Exciting drainage swales in urban areas

Traditional engineering tries to remove as much rainwater as fast as possible. Rain falls, pavement directs it into storm sewers. Outa sight, outa mind.

More recent storm water management for Ottawa streets reduces the permeability of the catch basin grate so water self-stores on the street (that’s  “puddles” to the rest of us) and runs off over time. Preston has this feature. Unfortunately, it makes walking the sidewalks within an hour or two of rainfalls a drenching experience. Some puddles remain for 24 hours.

It rains a lot in the pacific northwest.  They have installed a lot of “drainage swales” in the urban areas. Today, lets look at some swales — which are shallow, planted ditches or depressions — in downtown Poulsbo.

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the drainage swale shown above is on a steep downslope. A “bulb out” has been constructed, and the pavement behind it removed and plant material introduced. Gaps in the  curbs allow rain water on the street to wash into the swale.

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This swale was also used to “regularize” an irregular intersection, and to separate the sidewalk from the road surface.

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Swales usually include a catch basin in the centre of the plant area to take away surplus water. It is often elevated so the swale might fill with water before hitting the sewage system.

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the plants in this swale are low, and the ivy has thrived, creeping out over the road surface.

At the bottom of the hillside swale shown in these pictures (above) was a parking lot. It had numerous swale features in the parking lot and on the perimeter.

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the newly planted swale on the edge of the lot had some temporary fencing to let the plants get established, and to direct pedestrian traffic towards official crossings of the swale to get to parkland (was the parking lot or the parkland bigger?).

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Instead of being elevated, the parking lot island shown above drains water into the centre of the plant zone. Note the tree planted in a concrete ring; here is another, in closeup:

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Here’s some more nicely planted swales:

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All these swales were obviously of recent construction. Some public education is warranted both to inform and persuade people of their value and why one should respect them. Here’s such a sign:

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Lest to might think these are cute, and not terribly useful as plant and wildlife habitats, here is a photo that shows otherwise, from the next town, Port Townsend, where I was exploring some more drainage swales.  Yes, it’s real. Yes, it was shockingly tame and urbanized. It is about 10′ from me.

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And it wasn’t alone, it had friends and family on a nearby front lawn:

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Next: industrial park drainage swales