Tag Archives: bioswales

Green Streets for a Cleaner Harbour

Do you know which is the cleanest part of Sydney Harbour? I’m fortunate enough to get out onto the Harbour in a sea kayak on a regular basis. I know the clean parts and the dirty ones. I know where I can see the fish through the water, and where I can’t.

The correlation between the catchment area and the water quality is obvious and well documented – the more ‘nature’ there is in the catchment, the more the runoff is filtered before it reaches the Harbour.

I regularly post on ‘green streets’, and here’s another terrific source of case studies from the US, via the Montreal Urban Ecology Centre’s site. The main case study is Seattle’s Street Edge Alternatives project (SEA) where one neighbourhood street has been refurbished with bioswales, soil engineering and extensive landscaping. The aim of the project was to test ways in which runoff water quality could be improved so that local Salmon stocks could be protected.

seattle green street

photo: City of Seattle photo archives

The results speak for themselves. The streetscape is beautiful, full of vegetation and shade [reduced heat island effect], and 99% of the stormwater runoff now stays on site – pretty much as would have been the case pre-development. The water that does leave the site is clean.

The Urban Ecology site also provides a Google street map interactive so you can take a walk down the street and check out the detail. Apparently well loved by the residents and locals.

The price tag for this pilot project was some $850k US, which seems to be approximately $40k per dwelling. Assuming that this cost could be halved through improvements in the process and building from lessons learned, I’d be fascinated to understand what the payback for this might be. I’ve posted thoughts around this before so I won’t repeat here. Might make a good Masters for someone ; )

And the cleanest part of Sydney Harbour? The upper half of Middle Harbour wins hands down, and most of it is surrounded by State parks.