Rain Garden Reality Check

Comparing LID to conventional system failures.
This post is part of the research project: Stormwater Solutions: Curbing Toxic Runoff
ScreenHunter_32 Apr. 17 11.50

Roadside rain gardens are, for the most part, enormously popular. Yet after a recent faulty installation in Ballard, which was later corrected, some folks have begun loudly criticizing them as a threat to health, safety, and quality of life. Check out the comments section on Lisa Stiffler’s recent blog post, Rain Garden Backlash is All Wet, for a good example of the controversy.

I don’t want to minimize the concerns that some neighbors have. That said, I do think it’s useful to remind ourselves that the status quo isn’t exactly wine and roses. The system we have now is aging, challenging to maintain, prone to frequent failure—and fixing it with conventional technology will be extremely expensive.

For example, it never seems quite fair to me that people grouse about the mere possibility that a rain garden might contain standing water for a day or two after a heavy downpour when the system we have now looks like this:

After the rain, standing water covers a sidewalk and parking strip in north Seattle. (Photo by Lisa Stiffler)

And this:

During a rainy period, open water exceeds a foot in depth in a north Seattle drainage ditch. (Photo by Lisa Stiffler)













Now, I’m not saying that deep standing water is what we should aspire to—far from it—but it’s useful to remind ourselves that the existing system is much worse than even the worst rain garden installation.

Yet the failures of the conventional system don’t result in neighborhoods plagued by West Nile virus or hordes of rats—the sort of things that critics say rain gardens could mean.

Will children be at risk of drowning in rain gardens as opponents allege? It seems highly unlikely given that children do not presently drown in the much deeper and more dangerous pools of water created by the existing system. (Though let’s not forget that the failures of the existing stormwater system resulted in a tragic death in Seattle’s Madison Valley neighborhood when a resident’s basement was flooded with runoff that couldn’t drain properly.)

Will rain gardens present challenges for maintenance and upkeep? Perhaps. It’s a perfectly legitimate concern, although it’s hardly unique to newfangled water management technologies like rain gardens.

Here’s an example of what the maintenance on the existing drainage system looks like:

Dirt and debris clog a storm drain in downtown Seattle. (Photo by Eric de Place)

Seattle’s utility already calls on neighbors to “adopt a drain” to keep the old conventional system functioning. In that context, a little community-spirited upkeep of rain garden infrastructure hardly seems unreasonable.

While concerns and worries about roadside rain gardens deserve serious answers, it’s useful to benchmark their performance and risks to the conventional system we have now. Rain gardens, like any technology, are not a panacea. But they almost certainly do represent an improvement.

Consider that while our aging system of pipes and drains is mostly successful, its failures can be spectacular. As in Spokane last winter:

Melting snow and rain left deep standing water on some area highways… forced the closure of Prairie View Rd. Authorities estimated the pool of water to be 400 feet long and 150 feet wide.

Or in Everett:

On Nov. 23, the city released an estimated 25 million gallons of untreated sewage and stormwater straight into the Snohomish River and Port Gardner. If it hadn’t, the city risked an uncontrolled spill that could have sent even more waste into a nearby wetland and damaged the sewage plant.

“We could have had something catastrophic,” public works Director Dave Davis said.

Unfortunately, maintaining and improving the existing system is proving very costly. As an article in the Seattle Times pointed out:

King County’s $711 million plan pencils out to a wastewater rate increase for a typical customer of $7.61 a month by 2030. Seattle’s plan costs $500 million and would raise rates by $7.41 a month by 2025 for a typical single-family customer. Seattle residents would pay both increases.

Given the costs, hazards, and pollution from the existing system, I think it’s time for Northwesterners to get serious about new low-impact development technologies.

Often proving to be more effective and less expensive than conventional means of managing runoff, roadside rain gardens are a part of the low impact development solution. They won’t usher in utopia—and they won’t fix all our stormwater problems—but it’s good to remember that rain gardens are all over the region, they’re quite popular where they exist, and they are making documented improvements to our cities.


Thanks to Seattle resident David Jacobson for research assistance.

