behold the notoriously wet and wild pacific northwest winter

Unrelenting atmospheric sheets of rain move eastward, trickling off roofs, clattering down rain gutters, spilling across pavement, flooding ditches and swelling streams. Inhabitants of the Salish Sea regularly witness the most efficient transportation system in the world: the water cycle. Due to their ability to change forms, water molecules are literally air-lifted from the ocean and carried as gas on the wings of the wind across hundreds of miles. Then, like mythical shapeshifters, change form again as they are cooled into liquid rain or crystalized snow. We are dependent on this cycle for the health of forests, inland water systems, wildlife, and our own water supply.

Most veteran Northwesterners feel sweet relief when such watery excess conveniently disappears down storm drains and roadside ditches, into streams and creeks, then ultimately into the Salish Sea. Over time, communities have designed clever ways to keep rain from inundating our towns and cities with engineered systems of drains, culverts, and reservoirs often referred to as “grey” infrastructure. However, keen observers notice far-reaching changes in the health and vitality of the environment and in our food and water supplies. When researchers search for potential reasons for these changes, they are invariably led to the same major culprits, one of which is the downside of our efficient rainwater drainage systems: storm water runoff. 

a dirty solution

So if excess stormwater runoff is a big factor when it comes to flooding, erosion, water supply, and pollution challenges, what can be done to help rain soak into the ground as it should as well as reduce contaminants and pollution before it reaches waterways?

Once again, the secrets of nature provide an answer — soil. Often overlooked as just a dirty stabilizing structure upon which we live, move, and grow crops, soil is also a powerhouse for processing and cleaning water. By slowing the flow of water, directing it away from buildings to natural areas or mimicking the activity we observe in meadows and wetlands, we can greatly reduce the current detrimental effects of stormwater runoff and ensure a healthy water table as well. ​

Based on what we are learning about the powerful properties of soil, there is a growing movement to use that knowledge to replace the “grey” infrastructure of concrete components with green stormwater infrastructure (GSI). The good news is every citizen can participate. One GSI concept that is gaining traction nationwide is the installation of rain gardens in private yards and community spaces.

A rain garden is a small, sunken landscape area that rapidly collects, absorbs, and filters stormwater runoff from roof tops, driveways, patios, and other hard surfaces that shed water quickly. Simply by capturing rainwater and releasing it back into productive soil, we can each do our part to keep some water off of our roads and impermeable surfaces, drop by precious drop. The US Department of Agriculture published a short list of the benefits of rain gardens. For starters, they are relatively inexpensive as well as easy to install and due to their design, absorb about 30% more water than conventional lawns.

As with all changes to the natural landscape, it is important to consider the results of our actions over time. Some researchers wonder if rain gardens can become mini toxic waste sites within neighborhoods as contaminants accumulate. When measured by sheer weight, most contaminants moving through residential areas include mostly dirt, oil, and organic matter, but there are small amounts of more dangerous substances that sneak in, such as chemicals commonly found in consumer products like lotion and soft plastics. Some studies indicate that traces of heavy metals that find their way into residential rain gardens are captured in the mulch layer.

Sightline Institute in Seattle investigated concerns and found that due to the plant and microorganism activity in soil, the biodegradation process happening in rain gardens actually destroys many contaminants rather than just storing them. (See Rain and Soil: Partners in Sustaining Life).

It is also important to understand the limitations of rain gardens. For instance, appropriate rain garden placement is critical. If placed near a bluff, infiltrating water can destabilize bluff soil and accelerate erosion. If constructed too close to the water table, water will not infiltrate and may result in standing water, which is its own can of worms. Rain gardens are designed to handle moderate rainfall and are considered a supplement, not replacement, for adequate drainage and should include accommodations for overflow. It is wise to consult with local rain garden mentors to evaluate your space. Many communities offer assistance and resources to help residents get started.

General consensus overwhelmingly considers the benefits of rain gardens outweighing any concerns, but it is a discussion that will continue as communities search for creative ways to address environmental challenges. In the meantime, rain gardens should be regarded with common sense. They are beautiful, hard-working landscape features, not designed to grow edibles or serve as sandboxes for children.

Ready to jump in? Designing and constructing a rain garden can be a wonderful family or community activity. It provides an opportunity to dabble in garden design and experimentation in a smaller space. Involving children in the process exposes them to many useful skills and gives them a living, changing, earth-friendly experiment to monitor right in their own yard. (For more about involving children, see the 2 videos at the end of this article)

There are hundreds of books and websites on the subject of rain gardens that basically guide homeowners through four steps: planning, building, planting, and maintaining. One valuable guide for beginners is the Rain Garden Handbook for Western Washington. Washington State University Extension and Stewardship Partners have joined forces to see 12,000 rain gardens installed in the Puget Sound area. Their site 12000raingardens.org is a treasure trove of real time information, including workshops, grant information, and other valuable resources as well as maps that plot existing residential and commercial green infrastructure sites throughout the Puget Sound area. Their goal is to map 12,000 rain gardens spread across the lower Salish Sea watershed. Read the stories of “rain gardeners” across Puget Sound and view their projects at 700 Million Gallons or Sound Impacts. The Capital Regional District in Victoria, B.C. provides many resources on their website, including a list of rain garden examples to visit in the area.

The next time you notice rain flowing along the highways and byways of your daily sphere, ask yourself where it has been and where it is going. Be on the lookout for rain gardens and bioswales and take a moment to stop and study their intentional design. You may even decide to become a rain gardener yourself. You would be doing your community and the Salish Sea a favor.​​

12,000 Rain Gardens in Puget Sound

700 Million Gallons

Capital Regional District in Victoria, B.C.

Kitsap Conservation District offers technical assistance to landowners to help improve property resource management.

LOTT WET Science Center in Olympia, WA offers interpretive exhibits and events relating to water, water conservation, the urban water cycle story, wastewater treatment, reclaimed water, and protecting Puget Sound.

Rain Garden Handbook for Western Washington

Sound Impacts

USGS Water Science School, more about groundwater