10 the importance of vegetation and soils
TRANSCRIPT
10 ‐ The Importance of Vegetation and Soils
Mary HalleyMichael Brock
Module Content
Vegetationandsoilmechanismsforrunoffreduction
Vegetationrequirementsandguidance Soilrequirements Soilamendmentguidance
Vegetation & Soil Mechanisms
Infiltration(Soil):Runoffreduction&pollutantremoval(allpollutants)Evapotranspiration(Vegetation):RunoffreductionPlantUptake(Vegetation):Pollutantremoval(nutrients)Filtration(SoilandVegetation):Pollutantremoval(TSS,P,N,Metals)
Evapotranspiration
Filtration
Underdrain to storm sewer
Infiltration Filtration
Filtration
Infiltration Plant Uptake
GIP Reliance on Soil and Vegetation
GIP MechanismsUsedBioretention
UrbanBioretentionWaterQualityChannel(Dry)DownspoutDisconnection
Sheet Flow
Infiltration(withoutunderdrain)EvapotranspirationPlantUptakeSoilFiltration(withunderdrain)
InfiltrationTrench Infiltration
GreenRoofGrassChannel
EvapotranspirationPlantUptakeSurfaceFiltration
PermeablePavement Infiltration(withoutunderdrain)Soil/Media Filtration (withunderdrain)
Reforestation
InfiltrationEvapotranspirationPlantUptakeSurfaceFiltration
ExtendedDetention Infiltration(minor)SurfaceFiltration (minor)
Vegetation Guidance
Performance Standards
Vegetation• Healthy• Growing• Perennial• 75%Survival>1year
Preferences• Native• Zoneappropriate• Lowmaintenance• Landuseappropriate
General Vegetation Requirements
Temporarystabilizationmustbereplacedwithperennialvegetation(orotherpermanent,non‐erodingmeasure) beforeconstructioniscomplete
General Vegetation Guidance
Nativespeciespreferred(lowmaintenance) Ornamentalspeciesmaybeusedifnotaggressiveorinvasive
NativeplantspeciestableprovidedinManual.
General Vegetation Guidance
PlantSpacingguidanceprovidedinManual.
Table GIP‐01‐03 Plant Spacing for Perennials, Grasses, Sedges and Shrubs Spacing (O.C.) Plants per 100 sq.ft.
18” o.c. 51.2 24” o.c. 29 28” o.c. 22 30” o.c. 18.5 36” o.c. 12.8 42” o.c. 10 4’ o.c. 7.23 5’ o.c. 4.61 6’ o.c. 3.2 8’ o.c. 1.8
Specific BMP Vegetation Guidance
FoundinBMPDesignSpecifications• Section5‐ HamiltonCountyStormwaterMgmt.Manual
Mostdonotvarygreatly• Reforestationisexception
ThreePlantingTemplates• Ornamental• Meadow• Reforestation
DependsonscaleandtypeofGIP
Ornamental Planting
Perennials,sedges,grasses,shrubsandtrees(optional)inamassbed.
Recommendedforcommercialandresidential(commonarea)siteswheremanicuredlandscapeandvisibilityisimportant.
Highestmaintenancetemplate– reducedifnativespeciesareused
Ornamental Planting Examples
Ornamental Planting Examples
Ornamental Planting Examples
Meadow Planting
Grassesaretheprimaryvegetation,withlimitednumbersofshrubsortrees
Resemblesandwildflowermeadoworprairie Idealforareaswhereamorenaturallookisdesired Lowmaintenancetemplate,especiallywithnativespecies
Bioswale in London Olympic ParkSource: greenroof.com
Meadow Planting Examples
London Olympic ParkSource: greenroof.com
Residential meadow in VermontSource: Linden Land Group
Reforestation Planting
Treesaretheprimaryvegetation,withorwithoutnaturalunderstorygrowthandforestlitter
Goal:Establishamatureforestcanopy Speciesdistributionmodeledonlocalforestecosystems Bestforlargebioretentionareaslocatedatwoodededgesorforwoodedbuffers
PlantingTemplateprovidedinReforestationGIPspecs
Urban ForestSource: City of Virginia Beach
Reforestation Examples
Soil Guidance
Performance Standards
SoilforPlantGrowth• Healthy(pH,salts,nutrients)
• Un‐compacted• Supportiveoflong‐termvegetativehealth
Preference• Protectedfromcompaction
SoilforInfiltration• Native(notfill)• Un‐compacted• HSGA,B,orsomeC,orcompostamended
• InfiltrationRate<0.5in/hr
Preference• Protectedfromcompaction
Native, Un‐compacted Soil is Key
Highporosityprovides• Greaterinfiltrationrates• Betterfiltrationability• Agoodenvironmentforstrongrootgrowth
• Agoodenvironmentforwildlife,bugs,worms,andmicrobestobreakupsoilandoptimizepH,nutrients,etc.
