Imagine: Rain, rain, stored away
WHILE you watched much-needed showers race down the driveway and spill into street drains two weeks ago, did you perhaps think: How can I harness that rainfall? How can I save that water for a yard that has endured drought-like conditions?
It turns out that “harvesting” rainfall is not only good for the garden, but also good for the environment.
And there are several ways you can prepare for the next major storm to keep some of that moisture in your landscape and away from the drainage systems.
Increasingly, homeowners want strategies to capture and retain storm water, whether for irrigating the garden during dry spells or to divert it from gushing down the block.
In response, municipalities such as Santa Monica sponsor grant programs to help residents renovate their properties, and savvy designers offer solutions that are functional and aesthetically pleasing.
Peter Jensen, a landscape designer with Gaudet Design Group of Santa Monica, says rainfall isn’t polluted until it hits the streets. “That’s when it mixes with brake fluid, motor oil and gas spills that are concentrated on pavement, gets swept into the larger drainage systems and eventually spills into the ocean.”
To Jensen, traditional residential landscapes are water wasters. Expansive front lawns require irrigation and boost your water bill. Impermeable driveways shed precipitation into the streets. Downspouts dump water into municipal drainage systems. This waste adds up to thousands of gallons of water that otherwise could remain within the homeowner’s own landscape.
Jensen recently helped John Francis and Susanne Meline capture rainwater in their Santa Monica yard. With the added incentive of a city grant covering half of the project’s $5,000 price tag, the couple worked with Jensen to design a custom water-management system that holds as many as 450 gallons of rainwater. “Depending on the rate that rainwater seeps into the ground, the pit can accommodate more water over an extended time,” Jensen says.
To determine the ideal size and volume of the infiltration pit, Jensen calculated the potential rainfall that his clients’ roof would shed into the yard. The pit, about 200 cubic feet, is a straight-sided hole in the ground, lined with landscaping cloth and filled with variously sized rocks. It is topped off with larger rocks to emulate a dry creek. The system allows water to seep slowly into the ground rather than mixing with pollutants on the city streets. Some designs also have outlets to handle overflow during extreme storms.
In addition to rock-filled infiltration pits, commercial products are available. For example, a system by Australia-based Atlantis Corp. ( www.atlantiscorp.com.au) uses modular cubes fabricated from recycled plastic to filter water underground. “But all pits are still ‘custom dug’ based on the size of the project,” Jensen points out.
Whether the Francis-Meline property receives light mists or heavy rain, any water that hits their roof, combined with excess backyard water, moves through downspouts and is collected in drainpipes leading to the in-ground system. After meandering, stream-like, along the rocks, the water settles in the submerged pit. Some systems use a silt basin to remove debris, although Jensen’s design allows water to run through rock and landscaping fabric, which filters out the silt.
To neighbors who stroll along the sidewalk, the design’s above-ground portion resembles a stone creek bed dotted with rushes, sedges and native ground covers. A 15% grade change from the front door to the sidewalk puts gravity to work as water flows downhill. “I tried to make this look like a natural system using the topography of the yard with plants that grow along riverbeds,” he says.
Other water-capturing techniques enhance the landscape. Jensen shattered a large section of the two-car driveway and reconstructed it with ground covers and ornamental grasses. Silvery mats of Dymondia margaretae, a spreading perennial that can handle foot traffic, are knit together with flowering thyme between sections of concrete. Raindrops soak into the planted areas rather than wash down to the street. The front walkway uses a similar approach, recycling leftover broken concrete for steps rather than being sent to the landfill.
Where a traditional turf-style front lawn once stood, Jensen planted no-mow lawn, a grass that requires less water and eliminates use of an energy-hogging lawn mower. The parking strip is planted with a flowering evergreen yarrow, a good lawn substitute.
To irrigate the garden during dry times, Jensen installed a state-of-the-art drip system. Instead of operating on a timer, it is linked to an Internet weather site that calculates the property’s water needs, turning on during dry spells and off when it rains.
