Lots of rain this year in Los Angeles! We’ve been installing rain gardens all over the Eastside for several years now. It’s been fun watching them fill during the storms. Instead of rushing into the city storm drains, and then straight to the ocean, this nitrogen-rich, chlorine-free storm water is harvested in the gardens. It is quickly absorbed into the garden soil, where it will be available to the surrounding plants and trees as they need it for months to come. Here are photos of some of the rain garden swales we’ve installed…
All three gardens, above, harvest water from the roof gutters. We connected downspouts to the swales via underground drainpipes. Now the water is dispersed and absorbed. Extra water will filter through the soil into aquifers.
To calculate how much water you can harvest, estimate the square footage of your house footprint. Divide that by 12 to determine cubic feet of rain, in a 1” rainstorm. Then multiply that number by 7.48 to get the number of gallons of water falling on your whole roof in an average 1” storm. Note that LA gets between 5” – 30” of rain/year, averaging 15” annually. You can also divide the roof into the sections that feed each downspout to calculate the number of gallons per downspout.
Here’s a link to the City of LA LID codes and instructions: http://sustain.scag.ca.gov/Documents/2%20City%20of%20LA%20Bureau%20of%20Sanitation.pdf
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