suds in the city

SUDS in the City

Sustainable Urban Drainage Systems (SUDS) and their Role in the Dense Urban Realm

Robert Norris

MA Landscape Architecture

2011

Birmingham City University

ContentsAbstract �� 5Introduction �� 61�0 SUDS Introduced �� 91.1 Traditional Drainage Methods and their shortcomings ......................................................................10

1.2 The Alternative ....................................................................................................................................13

1.3 The Management Train .......................................................................................................................15

1.4 Sub-catchments ..................................................................................................................................16

1.5 The Benefits of SUDS ..........................................................................................................................16

1.6 SUDS components ..............................................................................................................................19

1.7 Summary .............................................................................................................................................20

1�8 Case Study: Oxford Services �� 221.9 The Main elements and the roles they fulfil .........................................................................................24

1.10 Summary ...........................................................................................................................................26

2�0 SUDS in the City �� 272.1 Multifunctionality .................................................................................................................................28

2.2 Non-Defensive Flood strategies ..........................................................................................................30

2.3 Decentralised Approach/regional wide approach ..............................................................................31

2.4 Singapore ...........................................................................................................................................32

2.5 SUDS Components in the City. ...........................................................................................................35

2.6 Keys Areas of Focus for SUDS in the City ..........................................................................................40

2�7 Case Study: Sponge Park, Brooklyn, New York �� 42Solutions ....................................................................................................................................................43

2.8 Sponge Park Stormwater management ..............................................................................................46

2.9 In Conclusion ......................................................................................................................................49

3�0 SUDS on the Street �� 503.1 The aligning properties .......................................................................................................................51

3.2 Kerb Extensions ..................................................................................................................................54

3.3 Street Trees .........................................................................................................................................55

3.4 Permeable Paved Streets....................................................................................................................56

3�5 Case Study: Learning From Portland �� 583.6 Green Streets ......................................................................................................................................58

4�0 SUDS In Development �� 614.1 The Ray and Maria Stata Centre .........................................................................................................62

4.2 Permeable Surfaces ............................................................................................................................63

4.3 Hazeley School, Milton Keynes ...........................................................................................................66

4.4 Large Scale Stormwater Storage .......................................................................................................66

4.5 Important Aesthetics ...........................................................................................................................67

4.6 Making the Most of Space ..................................................................................................................68

4.7 Green Roofs ........................................................................................................................................69

4.8 Retrofitting SUDS ................................................................................................................................70

Figure title page(source: Boer, Jorritsma and van Peijpe, 2010)

4�9 Case Study: Ekostaden Augustenborg, Malmö� �� 724.10 Community Involvement ....................................................................................................................74

4.11 Well designed SUDS Built around Community .................................................................................75

5�0 SUDS at the Park �� 785.1 Sherborne common, Toronto ...............................................................................................................79

5.2 Point Fraser .........................................................................................................................................80

5.3 Tanner Springs Park, Portland, Oregon ..............................................................................................82

5.4 Renaissance Park, Chattanooga, Tennessee .....................................................................................83

5.5 Olympic Sculpture Park ......................................................................................................................85

5.6 SUDS in School ...................................................................................................................................86

5.7 Augustenborg School .........................................................................................................................87

5.8 Mount Tabor Middle School Rain Garden, Portland, Oregon .............................................................88

5.9 SUDS on the River ..............................................................................................................................90

5.10 Summary ...........................................................................................................................................91

5�11 Case study: Watersquare, Rotterdam� �� 935.12 A Classic Example ............................................................................................................................94

5.13Summary ............................................................................................................................................97

Conclusion �� 99References �� 100

“Over two thirds of the 57,000 homes affected by the 2007 summer

floods were flooded not by swollen rivers but by surface water runoff

or overloaded drainage systems. The government’s Foresight report

estimates that currently 80,000 properties are at very high risk from

surface water flooding causing, on average, £270 million of damage

every year” (Interpave, 2008)

Acknowledgements

I would like to thank the following for advice and support over the

duration of this research:

Calah Norris, Professor William T. Norris, Jennifer Mohan and Ellie

Rivers-Mohan for proof reading and advice.

Dr Richard Coles for advice and support.

All my friends and family for support and understanding.

SUDS in the CIty-MA Landscape Architecture 4

AbstractSustainable Urban Drainage Systems (SUDS) are increasingly being

turned to as an alternative to traditional drainage, which use pipes,

canalised channels and sewers. The literature indicates that the use

of SUDS has increased dramatically in the last 10 years along with

government legislation and policy on the adoption of SUDS. SUDS

work on the principle of adopting natural water management systems

in order to deal with urban stormwater runoff. Because of this, most

SUDS schemes employ fully naturalised elements, such as constructed

wetlands or vegetated ditches to slow or collect rainwater runoff.

However these SUDS schemes often require a lot of space to function

effectively but in the dense urban realm, space is often short.

A review of relevant literature and case studies indicate that most of

the focus is on larger schemes, but not all. Some show that SUDS in a

dense urban environment is a very realistic option and there are several

schemes in place that perform superbly. They allow for the remediation

of problems associated with stormwater runoff without the need for

large sprawling systems. They integrate themselves in to the urban

realm combining the duties of drainage, provision of public amenity

and provision of wildlife habitat and biodiversity. They achieve national

standards of pollution and flood remediation.

The literature and case study review highlighted and defined current

thinking and practices involved in integrating SUDS into the dense urban

environment. In order to achieve this, innovation and multifunction are

imperative to get the most out of any given site. However, the individual

nature of different sites mean that requirements and possibilities vary.

The case studies show that while the principles, such as filtration and

attenuation of stormwater, remain constant, the methods can differ,

from rain gardens to floodable public squares. They illustrate that while

designs are different, they all achieve the same ends, a reduction in

flooding and a remediation of pollutants. They achieve this in limited

space, improve the urban realm and enhance urban life.


Introduction“SUDS started out being perceived as only ‘soft’ and

‘green’, and only for developments where open space

was available. Engineering solutions are increasingly also

required for the more densely built up parts of our cities”

-Professor Chris Jefferies, Principal Investigator, SUDSnet UWTC at

University of Abertay (Interpave, 2008)

Sustainable Urban Drainage Systems (SUDS) are being widely accepted

and implemented as the latest government legislation illustrates (RBA,

2010, CLG, 2009, DEFRA, 2008). SUDS use natural processes to

prevent flooding and to breakdown or remove pollutants and sediment

from urban runoff. However, what Professor Chris Jefferies (Interpave,

2008) illustrates is that in order to adopt SUDS in our dense urban

realm, we need to be a little more innovative in how we use natural

principles.

The literature (RBA, 2010, CLG, 2009, AW, 2010) shows that SUDS are

based on natural processes that revolve around some key principles:

• Attenuating, detention or retention: Slowing down or stopping

stormwater runoff in order to prevent flooding down stream. By

attenuating, detaining or retaining stormwater, closer to where it fell,

or ‘the source’, it is possible prevent an accumulation of water down

stream.

• Allowing infiltration: By enabling water a chance to sit or

dramatically slow down, it has the chance to soak into the ground, or

infiltrate, reducing the volume that needs to runoff over the surface or

in to streams and rivers.

• Allowing evapotranspiration: By enabling vegetation to absorb the

water, again, less water needs to runoff over the surface or in streams

or rivers. This water is then released into the air from the plants leaves.