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  1. John says:

    Reality Check? This is more propaganda. Eric apparently did not read my point by point response to “Rain Garden Backlash is All Wet.”
    The photos Eric provides are even more biased than those showing raingarden pooling. The main point that Eric avoids is that the photo examples he shows that both the city and the county do not maintain the system they currently have. Two of the photos could be pictures of rain gardens in action. The one shows an unimproved planting strip that has been compacted and parked on. It is not on a street with curb and gutter. The second photo could be a rain garden.

  2. Eric de Place says:


    I hardly thinking I’m avoiding the point. In fact, I wrote: “Here’s an example of what the maintenance on the existing drainage system looks like…”

    And: “Seattle’s utility already calls on neighbors to “adopt a drain” to keep the old conventional system functioning.”

    Anyway, I stopped reading your previous comment somewhere around the word “agitprop.” If you have evidence-based points to make, please make them and I’d be happy to engage in a respectful tone.

    • John says:

      Thanks for reading all the way to agitprop, which is the correct term for such propaganda.
      Responding snippishly that you have stopped reading is no response to the point by point response to Lisa’s piece. I raised legitimate concerns and their has been no defense of what was written.

      • Eric de Place says:

        Feel free to cool it with the ad hominems, John.

        I don’t see much in your comment on that post that warrants rebuttal. Mostly, it’s just unsupported assertion and insults. Anything in particular you’d like to draw attention to?

  3. John says:

    The “adopt a drain” program illustrates the same fate as county run rain gardens. The city nor county currently can’t maintain the street drains so the ask for the community to volunteer with the obvious results. Why will that be different with county maintained rain gardens?
    Downplaying the drowning risk is a natural impulse, the odds must be extremely low, but defending them with a proposal for hundred or thousands of additional puddles does not make sense. Tying rain gardens to the Madison Valley tragedy is plainly desperate.

    • Eric de Place says:


      As I’ve tried made clear, there are legitimate concerns that need fair-minded answers. But—and this is the thrust of my argument—it’s useful to benchmark the performance and risks of rain gardens to the conventional system we have now.

      Q. Will rain gardens be adequately maintained solely by local agencies?
      A. We’re not sure, and there’s reason to worry they won’t be.

      Q. Is the existing system adequately maintained solely by local agencies?
      A. No. Maintenance is spotty and requires community support.

      Q. Will people drown in rain gardens?
      A. Highly unlikely given that the world is already full of standing water and drowning is exceedingly rare.

      Q. Will people drown in the existing system?
      A. It’s highly unlikely, but one tragedy has occurred that resulted directly from a failure of the status quo.

      Do you disagree with these assessments? If so, why?

  4. John says:

    Thanks for responding so directly.
    I was not aware of the legitimate concerns through reading Lisa’s piece.
    In fact, the title alone, “Rain Garden Backlash is All Wet” challenges legitimate concerns.

    I am not aware of your airing the legitimate concerns that you have tried to make clear until now, so I thank you and apologize for having missed prior pieces that may bring them up.
    I do agree with most of the answers you pose. This is getting somewhere.

    We can agree:
    Maintenance is an issue whether past, present or future. Adopt a drain can not be counted on.
    It is highly unlikely that someone will somehow drown in such a system, just as it was extremely unlikely that a person did drown in Madison Valley. (In that case, I believe the utility was found responsible in an expensive civil court award.)

    Questions remaining:
    Seniors or disabled falling into rain gardens.
    Mosquitoes breeding in water pooled on trash, small lids and discarded containers in rain gardens.
    Plants and trees causing damage to sidewalks (homeowner’s responsibility), power lines, vehicles and people.
    Rat and vermin habitat with food, water and shelter.
    Parking will be impacted. Some homeowners will loose street parking in front of their homes.
    Access will be limited to homes, whether babies, Costco loads, home repairs or moving in a furniture.
    Many people do not find the reflective warning street signs attractive.
    Some people prefer the traditional “pride in ownership” that a manicured lawn displays.
    We do not definitively know about any change to property value.
    Although there may be “thousands” of rain gardens operating successfully in the northwest, there are few examples of major
    systems such as this.
    The soils testing at the Sunrise Heights/Westwood project area did not confirm expectations.
    Where will the hundreds of millions of gallons of polluted street run-off being injected under the cap of impervious clay go?
    Have massive retrofit projects like this been successful or even done before? If yes, were they done on a steep slippery hillside of clay?

