Friday, July 24, 2015

Why is the grass brown along the highway?

SR 14 and I-205 in Vancouver, July 2015
 By Bart Treece

The green grass of home in the northwest is turning a different color with the unusually hot and dry weather. Lawns and areas along state highways are a pale-brown, which is a stark contrast to our nickname of the “Evergreen State.” WSDOT uses mostly native grasses along the roadsides that naturally go dormant in the summer after setting seed, but this has happened earlier this year due to the hot and extremely dry weather.

Vegetation plays an important role in keeping the soil in place along sloped areas, filtering stormwater runoff, and absorbing pollution, among other things. When designing a transportation improvement project, we use native plants that require little maintenance. This helps reduce staff and equipment costs.  Many native shrubs go dormant in the summer and may lose some of their leaves.  Some new planting areas are irrigated the first few years so they can firmly take root.

SR 529 Ebey Slough in Marysville, Feb. 2013
There are some exceptions. We work with local agencies and groups to keep certain areas green, like the irrigated lawns near the “Welcome to Washington” sign on northbound I-5 in Vancouver and the signs leading into Camas on State Route 14. Folks like the Master Gardener Foundation of Clark County and the city of Camas participate in the upkeep and absorb some of the costs for maintaining these areas. This allows us to focus our limited maintenance resources on roadway safety needs, such as repairing guardrails or patching potholes.

I-5 at Mill Plain in Vancouver
We still work in the medians and the sides of the highways by mowing the edges at least once a year. However, state guidelines limit this work to the early hours when the humidity is high and the fire risk is low, which is generally in evenings and early mornings, from 8 p.m. to 1 p.m.

This summer the brown along our roadways has come early with the extreme and early heat we’ve experienced. Further, expect this to be an especially brown summer as we are currently experiencing a statewide drought. Allowing our roadsides to ‘go brown’ follows the natural life cycle of native plants and conserves limited financial and water resources.