• Using Bioremediation: Pollutants and dusts tend to be more

concentrated in urban areas, so when the rain falls, it washes

these pollutants with it. Bioremediation (sometimes referred to as

phytoremediation) is the use of vegetation to breakdown these harmful

pollutants or extract them from the water or soil.

• Filtering: A lot of sediments and particles, often polluted, can be

collected by urban runoff, which can accumulate down stream along

with the water. By allowing water to pass through vegetation and

allowing it to infiltrate into the ground, sediments and silt will be filtered

out from the runoff and then broken down or assimilated.

As may be apparent, all these principles are interrelated and support

each other. Through the literature and case study review, it is possible

to establish how, where and why these principles are applied in SUDS

schemes and how to apply them in the dense urban realm.

Possibly the main factor for the need for SUDS in cities is the extent of

hard surfaces and the volume of runoff it produces (CIRIA, 2009, EA,

n.d.). Hard surfaces appear to be the antithesis of SUDS but in the

dense urban realm they are arguably a necessity. So what this research

shows is that it is possible to introduce SUDS principles into the city.

By reviewing current literature and case studies it will establish the

various ways in which SUDS principles are being applied in the city:

projects that break away from the norm, but still apply SUDS principles,

common SUDS features that are often utilised and SUDS techniques

that have been adapted to particular scenarios.

SUDS schemes should also enhance biodiversity and improve the

quality of public space and amenity (AW, 2010, RBA, 2010). These are

secondary considerations to urban stormwater or runoff management,

but almost as important. All schemes covered in the research also

performed at least one of these tasks as well. Multifunction is a major

part of any dense urban SUDS scheme due to space being so short

and SUDS not being fully utilised a lot of the time. Rainfall is intermittent

in its very nature, so schemes must have alternative functions other

than those of urban runoff management.


The findings of this research is presented 5 chapters:

• The first chapter introduces SUDS and establishes the basic

principles and methods of SUDS schemes. It provides a framework

and a guide to understanding SUDS.

• The second chapter establishes how these principles and

framework have been adapted to the dense city environment, what

considerations there are and challenges there might be.

• The third chapter concentrates on SUDS that mainly remediate

stormwater issues on the street and any special opportunities or hurdles

that arise.

• The forth chapter looks at SUDS in building, residential, commercial

and industrial developments.

• The fifth and final chapter looks at the potential of SUDS in our

urban parks, the last areas of open green space with in the city

Each chapter is followed by a corresponding case study that highlights

some important aspects raised in that chapter. The case study may not

cover all points, but rather serves to stand as an exemplar in that area.

Within each chapter, examples of other projects are used to illustrate or

reveal practices relevant to the use of SUDS in the City.

SUDS schemes in the dense urban realm can greatly improve our urban

environment and prevent flooding and pollution. It can part of an urban

park, street or building development and have wider benefits beyond

that of the stormwater management, biodiversity or public amenity. This

thesis aims to illustrate the diverse and innovative ways in which SUDS

schemes can be implemented in to cities and the benefits they can

bring. It also aims to highlight specific projects to show how they are

guided by SUDS principles and have improved their environment.


1.0 SUDS Introduced

“Traditionally water has been moved away as quickly as possible but

to meet future challenges we now need slow water, managed at a

catchment level.” Mark Worsford (Anglican Water, 2011)

Sustainable Urban Drainage Systems (SUDS) seem to indicate the urban

environment but the distinction of what is “urban” is not always clear.

In fact, the term SUDS can be used to cover almost any sustainable

water management system that deals with a change in the way water

behaves in the landscape as a result of human intervention. SUDS are

a way of dealing with rainfall and stormwater runoff that is modelled

on natural drainage processes and behaviour (Anglian Water, 2011,

DEFRA, 2004a).

Figure 1.1Comparing the proportion of surface runoff of typical urban and natural ground cover. Note especially the reduction in infiltration.(source: EPA, 2003)


1�1 Traditional Drainage Methods and their shortcomings

Rainwater falling on the urban realm can cause a number of problems,

both for us and for the natural world. The impermeable nature of these

areas mean that water is unable to infiltrate into the ground, as Figure

1.1 illustrates: With natural groundcover about 10% of the rainfall will

be surface runoff, but in an urban situation with 75%-100% impervious

surfaces, this is more like 55%. This runoff has to be dealt with and

the larger the area the more water is collected and remains as surface

water. As the Environment Agency (n.d.) explain, this normally means

that water is quickly moved off the impermeable surfaces, and into

drains, down canalised channels designed to rush water to the nearest

water courses and away as fast as possible (see Figure 1.2). Robert

Bray (EA, n.d.), one of the leading SUDS experts in the country, states,

“We know that the systems we have in place now don’t work”.

The Environment Agency (n.d.) state that flash flooding is caused by

the cumulative effects of all this runoff from the catchment area. Figure

1.3 shows how the roads alone contain huge amounts and varied

Figure 1.3Sources of road pollution(source: Guz, 2011)

Figure 1.4The effects of silt and sediment build up in traditional drainage. The main outflow (centre) is completely blocked.(source: SNIFFER, 2004)

Figure 1.2Large canalised channels to move large amounts of water, fast.(source: EA, n.d.)


types of pollutants that are washed from our roads in to the drainage

system. The Environment Agency (n.d.) summarises this list to metals,

oils, dust, effluent, dog fouling and rotting organic matter, and extra

contaminants from accidental spillage and misuse of the drains. They

also point out that increased flow rate and volume in watercourses

will cause erosion of banks and wildlife habitats and deposit polluted

sediments. When these Sediments get washed into the sewer systems,

they can accumulate, causing blockages, which need expensive

maintenance (see Figure 1.4). They go on to say that even special silt

and sediment traps within the drainage system still have to be cleaned

and unblocked at great expense.

Apart from all the flooding and damage caused by these methods, it

can also have a seriously detrimental effect on the safety and quality

of the public realm. The large concrete channels look ugly, and the

huge underground drains and outlet pipes can become a dangerous

playground. These regularly get clogged up with debris and detritus

meaning more ugly and expensive mess to remove and damage to fix

(see Figure 1.5).

Figure 1.5Ugly, dangerous and clogged up drainage outlets.(source: EA, n.d.)

Figure 1.6Combined Sewer System. When there is a heavy storm event, the extra water in the system means that untreated sewage over flows into local water bodies.(source: dlandstudio, 2011)


Many of these traditional options are huge civil engineering works that

are very expensive in terms of installation and maintenance, as well

as causing disruption to the city and its infrastructure (Environment

Agency, n.d.).

Many of our sewers are combined waste and stormwater drains and do

not have the capacity to deal with heavy rain fall. This is seen in Portland,

Oregon (ASLA, 2007) and Philadelphia, Pennsylvania (GreenTreks

Network, 2011), where the problem of combined sewer inundation

caused serious basement flooding. The Environment Agency (n.d.)

explain that these outdated sewers backup and flow on to the street, or

usually, as these sewers have an overflow designed into them, release

untreated, combined waste, foul and storm water into the nearest

open watercourse. Figure 1.6 illustrates how the combination sewers

have an over flow, and when floodwater fills up the sewer, the overflow

discharges this combined waste and storm water into the watercourse,

untreated.

