storm occurs, there will not be large turbidity plumes. 

About the Author

Carol Brzozowski

Carol Brzozowski specializes in topics related to resource management and technology.