What are the key principles of low-impact development and how can they be applied in different contexts?

1 Site assessment

Before designing a LID project, you need to conduct a site assessment to understand the existing conditions, opportunities, and constraints of the site. A site assessment should include a topographic survey, a soil analysis, a vegetation inventory, a hydrologic study, and a stakeholder consultation. The site assessment will help you identify the best locations and methods for managing stormwater runoff, preserving natural features, and enhancing the site's functions and values.

2 Minimize imperviousness

One of the main goals of LID is to minimize the amount of impervious surfaces, such as roads, parking lots, roofs, and sidewalks, that prevent water from infiltrating into the ground. Impervious surfaces increase the volume and velocity of stormwater runoff, which can cause erosion, flooding, and pollution. To minimize imperviousness, you can use techniques such as reducing the width and length of roads and driveways, using permeable paving materials, clustering buildings and lots, and incorporating green roofs and walls.

3 Maximize infiltration

Another key principle of LID is to maximize the infiltration of stormwater runoff into the ground, where it can replenish groundwater, reduce surface runoff, and filter pollutants. To maximize infiltration, you can use techniques such as rain gardens, bioswales, infiltration trenches, dry wells, and porous pavements. These techniques create shallow depressions or channels that collect and infiltrate runoff from adjacent impervious areas. They are often planted with native vegetation that can tolerate wet and dry conditions, and provide habitat and aesthetic benefits.

4 Harvest and reuse water

A third principle of LID is to harvest and reuse water that is not infiltrated into the ground, such as rainwater, graywater, and condensate. Harvesting and reusing water can reduce the demand for potable water, lower utility bills, and conserve water resources. To harvest and reuse water, you can use techniques such as rain barrels, cisterns, rain chains, and irrigation systems. These techniques collect and store water from roofs, gutters, downspouts, and air conditioners, and use it for non-potable purposes, such as watering plants, flushing toilets, and washing cars.

5 Maintain vegetation

A fourth principle of LID is to maintain and enhance the vegetation cover of a site, especially native and drought-tolerant plants. Vegetation can reduce runoff, erosion, and heat island effects, by intercepting rainfall, stabilizing soil, and providing shade and evapotranspiration. Vegetation can also improve air quality, biodiversity, and aesthetics, by absorbing carbon dioxide, providing habitat and food for wildlife, and creating visual interest and diversity. To maintain vegetation, you can use techniques such as preserving existing trees and shrubs, planting new ones, using mulch and compost, and avoiding invasive species.

6 Educate and engage users

A final principle of LID is to educate and engage the users of a site, such as residents, visitors, employees, and managers, about the benefits and functions of LID. Educating and engaging users can increase their awareness, appreciation, and participation in LID, and foster a sense of stewardship and responsibility for the site. To educate and engage users, you can use techniques such as signage, brochures, workshops, tours, and interactive features, that explain how LID works, why it is important, and how to maintain it.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?