Associated with this high speed, high volume urban runoff is the

concept of ‘first flush’ (see Figure 1.8) which DEFRAs (2004a) ‘Interim

Code of Practice for Sustainable Drainage Systems’(ICOP) defines as:

“The initial runoff from a site or catchment following the start of a rainfall

event. As runoff travels over a catchment it will collect or dissolve

pollutants, and the “first flush” portion of the flow may be the most

contaminated as a result. This is especially the case for intense storms

and in small or more uniform catchments. In larger or more complex

catchments pollution wash-off may contaminate runoff throughout a

rainfall event.”

Figure 1.7Manhole cover forced up due to the pressure of an overloaded underground drainage system.(source: EA, n.d.)

Figure 1.8The lighter shade at the bottom is polluted silt and road dust being washed from the roads.(source: EA, n.d.)


This can be an issue because as more pollutants are gathered up in

the runoff, all these pollutants will accumulate and spread out causing

damage and pollution to a wider area. This is known as ‘Diffuse

Pollution’, which the Scottish Environment Protection Agency (SEPA,

2011) define as “the release of potential pollutants from a range of

activities that individually may have no effect on the water environment,

but at the scale of a catchment can have a significant impact” (see

Figure 1.9).

The issues that arise from traditional urban drainage methods stem from

the impervious nature of the urban realm and the method of removing

runoff as fast as possible. This causes an inundation downstream by

the water and its contaminants, which heap all of the accumulated

problems on a more concentrated area, rather than dealing with them

in smaller, more manageable volumes.

1�2 The Alternative

Sustainable Urban Drainage Systems (SUDS) work using natural

processes, such as wetlands or ponds, or abstracted naturalised

mechanisms, such as under-drained swales, These aim to slow runoff

rate, reduce the peak flow down stream and remediate the pollution

associated with urban stormwater runoff. DEFRA (2004a) state that

the “philosophy of SUDS is to mimic as closely as possible the natural

drainage from a site before development”.

“Sustainable drainage systems (SUDS) constitute an approach to

drainage which uses a wide range of techniques – for example

rainwater harvesting, wetlands and swales – either alone or (more

effectively) in combination to provide for a site a drainage solution that

is more sustainable than conventional drainage. The SUDS approach

has the potential to reduce flood risk, where appropriate capacity

has been included in the design, while achieving multiple benefits in

improvement water quality, recharging of groundwater, and enhancing

the potential for biodiversity.” (DEFRA 2004b)

Figure 1.9It is estimated that between 20% and 50% of poor river water quality is caused by diffuse pollution from urban runoff (EA, n.d.)Source: EA, n.d.)


Figure 1.10 shows the basic SUDS techniques of rainwater harvesting,

green roofs, swales, filter strips, reed beds and treatment ponds. This

illustrates the various techniques that hold water, reduce flow and allow

the infiltration of water into the in order to reduce the volume and rate of

surface runoff and improve water quality. The Governments ‘Planning

Policy Statement 25’ (CLG) (2009) add to this the additional benefits

of increased amenity, recreation and biodiversity and is backed up by

nearly all other documentation on SUDS.

Maintenance and repair are also very easy and simple compared to

traditional drainage systems (DEFRA, 2004b, Green streets, 2011, AW,

2011, RBA, 2010). Since they are all surface management practices,

accessibility is easy, and most maintenance can fall under general

landscape maintenance.

“The vast majority of SUDS, whether “hard” or “soft”, do not seem to

suffer from problems with excessive silt accumulation if they apply

the key concepts of the SUDS philosophy, i.e. source control with a

correctly designed treatment train.” (Wilson and De Rosa, 2011)

This supports Robert Brays comment for the EA(n.d.), which is echoed

through a lot of SUDS literature (DEFRA, 2004b, Green streets, 2011,

AW, 2011) indicating that as long as the design and construction are

done correctly, SUDS schemes require virtually no maintenance.

Water butts

RainwaterHarvesting

InfiltrationInfiltration

Infiltration

Permable paving

Swale

Swale

Filter strips stop sediment from entering swales

Reed beds

Treatment pond River

Green Roof

Figure 1.10Diagram illustrating all the basic SUDS principles of catching rainwater as close to where it lands, maximising infiltration and bioremediation and holding or storing water to prevent a build up down stream as well as for reuse.(source: CLG, 2009)


1�3 The Management TrainThis is the basic framework that should be understood and which

underlies the planning of any SUDS system. It is the hierarchy of

systems that should reinforce and where possible follow the natural

pattern of drainage, as set forth in ICOP (DEFRA, 2004a) (see Figure

1.11):

1. Prevention – the use of good site design and housekeeping

measures on individual sites to prevent runoff and pollution (examples

include minimising paved areas and the use of sweeping to remove

surface dust from car parks),

2. Source control – control runoff as near as possible to its source

(such as the use of rainwater harvesting, pervious pavements, green

roofs or soakaways for individual houses).

3. Site control – management of water from several sub-catchments

(including routing water from roofs and car parks to one large soakaway

or infiltration basin for the whole site).

4. Regional control – management of runoff from several sites,

typically in a detention pond or wetland.

Figure 1.11Showing the hierarchy of the Management Train. When ‘Prevention’ has been deemed impossible, you must first look to ‘Source Control’, then to “Site Control’ and lastly ‘Regional Control’.(source: RBA, 2010)


1�4 Sub-catchments

As Robert Bray Associates (RBA) (2010.) highlight: Of all of these stages

in the management train, it is source control that is the most important.

As soon you make an intervention in the landscape you change the

behaviour and quality of any water entering that site. In larger sites,

where water quantities would be larger too, sub-catchments are also

preferable in order to deal with the water in as small amounts as

possible.

“A major advantage to splitting the site into sub-catchments that run

off attenuation is distributed around the site within construction profiles

that provide cleaning at source, minimise the risk of failure and reduce

costs” (RBA, 2010).

Serious problems arise when we allow the accumulation of water and

pollutants. The earlier we can prevent this accumulation the better, and

this is where the management train and source control come in. By

slowing stormwater runoff down, allowing infiltration and filtering out

any pollutants as close to where the water falls, we can reduce the

chance of problems building up.

1.5 The Benefits of SUDS

The concept of the management train is a widely accepted concept

(Kirby, 2005, CLG, 2009, DEFRA, 2004a) as it reflects natural water

behaviour. It allows as much water as possible to infiltrate, recharging

ground water and aquifers, using vegetation to retard flow rate over

ground, taking it up and releasing it via evapotranspiration and

improving water quality via sedimentation and biodegradation. Further

down the chain, ponds and swales will hold and retain water allowing

time for more bioremediation, replacing some of the 75% of ponds lost

in England and the wild life that depend on them (EA, n.d.).


A good SUDS scheme will provide much for wildlife and increased

biodiversity which can only improve the effectiveness of the schemes

(DEFRA, 2004a): It holds massive potential for providing public amenity,

through the provision of open public space, and can also increase the

value of housing and increase the quality of public space (Petrova,

2011, Arthur, 2011, Heal, 2011). It aids public health, by providing the

restorative effects of nature and wildlife, improving air quality through

the provision of green space, reducing the Urban Heat Island effect

and providing space for exercise (DEFRA, 2004a).

The benefits of SUDS are

-reducing peak flows to watercourses or sewers and potentially

reducing the risk of flooding downstream

-reducing volumes and the frequency of water flowing directly to

watercourses or sewers from developed sites

-improving water quality over conventional surface water sewers by

removing pollutants from diffuse pollutant sources

-reducing potable water demand through rainwater harvesting

-improving amenity through the provision of public open space and

wildlife habitat

-replicating natural drainage patterns, including the recharge of

groundwater so that base flows are maintained.

