Bioswales Change Channels

Turn your runoff hazard
into a dream environment

© 2004 Wendy Dager

If look up the word "swale" in the dictionary, you’ll find the following definitions:

1. A low tract of land, especially when moist or marshy.
2. A long, narrow, usually shallow trough between ridges on a beach, running parallel to the coastline.
3. A shallow trough-like depression that carries water mainly during rainstorms or snow melts.

These descriptions are adequate for the layperson. However, for landscapers, "swale" has taken on a new meaning—and a new place in the technical requirements of many urban projects. For those who deal daily with the problem of stormwater runoff, plain old "swale" has evolved to become "Grass Swale Filters" or the more compact term "bioswale."

According to the document "Environmental Limitations to Vegetation Establishment in Vegetated Stormwater Biofilters"
(http://depts.washington.edu/cwws/Research/Reports/rc2.htm) by Greg Mazer, a graduate research assistant for the University of Washington, "Bioswales are open channels possessing a dense cover of grasses and other herbaceous plants through which runoff is directed during storm events."

Even though The Clean Water Act has been around since 1972, newer state and federal laws mandate increased environmental responsibilities for institutions both public and private. Landscape professionals who must effectively address stormwater runoff in an environmentally-friendly manner have found bioswales to be the perfect solution.

While hard engineering in the form of concrete conduits was once the way to literally channel the problem, landscapers are now taking a greener approach (see "Albright’s Living Channel Liner," The Best of the Leaf-let, http://www.albrightseed.com/livingchan.htm) when addressing the threat of stormwater runoff—a threat that can easily turn into hazards such as decreased water quality, hillside erosion and pollutants entering storm sewers. Bioswales, or Grass Swale Filters (GSWF), are a relatively simple answer to a complex problem.

As densely vegetated drainage ways with gentle side slopes, bioswales collect and slowly convey the runoff flow downstream. The result is an economical, ecologically sound, self-maintaining system that physically secures both the structure and trapped pollutants.

For government agencies, including the Ventura Countywide Stormwater Quality Management Program (VCSQMP), the main objective of a bioswale is to control pollution for the life of the project. Bioswales, which can be incorporated into the landscape design of residential, commercial, industrial and institutional settings, consist of primarily herbaceous plants whose stems and leaves retard water flow, settling pollutants, which, with the aid of the roots, decompose into the soil.

In July 2002, the VCSQMP issued a technical guidance manual for stormwater quality control measures (http://www.vcstormwater.org/tech-man1.03.pdf), which includes detailed information about Grass Swale Filters, as well as extended detention basins (EDB), permanent basins formed by excavation or construction of embankments to temporarily detain runoff.

"This manual is pretty much a statewide model for use by all city, county and state agencies," said S&S Seeds’ Paul Albright. "It describes application techniques, as well as maintenance requirements."

S&S Seeds has a handle on current specifications, as well as ongoing scientific studies that address the best way to change channels into ecologically sound environments.

Going Green

"At S&S Seeds, we’ve been closely monitoring the study of phytoremediation, which is a set of processes that uses plants to clean contamination in groundwater, surface water, sediment and air," said Albright.

With phytoremediation, natural substances are released by plant roots that supply nutrients to microorganisms, enhancing their ability to biodegrade materials. These plants’ roots also loosen the soil, aerating it and leaving paths for infiltration of water.

"We’ve also taken into consideration that our customers, including landscape architects, contractors and biotechnical engineers, are often responsible for watercourse erosion prevention (see "Watercourse Erosion Control," the Best of the Leaf-let, http://www.albrightseed.com/watercourse.htm)," said Albright. "Between the scientific research on phytoremediation and our analysis of customer needs, we’ve found that vegetation is clearly the cheapest and most effective way to protect the soil."

Sometimes, however, contractors may not have the time or ability to grow plants on site from seed given construction projects with ever-changing timelines and unpredictable natural rainfall conditions. That’s why S&S offers a sound alternative.

Living Channel Liner

S&S Seeds offers its customers the Living Channel Liner, an appropriate erosion control alternative that uses phytoremediation processes to combat environmental concerns such as groundwater pollution and erosion.

Living Channel Liner is a lightweight soil-less sod, reinforced with geotextile material that’s suitable for use in storm drains, sediment basins, creeks and riparian channel revegetation. It meets federal and state specifications, holds the soil and strengthens the structure, and also becomes the basis for a full ecosystem.

"Some of the benefits include an instant visual effect and reduced weed control maintenance costs," said Albright. "Customers can give us a call at (805) 684-0436 and we’ll customize a Living Channel Liner that’s just right for their construction projects."

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