A stroll down a stretch of 2nd Avenue Northwest in Seattle is practically a walk in the park. The slightly meandering residential street is lined with wide strips of native grasses, small shrubs, and trees. Along the shoulder, interspersed among parking spots, are ponds and swales—gentle depressions—that fill with water during a downpour. What you won’t find are sludgy gutters brimming with muddy water and trash, or deserts of black asphalt stretching from property lines to the roadway.
The street was the city’s first experiment in what it calls “natural drainage systems.” A decade ago, the block was jackhammered up and rebuilt to catch and clean stormwater the way it’s done in a forest: by helping rainstorms soak into the ground, get sucked up by plants, or captured in their branches and leaves where the water evaporates slowly. The project—called SEA Street—has been wildly successful, nearly eliminating stormwater runoff even during heavy rains. That’s right, runoff on this street was reduced 98 percent during winter rains.
Natural drainage systems are cropping up slowly on streets across Seattle. And other Northwest cities are doing similar projects to curb runoff without pipes and holding tanks. The city of Portland even has an “ecoroof” blog site geared toward innovative stormwater solutions. Vancouver, BC, is building rain gardens at bus stops, among other projects. It’s all part of a movement called “low-impact development” or LID.
For years we’ve known that traditional infrastructure for funneling stormwater away from buildings and roads and into lakes and bays by using pipes and ditches doesn’t work. It fails for people: the systems are regularly overwhelmed, leading to flooded basements and raw sewage pouring into public waterways. It fails for nature: salmon and other species are poisoned by the polluted stormwater and quiet streams are transformed into torrents of filth.
The logic of LID is to try to replicate what Mother Nature does naturally by using engineering tricks and limiting sprawl.
Washington is at a crossroads for low-impact development. The state Department of Ecology, working with a technical advisory committee, is crafting a set of requirements specifying where and how to use LID. The stakes are high. If Ecology comes up with stringent standards that require widespread use of legitimate LID strategies, Puget Sound could reap great benefits. If it doesn’t, the fight to save the Sound could be lost due to the steady drumbeat of destruction from stormwater.
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“Time is not on our side,” said Tom Holz, a stormwater/LID expert who’s on the advisory committee. “We may lose the battle just simply through dallying.”
Dealing effectively with stormwater requires a two pronged approach:
- Stop sprawl—In an undeveloped setting, stormwater is essentially non existent. The best way to reduce runoff is to minimize the footprint of development.
- Use low-impact development—When development does happen, it must be LID. Already built neighborhoods should be retrofitted over time using LID techniques.
Both strategies are important. Limiting development is critical because you can’t cut down very many trees or lay much pavement before getting damage from stormwater. In fact, top stormwater scientists say that when as little as 10 percent of a watershed is covered by impervious surfaces, streams and wildlife begin to suffer.
That realization led local stormwater experts to develop what is called the “65-10-0” rule or just the “65-0” rule for development. It’s shorthand for the need to leave 65 percent of the landscape in vegetation, while allowing a maximum of 10 percent “effective” impervious surface, which should result in zero runoff. (See this explanation of the science in a paper by University of Washington professor Derek Booth).
Right now the 65-10-0 rule is just a recommendation, not a requirement, in Ecology’s “Stormwater Management Manual for Western Washington,” the document that serves as the stormwater-regulation bible for the state’s largest cities and counties. But that could change with the work being done to update Ecology’s LID rules, an update that’s required because of a successful legal challenge of the existing guidelines by a coalition of conservation groups. The new rules are expected next summer.
So how do we get to 10 percent effective impervious surface in new development, and what on earth does that actually mean?
It means taking surfaces that normally repel water—roofs and driveways—and making them spongy. For roofs, that can mean building green roofs that are covered in soil and plants that trap and hold water where it falls. Seattle’s City Hall, the new Bill & Melinda Gates Foundation building, and the Portland Building are all capped in green roofs. Other LID strategies include downspouts hooked to rain barrels to store the water that does run off, or perhaps the downspouts flow into a rain garden landscaped with ponds that are lined with specially engineered gravel and soil that soak up larger volumes of water. Driveways are built from a lattice of pavers that leave some of the soil exposed. There’s also permeable concrete that allows water to soak through it, which can be used for sidewalks and roadways.
