Low Impact Development (LID) in Landscape Design

Low Impact Development (LID) is a design concept that stresses the role of rainwater and local landforms in creating a healthy landscape. Sustainable landscaping creates beauty with the lowest possible impact on the natural environment and LID adds a strong emphasis on rainwater retention––preserving and enhancing the natural flow of water. Using LID in your design helps end the destructive water-wasteful practices humans have employed in the past.

There are several reasons humans have developed water wasting practices, the main one being fear of floods. Another practice––overuse––developed from using the most rainy years as an indicator of how much rain we can expect each year. Building cities out of concrete and asphalt has caused unforeseen problems, and sucking up groundwater to use for agriculture exacerbates damage from drought. These have especially been problems in the southwestern United States.

Fear of Floods––Due to human fears about floods, city planners developed extensive storm drainage systems that took rainwater straight to the sea. But recent droughts caused a reconsideration of such systems. Storm drain systems are now being recognized as a way of throwing away rainwater, before the earth can store it and utilize it to support life.

Overuse––When humans first inhabit a new area they note weather patterns, and often assume those patterns will continue over the years. If they happen to arrive on rainy years and then plant water-hungry crops, expecting the same amount of rainfall in the future, they could be in for a nasty surprise. This happened in California, where groundwater rights were given out during wet years that exceeded the amount of water available in regular and dry years.

Concrete Cities––Earth's rainwater storage system includes underground basins called "aquifers," which are filled by rain sinking down through the earth. Unfortunately, in addition to whisking rain from rivers to storm drains, humans have blocked the earth's replenishment by covering the ground with concrete, asphalt, and buildings, so rain can't sink down. These cities also absorb and reflect heat back from the sun, causing heat waves that prevent raindrops from descending to the earth.

LID design principles reduce such problems from the beginning of the design process, by especially emphasizing water retention as a major part of sustainability. The principles can be applied to almost any kind of design––to buildings, landscapes, storm drain systems, parks, transportation routes, or city streets.

The key to designing a sustainable landscape is to pay attention to the role of water availability and flow, noting what normally accrues in a particular location and seeing where it goes. Then you incorporate that flow as an inherent part of your design.

Bioswales, pervious concrete, green roofs, retention basins, and rain barrels are all tools related to the use and sustainment of water in an area. They are all resources that can be used in designing sustainable landscapes. Below are a couple of projects that utilized LID design principles in their construction.

The Arizona Landscape Contractors Association offers annual awards to designers who design creative landscapes that harmonize well with the environment.

One of their recent winners, Enchanted Garden Landscapers (EGL), designed an exceptionally attractive water-saving landscape in the Arizona desert, based on the xeriscape concept (see photo).

Xeriscape is a term used to describe a landscape especially designed around a minimal use of water (but it's also patented, hence is not as widely used now as it was). Below the photo of the winning landscape is another, similar project designed by EGL.

Here is an example of a LID community built in Brevard County, Florida. The semi-tropical area includes 1,000 acres of upland (high and hilly) and wetland preserves, with over 400 acres set aside to be enhanced specifically for the Florida scrub jay and gopher tortoise.They designed the housing development around keeping and improving habitat for the jay, paying attention to wildlife corridors, as well, so that animals could continue to migrate to and from feeding areas.

The developers built the community with the smallest possible destructive impact on the environment, preserving it for the exploration and pleasure of residents, including creating small lakes as an integral part of the wetlands.

An environment, planted or natural, should be able to sustain itself over time with a minimal amount of care. Sun, water, and soil are some of the environmental factors that affect what will grow in a particular area. The shape of the land and the insects and other wildlife in the area also affect what will grow and define what will be supported by it.

Different environments provide different sets of characteristics that can help or hurt a designer, depending on what the aim is. They will still need to be worked with, so aiming for sustainability encourages a designer to recognize, use, and even enhance whatever those characteristics are.

With a site that is located in a valley, water will flow downhill when it rains, which provides the potential to create a retention basin, natural lake, a rain garden, or at least to collect water in a cistern. With a site located in the foothills, you can expect some soil runoff as well. A retaining wall will hold it back, creating a bank that you can then plant.

The overall look of an environment is a characteristic that can be brought into your own home, using local rocks and cultivars or native plant hybrids. These tools will help your landscape be sustainable, blend with the environment, and still look residential.

Note that a 1,000 acre golf course built in the middle of the Nevada desert would NOT be sustainable, whether or not it was labeled as such.

In built-out areas like cities, existing buildings are considered part of the environment you will need to work with. The aim there would be to restore whatever could be restored to mimic a more natural eco-system.

For example, the City of Los Angeles has developed plans to reconstruct the Los Angeles storm drain into a real river. There is strong support among developers and the citizenry alike for such a project, and the city recently received approval from the federal government to carry it out.

Many cities (such as Chicago) are building roof gardens on the tops of city buildings which are, in a sense, like the tops of mountains. Water pouring off a roof during a rainstorm mimics waterfalls flowing down a mountainside. It can be captured in pools to sink down slowly into the aquifer, or in barrels or buried cisterns to be saved for later use in a garden or park area. Low-lying areas in cities can sport rain gardens, which can be set up to mimic natural swamps.

When you design and plant for the native environment, you take advantage of the way local plants are naturally supported throughout the seasons. You save energy, work, and money in the long run by building a sustainable landscape with a year-round "shelf life," as opposed to replenishing plants every time the weather or water availability changes.

And just as nature modifies and shapes itself differently over time, so a new landscape doesn't have to be built overnight.

There will be no need anymore to spend money to go up into the mountains to experience the real natural environment, when you have a built one right where you are. Using sustainable landscape design, you will have created a new vacation spot right at home. You will be attracting back wildlife and birds that used to live there, making it feel "wild" once again. You can take your time, enjoy the process of creation, and when you need a break go watch a movie instead of leaving town . . . unless you like to hike.