    Now that we have established a dialogue, maybe you can respond, agree or rebut, to further the discussion.

    • Eric de Place says:

      Thanks, John.

      Briefly, here’s my take:

      1. People falling into rain gardens. I don’t follow your point here… the rain gardens are beside the sidewalk, not in it. Is the worry that someone would walk through one and stumble?

      2. Mosquitoes breeding on trash. I thought Lisa took a decent stab at this one in her post. There’s trash a-plenty around Seattle, not to mention the far more likely breeding grounds of bird baths, off-kilter gutters, trash can lids, kiddie pools, pots, and other items. But the city has no mosquito problem.

      3. Liability from damage inflicted by plantings. I agree with you. The city & county should hold homeowners harmless for that kind of thing, and they should say so clearly. If they won’t, I’d love to know why.

      4. Rat habitat. I don’t buy it. Rain gardens wouldn’t provide food, wouldn’t provide water (except in unusual circumstances and then only briefly), and offer much less shelter than a million other places. More to the point, is there any evidence that existing rain gardens shelter rats?

      5. Parking will be impacted. Yes, but not greatly and it’s parking in the public right-of-way, not parking on private property.

      6. Access limited. I don’t follow this one. How it will be limited? Is your point that in a few cases on-street parking is slightly farther away? Private driveways are unimpeded as are roadways and sidewalks.

      7. Reflective street signs. If I’m not mistaken there’s exactly one of these in the entire Ballard project. Perhaps there are ways of mitigating design issues around signs, but I guess it doesn’t feel like a major issue to me. The city has overhead power lines, fire hydrants, no parking signs, etc… it’s just life.

      8. Some people prefer lawns. I have no real response. It seems like one of those areas where we have to balance some peoples’ aesthetic tastes with our public policy objectives.

      9. Property values. We don’t know “definitively,” but we do have one analytical study. As you know, that study shows improved property values from rain gardens. That said, there are many rain gardens around the Northwest and I think we would all benefit from additional study and analysis.

      10 – 12. Site-specific engineering issues. I can’t speak to these with any credibility, but they seem like perfectly legitimate concerns to me. I would hope that the city/county can provide satisfactory answers to the community. Have they (or are they planning to)?

  5. John says:

    1. People attempting to cross a rain garden trough, people passing each other with strollers or dogs, the blind are just a few examples of people that may end up stumbling into the rain garden. If there are thousands, it must happen.

    2. Absolutely WRONG!
    Even Lisa’s article reports West Nile threat in the region.
    Seattle does have a mosquito problem as also reported by KING 5
    ” Now, KING 5 News has learned that Seattle will not be spraying storm drains and other mosquito breeding grounds due to the budget crunch.
    Experts say the wet spring has created a lot of standing water – perfect conditions for a summer of swatting. But Seattle Public Utilities won’t be doing its annual bug kill and the Seattle-King County Health Department has been forced to scale back West Nile Virus prevention efforts.
    “Given the circumstances, it is a matter of setting some priorities,” said Jim Henricksen, emergency preparedness supervisor for the health department.
    So instead of trapping and identifying mosquitoes before they do damage, the experts will be relying on people reporting dead birds and then testing them for West Nile Virus.” Note where they spray for infestation (storm drains).

    3. The city and county cannot afford to maintain the city owned space between the private property and the road, i.e. the planting strip and sidewalk. That is why the burden is shifted to the homeowner. How will this change with extensive county “maintained” rain gardens.

    4. Rat habitat, how can anyone deny that rats will occupy low lying ground cover, bushes and small trees lining the rain garden trough. There they will enjoy cover and safety from predators, fresh supplies of water and food in the source of anything flushed off the street and served directly to their habitat (the menu includes carrion, fast food leftovers, beer and soda remnants and general garbage that traditionally ends up in the gutter. Your claims that rats notorious for abiding in gutters, sewers and ivy along-side roads, will somehow vacate when those become rain gardens defies logic.

    5. Right, parking will be impacted. Now imagine that public parking directly in front of your house as it has been for 50 years is suddenly not available. Do you now wrestle your neighbor who has also been parking on the public street in front of his house for 25 years for his parking spot? Or do you drive to another block to park?