To reach that 10 percent goal, buildings need to get smaller, perhaps going vertical to shrink their footprint but maintain space indoors. These strategies generally are applied to new development, but are also applicable to retrofits of built areas.
The use of LID could get a
boost when Washington’s lawmakers convene next month. They’ll be considering legislation that would create a fee for petroleum products. Forty percent of the fee would be would available to cities for LID retrofit projects that cleanup and stop oil pollution from stormwater.
What’s great about LID is that when you consider all of the benefits from these strategies, it’s actually cheaper than the traditional storm-drains-and-pipes infrastructure. So you get the benefit of helping salmon and preventing flooded basements, all while saving money! And there are now lots of examples of affordable, successful LID projects from around the Northwest—examples that we’ll share in more detail in a post next week.
This post is part of a series on stormwater. Please also see:
- “Smart, Cheap Stormwater Fixes“
- “Water Pollution Enemy is Us“
- “Jesus Walking Salmon and Stormwater“
- “Stormwater’s Costly, Stinky Wake-Up Call”
SEA Streets photo courtesy of Seattle Public Utilities. New development in Snoqualmie photo courtesy of Flickr user midd1999 and driveway pavers photo courtesy of Flickr user Jamiriquai under the Creative Commons license.
Matt the Engineer
I wonder if simply replacing gutters with permiable surfaces would help. It certainly wouldn’t reduce runoff more than a few percent, but should be cheap and easy to do since its a fraction of the total existing permiable surfaces.Oh, and since we’re sharing examples… check the roof of my new garage. I had a bumper crop of veggies and see water trickling out of my gutter days after the rains have stopped (all of this water would have been part of the peak runoff without the green roof).
2nd Ave NW, surely (between 117th and 120th).
Eric de Place
Yes, it’s 2nd Ave NW. That was my mistake, by the way. I helpfully “fixed” Lisa’s post thinking that the location was on 22nd. Anyway, it’s now returned to Lisa’s original text, which was correct.
Matt – don’t take away the gutters – the water will fall too close to the foundation and not drain away very well – in fact you should consider a rain barrel or cistern to capture some and then redirect the rest at least 8 feet from the foundation. We use this rain barrel as it is the only one that had a 4 inch inlet and 4 inch overflow as they tend to fill rather quickly:http://www.aquabarrel.com/product_rain_barrel_complete_80gal.php
Matt the Engineers
[garden] Oops, I should have been more specific. I meant gutters on the sides of roads. I can see why we wouldn’t want roof gutters to be pervious.
65% vegetated area is completely inappropriate within an Urban Growth Area. These approaches to stormwater management lead to extreme sprawl. Green roofs, rainwater harvesting and permable pavement are our best options to absorb/reuse stormwater on site in urban settings.Please, let’s not continue requiring suburban areas to be developed with 65% of the land unused, in turn requiring homes to sprawl further away and rendering the automobile the only reasonable form of transporation. We need better solutions for stormwater in cities.
Thanks, Chad, for your questioning of the 65-10-0 rule. In fact, some folks think it could be the case that most of the watersheds around Puget Sound have already reached a point where only 65 percent of the native vegetation remains. That would mean that no more development of rural areas should be allowed, and all the growth should be in already urbanized areas, preventing the sprawl that you’re rightly concerned about.It seems that much of the power or weakness of 65-10-0 is determined by where you draw the line for measurement—is it 65 percent of a brand new development, or a whole neighborhood, or an entire watershed.
Yes, priorities! Dramatically increasing density and dramatically reducing auto-dependence probably much more important that leaving urban land undeveloped or imposing costly green roof requirements to eliminate runoff. (That’s not to say that we shouldn’t include attention to stormwater reduction where it makes sense, but ultimately, doubling down on compact development and walkability/transit is probably the more important goal for meeting multiple criteria…)