(DEFRA, 2004a)

SUDS should be designed to incorporate a whole range of features

and measures to work together, for back up and when heavier rains

do come and to cope effectively with different levels and possible uses

across changing conditions. A system that has to cope with a large

storm event may have elements that remain perfectly dry for most of

the time and have elements that are permanent pools or ponds and

therefore need to be recharged.

It is apparent that SUDS schemes are generally made up of many

different elements, as the design process involves a site analysis of

flow routes and potential storage and SUDS features (AW, 2011, RBA,

Figure 1.12A swale that collects filters and attenuates runoff from the road and path. Care has been taken over the design quality as well as the SUDS function.(source: Wong, 2011)

Figure 1.13Infiltration Trenches that have been designed to delineate space and act as stormwater retention.(source: Wong, 2011)


2010). DEFRA (2004b) also state that it is preferable and more effective

to have a combination of SUDS techniques and features. RBA (2010)

goes on to say that different sites will yield different opportunities, so

it is important to capitalise these, especially to maximise infiltration.

The use of vegetation will slow the runoff rate, allowing more time for

infiltration, as well as attenuating peak flow further down stream and

allowing more time for bio-remediation of pollutants. SNIFFER (2004)

reinforce this point, as Figures 1.14 and 1.15 illustrates, by stating the

results of studies that confirm that SUDS not only reduce peak flow but

also pollutant loads in the runoff compared to traditional drainage. This

combination of natural vegetation and processes not only remediates

Figure 1.14Graph showing the comparative reduction in peak flow, the highest rate of runoff after a rain fall, between traditional drainage and SUDS.(source: SNIFFER, 2004)

Figure 1.15Graph showing the comparative reduction in volume of pollutants washed from impermeable surfaces between traditional drainage and SUDS. The “first flush” is the peak.(source: SNIFFER, 2004)


flooding and pollution but as a by-product increases the amount of

vegetation and water and its associated benefits.

1�6 SUDS components

All SUDS features to varying degrees aid stormwater management

using the natural processes of sedimentation, filtration, absorption and

biological degradation. Most SUDS features are a version of what is

described in this list and most SUDS documentation describe their

mechanics in the same way (DEFRA, 2004a, DEFRA, 2004b, CLG,

2009, CIRIA, n.d.b). A summary of SUDS components (DEFRA, 2004a):

• Preventative measures: The first stage of the SUDS approach

to prevent or reduce pollution and runoff quantities. This may include

good housekeeping, to prevent spills and leaks, storage in water butts,

rainwater harvesting systems, and alternative roofs (i.e. green and

brown roofs).

• Pervious surfaces: Any surfaces that allow inflow of rainwater

into the underlying construction or soil.(This is different form permeable

paving, which is discussed further in later Sections 3.4 and 4.2)

• Green roofs: Vegetated roofs that reduce the volume and rate of

runoff and remove pollution.

• Filter drains: Linear drains consisting of trenches filled with a

permeable material, often with a perforated pipe in the base of the

trench to assist drainage, to store and conduct water; they may also

permit infiltration.

• Filter strips: Vegetated areas of gently sloping ground designed

to drain water evenly off impermeable areas and to filter out silt and

other particulates.

• Swales: Shallow vegetated channels that conduct and retain

water, and may also permit infiltration; the vegetation filters particulate

matter.

• Basins, ponds and wetland: Areas that may be utilised for

surface runoff storage.


• Infiltration devices: Sub-surface structures to promote the

infiltration of surface water to ground. They can be trenches, basins or

soakaways.

• Bio-retention areas: Vegetated areas designed to collect and

treat water before discharge via a piped system or infiltration to the

ground.

• Filters: Engineered sand filters designed to remove pollutants

from runoff.

• Pipes and accessories: A series of conduits and their accessories

normally laid underground that convey surface water to a suitable

location for treatment and/or disposal. (Although sustainable, these

techniques should be considered where other SUDS techniques are

not practicable).

These techniques in various forms will be discussed in Section 2.5, the

basic concept behind them are the same but they adjusted to various

extents to be able to apply them to the dense urban realm.

1�7 Summary

“Sustainable drainage is a departure from the traditional approach to

draining sites. There are some key principles that influence the planning

and design process enabling them to mimic natural drainage by:

• Storing runoff and releasing it slowly (attenuation)

• Allowing water to soak into the ground (infiltration)

• Slowly transporting (conveying) water on the surface

• Filtering out pollutants

• Allowing sediments to settle out by controlling the flow of the

water” (CIRIA, n.d.b)

By attempting to mimic as closely as possible natural flow patterns

we can greatly reduce urban runoff and remediate the flooding and

pollution associated with this. DEFRA (2004a), CLG (2009) and RBA

(2010) all state that the government requires developers to reduce

runoff rate to that of its pre-development green field rate. RBA (2010)


put these Figures, for the district of Islington, at reducing runoff rate from

200-350 litres/second/hectare for most existing urban development to

8 l/sec/hec. This may seem like a massive requirement, but systems

have been shown to achieve this.

With enough space it would probably be very easy for SUDS to handle all

of our stormwater management issues, as Case Study 1 demonstrates.

However, within our cities, in the dense urban environment, space is

a valuable resource. We may not have the space for large retention

ponds, swales and wetland filter beds next to our dense building grain,

paved carparks, industrial estates and roads.

However there are solutions that revolve around the idea of

multifunctionality and the retrofitting of existing structures and spaces

with new technologies. This is the way that SUDS can make a big

impact in the effort to make our cities more sustainable, healthy and

pleasant places to be. This report will review current practices and how

they have been used in certain situations to combat the issues of SUDS

in the dense urban realm.

Figure 1.16Linburn Detention basin. A good quality public space that enhances the area and provides stormwater attenuation. This basin alone provides four of the five points that CIRIA (n.d.b) sum up (see Section 1.7), with only “slowly conveying water” not being achieved. (source: SNIFFER, 2004)


1.8 case study: oxford servIces

The SUDS at the Oxford service station on the M40 has been in operation

from 1998 and still serves as one of the UK Environment Agency’s

Demonstration sites. They have been operating for 13 years now,

having to deal with heavy motorway traffic and the oil and pollutants

that come in with or leak from the cars and lorries. During that time they

have also seen the heavy floods that the systems are designed to take,

again proving the resilience of well-designed SUDS (RBA,2011b).

Oxford Services act as an excellent example of SUDS, demonstrating in

practice the benefits and claims made of them, tackling all the problems

that would face a drainage engineer and employing the basic principles

of SUDS. The SUDS at this reduces the need for underground drainage

systems, collects and utilises roof water, provides flood protection and

is able to clean and filter pollution from the sites rainfall runoff so it can

leave the site clean.

There is great benefit in reducing our reliance on underground pipes,

as the EA (n.d.) illustrate here (see Figure 1.17). Originally the service

station would have required a 1 meter diameter pipe in which to

handle the water from the site. This would mean runoff would need to

be discharged in to a river some distance away. With the new SUDS

design, the pipe needed was reduced to 150mm diameter and could

now be discharged into a small stream closer to the site. The result

of these changes alone resulted in massive savings in major ground

works, and less disruption and payments to local landowners.

