Low Impact Development (LID) is a comprehensive land planning and engineering approach to stormwater management that seeks to preserve and replicate the natural hydrologic behavior of a site by managing runoff at its source using decentralized, small-scale practices. The fundamental principle of LID is to minimize the impacts of land development on watershed hydrology by maintaining pre-development patterns of infiltration, evapotranspiration, and surface runoff.
In contrast to conventional stormwater systems, which typically collect and convey runoff rapidly through curbs, pipes, and centralized detention facilities, LID emphasizes distributed controls that are integrated throughout a site. These controls are designed to capture, store, infiltrate, filter, and slowly release stormwater close to where it is generated, thereby reducing runoff volume, peak discharge rates, and pollutant transport.
LID begins with site planning and design strategies that reduce impervious cover and preserve natural features. This includes minimizing land disturbance, protecting existing vegetation and soils, maintaining natural drainage patterns, clustering development, and reducing roadway widths where feasible. By preserving these natural elements, LID reduces the need for structural stormwater controls.
Where structural practices are required, LID employs a variety of techniques that utilize soil and vegetation to manage stormwater. These include bioretention systems such as rain gardens, permeable pavements, infiltration trenches, vegetated swales, green roofs, and rainwater harvesting systems. These practices promote infiltration and evapotranspiration while also providing filtration and biological treatment of pollutants.
A key objective of LID is volume reduction, meaning that stormwater is retained and treated on-site rather than being discharged downstream. This helps to reduce flooding, prevent stream channel erosion, and protect aquatic ecosystems. It also supports groundwater recharge, which is essential for maintaining baseflow in streams and sustaining water supplies.
LID is closely associated with the concept of green infrastructure, and the two terms are often used interchangeably, although LID more specifically refers to the design philosophy and planning framework, while green infrastructure refers to the individual practices and systems used to implement that philosophy.
From a regulatory standpoint, LID has become a cornerstone of modern stormwater management requirements, particularly in urban and suburban development. Many jurisdictions require or strongly encourage LID practices as part of site design to meet water quality and quantity standards.
Low Impact Development represents a shift from traditional, conveyance-based stormwater management toward a more sustainable, site-sensitive approach that integrates hydrology, ecology, and land use planning to reduce environmental impacts and improve watershed health.