Reducing the Impacts of Growth
by Denny Fleenor, Marketing and News Services
Growth happens. With it comes housing, stores, offices, schools, roads and other necessary infrastructure--and the challenge of stormwater runoff. The construction boom in the Puget Sound region is a prime example.
 Curtis Hinman, WSU Pierce County extension specialist, right, and Timothy Lowry from Pierce County Water Programs examine bioretention swales at a site in West Seattle that is being redeveloped using low-impact development techniques. |
But according to WSU Pierce County extension specialist Curtis Hinman, the traditional negative impacts of development, particularly to water quality, are avoidable with planning. The expert in low-impact development techniques has compiled and written a book on the subject.
“Low-Impact Development, Technical Guidance Manual for Puget Sound” is a 258-page guide providing stormwater managers and building site designers with an understanding of low-impact development concepts and objectives, as well as specific management practices they can apply. Hinman is planning a second edition next year.
Mimicking nature The objective of low-impact development, says Hinman, is to more effectively manage stormwater runoff and the pollutants it carries to protect streams, lakes, wetlands and Puget Sound. The goal is to closely mimic the way water flows in a natural landscape.
“In a natural landscape, precipitation is captured by forest canopies and vegetation and it evaporates back into the atmosphere,” Hinman says. “Water that reaches the ground is absorbed and filtered by the soil before slowly fl owing back into waterways.” By applying the tools detailed in the manual, architects, developers and builders can incorporate systems that effectively reduce runoff and provide a more natural system for drainage.
One tool that can be applied by homeowners, as well as incorporated in large developments, is the installation of a retention system or rain garden.
Installing a rain garden involves identifying a location to excavate a catchment basin, filling it with an appropriate soil mix for the location and planting it with a selection of native plants. Rainwater from rooftops, driveways and sidewalks is directed into the basin.
“The water soaks in, gets filtered through the soil and flows out into the surrounding soils,” says Hinman. His newest publication, “Rain Garden Handbook for Western Washington Homeowners,” is now available at www.pierce.wsu.edu and clicking the link on the right.
New workshops Other low-impact development practices include the use of permeable surfaces for such applications as parking lots and driveways that allow stormwater to be absorbed by the soil or gravel underneath, and the installation of so-called green roofs planted with vegetation.
“Green roofs make people think of the roof leaking or collapsing because of the weight,” says Hinman. “They can be made virtually leak proof, and we use lightweight soil mixes that are relatively shallow.”
Hinman says the green roof is a proven practice for absorbing water, and thus reducing runoff, and is required in new developments in some jurisdictions in Europe. Hinman is developing a new series of low-impact development workshops for the Puget Sound region, as well as revising a two-day course on the subject taught through the University of Washington’s civil and environmental engineering program.
“This next generation of workshops will be more technical and offer specific guidelines for performance and construction,” he says. More information is available here.
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