Hidden by undergrowth, a nameless trickle of a stream has carved a channel 10 feet deep into the red clay of a Cornelius neighborhood. County water-quality staff call it the Little Grand Canyon.
But this is not nature at work. It's a symptom of the development that is overwhelming Charlotte-area suburban streams, threatening water supplies, while gobbling 56 acres of raw land a day.
Nearly three-fourths of Mecklenburg County's major streams are considered impaired. Those new to that list are usually on the city's outskirts.
The Cornelius stream collects rainwater charging off the neighborhood's hard surfaces, where it can't soak into the ground. Each new roof, driveway and cul de sac adds to the volume.
The force of water dug the channel so deep that rising water can no longer spread into the floodplain. Instead it gnaws at the stream banks, undermining trees and widening the chasm.
That's how tons of dirt and fertilizers wash into Mountain Island Lake, Charlotte's water supply, each year.
It's why suburban streams that were fairly clean 20 years ago are sterile ditches now.
And why taxpayers will pay millions to clean up McDowell Creek, whose headwaters include the Little Grand Canyon, and whose muddy, lifeless water drains into Mountain Island.
“I can straddle this stream, but it did all this damage,” marvels county water official David Kroening, as the collapsing banks in Cornelius dwarf his 6-foot-3 frame.
Kroening is part of a team working to revive McDowell Creek. “The goal for us is to have measurable results within 15 years,” he said.
Ten projects are planned in the 30-square-mile McDowell watershed to restore portions of the creek and its tributaries, and to build wetlands and berms to slow stormwater. The projects are expected to exceed $4.9 million, much of it from state or federal grants.
A major shift in development philosophy by sprawling Huntersville, which covers much of the basin, prompted the work.
In 2003 a town ordinance embraced low-impact design standards that encourage stormwater to soak into the ground instead of pouring into creeks. The ordinance controls new development. Mecklenburg County's stormwater and water-quality programs focus on fixing old problems.
County water-quality staff estimates that pollution from runoff – pouring off developed areas – has increased 55 percent since 1987. In the same period, the county has lost 70 percent of its trees and other pollutant-soaking plants.
An acre of forest can fully absorb an inch of rainfall. The same inch falling on an acre of asphalt produces 27,000 gallons of stormwater.
The result? A slight decline in aquatic life in suburban watersheds between 1999 and 2007, county data show, while urban streams improved.
Much of the county's effort will try to undo work done decades ago.
Government agencies straightened many streams in an attempt to efficiently drain stormwater. But the idea only increased the force and volume of water, scouring stream bottoms and digging channels deeper. Even now, mounds of dirt scooped from streambeds long ago send torrents of silt back into creeks during rain.
The county will complete this year five projects to install “rain gardens” and berms that help rainwater soak into the ground as it pours off parking lots and subdivision streets.
At the Little Grand Canyon, the county bought five acres, removed the house that stood there and will build two artificial wetlands to absorb the neighborhood's stormwater. It will restore 1,850 feet of the stream, rebuilding curves and riffles to slow down the surge of water, stabilize the banks and provide niches for fish and other aquatic life.
Downstream, the county will restore a mile and a half of Torrence Creek in Huntersville. Straight as Interstate 77, which crosses it, the stream is a listless murk lined by kudzu-covered banks.
“It's just kind of a lifeless ditch,” Kroening said.
History shows that streams can revive. Fecal bacteria counts in Mecklenburg streams have dropped by nearly half in the past 20 years after steps to improve sewage discharges and control spills.
Don't expect quick results from the McDowell Creek restoration, warned Melanie Williams, a Catawba River basin planner with the N.C. Division of Water Quality.
“Nature takes time to heal itself,” Williams said. “Even after the project is finished, it's not like the water is going to be immediately clean.”
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