Figure 1.17Top, river originally chosen for stormwater discharge. Middle, location relative to site. Bottom, stream that now take all discharge from the site.(source: EA, n.d.)

Figure 1.16Interception Pond at Oxford Services(source: RBA, 2011b)


Figure 1.18‘Source Control, Design Overview’, Stormwater Strategy plan for Oxford Services showing main SUDS elements.(source: RBA, 2011b)


1.9 The Main elements and the roles they fulfil

EA (n.d.) and RBA (2011b) describe several measures put in place that

work as a system, providing many fail safes. These reduce the peak

flow, overall flow and clean the water before it leaves the site, as can

be seen in Figure 1.18.

The Roof System (Figure 1.19): collects the water from the roof, and

stores it in a series of ponds around the buildings. The water collected

here is naturally treated in water features around the building, also

providing amenities and ornamental features for the visitors to the

Services. In order to keep this system topped up to retain its amenity

value, waste water from the site is also recycled on an on-site lagoon

and reed bed treatment system.

Porous Paving (Figure 1.20): Installed in the car park, this allows water

to be stored and cleaned before it filters and percolates through to the

wetlands lower down the system or into the infiltration trenches. As will

be discussed in Sections 3.4 and 4.2, porous paving is very efficient

and effective at dealing with polluted runoff water.

Infiltration Trenches (Figure 1.21): Essentially filter drains and strips

(as discussed further in Section 2.5), these run around the perimeter

of the car park and collect all the extra runoff. The pollutants in the run

off can be very high on this site, especially from the HGV park, with

oils, hydraulic fluids and brake fluids, as well as ‘normal’ pollutants like

road dust, and drinks spills. This is often the first stage of the cleaning

Figure 1.19One in the series of treatment ponds that receive the roof water and store it for attenuation purposes, as well reuse and ornamentation(source: EA, n.d.)

Figure 1.21The gravel infiltration trenches, allow polluted car park runoff through the inlets and from here the water slowly flows and filters its way through the system.(source: EA, n.d.)

Figure 1.20The red parking spaces constructed of porous paving allows the water to pass through to the substrate where it can infiltrate or be directed into the system.(source: EA, n.d.)


process and like the rest of the system, the longer the spills stay in

there, the longer the cleaning process can go on.

Interception Pond (Figure 1.22): Combined with the reed bed, provide

the storage, sedimentation and filtration of most of the day-to-day run

off. Here it sits and is allowed to break down the oils and organic matter.

It is collected slowly and allowed time to move through the system and

leaves as if “though it were, a green field site” -Robert Bray (EA, n.d.).

This is also large enough to handle more rain, but is in fact just a part

of the larger flood protection system.

Floodway and Balancing pond (Figure 1.23): In the event of very

heavy rain fall there are two main back ups to accept over flow form

the interception pond that will slow flow rate and act as an attenuation

pond, absorb pollutants and allow infiltration: acting as an emergency

environmental ‘buffer’.

This combination of systems all fight towards the same goal: source

control of flooding and pollution. Working as a system, the elements

tackle the problems in sequence. Robert Bray (EA, n.d.) indicates, the

water moves slowly through the site, allowing time for the breakdown

and removal of solids and pollution before it leaves the site to the local

stream.

Figure 1.22Interception Pond in normal circumstances, all water that has not already infiltrated will find its way here for bio-remediation. The pollutants slowly break down through organic bioremediation (EA, n.d.)(source: EA, n.d.).

Figure 1.23Interception Pond (front), Balancing Pond (middle) and Floodway (right).(source: EA, n.d.)


1�10 Summary

By looking at the systems and elements in place it is evident that this

site neatly demonstrates all of the basic elements of SUDS design:

Source control: dealing with issues as close to source as possible

Attenuation and Detention devices: Designed to slow the rate of

water by collection and slow release. They also function as filtration

bioremediation devices. They also decrease the peak levels of flow

and first flush pollutants.

Infiltration devices: allow water to soak away into the ground to reduce

outflow volumes and filter pollutants and restock ground water.

CIRIA (2002) highlight that the main issue with this site is the single

catchment area. If designed now they may have used two sub-

catchments in order to further strengthen the resilience to heavy

flooding, as they did at Hopwood Services. However RBA (2011b)

state, “The inherent design tolerances of (SUDS) techniques prevent

catastrophic failure as well as background pollution of the environment”

which is something that pipes do not do.

It has proved itself a very successful scheme, and a questionnaire

was sent to the management of this sister site at Hopwood Motorway

Service area on the M42 and to the Environment Agency (2002). The

main points picked out were:

-Ease of maintenance

-30–50 percent cost savings in maintenance

-Attractive landscape features

-Reduction in heavy metals, silt and BOD

-Filter strips and treatment trenches protect wetlands

-The “management train” enhances water quality.

All of which, for a scheme built in the early days of SUDS, seems to

demonstrate the effectiveness of a well-designed SUDS scheme.


2.0 SUDS in the CityWhile the widespread adoption of SUDS may still be gathering speed,

as the previous chapter explains, the advantages of it over more

traditional methods are huge. It is cheaper and easier to both install

and maintain (EA, n.d.), and provided it is designed properly it will

handle large volumes of almost any quality of water: given enough

space. However, due to lack of space:

RBA (2010) explain that in order for SUDS to be successful in the

more dense urban realm, they need to be adopted in more imaginative

and innovative ways. The need for SUDS is most desperate within the

dense urban realm and it is here that space is at a premium: there

isn’t generally room for large scale wetlands and empty swales. The

principles of SUDS can still be followed but the schemes need to be

more innovative and abstract in their adoption of natural processes.

“In urban areas, particularly in very dense developments [….] Every

hard surface becomes a rain water collector and the construction

profile must be considered for runoff management” (RBA, 2010)

In 2005, the London Assembly reported that several thousand front

gardens in London had been paved over, equating to an area 22

times the size of Hyde Park, or approximately 2.5% of the total area of

London (CIRIA, 2009). It is explained that extra stormwater runoff can

be attributed directly to this and this contributes to the bigger problem.

As a result of this, both CIRIA (2009) and CLG (2009) state that as of

October 2008, any one wishing to lay more than 5m2 of impermeable

paving has to apply for planning permission, whereas this is not the

case with permeable paving.

The design of each scheme is should be site specific, but by looking at

some current exemplar schemes we can see how they have dealt the

problems of space and other issues that arise from putting SUDS in the


City. This review of current schemes and literature will highlight some

more common elements and systems as well as showing some of the

more innovative ways in which drainage in the dense urban realm has

been tackled.

2�1 Multifunctionality

One thing that is most prevalent in the research is that within the dense

urban setting, multifunctionality is an extremely important consideration,

and this can be seen throughout all the chapters and case studies. The

information suggests that because space is so restricted and there are

many different uses that require this space. It is important that SUDS

schemes and their build elements can perform more than one function.

Multifunctional design and use should always be a characteristic of

inner city SUDS (Bray, 2011a).

For instance Figures 2.1 and 2.2 show that by creating low-lying areas

in an urban park, space can be provided for temporary water storage.

Boer, Jorritsma and van Peijpe (2010) describe the concept of the

Rotterdam Watersquare which provides a place for water storage and

attenuation in predominantly hard landscaped city squares. Rotterdam

lies below sea level so it is unable to allow water to infiltrate, therefore the

best way of preventing urban flooding is attenuation. Most attenuation

devices will be naturalised ponds or infiltration basins that retain and

release water at a slow and steady rate naturally. These watersquares

take this concept, but urbanise it by retaining the water in hard surfaced,

man made basins and then slowly pump it out.

