Portland is known for getting a lot of rain. Not now, of course, it has been dry and in the 80s! Most years, in fall, winter and spring, we get about 36 inches, or three times as much as you do in Salinas. Building a city where there is that much rain has its own problems.
You want to make sure the streets drain nicely so houses don’t flood. You want to make sure soil doesn’t erode and turn hills into mud slides. And you want to make sure that pollution and trash from city streets don’t end up in the Willamette River.
City engineers work hard at making sure the first two problems are solved. Storm drains are kept clear and streets are graded so they carry water away quickly. But keeping trash and pollution out of the river has become something a lot of homeowners are helping with.
Bioswales are part of this solution. They are a sunken part in a garden, designed to catch rainfall from the roof of buildings. The water flows into the bioswale and slowly soaks into the ground water, or aquifer. This keeps it from running along the street picking up oil and trash, and also helps clean it before it goes back into the water cycle.
I am noticing small bioswales in front yards all over our neighborhood. They are all set up with conduits from the downspouts to direct rainwater into them. They are lined with rocks and gravel to resist erosion, some lined with plastic except at the bottom. The prettiest ones are landscaped with plants that are comfortable being very wet (even underwater) for part of the year.
I love that people here are taking responsibility for helping keep our beautiful Willamette River clean. For many years, factories along the river dumped all sorts of nasty chemicals into the river, hoping they would just wash away. Now there are companies helping clean the river, and people want to help, too.
Yay Portlanders! Yay bioswales!