Sustainable Landscaping Principles for Green Parking

by Buck Abbey, ASLA, Robert Reich School of Landscape Architecture, Louisiana State University

This example of LEED Platinum green parking incorporates permeable pavers, vegetated bioswales and screening with hedges.

Water: One sustainable landscape principal is recognizing storm water as a resource. Water should be harvested, conserved and reused. This principle requires more use of rainwater and less use of potable water for landscape irrigation. Storm water may be taken from parking lot surfaces and cleaned of nonpoint pollutants and pumped from parking lot detentions. Once filtered and cleaned, it may be recycled through irrigation systems or allowed to infiltrate back into the ground. Water from nearby rooftops or even domestic greywater can be harvested.

Air: A second sustainable landscape principal recognizes air as the most important resource on the planet. The goal of this strategy is to reduce air pollution and air-born particulate matter. Since oxygen is generated by vegetation and carbon dioxide, a poison, is removed, plants are an integral part of generating cleaner air. Trees and shrubs can be used in and around parking lots to help purify the air and to sequester carbon dioxide one component of green house gas.

This green parking plan by Martin Moser Louisiana State University specifies a parking lot constructed of permeable concrete pavers. Stormwater from the lot is directed over the pavers. Water not infiltrated is piped via a catch basin to a planted bioswale that slows and cleanses the water. Any overflow from the bioswale is piped into a catch basin to a retention pond. The plan calls for planting of edible fruit trees like orange or pecan trees, plus holly and evergreen trees to help screen the lot from view from the conference center located down the hill, and the driveway entrance.

Soil: A third sustainable landscape principal recognizes productive soil as a resource to be protected and rebuilt in regard to fertility. Washed away and wasted soil often enters fresh water bodies as a pollutant. Vegetation, mulching and proper earth grading will minimize topsoil loss and polluted runoff. Sediment basins or parking lot detentions should be used to trap sediment, solid waste and heavy metal from runoff. Productive topsoil is essential for growing healthy vegetation so blending organic waste back into the ground reduces the waste of biomass. Permeable soil must remain on the site for planting, nurturing and allowing infiltration of rainwater.

Vegetation: A fourth sustainable landscape principal recognizes vegetation as one of the most important elements of nature in the city. Vegetation goes well beyond merely providing beauty and tranquility to urban life. In most of the principles set forth here, vegetation plays a role as an agent of environmental work so therefore it is an essential resource for urban areas. Vegetation in its many forms such as forbes (herbaceous flowering plants), ferns, grasses graminoides, (grasses, sedges, rushes), ground covers, vines, shrubs, trees and flowering perennials plants are important environmental workers. Importantly, plant materials gather the energy of the sun and return nutrients and biomass to the soil. Plants are involved with many of the principles listed here. Of course every landscape architect understands this.

The Santa Monica Civic Center garage has 900 parking spaces spread out over six aboveground stories and 1.5 stories below ground. Fourteen spaces are designated for electric vehicles and have public electrical outlets! A solar photovoltaic array on the roof doubles as a shade structure for vehicles on the top-level. There is also a free bicycle storage area. The design is by Moore Ruble Yudell Architects and Planners of Santa Monica. The building used recycled construction materials with low-VOC paints and finishes. A storm drain water-treatment system helps cleanse runoff; greywater harvesting irrigates the landscaping and is used for onsite facilities.

Wildlife: A fifth sustainable landscape principal recognizes wildlife as an important resource of the city. Not only for the way little creatures entertain us, they also measure the quality of the environment we live within too. Certainly many forms of wildlife will not co-habit the city with mankind, but some species do. They need shelter, food, water and land area to allow them to properly reproduce their species. Preserved habitat in various forms within the city serves this purpose for small animals, birds, insects, and reptiles. Parking lots should be designed as habitat for urban wildlife so they can continue to provide the ecological services wildlife is known to provide. A city without songbirds is not a pleasant place to be.

Food Production: A sixth sustainable landscape principal recognizes food production. This may be food for wildlife or for hungry mankind. Green parking lots should use fruiting plants that will produce edible nuts, berries, drupes, legumes, pomes, tubers, rhizomes, bulbs, corms or stem shoots. Green parking lots can easily feature plants that provide a variety of edible plants. Be aware many plants have toxic parts so care should be taken in specifying which plant to use in public places. Toxic plant rule number one is "always suspect a plant to be toxic, unless known otherwise."

Recycling: A seventh sustainable landscape principal recognizes recycling of used construction materials as an element of sustainable design. Parking lots might be designed to be deconstructed at a future date with all materials being salvaged for reuse. Recycling nonrenewable resources can preserve scarce environmental assets while reducing construction costs. Eliminating waste to the landfill is an important idea of sustainable design realized through recycling. For instance, planted areas in and around green parking lots should be used as disposal sites for biomass, natural mulch and yard trimmings. Natural stone once used may be taken up and used again. Reusable precast pavers reduce the huge amount of carbon-based energy used in the production of cement. It is interesting how relic pieces of culture can become elements of art in a designed parking lot.

Regional Design: And finally, an eighth sustainable landscape principal, the last but most important element of sustainable design directed toward green parking lots, is a regional-based design strategy. Regional design takes an earth systems approach to the design, construction and maintenance of landscapes. Earth systems of water, sunlight, soils, climate, vegetation, urban forests, natural habitat preservation and natural recycling ought to be incorporated into any landscape design for parking. Since any project in any state is in fact built into a functioning ecosystem, it is important for that project to fit in with the wider regional system of climate, soils, sun, rainfall and vegetation. Earth friendly landscape design will utilize native plants and native landscape character. Invasive plants should not be used and exotics should be minimized. The site designer's first concern should be in preserving regional habitat and regional forms. The second concern should be rebuilding native habitat in regard to water, soil and vegetation. And finally, the third concern should be capturing regional character in the design of housing, industry, commerce and open space systems. Sense of place results when all regional factors are respected and included in the design.

Regional character is derived from each state's various landscape features. In Louisiana these would be design concepts based upon the ecology of prairies, deltas, savannahs, beaches, ridges, cheni????(R)??ures (a Cajun word from the French "ch?'?N?????????ne" meaning oak, describing groves of coastal moss-cloaked oaks bent by the Gulf of Mexico winds in Vermilion and Cameron parishes), terrace faces and upland and wetland forests. These ecologies can all be utilized as regional concepts for the design of green parking lots as well as site open spaces. Regional based landscape design will eliminate the use of invasive species that tend to push native plants out of their way. Regional based design will use plant material that supports the native wildlife population with fruits, drupes and berries.

As can be seen, the above argument based upon sustainable design principles makes a strong case for changing the way we design parking lots. It is time to remove the sea of sterile asphalt and idle concrete that is the city center and replace it with a green open space system that can do environmental work while parking cars. Parking lots designed to be green can do important environmental work while storing cars and providing additional green space that people can use for various activities other than driving and parking cars.