Infiltration, Filtration, Detention, and Retention Systems

What is it?

Infiltration, filtration, detention, and retention systems are stormwater management strategies used to capture and control the release of storm water runoff and/or improve runoff water quality.

  • Infiltration systems intercept and store stormwater runoff for slow infiltration into the ground
  • Filtration systems use filtering mediums (like sand, gravel, compost, or biological systems) to remove pollutants from stormwater to filter runoff
  • Detention systems capture storm water runoff in lined ponds for storage and slowly release the water to be treated in sewer systems
  • Retention systems capture storm water runoff and permanently hold the water through a system of pipes or tanks. Retention systems improve water quality through filters and other mechanisms

Conservation Benefits

  • Promotes water infiltration
  • Reduces amount of sediment entering streams after storm events
  • Reduces chemical and nutrient runoff into streams

What does it include?

Infiltration systems: intercept and store stormwater runoff for slow infiltration into the ground. Systems can include ponds, trenches, or ditches and increasing porous areas (like parking lots, sidewalks, and roads).

Filtration systems: uses filtering mediums (like sand, gravel, compost, or biological systems) to remove pollutants from stormwater to filter runoff. Filtration systems are typically used in conjunction with infiltration, detention, or retention systems since the primary function of filtration systems is to remove sediment or pollutants and not infiltration or storage.

Detention systems: capture storm water runoff in lined ponds or pipes for storage and slowly release the water into streams or to be treated in sewer systems. These systems decrease the velocity of runoff entering streams which protects riparian and instream habitat and reduces flash flooding. Some removal of sediment and pollutants will occur in detention systems.

Retention systems: capture storm water runoff and permanently hold the water through a system of ponds, pipes, or tanks. Retention systems improve water quality through filters and other mechanisms and can provide urban wildlife habitat.

 

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