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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,NH03824ph603-862-4024fx603-862-3957robert.roseen@unh.edu

PROJECT INVESTIGATORS AND CONTRIBUTING AUTHORS:Todd V. Janeski•EnvironmentalScientist,VirginiaCommonwealthUniversity 1000WestCarySt,POBox843050,Richmond,VA23284ph804-371.8984 fx:804-786-1798tvjaneski@vcu.edu

James J. Houle,CPSWQ•OutreachCoordinatorandProgramManager,TheUNHStormwaterCenter EnvironmentalResearchGroup,DepartmentofCivilEngineering,35ColovosRoad,UNH,Durham,NH03824ph603-767-7091fx603-862-3957james.houle@unh.edu

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ThisprojectwasfundedbyagrantfromNOAA/UNHCooperativeInstituteforCoastal andEstuarineEnvironmentalTechnology,NOAAGrantNumbersNA06NOS4190167