Figure 2.1Parc Jean Mermoz, in Villemomble. The undulating landforms create a soft relaxing area of grass.(source: Brattli and Sørensen, 2011)

Figure 2.2Parc Jean Mermoz. As the runoff in creases the low points fill up in sequence, enhancing the visual qualities and changes as the storm event changes.(source: Brattli and Sørensen, 2011)


Figure 2.3 shows, sports pitches and skate parks can be sunken and

filled with storm water. Space can also be provided under floating

squares allowing dirty sewage to overflow from combined sewers.

This shows the possibility of multifunctionality with public space and

sewage water. Figure 2.4 shows how this water storage can be used

to change and enhance public space. It shows how rising water levels

can create islands, redefining the space and completely changing the

character of the square.

There is a more detailed case study on another version of the Rotterdam

watersquares in Section 5.11. This will describe in more depth the

technologies and processes that are used in that particular example.

It will illustrate how they have incorporated SUDS principles in an

innovative way

2�2 Non-Defensive Flood strategies

Some times it could be beneficial to allow passive, non-defensive flood

measures (Figure 2.5). Flood water needs space to go, as discussed,

and what the LifE project (2011) champions is ‘making room for water’.

When we have the opportunity to, we should build floodplains and

areas of temporary flooding into our urban fabric. This will alleviate

flooding downstream and cause less damage and problems. If we can

plan for floods and accept that they will happen we will do less damage

and save more money on expensive flood defences in the long run.

Figure 2.4Using water storage to alter and enhance public space.(source: Boer, Jorritsma and van Peijpe, 2010)

Figure 2.3 (previous pageDifferent ways in which hard surfaces public space can be used to temporarily store storm water.(source: Boer, Jorritsma and van Peijpe, 2010)


Hargreaves and Campbell-Kelly (2007) explain how we can “coexist

with the dynamics of the river” by consideration of use and activities.

Louisville Waterfront Park in Kentucky is sloped to allow interaction with

the natural water cycles of the river. Instead of building a bulkhead that

will block out the water completely and force this flow downstream, they

have provided a sloping park that becomes partially submerged when

river levels rise. A lawn planted with resilient native grasses occupies

the riverside portion of the park, so that it can withstand flooding.

Located at the highest point is a sculpture park that will not get flooded,

thereby arranging the park by use and resilience.

This park is fitted with water hydrants that can be used to wash the

debris left behind after a flood back in to the river (Hargreaves and

Campbell-Kelly, 2007). This ensures that the park can adapt to regular

flooding and still remain attractive. Gabions at the waters edge allow

easy access to the waterfront and allow for plant colonisation and

filtering. Since this park has been opened and allowed to interact with

the natural cycles of the river, there has been an increase in biodiversity

with native migratory plant species colonising the gabions

2�3 Decentralised Approach/regional wide approach

Source control is always the preferred tactic when designing a SUDS

scheme because it is so effective at reducing the cumulative effects

of flooding and pollution. This works because the combined efforts of

several schemes reduce the impact downstream. In order to deal with

an urban watershed where most precipitation will become runoff, the

concept of source control will ensure it is dealt with as soon as possible.

To avoid this accumulation of water and concentrated pollution, lots of

smaller interventions will not only be much more effective and efficient

but more suited to the urban fabric. As will be discussed later in case

study (see Section 3.5) Portland’s Green Streets (2011) employ exactly

this tactic to great success. By installing lots of small SUDS features on

Figure 2.5Using non-defensive flood-risk management, open spaces are designed to accommodate rainwater in rain gardens and on green roofs. Floodwater is directed into planted channels, retention ponds or multi-use recreation areas. Top: everyday scenario: middle: 1 in 20 year storm: bottom: 1 in 100 year storm. (Barker and Coutts, 2009)(source: Barker and Coutts, 2009)


the streets and small tracts of land, they have successfully addressed

the problem, but it is an ongoing issue and they continue to install

SUDS features around the city. Green Streets (2011) say that a major

reason why this solution is so workable is that individually they are fairly

cheap to install and maintain and the reduction of stormwater runoff

into the drains can save the city money by avoiding upgrade costs of

underground sewerage and drainage.

It is a governments responsibility to ensure that there is a SUDS strategy

across a region, which should not just extend up to political boundaries

but, more importantly, topographical region, i.e. Watersheds. However it

still requires the engagement of all the stakeholders to implement these

schemes in order to get the most from SUDS; a “collaborative effort is

considered to be more cost effective and beneficial than stakeholders

acting individually” (CIRIA, 2009)

There are several governments and city councils that have instigated

integral SUDS planning into their city policy as part of sustainable

development: Portland (Green streets, 2011), Malmo in Sweden

(Kazmierczak and Carter, 2010) and the British government have

made it policy to integrate SUDS into new developments (CLG, 2009).

These examples demonstrate that it is important to ensure that these

schemes are taken on and instigated region-wide so that everyone is

aware of the benefits.

2�4 Singapore (Dreiseitl, 2007,2010)

Singapore is currently undergoing a massive change in the way it

deals with its urban runoff management. Singapore have initiated a

programme to simultaneously deal with the water shortage within the

city, clean the urban runoff and beautify the existing stormwater canals.

Currently Singapore have a highly developed water management

strategy compared to many European and American Cities. The city

has an extensive network of water treatment facilities, most of the city


has separate sewer and stormwater systems and it even has a waste

water recycling scheme which provides “hygienically faultless water in

bottles and pipes” (Dreiseitl, 2007).

However this is not enough, as they still have to import 40% of their water

from a river in neighbouring Malaysia. This water shortage is not due

to lack of precipitation either, but because currently water is collected

and channelled straight into the ocean. These appropriately large ugly

channels remain empty for most of the year and form insurmountable

barriers dividing up the city. They also collect ‘first flush’ pollutants and

litter from the urban realm and wash all this into the canals. Figure 2.6

illustrates the current state of canals of different sizes and potential

scenarios that could clean the urban runoff, provide beatification of

these canals and develop links into and across them. As they show, this

can be fully naturalised, with the provision of walkways and planted-up

banks or by the use of cleansing marginal planting in the bottom of the

canals.

This is all part of a much wider plan, in which the water captured by

the canals will be stored in reservoirs and cleaned in the canal and

reservoir system for reuse around the city. The city will add to, improve

and regenerate its “pervasive network of fourteen reservoirs, 32 major

rivers, and more than 7,000 kilometres of canals and drains”. It is

important however, to deal with as much urban runoff before it reaches

the rivers and canals in order to reduce peak flow and make sure that

the water is as clean as possible before entering the canals. Singapore

also intend to increase the catchment of this island city in order to

maximise the water that is captured and utilised.

