ISSUE 61  |  Bath & Spa

A Garden That Can Water Itself

February 26, 2013 11:00 AM

BY Michelle Slatalla

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For centuries, little brooks and springs ran like spider veins through the land in San Francisco. Most have been paved over. But the water has to go somewhere. In a house built in 1930 on a sloping 100-foot-deep lot, an underground spring announced itself by emerging from the foundation to produce 100 gallons a day. What do you do with all that water?

For San Francisco-based Bionic Landscape, the answer was obvious: use the natural elevation of the site to capture the water and recycle it, to use in the garden. The innovative site plan and design won an Honor Award last year from the American Society of Landscape Architects. Here’s why:

Above: “This project challenges the widespread convention of suppressing urban water systems in favor of the wide array of common justifications—safety, mosquitoes, costs, progress, maintenance, etc.,” the American Society of Landscape Architects noted. “Like many cities San Francisco has paved and piped its hydrology away along with the benefits that it could offer an ever growing and densify-ing city. While it is a small site, and a relatively small amount of water, this project demonstrates the life enabling possibilities of inventive design in combination with urban waters.”

Above: The process of capturing water starts from the back deck of the house, where a rain chain (C) helps direct flow into a system of spring basins below.

Above: The view from the house. From a deck above the boardwalk, it’s easy to see the path the water travels: it runs down a rain chain (L) into a basin, and then flows downhill through wetlands to be captured at the edge of the backyard at the site’s lowest elevation.

Using the natural elevation to encourage water to run downhill, Bionic Landscape designed a system of runnels, basins, and wetlands to re-capture 100 gallons a day. “The spring emerges through a shallow clay layer in the soil eight feet off the back facade” of the house, the American Society of Landscape Architects noted. For more, see ASLA.

Above: An aerial view shows the copper rain chain (L) above a spring basin surrounded by ferns and Japanese maple trees.

Above: A sharp slope in the backyard naturally aids water’s trip downhill to the catchment area.

Above: At the edge of the property, white clematis vines grow up a red cedar screen behind a patch of purple irises in wetland at the lowest elevation of the site. A layer of pebbles aids drainage. Throughout the property, a system of valves and overflow make it easy to redirect the flow for maintenance.

Above: A wood boardwalk in a backyard wetland. A downhill neighbor “planted three corkscrew willows to address the wet soils from the uphill springs,” the American Society of Landscape Architects noted.

Above: The site plan shows the property, which slopes downward from the house where the upper deck is labeled No. 1 to the wetlands deck at the edge of the lot labeled No. 17.