Flow control

On a watershed scale, factors contributing to flooding include the total volume of stormwater, the peak flow and the duration of peak flow. All low impact development facilities can help to prevent flooding by providing watershed distributed stormwater storage, and most feature some form of peak flow control device at the outflow or overflow. The limiting factors in the contribution that a system can make to flood control include the total storage and the rate at which the system can be emptied between events. Flow is controlled by:

• the properties of the filter media. See flow through media,
• the exfiltration of water from the practice through an underdrain. See flow through perforated pipe,
• one or more orifices,
• weirs, or
• proprietary low flow devices.

Where either device may be installed, a weir is recommended over an orifice, as they are less susceptible to blockage under freezing conditions.

Weirs

https://books.google.ca/books?id=fTQWDQAAQBAJ&dq=Jefferies+Scotland+Swales+2004&source=gbs_navlinks_s

Proprietary links

In our effort to make this guide as functional as possible, we have decided to include proprietary systems and links to manufacturers websites.
Inclusion of such links does not constitute endorsement by the Sustainable Technologies Evaluation Program.
Lists are ordered alphabetically; link updates are welcomed using the form below.

• Echelon vortex valves
• Hydrobrakes

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

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 engineered soil component of bioretention cell or dry swale designs, typically with a high rate of infiltration and designed to retain contaminants through filtration and adsorption to particles.

The downward movement of water through the soil, the downward flow of runoff from the bottom of an infiltration BMP into the soil.

Loss of water from a drainage system as a result of percolation or absorption into the surrounding medium (e.g., the infiltration of water into the native soil through a perforated pipe wall as it is conveyed).