Helping highways better handle water runoff

Natural dispersion along state highway 195.
PULLMAN – WSU is helping the state lessen the environmental impact of its highways.
With support from a Transportation Northwest (TransNow) grant, researchers in the Department of Civil and Environmental Engineering are working with the Washington State Department of Transportation, which is one of the biggest producers of stormwater runoff.
A national permitting process that is meant to protect the environment and regulate pollution is slowly being implemented, and low impact development (LID) has become a priority in the state of Washington, said Liv Haselbach, associate professor in civil and environmental engineering.
The simple idea of LID is to design buildings and roads that keep water where it falls, rather than directing it elsewhere where it can cause pollution, flooding and damage to property. The stories happen every year in Washington and elsewhere: Heavy rainstorms bring flooding and overflowing creeks. Homes are damaged, and occasionally lives are lost.
A not-so-diverting idea
Haselbach is working with WSDOT transportation engineers on ways to increase the use of natural or engineered dispersion and other similar techniques, rather than diversion, on roadways.
Sometimes when roads are built, a retention pond or culverts are constructed to direct storm runoff downstream. Such systems have to be continually maintained, or they can contribute to flooding problems.
Low impact development instead aims to mimic natural processes and let water run off the roadways and seep into or evaporate from the ground nearby.
“Natural dispersion is a best management practice for managing stormwater and is considered the most Low Impact Development option, since it both treats the stormwater and disperses the runoff,” said Aimee Navickis-Brasch, a graduate student working on the project.
Dispersion commonly is used in rural areas because it requires a lot of area for the water to be absorbed into the ground.
The researchers are working to better understand and incorporate the entire hydrology of dispersion areas, including the stormwater that may disappear through evaporation or transpiration from plants. Their goal is to use smaller areas for dispersion, so they can be used more often, even in urban areas.
State leading the way
The engineers at WSDOT, Haselbach said, already are doing a lot to minimize the impacts of the roads that we drive on.
“They already know about good designs, but they are trying to modify their practices so they are more LID-friendly,” she said. “Around the country, Washington is going to be a leader in this area.”
The WSU researchers plan to have recommendations for WSDOT engineers by the end of the year.

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