Monday, October 7, 2013

Sustainable Landscaping with Passive Stormwater Management in a Residential Garden: Three Case Studies

Discussed and pictured here are three small residential gardens in dry climates that receive infrequent but sometimes quite heavy rainfall and accumulation of stormwater. Each of these gardens meets multiple needs and receives intensive use, while passively accepting rain and encouraging infiltration, solving problems and creating opportunities within significantly different budgets.

Case Study 1:  This contemporary courtyard garden located in a mid-century development on coastal floodplain in Torrance, CA was designed for dog-loving, active grandparents of teens and a toddler, who are also engaged as artisan/art student and entrepreneur. They desired relief from battling seasonal flooding, a place for dogs to play, equipment storage, view-screening and privacy for relaxation on weekends, and an elegant entertainment space all within a mere 1,200 square feet. Patio and walkway paving consists of pervious concrete pavers bordered by large-scale Narrow Modular Pavers, all manufactured by Stepstone, Inc. a company located in nearby Gardena, CA. This surface is stable under feet or wheels.

Lawn was reduced to little "area rugs", totaling a mere 182 square feet. The lawn material, a hybrid of Seashore Paspalum (Paspalum vaginatum 'Aloha') developed by and trademarked to Environmental Turf Inc., was selected for its lower water use, ability to withstand inundation of water, deep color, trim appearance, and ability to repair itself from pet soiling/spots and active use. Lawn is professionally maintained using dedicated, hand-powered mower kept on site.

Pavers are laid over a base/sub-base of aggregate rock material kept separate from native soil by a layer of geotextile. This system allows stormwater to filter through pore spaces of pavers and aggregate material, gradually infiltrating the soil beneath.

In this case, significant ponding following rain events was eliminated, and the clients now have an outdoor entertainment area they can use year round. As is probably apparent from these images, the type of landscaping in Case Study 1 requires professional installation as well as professional design.

In-progress photo shows within the walkway -- lower center of photograph -- the compacted base layer within mortar-set narrow modular pavers (also by Stepstone) prior to installation of pervious pavers. Mortared pavers also form the mow strip around lawn sections.

Close-up of pervious paver (Stepstone, Inc.) Clients favored this aesthetic for its rugged texture as well as the way it contrasts with the smooth-sandblasted surface of mortared pavers shown alongside. This combination was not only a great solution to a significant functional problem in their garden, it very strongly states their industrial modern preferences.

"King" and "Queen" of the garden, Jasper and Juba, checking out their new digs.

Case Study 2: On the other end of the spectrum in aesthetics and budget is this simple "woodland cottage" garden. Located in Woodland Hills, CA on foothill drainage to north slope of the Santa Monica mountains in a quaint neighborhood of artists, artisans, and professionals this garden features a pathway surfaced in decomposed granite and steps formed with recycled lumber. Soil sculpting on the gradual slope mitigates run-off in both wet and dry (irrigation) weather. The steps and pathway evoke a mountain stream flowing down a gradual course, ending with large scale, round exposed aggregate pavers zig-zagging to form a stylized "alluvial wash" across the parkway.

The type of landscaping in Case Study 2 benefitted from professional installation as well as professional design. However, for homeowners willing and able to do heavy physical work and who are interested to learn aesthetic placement of plants, rocks and other materials, proper plant spacing, and plant selection to fit site conditions, it may well be within reach to "DIY". In this case, and owing to its urban, streetside location, drip irrigation, two stations only, was installed to be operated by automatic low-flow valves of brass construction and a secured and programmed, wired irrigation clock. Alternatively, irrigation system could be connected to hose-end adapters and set to run by battery operated timers. Or, with enough time on one's hands, irrigation could be done by hand only.

Path and parkway detail.

In progress image showing gentle soil sculpting and layout of in-line drip tubing to be disguised under mulch.

Generous layer of shredded mulch spread over drip tubing and after planting acts as wicking material to further improve soil retention and stormwater infiltration.

Case Study 3: This rear garden in an area of cold air drain at the base of north-facing foothills to the Santa Monica Mountains in Woodland Hills, CA utilizes every square foot for growing food, passive rain collection, testing plant material and landscape techniques, propagating plants, designing and creating container gardens, and entertaining. Compacted but un-stabilized decomposed granite over landscape cloth provides a porous surface for pathways and rain garden beyond. This surface is reasonably stable in dry weather. However, foot depressions and ruts from wheels can occur in wet weather.

Flagstone "landings" reduce migration of loose material to concrete patio at right in photo. Raised beds help amended soil within to remain loose and well-draining, while concrete-walled planters increase soil temperature for year round fruit and vegetable gardening.

The garden shown in Case Study 3 was professionally designed. The type of landscaping used benefitted from a combination of professional installation along with much of the work being done by the designer/owner (myself). While essentially complete, as with any "gardener's garden" it will always remain a work-in-progress. Citrus trees (top left) are mature. The balance is recent planting. What is shown here is the culmination of my experimentation, hands-on self-education in sustainable landscape design, and many project phases, spanning a 6-year period. Some of the features may be within reach of an ambitious "DIY" homeowner. However, it would take a fair amount of study and much more than a few weekends of heavy work to install!

Rain garden with planting selected for adaptation to both drought and saturated soil conditions, features volcanic lava rock reclaimed from a neighbor's landscape demolition.

Herb garden in Spring:

Herb garden in early Autumn:

This section of the herb garden with young dwarf citrus borders a patio along the west side of my home. It is mostly out of frame in the overview shot of Case Study 3. Here it is shown in closer view.

Herb garden -- foreground right -- with rain garden from center toward rear. (This photo was shot through a south-facing window.) In the background to right is my work "pavilion" with potting table, garden valve and grounded, covered electric outlet. Lattice above fence boards screen out unwanted neighboring views. The raised bed to the right center is where I am experimenting with a collection of succulent plants resembling coral and other undersea creatures. It will be the subject of a later post. Stay tuned!

Thank you for viewing my work. I welcome your questions and comments. For professional garden design services and consultations, I can be reached via my website:

All designs and photos: Janis Hatlestad, Better Earth Garden Design (