Planting to the conditions - a rain garden in California

Persistent drought, excessive heat, and very high fire risk are the new normal in California’s scenic hillside communities. And water sustainability collective, Urban Water Group, has made a business out of devising creative solutions for more resilient landscapes that enhance and support that environment.

One such project is a hilltop home in Brentwood’s Mandeville Canyon, which has been landscaped with water-saving plants and installed with rain storage tanks. It won the American Society of Landscape Architects’ national Quality of Life Award of Merit in 2018 in the “Projects over $300,000” category.

Simply designing an arid, desert landscape isn’t enough, says the Urban Water Group. The landscape must convey a sense of place, be aesthetically pleasing, have shade and shelter, reduce ambient temperatures, provide habitat and food for wildlife, and most importantly give inspiration and a sense of well-being. Photo credit: Saxon Holt

Urban Water Group says prior to renovation,  the two-acre landscape was comprised mostly of thirsty exotic plants, over 650 square metres of unused lawn, many flammable palm trees, and invasive species such as Brazilian Pepper. The project scope included replacing 2,322 square metres of existing landscaping with California climate-appropriate plantings, native to California, South Africa, the Mediterranean, and Australia.

Stormwater is captured from the roof, filtered and stored in ten underground plastic tanks of 6,764 litres each, plus one above-ground 18,927 litre tank which is housed in a Spanish-tiled water-house building that matches the architecture of the residence. The total stormwater capture capacity is 87, 065 litres.

Even in the driest times, the Southern California climate can sustain a rich and diverse landscape with few resources if the plant palette is climate-appropriate, and rainwater is captured and stored. Photo credit: Saxon Holt

The automated water management system maximises this storage capacity by deep watering shrubs and trees in advance of storms during the winter season when they need it most. Overall, water consumption will be decreased by 80% once the new plantings are established, the designers say.

Several thousand new plants were organised into a hierarchy of plant communities: a native Carex praegracilis lawn adjacent to the pool and terrace, mixed native meadows in the middle grounds of canyon vistas, native oak woodland on the perimeter slopes, succulent gardens visible from the kitchen and dining rooms, rain gardens, and an edible garden consisting of raised beds, wash station, a sitting area, and perimeter fencing.

Urban Water Group strongly believe that technology can enable drought resilient landscapes to become self-sustaining. Photo credit: Saxon Holt

The rain garden renovation was nearly three years in the making, from planning and consents to 13 months of construction. It’s called a rain garden because rainwater is diverted into tanks with a series of rain gutters and pipes. Then a water pump sends the water back out as needed for drip irrigation. That irrigation system, and the fullness of each tank, is monitored by a cellphone app.

Urban Water Group president, Marilee Kuhlmann, told the Los Angeles Times the tanks got plenty of use during February’s record rainfall. But water was dispersed slowly through the drip system so it had a chance to soak into the ground rather than run off down the hill.

Because Urban Water Group automation systems have designed and integrated the rainwater harvesting and irrigation systems, they require little, if any, interaction with the client. Photo credit: Saxon Holt

Small stone ponds are set around the property, just two centimetres deep, to collect drinking water for pollinators and other critters who wander the hills around the property. Kuhlmann installed little lights by each water station so anyone sitting outside a night can see what kind of wildlife is sipping at the ponds.