Susanne Charlesworth SUDS Overview.pdf

Sustainable DrainageDr Sue Charlesworths.charlesworth@coventry.ac.ukGeography, Environment and Disaster ManagementBESSUDS ARG

What are the problems / issues? Water quantity Water quality Environmental quality (aesthetics, biodiversity,amenity) Climate change?

Climate Change Annual summer rainfall has fallen byaround 20 per cent since about 1900. Winter rainfall is greater. A larger proportion ofwinter precipitation falls in heavy rain showersthan 50 years ago (National Trust). Many rivers reached their highest ever recordedlevels in 2002 (Environment Agency).

Flood risk, Coventry (EA)Flooding from riverswithout defencesExtent of extremeflooding

Impacts of flooding on impermeablesurfaces Increased flow = increased erosion Evidence of the polluting effects of urban deposits –Charlesworth & Foster, 2005: some street dusts exceedthe 1mSv yr -1 limit to members of the publicrecommended by ICRP (1991). Above background levels of metallic elements in streetdusts and sediments Zn and Cu exceeded ICRCL action levels Removed from street surfaces as a “first foul flush”

Evidence for First Flush> 4500 mg l - 1 pollutedsuspended sediment

Mitigating the effects of urbanisationNeed to: attenuate the storm peaktackle contaminationTraditional hard options vs softengineeringSustainable Drainage Systems(SUDS)Sustainability: “Development thatmeets the needs of presentgenerations without compromisingthe ability of future generations tomeet their own needs.” OurCommon FutureThe Brundtland Report, 1987SUDS triangleWater QualityHabitat/AmenityWater Quantity

Sustainable DrainageSystems (SUDS) Differ from the traditional systems: encouragesinfiltration and detention Limits discharge of stormwater from an area,both in flow rate and in volume Enhances discharge water quality Incorporates devices which provide habitat andenhance the environment. It is a way of thinking, , a philosophy

SUDS installations Above-ground / belowground New-build / retrofit Suitable / not!e.g. Filter strips and swalesSwale, Dundee

PermeablesurfacesInfiltrationdevicesAll can be used incombinationSoakaways, , infiltration basins etc

Green walls/ roofsGreen roofs: retain up to80% of rainfall duringsummer and 40% in winterCan reduce energy use byproviding better insulationExternal noise pollution isreducedReduction in the Heat IslandEffect which can be up to5ºCFilter atmospheric pollutants

Basins and pondsBasins and pondsSutton Coldfield_Pond under motorwayintersection

Constructedwetlands:London

SUDS trainsEnvironment Agencydemonstration sitesConsultants: Robert BrayAssociatesHopwood Motorway Service area M42

Other sustainable approaches River Restoration:http://www.therrcwww.therrc.co.uk/index.php.co.uk/index.php

River RestorationProject: R Cole

Retrofit Car parks: replace using porous materials, installinfiltration devices Green roofs and walls Trees: can reduce atmospheric-derived dusts. Plant inassociation with infiltration devices e.g. gravelsoakaways. Rainwater harvesting: Reduces storm water run off.Free/un-metered water for e.g. watering hangingbaskets, flushing toilets. Can reduce the use of mainswater by up to 50% (UK-RHA).

Limits to SUDSLand-takeDifficulty with retrofit of some installationsSUDS designed for specific circumstances e.g. 10-year, 60 minute storm e.g. treat runoff from 90% annual stormsPoor design, construction and maintenance (bollards through geotextile; ; hard drainageput in below PP; storage of building materials on PP; etc etc etc) Lack of experience in E & W: Reflected in lack of research: few long term monitoring studies Does it work? Where is the evidence???? Lack of communication between academia and practitioners Ownership… Treatment facility ≠ pristine ecosystem No one correct solution: in some situations conventional drainage e techniques (ormixture) is most sustainable option SUDS only one part of solution to urban drainage problems

Perceived barriers Green roofs / walls: too heavy, pulls offrendering, looks untidy, “the City Council willnever go for it”. Health and safety issues Expense They block up PP needs replacing

Addressing the issues Planning: PPS/G25:1. don't build where it mayflood2. don't create floodingelsewhere3. don't make existingflooding worse Increasing costs of water “consumer” preferences Building Regulations:Surface water drainagehierarchy:1. Infiltration on sitepreferred disposaloption2. Then discharge towatercourse3. Then connection to asewer

European wide Water Framework Directive: “joined up”approach to surface water management Whole river catchment management plans Integrated land-water management for flooddefence Ecological approach to protection andenhancement of water quality

Benefit of SUDS? Cost: studies show longterm economic benefits Pro-active regardingclimate change Not limited to urbanareas: buffer strips,shelter belts in rural areastooFrom thisTo this!

More benefits Increased value ofhousing fronting a SUDSdevice e.g. pond orwetland Multiple use Bicester

Future for SUDS? Education, information, R & D Coventry University: SUDS ARG MSc: Sustainable Drainage and River CatchmentManagement MRes Water Science PhD CPD SUDSnet

Summary Urbanisation significantly effects hydrology, strainswater resources, increases pollution and flood risk Unsustainable, mitigated against using SUDS Reluctance to embrace SUDS in E&W Treatment trains possible, but application is site specific Once implemented, responsibility for installation andmaintenance needs to be sorted out Future of SUDS is procedural i.e. education andinformation