According to the United States Environmental Protection Agency, the term low impact development refers to “systems and practices that use or mimic natural processes that result in the infiltration, evapotranspiration or use of stormwater in order to protect water quality and associated aquatic habitat.” The habitats of natural waterways have many beneficial purposes and should be maintained in their natural state whenever and wherever possible.
Low impact development (LID) is also referred to as green stormwater infrastructure or green stormwater management practices. LID practices reduce the impact that runoff has on lakes, streams, rivers and estuaries by allowing it to filter through vegetation and soil where it is purified naturally. Additionally, LID practices reduce the amount of untreated and contaminated water flowing into local waterways and storm drain systems. The intention of LID practices is to restore and protect the landscape so that new developments have a reduced impact on local and regional water resources.
Many types of LID strategies feature options to be used in urban environments. These options can be used as standalone features, or in combination with other strategies, to reduce the amount of runoff that occurs from urban areas. The intent of LID strategies is to capture runoff, then naturally filter it through soils and vegetation, and allow it to percolate into the ground. LID strategies reduce localized flooding and help to protect waterways from erosion. Additionally, conservation landscapes created using LID strategies typically need less water, pesticides and fertilizer when compared to their traditionally used counterparts. They also generally require reduced use of power equipment in their upkeep, leading to lower fuel costs and energy consumption.
The purpose of low impact development principles is to preserve and recreate natural landscape features and to design appealing and functional site drainage that handles stormwater as a resource instead of a waste product. Implementation of low impact development practices and principles means that stormwater runoff is managed in a way that reduces the impact of development and promotes the natural movement of water within a watershed or ecosystem.
Low-impact, development strategies manage stormwater to obtain the same benefits that would otherwise occur naturally in an undeveloped site. Examples of LID strategies include:
- green roofs
- conservation landscaping
- rain gardens
- bioretention areas
- disconnected downspouts
- water harvesting
- catch basins
- retaining ponds
- stormwater/rainwater art
- infiltration or flow-through planters
- curb cuts
- overflow inlets
- permeable pavement / porous paving
- planting or retaining trees and forests
These and other strategies allow more harmony to exist between urban developments and the original ecological and hydrologic functions of the natural environment.