carpark developmentsretrots · melbourne, australia: cooperative research centre for water...

Water sensitive urban design

Carpark developmentsretrofits

wwwnewwaterwaysorgau

SummaryCarparks are necessary urban infrastructure and provide a significant opportunity for the creation of multifunctional and green urban space Carparks and roads have a significant impact on localised warming known as the Urban Heat Island Effect Dark coloured and dense surfaces absorb the sunrsquos heat resulting in increased surface and ambient temperatures On hot days these areas can be substantially hotter than their surrounds Carparks also produce pollutants from car exhausts oils and degrading bitumen Increased tree canopy coverage raingardens swales tree pits pervious paving infiltration systems and other water sensitive urban design (WSUD) measures reduce heat reduce pollutant mobilisation through onsite treatment reduce stormwater runoff volumes and velocities and increase groundwater recharge These WSUD measures also reduce construction and maintenance costs through reduced infrastructure costs reduced replacement costs and extended lifespan of shaded bitumen

Design scale

DistrictPrecinct

(subdivision)Street Lot

Treatment train

Land useand planning

Total watercycle outcomes

through location and good design

Capture use and inltrate

rainfall

Retentiondetention and conveyance

Flood management

Appropriate discharge and

reuse

Protect people and buildings from ooding

Reduce transmission of

pollutants

Prevent and reduce

pollutants at their source

Minimise runoff Minimise erosion

Up to the 1 in 1 year ARI event

Up to the 1 in 5 year ARI event

Up to the 1 in 100 year ARI event

Source control Runoff controlSafe

conveyance and discharge

Design processbull Establishamulti-disciplinaryprojectteamincluding

engineersparkingofficersrangerslandscapearchitectsassetmanagementandenvironmentalofficerstoclearlydefineanddocumentobjectivesofthecarparkintheprojectscopingandplanningphasetoinformfuturedesign

bull EnsuretheprojectplanincludesspecificoutcomesforwaterqualityandincreasedtreeplantingThisshouldincludeprotectionofexistingtreesandvegetationwhereappropriate

bull Developamaintenanceplanintheearlystageoftheprojectsothatoutcomesrolesandresourcingareoptimised

Design considerationsbull Delivermultipleobjectiveswhilstprovidingadequate

spaceforparkingandmaneuveringConsiderexistingflowpointsandlocatevegetatedstructures(treepitsraingardensandbiofilters)atthelowestpoints

bull Setvegetatedareasbelowpavedsurfacestoaccommodateincomingwater

bull ProtectexistingtreesMaximisetheuseoftreesincarparksdirectingflowsthroughwheelstopsandkerbopeningsforpassivewatering

bull SelectsuitablevegetationtoprovidecanopycoverduringthewetseasonandtoreducepollutantsinstormwaterrunoffandtheairNativespeciesarepreferredDeciduoustreesshouldbeavoidedduetotheirlackofcanopycoverduringthewetseasonandhighleaflitterload

bull Ensureenoughfreesoilvolumeisprovidedfortreerootstoincreasetreegrowthandmaximisecanopycoveregrootcells

bull Arrangewateringprogramtoensureplantestablishmentforfirst2summersFailuretodosowillresultinunnecessaryplantdeathandadditionalcosts

bull InstallsignageorQRcodesthatdescribethefunctionofWSUDmeasures

Suggested readingDetermine the microclimatic influence of harvesting solutions and WSUD at the micro-scale Presented as frequently asked questions MelbourneAustraliaCooperativeResearchCentreforWaterSensitiveCitiesCouttsATapperNLoughnanMDemuzereMBroadbentAMotazedianAWhiteEPhanTThomJGebertLPankhinaD(2015)Adoption Guidelines for Stormwater Biofiltration SystemsMelbourneAustraliaCooperativeResearchCentreforWaterSensitiveCitiesPayneEGIHattBEDeleticADobbieMFMcCarthyDTandChandrasenaGI(2015)Ranking projects for water-sensitive cities a practical guideMelbourneAustraliaCooperativeResearchCentreforWaterSensitiveCitiesPannellDJ(2015)WSUD maintenance guidelines A guide for asset managersMelbourneWater(2013)Introducing water sensitive urban design MaintenanceNewWAterWaysDepartmentofWater(2016)1The Sources Impact and Management of Car Park Runoff Pollution A ReviewMiddlesexUniversityUKRevittDetal(2014)

Opportunities and benefitsbull Treesincarparkscanreduceambient

temperaturesbyanaverageof25-30CthroughevapotranspirationandprovisionofshadeThisimprovesthermalcomfortofpeoplereducestemperaturesinparkedcarsandextendsbitumenlifebyseveralyears

bull Highlevelsofpollutantsareemittedbycarsincarparks1includingtotalsuspendedsolidshydrocarbonsheavymetalsandotherpollutantsStormwatermanagementsystemssuchastreepitsvegetatedswalesandperviouspavingtreatpollutantsatsourceThisreducesthemobilisationofpollutantstoreceivingwaters

bull Vegetationimprovescarparkaestheticsandamenityandcanreflectandenhancelocalnaturallandscapes

bull VegetationespeciallytreesthatprovidecanopycoverduringthewetseasonandinfiltrationsystemswithincarparkswillreducestormwaterrunoffvolumesandvelocitiesThisreducesthequantityofstormwatertomanagewithinthelocal(road)drainagenetwork

bull KerbopeningsandwheelstopscanbeusedtoallowrunofffromsmallrainfalleventstoentervegetatedareasRunofffromminortomajorrainfalleventscanthenbypassthekerbopeningsreducingerosionandmovementofmulch

bull PerviouspavingincreasesinfiltrationanddisconnectsimperviouscatchmentsThisalsoreducesrunoffvolumesandincreasesgroundwaterrechargeandpollutantremoval

bull Stormwaterrunoffthatisdirectedtolivingwallsinstalledonadjacentbuildingsincreasesevapotranspirationandcooling

Urban Heat - Surface temperatures on a 42 degree day

Bitumen in full sun658 C

Bitumen under tree canopy (two metres away

from full sun)385 C

Playground rubber softfall972 C

Urban Heat Surface temperatures on a 42 degree day

Bitumeninfullsun658degrees

Bitumenundertreecanopy(twometersawayfromfullsun)

385degrees

Playgroundrubbersoftfall972degrees

Water sensitive urban design

Carpark developmentsretrofits

wwwnewwaterwaysorgau

Kerb openingsaround tree pits

PerviouspavingWheel stops

Kerbless biofilter

Kerb openings

Biofilter

Tree pitRoot cell

KerbswithrunoffgapsallowwatertoenterthetreepitConsiderroadgradesandlocatestructuresinsagstomaximiseinfiltration

Wheelstopscombinedwithkerblessswalesandkerbopeningsmaximisestormwaterentryintovegetatedareasandreducetheneedforsoakwells

Onetreecanreduceairtemperaturesbyupto12degreesunderthecanopywithanimprovementinthermalcomfortofupto7degreesTreeshadecanreducesurfacetemperaturesby25-30degreesLargetreescanalsocaptureamajorityofrainfallwithinthecanopywhichalleviateslocalflooding

Kerbopeningsdirectwaterintovegetatedassetsandprovidesufficientbarriersforcars

Stormwaterrunoffdirectedtolivingwallsinstalledonadjacentbuildings

Trafficableinfiltrationcellsprovideroomfortreerootgrowthandstoragevolumesforstormwatermanagement