Withprotection,areasofporoussoilscanbelargelyself‐maintaining Plant roots in compacted soil (left)
and un-compacted soil (right)
Soil Amendment
Soil Amendment
Enhancestheinfiltration,filtrationandporosityofcompactednativeorhighlymodifiedurbansoils
Well‐suitedforsoilswithlowinfiltrationrates(someHSGB,HSGCandHSGD)
TypicallyappliedafterconstructionInvolvesdeeptillingofcompactedsurfacesoilsthenaddingandmixingcompost
Soil Amendment
Soil Amendment
Soil Amendment
Performance• Runoffslowsandinfiltratesintotheamendedsoilsurface/subsurfacelayers
• Recommendedforsitesthatwillexperiencemassgradingofmorethanafootofcutandfillacrossthesite
• Notrecommendedfor: Soilsthathavehighinfiltrationrates(e.g.,HSGAandB),althoughcompostamendmentsmaybeneededatmass‐gradedBsoilsinordertomaintainrunoffreductionrates SoilsthataresaturatedorseasonallywetWatertableorbedrockislocatedwithin1.5feetofthesoilsurface Slopesexceed10%ordownhillsloperunstowardanexistingorproposedbuildingfoundationHarmrootsofexistingtrees(stayoutsidethetreedripline)
Soil Amendment
SpecialConsiderations• Requiresrepresentativetestingofsoilstodetermineinfiltrationrate
• Requiresrepresentativepreandpostamendmentsoiltestingtodeterminebulkdensity,pH,saltsandsoilnutrients(properties)
• Key‐ contributingimpervioussurfaceareatobelessthansurfaceareaoftheamendedsoils.
Soil Amendment
SoilTestingRequirements• Soiltestingshouldbeconductedbyreputablelaboratory• Representativesampleofinfiltrationtestsneedtobeconducted.
• Representativesampleofsoilspropertytestsneedtoberunateachteststage. Stage1 ‐ Firsttesting(bulkdensity,salts,pH)toascertainpre‐constructionsoilpropertiesinproposedamendmentarea(s)toadepthof1foot Stage2 ‐ Secondtesting(todeterminefurthernutritionalrequirements,pHadjustmentororganicmatteradjustmentsecessary forplantgrowth)istakenatleastoneweekafterthecomposthasbeenincorporatedintothesoils.
Soil Amendment
CompostMaterialRequirements• Derivedfromplantmaterialonly•Wellcomposted,freeofviableweedseeds,andstablewithregardtooxygenconsumptionandcarbondioxidegeneration
• Novisiblefreewaterordustproducedwhenhandlingthematerial(idealmoisturecontent)
• ProvidedbyamemberoftheU.S.CompostingSealofTestingAssurance(STA)program
Soil Amendment
MixingDepthandCompostVolume• Areaanddepth(imperviouscover/surfacearea)
• Compost volumeC(cyds)=A(sf) xD(in) x0.0031
Soil Amendment
ConstructionInspection• Testpittoverifythedepthofmulch,amendedsoilandscarification
• Penetrationtesting(rodpenetrometer)shouldbeusedtoestablishthedepthofun‐compactedsoilatonelocationperevery10,000squarefeet
Soil Amendment
GeneralConstructionSequence• Deeptilltoadepthof2to3feetcreatingripsperpendiculartothedirectionofflow.(Thisstepisusuallyomittedwhencompostisusedfornarrowerfilterstrips.)
• Seconddeeptilltoadepthof12to18inchesaftersitefinalgrading.
•Mixcompostintothesoilathevolumetricrateof1partcompostto2partssoil.
• Gradedandseedtoestablishavigorousgrasscover(orvegetateperLandscapePlan)
• Temporarilystabilizeamendmentareasover2,500ft2
Module Topic Summary
Vegetationandsoilmechanismsforrunoffreduction
Vegetationrequirementsandguidance Soilrequirements Soilamendmentguidance
Questions?