Creating a wetland to improve water quality

A year ago, Dingle Creek, which runs through South Asheville and developed areas of Hendersonville Road, was on a short list of at-risk streams experiencing erosion and heightened sediment pollution due to increased development in the area. A 2008 City of Asheville study of the Dingle Creek watershed funded by a grant from the Clean Water Management Trust Fund found that increased stormwater runoff from impervious surfaces had intensified the volume and speed of the creek, adding to the depletion of its banks and allowing more water quality contaminants to flow downstream toward the French Broad River.

The construction of a one-acre wetland, contracted through the City of Asheville’s Stormwater Services division of the Public Works Department and completed over the summer is already showing signs of stemming the flow and allowing Dingle Creek to recover. A mix of stream bank stabilization, water flow diversion, plantings, and a series of bends, channels and steps have been installed, slowing down the water and allowing sediments to settle and keeping erosion in check. The design also resulted in several diversions and branches in the flow of the creek, with side streams and dry beds allowing the wetland to absorb the energy of flooding in the case of large rain events.

The Dingle Creek wetland project is located within the Ramble community, on a conservation easement donated by Biltmore Farms, Inc. The project was partially paid for by grant funding through the American Recovery and Reinvestment Act. Matching funds will be paid over the next 20 years by the the Clean Water Management Trust Fund and the City of Asheville.

“We are most appreciative of the partnership with Biltmore Farms in providing the City an easement to construction the wetlands,” says Public Works Director Cathy Ball.  “Without this easement, this project would not have been possible.”

Since construction was completed in June, netting used to shore up banks has begun to be concealed by soil and vegetation, water plants installed during construction have spread, and most importantly, sediment deposits are clearly visible in pools along the creek.

“That’s what we want to see,” says City of Asheville Stormwater Services Manager McCray Coates. “Our main goal is to remove the sedimentation.”

Wildlife in the area has also responded to the habitat recovery. Deer and turkey regularly visit the site and fish have begun to populate the pools created in the wetland project.

Wetlands are a natural guard against water quality degradation. Sediment removal keeps downstream waters and wildlife from being adversely affected, and vegetation removes nitrogen from the water that may have seeped in from fertilizers used in lawns and agriculture.

As part of its strategic goal of sustainability, the City of Asheville employs landscaping and natural features to retain and manage stormwater flow. The Parks, Recreation and Cultural Arts Department has established such features at Richmond Hill Park, Carrier Park, the WNC Nature Center, and Reed Creek Greenway. But the Dingle Creek watershed project is the first of this scale.

“It’s a real good project,” Coates says. “This is the largest one we’ve done so far.”