“With the storage and reuse of run-off rainwater from the densely built

city, the catchment area takes on particular importance. The delivery

of clean and hydraulically slowed rainwater to the rivers will be a

necessity. This can only mean the step-by-step rebuilding of the storm

water management in an integrated, decentralised urban system. In

principle, the task is to manage (infiltrate, evaporate, cleanse, reuse)


rainwater where it falls and to ease the pressure on the rivers during

peak storm events. At the same time, the run-off water should arrive

clean at the river banks which means managing the ‘first flush’ through

the likes of green roofs, rain gardens, cleansing biotopes, and trash

filters.” (Dreiseitl,2007)

Dreiseitl clearly indicates the uses of SUDS techniques, philosophies

and aims showing the intention to deal with these problems using

natural systems. However, the important phrases here are “step-by-

step rebuilding” and “integrated decentralised urban system”. Figure

2.7 illustrates that currently when it rains, large volumes of untreated

stormwater flow rapidly into the island’s canal network (left). Future

stormwater management efforts will focus on a de-centralised approach

Figure 2.6Potential scenarios for the canals of Singapore. Decentralised, smaller interventions have a bigger impact which can be felt across the city, both in terms of stormwater management and improvement of public space.(source: Dreiseitl, 2007)


that reduces peak flows (right). This needs to be achieved step by step

with the full involvement of the development companies, investors, city

officials and the residents of Singapore.

By using this strategy, Singapore can regenerate its stormwater

management system, providing links and green spaces in and around

the city, and increase the efficiency of its water supply system. This is

achieved by a strategy that starts with a council plan but involves all

stakeholders in order to maximise the chances of success.

2�5 SUDS Components in the City�

There are some SUDS elements that are especially suited for the urban

environment or undergo subtle changes that make them more workable.

They all operate on the principles of SUDS and most are the same as,

or adaptations of, the SUDS components introduced in Section 1.6.

Because of lack of space or the multifunction required of space in the

dense urban environment, adaption is sometimes required.

Rain gardens are a vegetated infiltration device and one of the main

types of SUDS features employed by Portland City council (Green

Streets, 2011). This is because they can be easily retrofitted into

a suitable plot of land and can often be relatively small. As will be

discussed in Section 5.8, Mount Tabor Middle School has proved the

effectiveness of such measures (Figure 2.8). They have an in built

depth and can be flooded or left dry. Consideration should be paid to

vegetation that is resilient to periodic inundation and pollution. As OSU

(2011) describes when demonstrating Portland’s private residential

raingardens, they can be multifunctional as well, by being productive

and ornamental, for example. This illustrates how SUDS features can

constitute improvements to the urban realm and not just be a way to

provide urban runoff measures.

Figure 2.7Left: when it rains, large volumes of untreated stormwater flow rapidly into the islands canal network. Right: Future stormwater management efforts will focus on a decentralised approach that reduces peak flows (Dreiseitl, 2007)(source: Dreiseitl, 2007)


In general, these types of devices are not designed to take all rainfall but

hold and attenuate some rain and to work in unison with other features.

Similar features that work in the same way are Kerb Extensions, which

also work as traffic calming, and stormwater street planters, which

provide planting on or next to the sidewalk (Green Streets, 2011).

These will be discussed further in Section 3.2.

Infiltration strips and swales (Figure 2.9) are the best option if possible

as these can accept sheet water runoff rather than from a single point

inflow. AW (2011) describe filter strips as vegetated strips of land that

accept water as sheet flow from impermeable surfaces. The vegetated

surfaces slow down the flow rate, allowing some initial infiltration,

filtration and sedimentation, but its main job is to slow the water down

before it moves to the next stage. AW (2011) point out that sheet flow

Figure 2.8Glencoe Elementary school rain garden. Protects homes from sewer backups, serves as an educational resource and provides public amenity (Green Streets, 2006)(source: CPBES, 2004b)

Figure 2.9Retrofitted raingarden within a housing estate. The rain gardens can be permanent water if required and also be underdrained.(source: RBA, 2010)


is also preferable as there is less pressure and volume of water that

if all the water was collected and sent through a small aperture. This

reduces erosion at and near these narrow inlets and outlets and allows

water to spread more evenly over the system.

Swales are flat-bottomed vegetated channels that allow conveyance

of stormwater runoff (AW, 2011) (see Figure 2.10). The flat bottom

encourages sheet runoff through it and the dense vegetation

slows water even more, facilitating more infiltration, filtration and

sedimentation. Some times these swales will be under-drained to allow

faster conveyance of filtered stormwater.

Filter strips are also similar devices, but as Figures 2.10 and 2.11

illustrates, some filter strips and filter drains don’t hold water on the

surface but allow faster infiltration (RBA, 2010). They have specially

engineered soils that allow quick infiltration to deal with runoff,

and sometimes have perforated drains buried to allow even faster

conveyance. RBA (2011a) highlight the fact that water entering the

perforated drain has already undergone a filtering process through the

vegetation and soil so it is clean water that can be stored or moved on.

Figure 2.10Filter strip and Swale. It gathers water off the road and holds it in the basin. The crushed stone and perforated pipe in the trench allow for faster drainage.(source: RBA, 2010)


Permeable paving is another form of infiltration device and has all the

associated benefits, but additionally is a hard surface that can be used

as a car park or play surface. RBA (2010) state that this is important

for space saving in a dense urban environment. They also mention

that these can be combined with a raised kerb to provide additional

attenuation. This will be discussed further in Section 4.2.

As RBA (2010) tells us, like Permeable paving, Green roofs are the

only other SUDS device that require no additional land take and so are

important in an urban environment where space is lacking. More will be

said on this in Section 4.7.

Storage and attenuation devices must also adapt to the urban realm.

Sometimes this is simply adjusting the scale or using a barrier to ensure

water will not effect the structure of a nearby building (RBA, 2010).

Sometimes water has to be stored underground, as Dreiseitl and Grau

(2001) demonstrate in Potsdamer Platz. They explain how massive

underground storage cisterns collect rainwater after it has been filtered

through the artificial treatment wetlands in a ground level water feature.

The cisterns also allow settling of sediments, giving further purification.

This storage is used for toilet flushing in the buildings surrounding it

and for irrigation of the planting. Potsdamer Platz is large urban square

and serves lots of building around it. The cisterns and the ground level

water feature have a built-in buffer volume so that they can temporarily

store water in times of large storm events.

One does not have to consist of large tanks or cisterns, as Figure

2.12 illustrates and the EA (2008) explain. By providing a coarse grain

Figure 2.11A more conventional filter drain. A lot more space saving.(source: AW, 2011)


substrate which contains lots of voids between the particles, water

can be stored there, similar to the engineered soil structure of filter

drains and allowed to drain away. An even more engineered solution

is the provision of plastic modules, or geocellular support that hold

up a hard surface on top creating a void (Figure 2.13). These can be

situated under car parks thus taking no extra land and can be used

for rainwater harvesting or as an attenuation or retention device after

filtering through SUDS.

While underground storage is not a SUDS feature in its own right, they

can be useful in combination with SUDS for rainwater harvesting, water

storage or attenuation. It provides space for stormwater, which will

prevent flooding and diffuse pollution further downstream.

Figure 2.12Illustration of how the voids between particles in substrate can provide water storage opportunities. The larger the particles, the more large the voids.(source: Dearden and Price, 2011)

Figure 2.13A geocellular structure under permeable paving can have the strength to take the weight of heavy vehicles, but the void created can provide essential storage space(source: Interpave, 2008)


2�6 Keys Areas of Focus for SUDS in the City

Within a city there are often very defined areas of use and ownership

and they have different constraints on them. Each area and each plot of

land can have different challenges and potential benefits for possible

SUDS schemes. These can be described in three main categories:

Roads, Building developments and Open Public green space. These

will be discussed in the following chapters.

