SuDS – A Developing Landscape

Jonathan Glerum, CIRIA, outlines how SuDS can be integrated into our urban landscape using best practice solutions.

Sustainable drainage systems(SuDS) are an approach tomanaging rainfall that mirrornatural systems. They providedevelopers, designers andlandscape architects with theopportunity to manage local floodrisk and improve water quality inlocal watercourses whilst creatingexciting and interestingdevelopments that can increaselevels of biodiversity and amenity.

The SuDS scene in NorthernIreland differs from that in GreatBritain, as Anthony McCloy, anenvironmental engineer withmany years experience ofdesigning SuDS schemesexplained:

“Unlike Great Britain, SuDS inNorthern Ireland does not yethave sufficient legislative or policydrivers to enforce use. However,SuDS components such aspermeable pavement are beingintegrated and implemented aspart of many social housingschemes throughout NI as part ofthe Code for Sustainable homesaccreditation schemes.”

Anthony also outlined his hopethat “over time, practitioners,developers, planners and thepublic alike will realise the fullbenefits of SuDS through theintegration of systems as part ofdevelopments, as a way ofreconnecting with the environmentand enhancing the quality of ourbuilt environment”.

He added: “A SuDS approach canalso actually reduce the cost ofthe drainage, in comparison withconventional drainage systems,without any significant land takeas a consequence.

“In order to achieve this thedesigner will require anunderstanding of how waterbehaves naturally and howengineered structures can beintegrated into an attractive anduseful landscape setting.”

SuDS and Landscape Design

SuDS which are based onexisting features of a site are themost appropriate method ofproviding efficient drainage tonew developments.

However, the use of SUDS willonly help deliver better qualitydevelopment and amenityimprovements if they aredesigned correctly and fullyincorporated into the master planat the earliest stages. GoodSuDS schemes should combineengineering principles withinteresting landscape design, andthis is most successfully achievedat the beginning of the designphase.

Creating good SuDS schemes

So how do we go about creatinggood SuDS schemes? GoodSuDS design should start byfollowing the SuDS philosophy,which calls for the inclusion of:

1. A management train – using a number of SuDS components in series
2. Source control – managing runoff as close as possible to where it falls as rain
3. Sub-catchments – characterising areas into land use and drainage type

The management train is ofparticular importance, as it can beused to explain the other twofeatures of the SuDS philosophy.

Figure 1: The SuDS management train

(courtesy Catherine Greene & Eithne Flanagan)

The management train starts withPrevention – i.e. goodhousekeeping and site designthat reduces and manages runoffand pollution.

Next is Source Control, managingrunoff as close to its source aspossible, and Site Control, whererunoff is managed in a networkacross a site in sub-catchments.Finally, the last component of theSuDS management train isRegional Control, where runoff ismanaged for a whole site orseries of sub-catchments.All sections of the managementtrain can be designed toeffectively suit the development,thereby enhancing the visualenvironment of a development.

SuDS Component Selection

There are many different SuDScomponents, and those used willoften depend on the specificcharacteristics of the site onwhich the SuDS are to be builtand the effect the designer istrying to achieve.

Not all SuDS components will besuitable for all sites, so it isimportant to understand thecharacteristics and likely use ofthe site as early as possible.As David Singleton, a landscapearchitect who has designed SuDSfor schools explains: “SuDS notonly provide an economicaldrainage solution specific to thesite, but they also allow youngchildren to learn about theirenvironment in a safe, dynamicand meaningful way”.

Typical SuDS Components

SuDS components can bebroadly broken down into sevenseparate groups, all of which takeup different levels of land andhave different effects on thelandscape. These are:

1. Source control – this includesgreen roofs, rainwater harvesting,rain gardens and permeablepavements, all of which managerunoff as close to the point whereis falls as rain as possible.
2. Filtration – this group ofcomponents includes filter strips,filter drains or trenches which areoften gravel filled and used nextto roads, and surface and subsuface sand filters.
3. Infiltration – this groupincludes soakaways and trenchesdesigned to allow water to seepslowly into the ground.
4. Detention – detention basinsare often designed as a drylandscaped area that can be usedto detain large volumes ofstormwater when required.
5. Retention – this groupincludes retention ponds (similarto traditional ponds) that aredesigned with water treatmentand runoff volumes in mind. Thisgroup also includes subsurfacestorage such as geocellular systems.
6. Wetlands – this group ofcomponents includes wetlandsthat are often designed to treatwater and provide increasedbiodiversity. Due to the sensitivityof plants used in wetlands, theyoften need protecting with otherSuDS further upstream which mayremove heavy pollutant loads.
7. Open channels – this groupincludes swales (shallow grasschannels) which convey water aswell as provide some infiltrationcapacity, and other harderengineered open channels suchas canals and rills.

Where can I get furtherinformation?

The SuDS Manual (CIRIA C697)is a comprehensive guide tosustainable drainage, providingthe background, design andselection criteria, details ofcomponents and how they shouldbe built, operated and maintained,for all SuDS. However, if a moreinteractive approach is needed,then CIRIA also provide training

courses (in conjunction with

Anthony), either in-house orexternally. Your contacts are:

Jonathan Glerum –

jonathan.glerum@ciria.org

Anthony McCloy –

anthony@mccloyconsulting.com

or visit www.ciria.org/suds