Stormwater Runoff and Low Impact Development


Image courtesy NCDENR

Stormwater runoff is excess water from rain or snowmelt events that does not permeate into the ground. Stormwater runoff is a natural part of the hydrologic cycle.  How much water and the timing of when it reaches local bodies of water depends on the watershed area, the slope of the land, soil types, and the condition of the surface.  Development can alter the hydrology of our local watersheds and increase the chances of flooding and degrade water quality by preventing rainfall and snowmelt from absorbing into the ground.  

Fortunately there are many options to prevent problems associated with excess runoff.  Low Impact Development (LID) is an innovative stormwater management approach with a basic principle that is modeled after nature: manage rainfall at the source using uniformly distributed decentralized micro-scale controls.  LID's goal is to mimic a site's predevelopment hydrology by using techniques that infiltrate, filter, store, evaporate, and detain runoff close to its source.  Techniques are based on the premise that stormwater management should not be seen as stormwater disposal.  Instead of conveying and managing / treating stormwater in large, costly end of pipe facilities located at the bottom of drainage areas, LID addresses stormwater through small, cost-effective landscape features located at the lot level.  These landscape features are the building blocks of LID.  Source - Urban Design Tools - www.lid-stormwater.net.

LID focuses on using the excess runoff from stormwater as a resource, not a problem.  It is flexible and has many benefits

  • Improves curb appeal
  • Increases home value.
  • Decreases infrastructure costs.
  • Protects water quality.
  • Helps to replenish aquifers. 
  • Provides wildlife habitat.

Retaining excess runoff with rain gardens or other types of bio retention designs is an attractive option for many landowners.  Rain gardens improve landscape aethestics and increase the value of your home.  For more detailed information on rain garden construction see the links below.  Rain gardens should be designed according to the amount of surface area that will be drained into it, the slope of the surrounding area, climate factors and local soils.  Plant the rain garden with native plants that will natural thrive on your landscape. Bio retention designs are very flexible for many different types of landscapes.  These designs can also be used to absorb runoff from roads.  They provide a space for excess runoff to absorb into the ground rather than flowing to the local waterway. Images  below courtesy NRCS. Rain Garden

Bio Retention

Rain Barrels are another good option for landowners wishing to reduce runoff from their property and conserve water.  Rain barrels collect the runoff from the roof and funnel it into a barrel.  The water can later be used to for gardening or your landscaping.  The barrel needs to a have a screen, an overflow valve and should be childproof.  Images below courtesy www.howtobuildarainbarrel.com and www.uwsp.com

Rain Barrel  Rain Barrel

Controlling runoff from construction sites is an important aspect of water protection.  The Montana Water Center has a valuable resource tool for understanding the methods to controlling stormwater runoff from construction sites.  Please visit this interactive stormwater education resource. A stormwater construction plan and well mantained best management practices (BMP) will protect local water quality, property values and the local economy. The first image shows a poorly installed BMP that allows sediment to enter the stream.  The second image shows well maintained and properly intalled BMP measures.  Images below courtesy Debra Earl.

 Good example of Stormwater ManagmentBad example of stormwater management

 

 

The Greater Gallatin Watershed Council partnered with the Montana Watercourse to research the best options for low impact development designs in the Gallatin Valley.  Through a focus group with diverse representatives, a document highlighting some simple LID designs that will work in Montana was produced.  Please see the LID Guidelines Document for more information.

Please visit the links below for many more resources on Low Impact Development.  Encourage new landowners, local officials, developers and contractors to learn more about these exciting, innovating and cost saving measures.


Low Impact Development
  1. Low Impact Development Center Publications
  2. Center For Watershed Protection
  3. MT Water Center Stormwater BMP Training
  4. Rain Garden Manual, University of Wisconsin
  5. LID Design Manual
  6. LID Techniques
  7. Eco Northwest Economics of LID Literature Review
  8. National Institute of Building Sciences, LID Technologies


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