Beneficial Landscaping - Surface Water Runoff | Region 10 | US EPA

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Beneficial Landscaping - Surface Water Runoff

Treatments for Traffic Areas Can Help Salmon
Believe it or not, walkways, driveways, and parking areas (even roof tops!) can be “beneficially landscaped” too. These high traffic areas---usually covered by compacted gravel, concrete, or other hard surfaces---can be designed to improve permeability, to allow water to get through. Increasing permeability in our watersheds is important for controlling water runoff. Research has shown that once a watershed is covered by 5 to 10% impervious surface, the quality of aquatic habitats declines and their inhabitants, such as our threatened salmon, suffer. Nearly all traditional development designs (TDD) will exceed the 5 to 10% threshold. So what can we do differently to save the salmon?

The Spring issue of EPA Region 10's "WaterTalk" newsletter shared news of the May “Soils for Salmon” Seminar. We discussed the benefits of using compost so that soils can better soak up the rain, and to improve plant growth and aesthetics. Another approach for controlling surface water runoff covered at the seminar (which enjoyed a sell-out repeat performance in Tacoma on October 6), was to apply innovative development designs (IDD) or better yet, zero impact designs (ZID).

IDD refers to site planning techniques that provide for open space, narrower streets, greener and smaller parking lots, stream buffers and other measures to control stormwater and conserve natural areas. ZID goes beyond IDD to sharply reduce the “effective impervious area” of new development with practices such as eco-roofs, roof gardens, rain barrels, alternative paving surfaces, soil amendments, bioretention, reforestation, and filter-swale systems. ZID is not widely applied in the Pacific Northwest, but is used extensively in Europe. Greater emphasis upon ZID is important, though, because IDD techniques alone may not be enough to maintain watershed functions to protect salmon habitat in most future growth areas (1).

We thought you might like to know about examples of a few of these techniques, and consider applying them in new developments, or possibly in retrofitting existing ones. There are a few beneficial landscaping demonstration gardens in the Puget Sound area (sponsored by the Washington Department of Fish and Wildlife) that include alternative paving surfaces. Of course, the gardens feature many other plantings and structures as well that benefit wildlife and the environment:

Carkeek Park Environmental Education Center
950 NW Carkeek Park Road, Seattle
Contact: (206) 684-0877

Lake Hills Greenbelt Ranger Station, Bellevue Parks and Recreation
15416 SE 16th, Bellevue (next to Phantom Lake)
Contact: Ranger Station (425) 452-7225

Auburn City Park Wildlife and Water Conservation Gardens
405 E Street NE, Auburn
Contact: B. Sanders (253) 804-5031

Also, see a permeable spillover parking lot in the northwest corner of PCC-Kirkland’s parking area at 10718 NE 68th, Kirkland.
Contact: (425) 828-4621

(1) Tom Holz, T. Liptan, and T. Schueler. Beyond Innovative Development: Site Design Techniques to Minimize Impacts to Salmon Habitat. In Salmon in the City Conference proceedings, 1998, American Public Works Association.


This Year, Have a Salmon Friendly Yard
If you care about salmon (and even if you don't!), it's time to Just Say No! to lawn and garden chemicals, particularly the ones that are designed to kill. Recent studies by the Northwest Fisheries Science Center and other researchers have found that toxic stormwater runoff -- full of oil, grease, anti-freeze, pesticides, and other pollutants -- is killing the salmon returning to spawn before they are able to do so (see Seattle Post-Intelligencer story, 2/6/03).

This "pre-spawn mortality" occurs in spite of restored habitat conditions and is apparently caused mainly by pesticides that landowners apply to urban and suburban lawns. "Pesticides are designed to kill, and they do it very efficiently," said a fisheries biologist commenting on the study results, which found for Longfellow Creek in West Seattle an 88% pre-spawn fish kill. The highest pesticide concentrations were found in an Eastside suburb.

"Perfect" weed and insect free lawns and gardens that are achieved through chemicals may not be fish, wildlife, or even people friendly - particularly for young children. Why not kick the habit and help save the salmon?


A Stormwater Story: “Drip and Splat”

Now that raindrops have names, we'll never think of them the same! Our thanks to the Jefferson County Natural Resources Division and author Tami Pokorny for allowing us to print this wonderful, and true, story.

By Tami Pokorny, Jefferson County Natural Resources

There were once two raindrops, each searching for a pool of friends. One raindrop, Drip, preferred the slower pace of the country life. He descended through the sky towards an expansive forest of older trees. The second raindrop, Splat, rode the nearest breeze toward a suburban rooftop.

Drip landed on the bough of a cedar, dropped from one branch to another, trickled down the tree’s trunk and onto a pillow of moss. He stayed with the moss for quite some time. Then more rain fell and Drip washed out of the moss and into the soil. He meandered slowly downward through decaying leaves, forest duff, and into a thick layer of organic soil called humus.

Time passed and then there was an even bigger storm. Drip joined other raindrops making their way to the water table. Together they percolated through the gritty remains of a glacier’s passing until they reached the aquifer. They occupied countless tiny spaces between pieces of sand and gravel and permeated the bedrock in little cracks and crevices. Many wonderful years passed cavorting with the other raindrops until one day Drip emerged into a beautiful river and flowed into the sea, to begin his next journey in the great water cycle.

In established forests like the one Drip landed in, there’s no natural fast lane for water—except rocky outcrops or cliffs. Slick, non-porous surfaces are rare otherwise, so Drip’s route through the soil was anything but a straight line. He was coaxed along by gravity and, alternately, held back by plants and decaying vegetation. In forests, the rich layer of decaying leaf litter, duff, and humus acts like a very large and very absorbent sponge.

