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Low Impact Development (LID)

What is LID?

Low Impact Development (LID) -is a basic principle that makes development and specifically storm water controls mock the natural environment. LID comprises a set of approaches and practices that are designed to reduce runoff of water and pollutants from the site at which they are generated. The concepts of infiltration, evapotranspiration, and reuse of rainwater are key to a successful LID development strategy.

What are some Common LID practices?

There are many different LID designs that can impact water quality. The most common in use today are bioretention facilities, rain gardens, vegetated rooftops, rain barrels, bioswales, and permeable pavements.

 Bioretention facility

Bioretention is used to detain runoff in a surface or underground reservoir, which then filters the water through plant roots and biologically active soil mixes, and then infiltrates it into the ground. A pipe is constructed to allow excess water from the system to empty into a storm drain or some other type of surface drainage. Bioretention facilities can be BioRetention[1].jpgused in a variety of different areas due to the man different shapes that can be constructed. The most common shape is the linear swale which can convey high flows while allowing percolation of normal low flow rain events. Bioretention facilities also have the benefit of being constructed as an in-ground or above-ground planter box system, with an open bottom to allow for infiltration to the native soil or if soils are not very conducive to infiltration then a flow-through planter box can be used.

Here are some facts about bioretention facilities that can be useful:

Best Uses 

  • Commercial areas
  • Residential Subdivisions
  • Industrial Developments
  • Roadways
  • Parking Lots
  • Fit in setbacks, medians, or other landscaped areas

Advantages

  • Can be any shape
  • Low maintenance
  • Can be landscaped

Limitations

  • Require 4% of tributary impervious square footage
  • Typically requires 3-4 feet of head

Click Here for a downloadable cross section.

Rain Gardens

Rain Gardens are planted depressions that allow storm water from impervious areas such as roofs, driveways, walkways, parking lots, or compacted lawns to be absorbed back into the natural soil. The two main types of rain gardens used are self-contained and under-drained. Both can be used to improve storm water quality, reduce runoff volumes, and generate infiltration. Rain gardens are in most cases designed to handle lower volumes of runoff and a good rule of thumb to uraingarden04[1].jpgse is 1" in a four hour period. There are some important factors to be considered when constructing a rain garden these include: 1) use of native plants that are adapted to the soil types 2) Location near good runoff area 3) good soil conditions.

Here are some facts about rain gardens that can be useful:

Best Uses

  • Residential Subdivisions
  • Industrial Developments with low flow areas
  • Commercial areas with low flow areas
  • Behind Roadways
  • Parking Lots
  • Fit in setbacks, medians, or other landscaped areas

Advantages

  • Can be any shape
  • Can be landscaped
  • Provide aesthetic beauty
  • Can be tailored by the owner to show individual tastes

Limitations

  • Typically used in low flow areas
  • Only certain plant types should be used due to submersion by flow events, and periods of drought

Click Here for more information on Rain Gardens.

Vegetated Rooftops (Green Roofs)

Green roofs are when a conventional rooftop made out of asphalt or metal roofing is replaced by some form of planting or other natural application. Green roofs absorb, store, and later evapotranspire rain events decreasing the green_roof_250x187[1].jpgvolume of rainwater placed into the storm system. Green roofs have the potential to remove nitrogen and phosphorous due to soil microbial processes and plant uptake. Green Roof technology is geared more towards commercial and industrial development; however some residential applications can be found. 

Here are some facts about vegetated roofs that can be useful:

Best Uses
  • Industrial Developments
  • Commercial areas
  • Parking Decks
Advantages
  • Can provide a nice employee area
  • Can be landscaped
  • Provides aesthetic beauty
Limitations
  • Typically still costly to implement
  • Only certain plant types can be used to due to heat concerns and periods of drought

There are several places to find green roof information including EPA or locally at UAB.

Rain Barrels

A rain barrel is a system that is used to collect and reuse storm water from your roof that would otherwise be diverted directly into the storm drain. Usually this relatively inexpensive system is comprised of a 55 gallon drum, green-rain-barrel[1].jpga vinyl hose, PVC couplings, a screen grate to keep debris and insects out, and other off-the-shelf items. This system then is placed under the down spout and can collect "soft water" or water with no chlorine, lime, or calcium which is ideal for gardens, flower pots, car washing, or other cleaning. It is estimated these devices can save a homeowner around 1,300 gallons of water during the summer months.

Here are some facts about rain barrels that can be useful:

Best Uses

  • Residential Subdivisions
  • Industrial Developments
  • Commercial areas
Advantages
  • Can reuse existing roof water
  • Can reduce water bill
Limitations
  • There are few limitations to these devices and would be very rare

Click Here for more information from EPA on rain barrels.

Bioswales

A bioswale or vegetated swale is a ditch or drainage feature that is filled with vegetation, compost, or riprap. The purpose of a bioswale is to maximize the time water spends in the swale to remove additional pollutants and silt. Bioswales are very easily integrated into parking lots, road medians, and parallel to roadways to infiltrate storm water. Existing ditches and piping structures can also be retrofitted with bioswales to increase pollutant and silt removal.  The use of swales can reduce pollutant and silt levels dramatically in low flow rain events.

Here are some facts about bioswales that can be useful:

Best Uses
  • Residential Subdivisions
  • Industrial Developments
  • Commercial areas
  • Road Medians
  • Parking Lots
  • Parallel to Roadways
Advantages
  • Treat water along the ditch instead of end of pipe solution
  • Reduce total volume of runoff
  • Increase infiltration 
  • Can be landscaped
  • Improves conveyance system
Limitations
  • The limitations for this feature or more based on engineering requirements and soil conditions

Click Here for more information on bioswales.

Permeable Pavements

Permeable pavements consists of manufactured concrete units that reduce storm water runoff volume, rate, and pollutants.  The interlocking pavers allow water to infiltrate through small size aggregate that is placed in between the joints in the pavement. The water then enters a crushed stone aggregate  bedding layer and base that supports the pavers while allowing water storage and runoff treatment. close-up_splashpad_park_oakland[1].jpg

Best Uses

  • Residential Subdivisions
  • Industrial Developments
  • Commercial areas
  • Road Medians
  • Parking Lots
Advantages
  • Allows for water storage so may remove need for curb and gutter
  • Reduce total volume of runoff
  • Increase infiltration 
  • Aesthetic appeal
Limitations
  • Can not be installed on travel ways or other areas where traffic volume will be high

Click Here for more on pervious pavement.

 

Interested in More Information about LID

The links below will give good guidance and materials on LID development:

EPA National Menu of Storm Water Best Management Practices

EPA Low Impact Development (LID)

Auburn Extension Services LID Development

Low Impact Development Center