Wet
What to Do When It’s Drainage and Erosion Options to Help Keep Work Moving By Jennifer Howard
When doing a site walkthrough, you may cringe when you see pooling water on bare clay soil, or dry channels carved into steep slopes. Unfortunately, drainage problems can speed or slow rainwater movement, thereby dampening your work schedule. So, how can you keep clients happy and crews busy when a site is wet? Recently, horticulture experts from North Carolina State University shared some tips with us to help keep the water — and work — moving. Dual Drainage Culprits
Most site-drainage problems in North Carolina are primarily a result of two colliding conditions: increasing weather intensity and rapidly changing land use. “There has been a real change in the intensity and frequency of storm events, and the concentration and intensity of rainfall are no longer compatible with our native soil conditions,” said Julietta Sherk, NC State professor of landscape design. “As a result, although many past landscape designs may have been sound solutions in their time, they don’t necessarily work well in today’s climate conditions.” “Especially in the piedmont, the state’s rolling topography makes our clay soils highly erodible,” said Lee Ivy, NC State senior lecturer in horticulture. “They just can’t absorb the increasing 20 NURSERY & LANDSCAPE NOTES || SUMMER 2021
Photo courtesy of Denise Krebs on Flickr
amounts of sudden rainfall we have seen in the past 20-30 years. Clay soils can only absorb and percolate 0.2-0.3 inches of rainfall per hour, but recently we’ve been seeing 0.5-3 inches per hour. They just can’t handle that.” In addition to the increased weather intensity, the onslaught of building development amplifies our water-infiltration problems. Quick-turn building projects often clear-cut sites, stripping away any water-absorbing soil organic matter and leaving acres of bare subsoil. And the ground that isn’t scraped bare — such as driveways, parking lots and buildings — is often paved or covered with impermeable surfaces, which are only capable of shedding volumes of water elsewhere. Together, those conditions create a perfect storm for localized soggy sites.