When this forest sponge captures rain, surface runoff is reduced—at least until the sponge becomes completely saturated. In areas of extensive native forest, flooding is less frequent and less severe than in developed areas.

Our second raindrop, Splat, collided with a rooftop and took a wild, fast ride from there. He could have hit a road, driveway, parking lot, highway, or sidewalk, but his story would be pretty much the same. Even lawns wouldn’t have slowed his pace much because they’re not very sponge-like compared to forest soils. And lawns and landscaping also frequently contain animal wastes and pesticides.

Almost from the moment he hit the roof, Splat was practically run over by countless other raindrops, all rushing downhill. There was no time to talk. Gravity was in complete control. Splat sped on, via gutters, storm drains, and pipes to the nearest stream and then, in a rushing torrent, into Puget Sound. Along the way he and the other raindrops dislodged soil particles and rushed them along, causing erosion and sedimentation. They also picked up gangs of pollutants. Pesticides, heavy metals, motor oil, and animal waste: it all came along for the ride. Splat swirled around with countless raindrops, but hardly had a moment with any of them. Besides, they were all painfully aware of how dirty they all were.

Did you ever think about how water gets clean? A shower, for a raindrop, is a trip through plants, roots, bacteria and soil. Impurities get bound up or broken down into less harmful constituents. In developed areas, raindrops stay dirty because they aren’t filtered through the soils that would clean them up. Instead they’re forced into rivers and streams in a great pulse that can become a costly and dangerous flood. Stormwater, laced with pollution and laden with sediments eroded enroute, degrades the spawning and rearing habitat available to salmon and is one reason why several species are threatened with extinction.

By the way, raindrops that never touch soil don’t feed aquifers. That’s unfortunate because aquifers supply groundwater to wells, and “baseflow” to rivers or streams, during late summer and early fall when salmon and people need water the most. So, when native soils are damaged or removed, there are often two consequences for nearby rivers: flooding and, perhaps surprisingly, drought.

Fortunately, low impact development (LID) practices can help reduce pollution and flooding by protecting natural watershed hydrology. Permeable pavement, green roofs, rooftop rainwater harvesting, and innovative foundations reduce surface runoff. But the best answer to flooding and stormwater pollution is leaving the native vegetation and soils undisturbed. To the degree that they’re left in place during development, they’ll do an excellent job of managing your stormwater and helping to keep water clean and pure.

The moral of the story: Drip, don’t Splat! The forest soils of Puget Sound continue to be scraped up and compacted by pavement or lawns. For a future of clean water, a better water supply, more salmon, fewer shellfish closures, reduced danger of flooding and landslides, maintain as much natural forest and undisturbed soils as you possibly can on your lot or acreage.

For more information about this and other topics in Beneficial Landscaping, contact Elaine Somers at 206-553-2966 or Or, visit our website at

For more information on low impact development, visit the Puget Sound Action Team website: and download Natural Approaches to Stormwater Management at

Story by Tami Pokorny,, for the WRIA 16 Planning Unit newsletter, Rivers for Life, 2005 with contributions from Elliott Menashe, Greenbelt Consulting,


Rain Gardens – An Idea Whose Time is Now

Gardeners, this is the spring project for you! As the Pacific Northwest heads into a serious drought, we urge you to consider installing a rain garden. So what is a rain garden and why should you create one?

A rain garden is a garden designed to soak up rain and runoff from your roof, driveway, and lawn. It is a shallow depression or excavation (not a wetland), generally 4” to 8” deep, that is planted with wildflowers and other native vegetation rather than lawn. A rain garden, which absorbs about 30% more water than conventional lawn, is one of many tools or strategies used nowadays to lessen the amount of stormwater runoff from our communities. Such tools are referred to collectively as “low impact development” methods, and include other techniques, such as pervious pavements, vegetated rooftops, and curbless, narrowed streets.

We know that during wet periods, excessive stormwater runoff erodes and degrades stream channels, and salmon eggs and juveniles may be swept away. Flooding and drainage problems occur, and our municipal stormwater systems may become overloaded, resulting in release of untreated sewage and other pollutants.

But why are we concerned about stormwater during a drought? In our April 2003 WaterTalk article, we talked about pre-spawn salmon mortality, which occurs in our urban streams when toxic stormwater runoff full of oil, grease, anti-freeze, pesticides, and other pollutants, kills salmon returning to spawn before they are able to do so. These pre-spawn fish kills occur following periods of drought when the toxins have built up on roadways and landscapes treated with chemicals. The first flush of these pollutants with the autumn rains carry the highest concentration of toxins. Rain gardens would capture a portion of this runoff, infiltrate it and help to remove toxins.

In addition, rain gardens provide a way in which residents can personally contribute to cleaner water, healthier fish and wildlife populations, and a more beautiful and functional environment. Though each rain garden seems small, collectively they would help to restore a portion of the land’s ability to hold or retain water to perform ecological services. For example, freshwater would be captured and infiltrated to recharge groundwater/drinking water supplies, to sustain vegetation and wildlife, and to provide adequate flows in streams during dry spells, which sustains fish and other aquatic life.

Rain gardens are a simple and attractive way to absorb stormwater, while providing habitat for birds, butterflies, and dragonflies, and enhancing the beauty of our homes, neighborhoods, and communities. Our Washington State University Cooperative Extension liaison, Sharon Collman, can provide instructions for how to construct rain gardens. Contact her at 206/553-0038, For more information about this and other aspects of beneficial landscaping, contact Elaine Somers at 206-553-2966, 1-800-424-4372,, or visit our Beneficial Landscaping website at


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