Definition of Low Impact Development

This article is about definitions. The regional context for LID is presented in Urbanization and Climate change.

This guide has been developed as a tool to help developers, consultants, municipalities and landowners understand and implement more sustainable stormwater management planning and design practices in their watersheds. Many jurisdictions have defined the term low impact development. The Sustainable Technologies Evaluation Program uses the following definition:

Low impact development (LID) is a stormwater management strategy that seeks to mitigate the impacts of increased runoff and stormwater pollution by managing runoff as close to its source as possible. To accomplish this, it uses practices that help to preserve or to restore predevelopment hydrological and ecological functions. For preservation, it uses site design strategies to minimize runoff and to protect natural drainage patterns. For restoration, it uses distributed structural practices that filter, detain, retain, infiltrate, evapotranspire and harvest stormwater. LID practices can effectively remove sediment, nutrients, pathogens and metals from runoff, and they reduce the volume and intensity of stormwater flows.

The field of stormwater management has undergone considerable evolution in the last 40 - 50 years, from underground drainage systems for rapid water disposal, to stormwater management ponds, to today’s myriad of near-to-nature practices and technologies. This paradigm shift could be explained by a change of perception about water from a waste to a resource. With this evolution comes the evolution of terminology to describe the latest visions, practices and technologies. There are various terms used in stormwater management related literature across the globe. Some terms differ only in their geography while others differ in their connotation.

Regional terminology use

Terminology	North America	New Zealand	Australia	United Kingdom	Europe
Green Infrastructure (GI)	x
Low Impact Development (LID)	x	x
Water Sensitive Urban Design (WSUD)		x	x	x
Integrated Urban Water Management (IUWM)					x
Best Management Practices (BMPs)	x
Stormwater Control Measures (SCMs)	x
Alternative Measures					x
Source Control	x

LID and Green infrastructure

In many cases, the terms LID and GI are used interchangeably to describe an alternate management approach from the conventional ‘grey’ infrastructure approach. The inconsistent use of these two terms by different agencies and scholars across North America and other parts of the world contributes to the confusion already associated with these relatively new approaches to stormwater management. In this guide we make a distinction between LID and GI on the grounds of geographic and structural (engineered) scales of classification and implementation. Traditionally, the term "infrastructure" connotes a requirement that is necessary to keep an urban center functional, while green space connotes a want, putting it at the bottom of priority lists. The term GI emerged to put more emphasis on green space as a need rather than a want and elevate it within budget priority lists. As such, in addition to traditional water-related infrastructure, GI encompasses non-traditional infrastructure, such as:

• heritage features,
• parklands,
• street trees,
• natural channels, or

in other words any natural(ized) green space.

GI describes a strategically planned and delivered network of natural and semi-natural elements that collectively deliver a wide range of ecosystem, social and economic services to help reduce dependence on grey infrastructure and to address environmental resilience and climate change. The LID approach to stormwater management falls under the overarching umbrella of GI as a semi-natural element.

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Low Impact Development. A stormwater management strategy that seeks to mitigate the impacts of increased urban runoff and stormwater pollution by managing it as close to its source as possible. It comprises a set of site design approaches and small scale stormwater management practices that promote the use of natural systems for infiltration and evapotranspiration, and rainwater harvesting.

A stormwater management strategy that seeks to mitigate the impacts of increased urban runoff and stormwater pollution by managing it as close to its source as possible. It comprises a set of site design approaches and small scale stormwater management practices that promote the use of natural systems for infiltration and evapotranspiration, and rainwater harvesting.

A stormwater management strategy that seeks to mitigate the impacts of increased urban runoff and stormwater pollution by managing it as close to its source as possible. It comprises a set of site design approaches and small scale stormwater management practices that promote the use of natural systems for infiltration and evapotranspiration, and rainwater harvesting.

The portion of water precipitated onto a catchment area, which then flows as surface discharge from the catchment area past a specified point.

Water from rain, snow melt, or irrigation that flows over the land surface.

Relating to the properties, distribution and effects of water on and below the earth’s surface, and in the atmosphere.

Surface runoff from at-grade surfaces, resulting from rain or snowmelt events.

Soil, sand and minerals washed from land into water, usually after rain. They pile up in reservoirs, rivers and harbors, destroying fish-nesting areas and holes of water animals and cloud the water so that needed sunlight might not reach aquatic plans. Careless farming, mining and building activities will expose sediment materials, allowing them to be washed off the land after rainfalls.

Green infrastructure

Low impact development is a stormwater management and land development strategy applied at the parcel and subdivision scale that emphasizes conservation and use of on-site natural features integrated with engineered, small scale hydrologic controls to more closely mimic pre-development hydrologic functions.

A stormwater management strategy that seeks to mitigate the impacts of increased urban runoff and stormwater pollution by managing it as close to its source as possible. It comprises a set of site design approaches and small scale stormwater management practices that promote the use of natural systems for infiltration and evapotranspiration, and rainwater harvesting.

State of the art methods or techniques used to manage the quantity and improve the quality of wet weather flow. BMPs include Source, Conveyance and End-Of-Pipe Controls.

Natural vegetation and vegetative technologies in urban settings such as: urban forests; green roofs; green walls; green spaces; rain gardens; bioswales; community gardens; natural and engineered wetlands and stormwater management ponds; and porous pavement systems. These systems are designed to provide multiple benefits, such as moderate temperatures, clean air and water, and improve aesthetics.

A biological community, including humans and their natural environment.

Natural or artificial means of intercepting and removing surface or subsurface water (usually by gravity).