August 18, 2009

Out With the Old

Undoing what’s been done might seem like a funny way to approach stormwater management – let’s face it, most of us think about progress in terms of what we build, not what we dismantle. But mitigating urbanization’s impacts on stormwater runoff requires a different type of strategy – it requires Low Impact Design.

Low Impact Design (or LID for you hipsters) is a suite of technologies that replace impervious surfaces like paved streets and driveways with porous ones, like rainwater gardens, green roofs and swales (swales are low tracts of land used as open drain systems).


When these technologies are applied to urban designs such as street medians, parks and schools, rainwater penetrates the earth, reinvigorating groundwater tables and streams.

Mission Bay Swale installation, Channel Pump Station, San Francisco

And there’s more (wait for it…) As rainwater percolates through layers of soil, street pollutants like car oil, animal waste and heavy metals are filtered out – a natural, ancient and very efficient process.

So when you next watch as oily rainwater pours from your driveway into a gutter, and you think to yourself, “there must be a better way…”

You’re right. There is.

For more information on the SFPUC’s LID and stormwater management programs, please visit:

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