Roads, Driveways & Ditches

Paved, dirt or gravel roads; ATV trails; new roads and driveways close to the shore; culverts and roadside ditches—even worn footpaths—are all highways for sediment, nutrients and other pollutants to reach a stream or lake. Vehicles compact soil, reducing its ability to absorb and retain water. Compacted soil results in increased water flow across the ground, concentrating water and pollutants and increasing soil erosion.

It doesn’t take much to start the process. Water from a heavy thunderstorm will concentrate on roads and trails, picking up speed and energy. This water can scour open ground on a construction site, erode a sloping path or wash out a newly constructed roadside ditch. An erosion site located miles from the lake, but still in the watershed, can alter lake water quality because the sediment from the eroded site flows downhill until it reaches the lake. Numerous erosion sites along miles of roads and ditches have a severe, cumulative impact on water quality – especially during a downpour.

Flowing water scours erosion channels and picks up sediments, nutrients and other pollutants. The faster the water flows, the more pollution ends up in the lake. Roads also function as super highways for terrestrial weeds that can spread to the banks of lakes, rivers and streams. Once weeds become established along lakes, bank stability is compromised because weeds do not provide the same soil stabilizing root system as native plants. The deep root systems of native plant communities prevent erosion and sedimentation and should therefore be maintained.

Building Driveways and Roads Responsibly

  • Reduce the amount of roads, and keep road and driveway lengths to a minimum by clustering development. The longer the paved surface, the higher the velocity of water flowing over that surface and the more erosion and sedimentation. Reducing the length of roads and driveways lessens soil compaction and the flow of nutrients to nearby waterways.
  • Design and build new roads and driveways with culverts, drainage diversions, ditches and roadside buffers to deal with run-off from major storms. Ask your local conservation district for help.
  • Avoid construction on slopes greater than 20%. On all slopes use water bars and diversions to help reduce erosion.
  • Divert water flowing in roadside ditches that are U-shaped not V-shaped and have long sloping runs into flat wooded areas where sediments, nutrients and pollutants are filtered out. Use frequent ditch turn-outs to slow water flow.
  • Grade/crown roads and driveways to shed water to desired areas.
  • Retain or plant native plants/buffer strips along roads and uphill from ditches to intercept and filter nutrient rich run-off before it gets into the ditch.
  • Limit the clearing of vegetation and reduce disturbing the duff layer which stores nutrients. The duff layer is the organic material layer between the uppermost soil mineral horizon and the litter layer. It is organic material that has decomposed to the point at which there is no identifiable materials such as leaves or twigs.
  • Work with your county to adopt local road standards that will reduce nutrient run-off.
  • Organize volunteers to go out during or right after a heavy rainstorm to identify and trace sources of erosion. Determine which streams and rivulets are brown with silt to find out where erosion occurs. Then work with landowners to correct the problems.
Poor road building practices. Photo courtesy Whitefish Lake Institute

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