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Rain and the Urban Water Paradox
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[JASON PAUR] When it rains it pours, and it doesn't take a rocket scientist--or in this case a hydrologist, to figure out that even a light rain falling on endless miles of asphalt and rooftops can pour down the storm drains and blast right into local streams. But just in case, I asked one to make sure. Derek Booth is with the Center for Urban Stream Studies in Seattle and says before we starting sealing the surface of our neighborhoods, much of the water never even made it to the streams.
[DEREK BOOTH] A good part of the rainfall never even used to reach the ground. It would catch up on the tree canopy, it would re-evaporate into the air, and frankly the streams would never see it.
[JASON PAUR] So what's the big deal? Well for starters this means streams can get over loaded in a very short period of time, giving us the ubiquitous nightly news story. You know the one with the cars stalled in water up to their windows. Booth says this is because when the rain arrives in an urban drainage it not only has much more volume, but the water also comes in much stronger pulses.
[DEREK BOOTH] So for
any given rainstorm the channel will have to
accommodate a much higher discharge than it ever had seen in a
pre-development case.
[JASON PAUR] But this isn't exactly new information, many neighborhoods already have storm ponds where water can pool up to minimize flooding. But most of them aren't nearly big enough and they don't allow the water to be used when the rain has stopped and people need to water their lawns or wash their cars. This is where the new breed of planners and designers started thinking there must be a better way to build a mouse...I mean water trap. Andy Lipkis is with the Tree People, a Los Angeles area group that's developing innovative ideas on water management. He points out it's an expensive problem worth fixing in a place like LA.
[ANDY LIPKIS] Los Angeles city spends about a billion dollars a year on water. That's to bring it in and distribute it. At the very same time, a completely different bureaucracy spends about half a billion dollars to get rid of all the rainfall.
[JASON PAUR] And according to Lipkis, not all the solutions require major construction work or massive replanning. Some of his ideas for restoring the absorbent properties of the ground are quite simple. At a demonstration house in Los Angeles they moved a few down spouts and lined the front yard with a six inch berm that blended with the landscaping.
[ANDY LIPKIS] What we did is redirect that roof drain with about ten dollars of new gutter material and redirect that into the lawn so it could pool up to about six inches deep on the lawn. A front lawn that's about 20 feet by 30 feet and six inches deep can hold a couple thousand gallons of water.
[JASON PAUR] Multiply
that by...well...a seemingly endless sea of homes and you're talking about
alot of water. And it's just one small part of a plan Lipkis hopes will
recreate a city's ability to behave, at least hydrologically, like the
forest or grasslands it replaced. When similar ideas are applied to large
business parks, shopping alls and schools he hopes some of those billions
spent on exporting and importing water can be saved and bring an end to
the urban water paradox.
For Restoration Radio, I'm Jason Paur.
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