What is a Sustainability Feature?
The following are eligible methods to meet this participation requirement (every project needs at least 1 sustainability feature):
1. Eligible Tree *NEW*
Trees reduce stormwater runoff by intercepting rainwater through their canopy and trunk. Tree roots also help to take up water and improve soil absorption. View the Eligible Sustainability Feature Trees List of species that qualify as a sustainability feature for the program. The minimum number of trees required is 1 per 10,000 sq ft of project area. Receipts or invoices showing the tree size and tree species are required.
All Eligible Sustainability Feature Trees also qualify for the additional Tree Rebate! Trees must be a minimum size of 15 gallons and must be expected to grow at least 15 feet tall and 10 feet wide at maturity.
2. Rain Garden
A rain garden is a planted depression filled with a loose, permeable soil mix that allows rainwater runoff from impervious urban areas like roofs, driveways, walkways, and parking lots to be absorbed. Plants are distributed throughout the rain garden. Rainwater collects in the soil mix and ponding area and eventually seeps into surrounding soils rather than flowing into storm drains and surface waters. The rain garden must have enough of a side slope that the difference between level ground and the lowest point in the rain garden is visible to the eye.
Rain Gardens Explained in 2 Minutes
Coastal California Rain Gardens – a guide by UC Agriculture and Natural Resources
City of Los Angeles Rainwater Harvesting Program: A Homeowner’s How-to-Guide
Managing the Water on Your Land – Making A Rain Garden – video about the rain garden at the Santa Barbara City College
3. Vegetated Swale
A vegetated swale is a shallow channel with gently sloping sides. The swale must be visibly lower than the surrounding landscape. Plants such as 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.
Back to Basics Permaculture – Ep1: What is a Swale? – 2 minute video about swales
Rain Gardens and Swales by Napa County Resource Conservation District
4. Dry Riverbed
A dry riverbed is an area designed to slow heavy flows of water from rainfall and correct erosion problems. It is made up of a shallow swale and lined with stone substantial enough to withstand a serious downpour. Large rocks are used to slow the speed of storm water and prevent erosion. Plants that can tolerate periodic flooding during rain events, such as juncus patens (common rush), can be installed along the sides of the dry riverbed. The dry riverbed must have enough of a side slope that the difference between level ground and the lowest point in the dry riverbed is visible to the eye. Ideally, a dry riverbed ends at a natural settling area within your landscape where the water can percolate into the soil.
5. Rock Garden
A rock garden is a planted, shallow depression filled with 1–3 inch diameter gravel and/or other rocks. This shallow depression must have enough of a side slope that the difference between level ground and the lowest point in the rock garden is visible to the eye. 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. Flat landscape areas mulched with gravel/rocks would not qualify as a rock garden.
A rock garden is like a rain garden lined with rocks to prevent soil erosion. See this Coastal California Rain Gardens guide by UC Agriculture and Natural Resources.
6. Berm
Berms are mounds of compacted earth with sloping sides that are usually located along a contour on gently sloping sites or between areas of approximately the same elevation. Berms are designed to direct or redirect water to a permeable and retentive area and prevent water from flowing off the property. Berms must be visibly higher in elevation than the surrounding landscape. Berms must be firmly tamped and topped off with mulch to prevent erosion. Plants can be planted along the top of a berm.
When building the berm, you may use an inorganic permeable filling such as gravel or rock. Use dirt to fill in spaces between pieces of rock and to mound the berm in the desired shape. Be sure to tamp down the surface frequently. Firm tamping will help prevent erosion and reduce the chance of the surface slumping. Keep adding fill until the berm is about half the height you desire. At this point, switch to using topsoil, mounding, shaping, and tamping as you go. Then top off the berm with a layer of organic mulch.
Building a Hugellkultur Berm for a California Native Garden – a quick video showing the berm-building process
Landscaping with Berms by UC Master Gardeners
7. Rain Barrel
A rain barrel or cistern is a storage tank that captures runoff water from a rooftop. Cisterns are a larger version of rain barrels. Rain barrels/cisterns must be connected to properly installed rain gutters and downspouts for adequate water collection and meet all local and regional requirements. For the rain barrel/cistern to quality as a sustainability feature, the property must have existing gutters throughout all sloped or pitched roof areas. Existing rain barrels/cisterns satisfy requirement if they have been properly installed and can deliver water to the project area. The minimum size for a rain barrel is 50 gallons. Homemade or DIY rain barrels/cisterns do not qualify.
Rain Barrel Guidelines – see section on Rain Barrel Guidelines for proper installation requirements
Rain Barrels and Cisterns – A guide from Bay Area Stormwater Management Agencies Associations
Rainwater Capture: Rain Barrels and Cisterns – Chapter 14 from California Friendly® Maintenance: Your Field Guide
How large does my Sustainability Feature need to be?
Rain barrels must be 50 gallons or larger. The size of other sustainability features will depend on the size and type of your project as well as the type of feature you choose to install. The chosen sustainability feature should be proportional to the total project area. It should be able to capture a significant amount of rainwater that falls during an average rain event. It must retain or redirect rainwater to reduce runoff onto sidewalks, streets, and other hardscape.