    6. On blocks that do not have private driveways, as many do in the project area, people will have to park and unload at the ends of the block to avoid crossing the rain garden that you say no one will cross and stumble in. This greatly limits access.

    7.&8. We agree that they will affect some in a negative manner. Tough luck, the unlucky ones have been chosen to bear the public policy choices.

    9.Property values are probably not affected significantly. But I believe the study may have shown bias and cherry picked its sampling to exclude the Ballard project area. Was Ballard included?

    10-12. Site specific information is what your organisation and Investigate West should be investigating and reporting on not these soft PR issues. It is in your interest that the system that gets built performs as your organisations claim it will.

    • Eric de Place says:


      I think I’ve identified something that may be at the root of some of our disagreements. It seems like many of your concerns—hazards to pedestrians, mosquitoes, rats etc—stem from a belief that the rain gardens will be full of standing water.

      But that’s not the case. They are specifically designed to infiltrate water in a rather speedy fashion. Even the much-maligned Ballard rain gardens are fixed now, at the city’s expense, and do not hold standing water for any meaningful period of time. And if they’re not holding water, then it seems like most of the problems you describe go away, right? (Or else they’re just problems with landscape-quality bushes and grasses, which don’t seem like a large public health threat to me.)

      On the mosquito point specifically, I’m having a very hard time seeing how rain gardens could possible be a contributor. As you say, it’s the conventional system — the storm drains — that create the (very limited) issue. If anything, it seems like folks concerned about mosquitoes would be trying to get rid of the conventional drainage system. That said, there are hundreds of other things around the city that hold standing water semi-permanently.

      It might be worth visiting the High Point development, which isn’t too far from your neighborhood. They have extensive rain gardens installed and it might give a sense for just how benign they really are. Has High Point (or other neighborhoods with rain gardens) experienced any of the problems you’re describing? If so, I’m not aware of them.

      As for the parking and access issues, it sounds like something that could be worked out with the design. Perhaps parking on one side of the street with paved paths that cross the gardens at points? Other configurations are conceivable.

      A modest reduction in on-street public right-of-way parking may require a little more sharing and neighborly negotiation than folks there are accustomed to. But my sense is that folks figure out a way to make it work well, just as they do in most every neighborhood (including mine) where parking is tight.

      Finally, the LID property values study was published in 2008, which was before the Ballard rain gardens kerfuffle. As I said earlier, I quite agree that we could all benefit from an updated and more comprehensive analysis. It would certainly help inform discussions like these.

  6. Seattlepoppy says:

    well this about sums it up – how people feel about something determines what they support – evidence and expense be damned. Seattle is known world-wide for having undergrounded all the surface water(streams, rivers) A few little rain gardens here and there would be a pleasant change from the miles and miles of pavement. seniors and disabled get hit by cars all the time but we’re not getting rid of cars…rats? who cares – let the neighborhood cats and random visiting coyotes eat ’em …

    • John says:

      When you write, “A few little rain gardens here and there,” you are obviously not referring to the project in discussion that will inject hundreds of millions of gallons of polluted carcinogenic street run-off under a sealed cap of clay.

      I always enjoy the arguments like seniors, children and the disabled get hit by bicyclists, so do we outlaw bicyclists?

      You are also ignorant in claiming that a “few little rain gardens here and there would be a pleasant change from the miles and miles of pavement.” The rain gardens do not replace pavement. The street pavement remains as does the sidewalk pavement. Indeed, there could be an increase in pavement with the addition of the “paved paths that cross the gardens at points” that Eric suggests.

  7. John says:

    Eric, you seem to be missing the point, none of the issues you mention require standing water in the rain gardens.
    I have specifically written that the thousands of small rain retention receptacles such as bottles, cans, food containers that normally litter the streets will all be swept into and held in the rain garden. These can breed mosquitoes. These can sustain vermin.
    I live near the High Point system and have witnessed standing water there within the last two months.
    But you and I know that comparing this retrofit with the state of the art totally redeveloped High Point project with all new streets and drainage infrastructure with an ENORMOUS DRAINAGE POND, is apples to oranges.
    If you have been to the High Point system, you would have seen the way that access is limited from the streets to the homes and the ditches are something one could fall into even when totally dry.

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