Rain Gardens

Human beings appear to be relatively unique, as members of the animal kingdom go, because we learn from experience as a species, mostly by screwing things up and then having to figure out where we went wrong, and how to fix it. The more of us there are, and the more technology we acquire, the more massively we are able to screw things up. Lots of animals learn from experience individually, and can even pass their knowledge on to other individuals, but human beings store and codify the results of our mistakes, and communicate them to other human communities across the globe. We call this process "science".

All that runoff has to go somewhere...

One of the ways that we have relatively recently screwed up is something most city-dwellers take for granted; impermeable surfaces, like roofs and roads and sidewalks. We've paved our habitat, which is really convenient when you want to push a shopping cart from a store to your car, but creates a big problem when it comes to dealing with water falling out of the sky. Until recently, our way of managing this has been primarily to just capture this water in roof or road gutters and direct it quietly underground to the sewer system, which is the point in this process where my interest was piqued. The gutters are falling off my house so it's, y'know, immediately and possibly urgently relevant.

Right down into the ground!

As part of their Slough 101 series, the Columbia Slough Watershed Council offers a Rain Gardens 101 class. I knew little about rain gardens other than that they were a way of dealing with roof runoff, which lately has taken to seeping into my basement.

The class was offered at Whitaker Ponds Nature Park on NE 42nd, a lovely little bit of restored wetlands that itself has a history rich in human errors; nestled away in an industrial area, with a Boeing silo looming nearby, it seems like an unlikely place to find a nature park.

That white smudge on the horizon is a massive Boeing Quonset hut.

In fact, the ponds and surrounding area had been used as a dumping ground for many years, and restoration required the removal of a prodigious volume of garbage from the site, including appliances and empty barrels of unknown provenance.

You would never know by looking at it now; it's a green haven for frogs, fish, ducks, rabbits, and countless other creatures.

Heron just, like, chillin'.

The Columbia Slough Watershed Council headquarters are housed here, in a small house; a good place for housing headquarters. This is where I learned more about stormwater runoff and the mistakes we've made in handling it than I ever thought I'd know, and, more importantly, what we're trying to do to fix our mistakes now.
The class started with a brief overview of the problems we've generated for ourselves by capping off most of our habitat with impermeable surfaces. The main issue is, the soil we're covering up and the plants that would have grown there would normally act like a giant water filter, cleaning the rain as it soaks into the ground. Some of the water would then percolate down to the water table, and perhaps into wells dug by humans, clean and fresh and good for drinking. Most of it would be absorbed by plants and evapotranspired back into the atmosphere, eventually to make more rain. Very little of it would become runoff.

Command Central for the Columbia Slough Watershed Council.

The problem with runoff is not just that we are interrupting the water cycle and depleting our drinking water resources. It's also that runoff carries with it all the nasty stuff it picks up from roofs and roads, like lead, petrochemicals, and other pollutants, into the rivers and eventually the ocean. And that's not all; our runoff screws the guy downstream, and  there's always someone downstream. It erodes streambanks, destroys fish habitats, contributes to sinkholes and landslides, and causes flooding, among other problems. It overburdens sewer systems and causes waste overflows into waterways. It costs money as well as habitat.

The rain garden at the CSWC headquarters. 

By the 1970s, the earliest I was conscious of environmental issues, we had figured out that this runoff issue was a problem that needed to be addressed somehow. Urbanization - the flow of the human population from rural areas into cities - was accelerating, and the global population had reached an alarming four billion people. In Portland, combined sewage overflows, in which the volume of runoff when it rained overburdened the sewer system, causing untreated sewage to purge unfettered into the Willamette River (and giving new meaning to "the smell of rain") were typical. Believe it or not, this was an improvement; Portland didn't vote to approve a sewage treatment facility until 1938. Until the plant opened in 1952, raw sewage was simply piped directly into the Willamette River and Columbia Slough.

Downspout, disconnected.

In 1993, Portland launched its Downspout Disconnection program, offering free disconnection and incentives to city residents. The program was massively successful, but led to another problem; how are residents to deal with the stormwater puddling on their lawn, seeping into their basements, or, defeating the purpose entirely, running across the sidewalk and into the street drain? Here enters the rain garden.

A rain garden/bioswale in downtown
Portland, near PSU.

Also called a bioswale, rain gardens are, at their most basic, essentially just a hole in the ground that water can soak into. We see them most often, in Portland, in the form of curb improvements, as well as the reedgrass-planted depressions in between the paved areas in New Seasons' parking lots, but they are also starting to creep into yards and parking strips as homeowners become more aware of the benefits of using them to manage runoff. The city has also recently updated its building code to mandate onsite runoff management for new construction (I'm fuzzy on the details), so I expect we'll see many more rain gardens in our neighborhoods.

The interior of the rain garden at Whitaker Ponds.
Here thar be bunnies! Squee!

Of course, the garden part of rain garden implies that they are so much more than just a hole in the ground, and they are. A rain garden also consists of plants that are happy to be deluged with, and help soak up, lots of water at once, such as rushes and sedges (rushes are round, but sedges have edges) and they are carefully designed to direct runoff away from foundations as well as, importantly, to dry up within 48 hours so as not to become infested with pests that breed in stagnant water.

The promise of adventure ahead...

A well-designed rain garden is not only a pragmatic bit of drainage engineering, but also lovely to look at and a boon to small city wildlife like birds and beneficial insects. I won't go into the details of building and planting a rain garden here, because the East Multnomah Soil & Water Conservation District has put together a guide that is far more helpful than I ever could be. The Oregon Environmental Council has also put together a rain garden guide, and there's a helpful OregonLive article about them as well. So I will leave you to their more capable instruction, and add a couple of totally gratuitous shots of Whitaker Ponds Nature Park just because I love it so much.

The eco-roofed gazebo at Whitaker Ponds.

The Columbia Slough.

This rural home doesn't even have gutters... just long eaves that distribute runoff into thirsty plantings below.

My own putative rain garden.