Using a Sustainable Approach in Your Landscape Conversion
The Turf Replacement Program requires the inclusion of a rainwater capture or filtration system integrated into the landscape project. This sustainable approach integrated into the overall landscape design serves to reduce rainwater runoff onto sidewalks and streets and capture rainwater for reuse. The following are details of some eligible methods to meet this participation requirement.
A rain garden is a planted depression or hole filled with a loose, permeable soil mix that allows rainwater runoff from impervious urban areas like roofs, driveways, walkways, parking lots, and compacted lawn areas to be absorbed. Rainwater collects in the soil mix and ponding area and eventually seeps into surrounding soils over time. Plants are distributed throughout the garden. Storm water is soaked into the ground rather than flowing into storm drains and surface waters. Installation of a rain garden within your landscape project can reduce erosion, pollution, flooding and diminished groundwater.
A rock garden is a shallow depression filled with 1-3 inch diameter gravel. Rainwater is stored in the space between the stones and eventually percolates into the soil. Plants are distributed throughout the rock garden and there is no ponding area – so one can walk on it.
A vegetated swale is a shallow ditch that has gently sloping sides. Native perennial grasses are planted along the bottom and sides of the swale to slow runoff, filter sediments, and remove excess nutrients. A swale relies on gravity to move water and is designed to direct the water where you want it to go, such as flower or vegetable gardens. In order for the water to gravity flow it is recommended that there be a minimum 2% slope from beginning to end. Organic mulch should not be placed around any plants installed in the bottom or sides of the swale.
A dry river bed or dry stream is an area designed to slow heavy flows of water from rainfall and correct erosion problems. It is made up of a shallow swale (see section on vegetated swales) lined with stone substantial enough to withstand a serious downpour. Large chunks of stone are used to slow the speed of storm water and prevent erosion. In a garden, the careful placement of water-worn stone, or river slicks along a swale can be a beautiful design that also provides an ideal place for plants.
Berms are mounds of earth with sloping sides that are located between areas of approximately the same elevation. Berms are designed to direct or redirect water in order to keep water from flowing off the property.
Grades are surface grading of an area so that water collects and flows to a lower elevation away from the water collection site. Regardless of surface characteristics, when planning to add a grade for surface drainage, slope is the most important consideration. For efficient drainage, paved surfaces are recommended to have a minimum 1 percent slope. Turf or landscaped areas are recommended to have a minimum of 2 percent slope.
Rain barrels and cisterns are storage tanks that capture runoff water from downspouts from a catchment area such as a rooftop. Cisterns are a larger version of rain barrels, with a larger capacity for rainwater collection and storage. Rain barrels and cisterns must both be connected properly to installed rain gutters and downspouts. In order for the rain barrel/cistern to quality as a rainwater capture feature, the property must have existing gutters around the full perimeter of the roof and existing downspouts for adequate water collection. In the case of a partially flat roof, gutters and downspouts must be throughout all pitched areas in order to qualify. Installed rain barrels must meet all local and regional requirements. Newly purchased rain barrels may qualify for an additional rebate. Please visit the rain barrel and cistern page for qualifications. Existing rain barrels and cisterns will qualify provided that they have been properly installed and provide water to the project area.
The Metropolitan Water District of Southern California is a consortium of 26 cities and water districts that provides drinking water to nearly 19 million people in parts of Los Angeles, Orange, San Diego, Riverside, San Bernardino and Ventura counties.