Jensen adopted many of the same techniques in Sandi and Joe Lee’s property, also in Santa Monica. Their redesign transformed a grassy front lawn, a straight walkway and formal rose hedges into a modern, low-water-use scheme.
A new asymmetrical path of separated landings allows for better drainage. The infiltration system is topped with warm-hued river rock, and the garden is planted with geometric blocks of Agave americana ‘Mediopicta Alba’, rosy Echeveria ‘Afterglow’ as well as native deer grass (Muhlenbergia rigens).
“We could have hidden the infiltration pit underground and planted over the top,” Jensen acknowledges. “But I wanted to uncover it to show how it works in a natural system for channeling water.
“As more people do small things to save water, they will build up to be major things -- and help the environment.”
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Ways to catch every drop
Here are some rain-management techniques and resources suggested by landscape designer Peter Jensen and other designers:
Use a rain chain. In place of a regular downspout, hang a rain chain. It is a simple and attractive device for slowing rain that sheds from a gutter at the edge of your roof. You can find rain chains in copper, brass, aluminum and iron materials. A rock or gravel-filled hole at the base encourages water to seep slowly into the earth and can also be connected to an infiltration pit.
Add a rain barrel. With a typical capacity of 50 to 80 gallons and made from recycled plastic, a rain barrel collects precipitation for use during dry spells. Maximize the benefits by placing one at the base of each downspout. Some designs have spigots for filling a watering can; others have an on-off hose attachment.
Consider a cistern. Fabricated from reinforced concrete, galvanized steel or recycled plastic, cisterns can have a capacity of a few hundred to more than 1,000 gallons. They can be submerged or built above-ground using similar water-dispensing methods as a rain barrel. Cisterns traditionally have been used by farmers and ranchers. There is, however, increasing interest in residential applications, according to David O’Donnell, a project associate at TreePeople, a local nonprofit environmental group. A general rule to determine cistern size is that 1 inch of rainfall landing on a 1,000-square-foot roof yields about 600 gallons of water.
Install an infiltration system. Unlike rain barrels or cisterns, infiltration systems are designed to capture and filter precipitation before it soaks into the ground. Usually designed as an in-ground pit lined with landscaping cloth and filled with variously sized rocks, such a system prevents rainwater from spilling into streets and drainage systems.
Sculpt your garden with swales and berms. This technique is especially useful to change the topography of flat lots. To slow water’s race off of your property and to filter pollutants, build 18- to 24-inch-tall “islands” or rows of mounded soil, and then add ornamental plants. Select drought-tolerant or native varieties to save more water.
Spread mulch. “Mulch is a very effective way to reduce runoff and keep water on the property,” O’Donnell says. A few inches of organic mulch, such as finely shredded bark, organic compost, shredded leaves or gravel, will slow evaporation of moisture in the plants’ root area. Mulch shades and cools the soil, in addition to slowing water runoff and suppressing weeds. It also enriches plants, building healthy soil as it slowly decomposes.
Irrigate sensibly. Low-water drip systems apply water directly to the soil through tiny outlets called emitters or through microsprays plugged into flexible tubing laid on the ground and covered with mulch.
-- Debra Prinzing
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resources
“Rainwater as a Resource,” a free report published by TreePeople outlining three Los Angeles area projects, can be downloaded from www.treepeople.org.
“Gardening With Intent: Water Management Strategies” is the theme of the fourth annual Green Gardens Tour in Santa Monica from 10 a.m. to 4 p.m. April 26. A program of the Virginia Avenue Project, the tour will feature seven residential gardens using sustainable practices, including rainwater strategies. For tickets, call (310) 264-4224 or go to www.virginiaavenueproject.org
“Landscape Water Efficiency” competitive grants, offered by the city of Santa Monica to residents, will provide $20,000 in incentives for water-efficient landscaping. The applications can be downloaded at www.smgov.net and are due March 27. For more information, call the city’s Environmental Programs Division at (310) 458-2213.
Free mulch from yard trimmings is available at six sites throughout Los Angeles County. Find pickup locations by calling (818) 834-5128 or go to www.lacity.org/SAN.
-- D.P.