Ditch redesign draws on data from a digital age
By Peter Kent
Even ditch digging requires some college education these days. What was once a product of strong backs, picks and shovels, now involves PhDs, computers, digital mapping and a return to nature.
Hydrologist Anand Jayakaran, stationed at Clemson’s Baruch Institute of Coastal Ecology and Forest Science in Georgetown, researches both natural and developed watersheds.
Drainage ditches, he explains, were first built to handle water flooding from croplands. As towns and cities developed, they spread out, building more rooftops and parking lots for the rain to run off, spilling into streets and sewers.
“I study watersheds and how they are affected by rapid development along the coast,” he said. “I look at how urban development affects the quantity of runoff from storm events and study ways to mitigate that runoff.”
Public officials in Conway and Horry County know it takes brains as well as brawn to prevent the city from flooding. Working with Clemson, Coastal Carolina University, volunteer groups and federal, state and local governments, leaders have restored two sections of the city’s main stormwater drainage system.
As a result, Crabtree Canal – once a silt-filled, debris-laden, dead-water drainage ditch – is now on its way to be a model for managing rainwater runoff from roads and roofs in an environmentally sustainable way. Today, after much digging and hauling to rebuild the canal, fish and plants thrive.
The Crabtree project reshaped the ditch and restored the surrounding area to a floodplain, relying on native plants and grasses to slow the flow and filter stormwater. Dug by the U.S. Army Corps of Engineers in the 1960s, the ditch was a classic trapezoid – a U-shaped channel with a flat bottom. Thousands of ditches throughout the world look much the same, but research has shown there is a better design – the two-stage channel.
“When I was in graduate school at Ohio State University, we studied farm ditches,” Jayakaran said. “We saw that U-shaped ones collapsed as the water eroded the banks, filling the channel with sediment that had to be removed. Natural streams work differently, carving a channel and building a flat ‘bench’ that acts like a mini-floodplain in the lower part of the ditch. The two-stage design adds stability and encourages vegetation to grow in the channel.
“The design works in urban areas like Conway, too. Other communities can look at what was done here. It’s a way to manage the water, deal with changing conditions and meet environmental regulations.”
A stormwater specialist, Jayakaran works with developers, state and county agencies, homeowners and municipal officials to develop ways to reduce runoff. He has been part of the team since 2007, when the partnership began that monitors the Crabtree Canal improvements.
Other Clemson scientists at the Baruch Institute focus on the environmental impact of changing land-use patterns, coastal natural resource conservation, forestry, water quality and watershed management. Research areas include biochemistry, ecosystems, hydrology and data visualization.
On a rare dry day, Jayakaran, Horry County watershed planner Dave Fuss, and Crabtree watershed elected directors George Jenkins Jr. and son Hunter toured the improvements. The Jenkinses are the second and third generations to be involved with flood control.
“We learned a lot about what it takes to plan, build and maintain a project like this,” said the senior Jenkins. “A big lesson was to ‘let nature run its course’ and have the canal work like a stream flowing through a swamp. And it took commitment and coordination from many people and groups to get the project done.”
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