Recommended Wing Ditch Spacing

Definition: A water turnout or diversion ditch constructed to move and disperse water away from the road and side ditches into adjacent undisturbed areas so that the volume and velocity of water are reduced on slopes.

Purpose: To collect and direct road surface runoff from one or both sides of the road away from the roadway and into undisturbed areas.

Conditions where practice applies: Any road or trail section where water could accumulate or accelerate. The water should be diverted onto undisturbed areas so the volume and velocity are reduced.

RECOMMENDED SPECIFICATIONS

The wing ditch should intersect the roadside ditch line at the same depth and be outsloped to a maximum grade of 2%.

On sloping roads, the wing ditch should leave the road ditch line at a 30- to 45-degree angle to the roadbed and be downsloped less than 2% of the natural contour.

Wing ditches may often be needed to provide stable outlets for other water control devices such as water bars and dips, but additional turnouts may also be needed along stretches of road where water is expected to collect. The spacing of wing ditches will be determined by the topography and relief of the area. Soil texture should also be considered for wing ditch spacing. On highly erodible or sandy soils wing ditches/turnouts should be spaced closer together than on clay soils.

Wing ditches should not feed directly into adjacent drainages, gullies or channels.

Wing ditches should be installed or cut solidly into the soil and wide enough to allow maintenance with logging equipment, such as skidders.