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Research Collaboration Thwarts Runaway Gulley

Prof. Brad Johnson and David Rogers ’16 work in the field
Brad Johnson, associate professor of environmental studies (right), collects topographic data from research student David Rogers ’16.

With every rainstorm, the little streambed behind Davidson Elementary School grew deeper and wider.

A footbridge built by the PTA collapsed into its ever-widening maw, as the streambed became a gulley. Teachers quit taking their pupils out there for nature science lessons. Out of sight and out of mind, the gulley continued its destructive march, chewing up earth and toppling trees unhindered.

But a Davidson College environmental studies major and his geology professor were watching.

Now, thanks to the senior capstone research project of David Rogers '16, the Town of Davidson this summer will be able to stop the runaway erosion by turning the gulley into a gently-graded cascade of rock that will slow the water's flow and protect land upstream and downstream.

"David showed that the erosion problem was much bigger than we thought, and that the gulley was migrating at a much faster rate than we thought," said Brad Johnson, the associate professor of environmental studies who advised Rogers.

Pure Research, Applied

Johnson is also chair of the Mecklenburg County Soil and Water Conservation District. He wore that service hat, in addition to his geologist's and professor's hats, in conversations about the gulley with the conservation district, the Town of Davidson, the U.S. Army Corps of Engineers, and others. He helped shepherd applications for funding, including a Duke Energy Water Resources Grant.

"Brad was instrumental in helping us get the Duke grant," said Doug Wright, the town's public works director. "And the student's monitoring was really important, because the acceleration was not on our radar."

As the "headcut" of the gulley moved north, Wright said, it threatened upstream wetland ecological systems as well as nearby roads and neighborhoods.

"It potentially could have worked its way toward Spring Street and Eastway Drive, even Temple Kol Tikvah on South Street," Wright said.

Now, once the remediation bids are let, contractors will want to get busy with their bulldozers, Johnson said: "The project they bid on changes every time it rains!"

The Big Picture

Johnson taught Rogers to use a Leica Flex Line T-SO2 survey tool to create 3-D modeling graphics–one person holds a reflective survey stick, while the second person spots it from a fixed position.

Hundreds of data points converged to create a 3-D topographic model that shows the gulley’s rapid erosion over time.
Hundreds of data points converged to create a 3-D topographic model that shows the gulley’s rapid erosion over time.

Rogers enlisted help in the field from football teammates, by offering them dining hall swipes on his 'Cat Card meal plan. They collected many hundreds of data points from the muddy gulley to feed into the "Surfer" software program that created Rogers' final models.

Throughout, Rogers managed a challenging research-football-academic schedule, including rehab appointments for a knee injury.

"Thankfully I wasn't on crutches," he said.

Streams are dynamic, and erosion can be a naturally occurring phenomenon. But severe cases very often have human causes.

"I think this happened on every creek around here 100 years ago," said Johnson, citing the common agricultural practice then of straightening streams for irrigation or other agricultural purposes. That speeds up flow, which deepens the streambed, which speeds up flow, and so on. Some emerging evidence of agriculture's enduring effects on regional waterways goes back to the 1760s.

"This is a process common to the Carolina Piedmont," Johnson said. "There's a famous research paper from South Carolina in the 1930s that documents terrifying gullies."

Johnson is editing two other students' work for publication.

Roslyn Spell '17 documented the current state of numerous regional streams and gullies, and Hannah Rieden '17 researched the effect of mill dams on area waterways.

"Separate research projects are starting to inform each other," said Johnson.

And they're starting to re-form at least one runaway gulley.

Read more about Rogers' field research.

John Syme