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Welcome to the Low Impact Development Stormwater Management Practice Planning and Design Guide

This is a new kind of guideline document; intended to improve your experience:

• Recommendations have been pared down into tight, actionable articles. Expect to find a lot of data rich tables, lists and tools, rather than paragraphs of background material.
• The wiki format invites you to comment at the bottom of every page. If you believe the content to be incorrect or out of date, please let us know using ‘Help improve this page’ and we’ll make a rapid response. Minor changes will be made as soon as possible, significant changes may be delayed pending review by a panel of STEP members. Note that the comments you leave will appear in the ‘VIEW FEEDBACK’ link on the left.
• When you need to reference an article to support your decisions and designs, don’t forget to include the date and time at which you took the advice. Don’t worry if the content has changed since you used it, the website maintains a detailed history of the time and every content change made, see ‘VIEW HISTORY’ at the top.

This is a relatively young, living document; conceived earlier in 2017. You will find that we’re missing information, but we are growing quickly. An important part of this process is to know what you need, so please submit your feedback! Finally, if you are a subject matter expert and wish to contribute a new article, we would love to hear from you. lid.pd.guide@gmail.com

The Low Impact Development Stormwater Management Planning and Design Guide (LID SWM Guide) is currently being developed by Credit Valley Conservation (CVC), Grand River Conservation Authority (GRCA), Lake Simcoe Region Conservation Authority (LSRCA), and Toronto and Region Conservation Authority (TRCA) 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. For this document, the following definition, adapted from the United States Environmental Protection Agency (U.S. EPA, 2007) will be used:

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. LID comprises a set of site design strategies that minimize runoff and distributed, small scale structural practices that mimic natural or predevelopment hydrology through the processes of infiltration, evapotranspiration, harvesting, filtration and detention of stormwater. These practices can effectively remove nutrients, pathogens and metals from runoff, and they reduce the volume and intensity of stormwater flows.

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.

Sustainable Technologies Evaluation Program

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.

Stormwater Management

Credit Valley Conservation

Lake Simcoe Region Conservation Authority

Toronto and Region Conservation Authority

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.

The slow movement of water into or through a soil or drainage system.

Penetration of water through the ground surface.

The quantity of water transpired (given off). Retained in plant tissues, and evaporated from plant tissues and surrounding soil surfaces. Quantitatively it is usually expressed in terms of depth of water per unit area during a specified period. e.g. mm/day

The combined loss of water to the atmosphere from land and water surfaces by evaporation and from plants by transpiration.

The technique of removing pollutants from runoff as it infiltrates through the soil.

The temporary storage of stormwater to control discharge rates, and allow for sedimentation.

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