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The Benefits of Low Impact Development
The goal of LID is to mimic the
predevelopment hydrology of a site using a
combination of site planning and structural
design strategies to control runoff rate and
volumes.
LID approaches can be used in any type of
development scenario:
• newdevelopment,
• redevelopment,or
• existingconditionretrofitting.
LowImpactDevelopment(LID)isaninnovativeapproach tostormwatermanagementthatisbasedontheprincipleof managing runoff at the source.
WHY LID, WHY NOW?
Historically,wetlands,rivers,lakes,andestuariesprovidedtheworkofcleaningandprotectingwaterresources.
Intensedevelopmentcansignificantlyimpairwaterqualityandchangehowsurfaceandgroundwaterinteract.
Increases in impervious surfaces result in increasedrunoff,makingitharderandhardertoprotectreceivingwaters.
Not LID
F A C T S H E E T
LID IS:• Abalancedwatershedapproachto
managing altered hydrology
• Ascience-basedsolutiontomitigating
the impacts of smart development
• Awaytodecentralizeandintegrate
stormwaterbestmanagement
LID IS NOT:• Asilverbullet
• Asubstituteforproperplanning
• Awaytopermitunfavorable
development
• Asinglebestmanagement
practice
LID
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OLD DESIGN APPROACHES
Detentionbasinsdoaneffectivejobofaddressingfloodprotectionrequirementsbydetaining
largervolumesofrunofffromhighlevelsofimpervioussurfaces.However,researchhasshown
thatsolerelianceuponbasinstomanagestormwaterhasproventobeineffectiveinprotecting
waterresources.
TOWARD A BETTER APPROACH
Theworkofcommunityboardmembersand
municipaldecisionmakersintownsandcities
throughout the country is critically important for
shaping community character and protecting local
natural,culturalandeconomicresources.Thiscan
bedonebyrequiringeffectiveLIDdesignsthat:
• attempttodecentralizedrainageinfrastructure,
• maximizeonsitestoragefiltrationandinfiltration
• makeuseofnaturallandscapefeaturestobest
manage runoff
• reducetheneedforlargedetentionstructures
DEVELOPED WATERSHED
Evapo-Transpiration 25%
Precipitation
Groundwater32%
Surface Runoff43%
NATURAL WATERSHED
Precipitation
Evapo-Transpiration 40%
Surface Runoff10%
Groundwater50%
TYP ICAL PRE - AND POST-DEVELOPMENT HYDROLOGY PATTERNS
FORGING THE LINK: LinkingtheEconomicBenefitsofLowImpactDevelopmentandCommunityDecisions•www.unh.edu/unhsc/forgingthelinkChapter2:TheBenefitsofLowImpactPractices
PRINCIPAL INVESTIGATOR: Robert M. Roseen,Ph.D.P.E.,D.WRE•Director,TheUNHStormwaterCenter EnvironmentalResearchGroup,DepartmentofCivilEngineering,35ColovosRoad,UNH,Durham,[email protected]
PROJECT INVESTIGATORS AND CONTRIBUTING AUTHORS:Todd V. Janeski•EnvironmentalScientist,VirginiaCommonwealthUniversity 1000WestCarySt,POBox843050,Richmond,VA23284ph804-371.8984 fx:[email protected]
James J. Houle,CPSWQ•OutreachCoordinatorandProgramManager,TheUNHStormwaterCenter EnvironmentalResearchGroup,DepartmentofCivilEngineering,35ColovosRoad,UNH,Durham,[email protected]
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ThisprojectwasfundedbyagrantfromNOAA/UNHCooperativeInstituteforCoastal andEstuarineEnvironmentalTechnology,NOAAGrantNumbersNA06NOS4190167