May-2009

The Taming of Turkey Bay

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All photos: Land Between the Lakes National Recreation Area
First, a smooth and solid base was prepared. Then a geotextile fabric was laid down, followed by individual blocks on the fabric that were cabled together to form one continuous structure.

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Sediments and Settlements

For more than 30 years, dirt bikes, four-wheel all-terrain vehicles, and trucks tore up the 2,500 acres of rolling hills, ridge tops, and shorelines of Turkey Bay, in the Land Between the Lakes National Recreation Area (LBL) in western Kentucky. The US Forest Service took over the first federally designated area for off-highway vehicles (OHV) in 2005; but, by then, the damage had been done.

“It looked like something akin to abandoned strip mines,” says Jackie Franklin, a soil scientist and hydrologist with LBL.

LBL has slowly been restoring the site, which is made up of sandy, unconsolidated coastal materials and can get up to 50 inches of rain a year. It’s open year-round except for days when the soil is too saturated, which is both a safety and an erosion issue, says Kyle Varel, LBL Trails and OHV assistant manager.

The top priority has been to break up the sheet erosion down the hillsides, says Bill Ryan, LBL trails and OHV manager. “Over time, OHV riders created linear runs straight up and down the hills. They can be 25 to 125 feet long and 4 or 5 feet deep.”

The completed hardened stream crossing project

One of the seven creek crossings before the project began. The objective is to reduce the amount of downstream sedimentation after OHVs cross the streams and to minimize the impacts to the trails themselves.

The Forest Service has been closing off some of the most impacted and unsustainable trails and restoring the hillsides. This has the added benefit of improving rider safety, as many of these “rogue trails” are dangerous for riders, Varel says. The more sustainable ones have been designated as legal riding trails.

Some highly impacted and unsustainable trails are still open. These “challenge areas,” which range from less than 5 acres to about 10 acres, are some of the steepest and most difficult to navigate in the entire trail system.

“Restoration is ongoing,” Ryan says. “We’re taking one step at a time.”

Hillside Restoration
In the first step in restoring the hillsides, crews rough up the most-impacted trails with an excavator and the less-impacted ones with an ATV-mounted tiller, Varel explains. They typically plant seeds of a native grass such as annual rye as a cover crop, often with 10-10-10 fertilizer, to reduce erosion until native grasses, shrubs, and trees can establish themselves.

Their budget and access to the sites dictate the erosion control materials used. LBL prefers using strategically placed bioengineering materials that are already onsite, such as fallen trees, brush, root wads, rocks, and leaf litter to slow down the velocity of runoff water, says Ryan. Crews have tackled 8- to 10-foot-long trenches, some of them three times as deep, and covered them with bales of hay for additional organic matter.

“Three years later, we’re seeing small trees sprouting,” he says.

LBL has also installed American Excelsior Curlex III sediment mats and sediment logs. The products work well, he says, and have the added benefit of deterring riders from driving over them.

The 12-acre watershed, "The Wall," before it was closed in 2006.

The same area after it was restored. First, a trackhoe recontoured the hillsides and broke up the sheer sides of each trail. The, root wads, logs, rock, and bales of hay were put down to slow the velocity of stormwater. Perennial rye was broadcast as a cover until native grasses, shrubs, and trees could establish themselves.

In 2006, LBL closed “The Wall,” a 12-acre watershed that was very highly impacted by OHV use. Crews used a trackhoe to re-contour the hillsides and break up the sheer sides of each trail. They broadcasted perennial rye as a cover crop, and then covered it with root wads, logs, rock, and rolled-out bales of hay. The hay stayed together, Ryan says. “Roughing up soil first helped.”

Trail Maintenance
So far, LBL has designated approximately 106 miles of trails, which are used by about 82,000 riders each year. These legal trails are monitored, and LBL performs seasonal spot maintenance as needed. The trails usually just need some reshaping and smoothing out with a small bulldozer or tractor with a blade, Ryan says.

Streambed Restoration
When riders cross streambeds when the stream is flowing or when the bed is muddy, soil in the streambed erodes badly. Since 2006, LBL has installed seven hardened creek crossings to help reduce this erosion, as well as to provide riders with a stable surface across the creeks.

To create the crossings, LBL has used ArmorFlex blocks from Armortec Erosion Control Solutions. These concrete blocks consist of 20% open space, which eventually fills with native creek gravel and sand to increase stability.

Crews first excavate the creek bed, Varel says, put down an inch or two of dense-grade gravel for a solid working base, and cover it with a geotextile filter fabric. They use single blocks instead of factory-assembled mats because access to the creeks is a problem. Then they hand-place the blocks on the fabric and cable them together, forming a mat shaped to the trail. The mats span 80 to 110 feet long and 14 feet wide or more, depending on the crossing.

“It’s worked really well,” he says. Although the downstream sides have cut a little, the hardened crossings have stayed stable and have greatly reduced LBL’s maintenance costs. All restoration projects and trail improvements have been completed by LBL’s onsite maintenance contractor, Ecotone Services Inc., or through special volunteer workdays.

A typical user-created, rogue trail

Crews roughed up each trail and broadcast annual rye and 10-10-10 fertilizer, then installed American Excelsior Curlex III sediment mats and sediment logs over all the seeded res. These both slowed down the velocity of runoff and deterred riders from the area.

Working with Riders
Getting riders to cooperate is crucial in restoring and maintaining the area. LBL is installing signage to educate them and providing creative opportunities to attract riders who respect the trails. Many volunteer to work on projects.

“People are beginning to think, ‘Maybe we shouldn’t be tearing up the hillsides,’” says Ryan.

He arranged for a nearby rock quarry to donate its spoil materials. Now the site has a 1- to 2-acre rock garden piled with more than 350 tons of rocks, from refrigerator to basketball size, which provides a virtually maintenance-free opportunity for riders to drive over rocks. LBL is planning to make the rock garden even larger, with more challenges and obstacles and more lines of travel for high-clearance vehicles, he says.

Another addition is the half-mile-long children’s trail, which is designed for children operating vehicles with engines of 90 cubic centimeters or less. It has environmental education signs and small obstacles, and it is a safe place for parents to teach their children how to ride and for children to practice their riding skills.

“Land Between the Lakes is committed to moving forward by promoting OHV trails,” Varel says. “We’re trying to strike a balance by maintaining sustainable trails, minimizing OHV-related impacts to water quality, and restoring portions of a land base that’s been hit hard over the years by intense use... all while allowing public access to the trail system.