Roads are the connections that bind our city together, however due

to their nature they can be problematic when dealing with stormwater

runoff. They are hard impervious surfaces that contain no vegetation

and water is often quickly sheeted from them. This water carries with

it all kinds of associated urban pollutants as discussed in Section 1.2. They act as channels that accept any water from surrounding land

as well and often deposit it in drains. Even those that drain into local

streams and ditches can cause major erosions of banks and wildlife

habitat due to the large peak flow received from the roads (GreenTreks

Network, 2011). This is not surprising given their inherent need to be

hard wearing, but there are ways to address this without losing the

roads performance and benefits. In fact many of the solutions improve

the street, greening the appearance of it and its surroundings.

Building developments can include everything from industrial estates

to commercial, retail and education institutions and to residential

estates. Again these areas, in varying degrees, have become covered

in hard impervious surfaces. Building footprints take land from

permeable surfaces, as can car parks and some pedestrian areas.

Like the roads, these sweep all water collected, in huge quantities,

down the combined sewers. This water can be just as polluted as road

runoff and in the case of car parks and industrial estates, even more

so. With land so tight in the city and the uses so specific, it is important

that land use in the city should be as adaptable and multifunctional as

possible.


Parks and open public green space are very important in the

successful adoption of SUDS as they contain the largest areas of

green, natural habitat in our cities. These lend themselves perfectly to

the need for large open areas in which to place larger SUDS schemes.

We should try to deal with water as close to source as possible,

but this is not always possible and larger, regional controls are also

beneficial. Parks can provide this, serving a wider catchment area of

the local conurbation. It also provides large wetland areas for wildlife

and biodiversity that may not flourish in smaller areas closer to urban

activity. Other public green spaces that may be utilised include schools

and rivers, which are both ideally suited to multiuse SUDS due to their

public ownership and prevalence in the public realm.


2.7 Case Study: Sponge Park, Brooklyn, New York

The Gowanus Canal in Brooklyn, formerly a wetland creek, has become

severely polluted owing to heavy industrial processes and sewer

overflows. Energy companies that once bordered the canal have left

behind volatile toxins and pollutants in the soil and the sediments of the

canal and its neighbourhood properties. The once thriving industrial

corridor that gave the canal its character and life is now largely deserted

following a marked decline in the demand for water transport. The

departing industries have left behind a deteriorating and neglected

bulkhead and industrial lots which have turned their backs to the canal

(Drake and Kim, 2009).

Dlandstudio (2008) inform us that the industrial lots that line the canal

are mainly surrounded by residential properties, and the barrier-like

nature of these lots means that the residents are largely cut off from the

waterfront (see Figure 2.15). The need to provide waterfront access

has been voiced by the local residents, and there are certain groups

who would like boat launches in order to directly access the water itself

e.g. for canoeing, a further tie strengthening the link between land

and water. As the Gowanus Canal Conservancy (n.d.) inform us, in

2008 several meetings were held to introduce the community, elected

officials, and various government agencies to the Sponge Park plan.

Figure 2.15The current state of the water front. Industrial lots line the edge and the only real public water front access are these road ends.(source: Dlandstudio, n.d.)

Figure 2.14Sponge park concept: by diverting stormwater from the storm drains, the Sponge Park will soak up and clean the runoff.(source: Dlandstudio, 2008)


The combined geological and jurisdictional watershed for the Gowanus

Canal is 1,758 acres (see Figure 2.16. This takes the form of surface

water run-off, storm outfalls and combined sewer outfalls. In the event

of a severe storm event, the combined sewer outfalls overflow into the

Gowanus Canal, further adding to the pollution. Dlandstudio (2008)

have calculated that for the entire watershed, given that 62% of the

district is covered by an impervious surface, 11.4 acres of additional

permeable surface are needed.

Solutions

In order partly address these issues, Dlandstudio have proposed the

idea of Sponge Parks as illustrated in Figure 2.14. Drake and Kim

(2009) and Dlandstudio (2008) inform us that this proposal will provide

5.5 of those 11.4 acres of permeable surface as a strip park along the

water front. It will form a barrier to catch surface water runoff and to

collect stormwater before filtering, cleaning and releasing it into the

Gowanus Canal. The goals set forward by Dlandstudio are: to provide

a series of waterfront spaces that will slow, absorb and filter runoff in

order to simultaneously clean the water, activate the canal edge, and

engage public stewardship of the scheme.

Figure 2.16The watershed (blue), the sewershed (grey) and the proposed Sponge Park collection area (orange). The canal side Sponge Park will deal with the immediately surrounding neigh-bourhood.(source: Dlandstudio, n.d.)


There are already several schemes underway to clean the contaminated

water and the sediments in the canal so the Sponge Parks focus is on

managing stormwater runoff from the areas closest to the canal while

providing public amenity at the same time. As Figure 2.17 illustrates,

Dlandstudio propose an esplanade along the edge of the canal which

will run alongside, or over, a series of bioremediation basins and

wetlands to treat and attenuate stormwater before its release into the

canal (Drake and Kim, 2009).

The only real public access to this waterfront is currently from the

road ends, which continue upto the water’s edge and, as you can see

from Figure 2.15, they are low grade public space. Here there will be

a series of road-end parks that provide access to the esplanade as

well as providing space for community-orientated programmes such

as dog runs, community gardens, art exhibitions and farmers’ markets

(Dlandstudio, 2008). They will also act as the first of the waterside

SUDS measures, collecting excess stormwater runoff from the street.

Figure 2.17 (previous page)Site axonometric/masterplan.The Sponge Park runs along the edge of the majority of the canal and at places it expands or connects to larger open green spaces(source: Dlandstudio, 2008)

Figure 2.18Concept visual of a street end sponge park at Sackett Street(source: Dlandstudio, 2008)


2�8 Sponge Park Stormwater management

As shown in Figure 2.18, water from the rainfall will flow down the street

and will first be intercepted by the infiltration swales, very much like the

kerb extensions seen in Portland and any extra water will flow towards

the Sponge Park where it enters the first in a series of deepening and

wetter remediation basins (Dlandstudio, 2008, Drake and Kim, 2009).

As illustrated in Figures 2.18 and 2.19, the water first enters the

meadow basin, then gradually overflows into the wet meadow as the

flow increases. In bigger storm events the runoff will enter separate

storm drains and will be taken directly to the Sponge Park. The heavier

the rain and the greater the flow means that the water then enters the

shallow meadow, shallow marsh and deep marsh. After the water has

flowed through and been cleaned by this series of basins it enters a

Figure 2.19Indicating the different zones and their flooding depths. Note also the pedestrian walkway that is suspended above the bioremediation zones.(source: Dlandstudio, 2008)

Figure 2.18Controlled street measures and zonal flooding in average and heavy rain falls.(source: Dlandstudio, 2008)


storage cistern, (see Figure 2.20). Here the clean water can be stored

and used for irrigation in drier periods or for flow control of clean water

into the canal in heavy storm events.

The choice of planting was also carefully chosen here, with reference to

pollutants and bioremediation. Dlandstudio (2008) describe the three

main categories into which the basins fall. Zone 1 is designed to contain

no standing water and the vegetation either allows infiltration or lets the

water filter and flow through into the next zone. Zone 2 is a basin that

will accommodate up to 2 inches of standing water allowing chance for

infiltration and bioremediation of this standing water, before it overflows

into the final zone. Zone 3 will tolerate up to one foot of standing water

allowing more infiltration and bioremediation. These zones correspond

to the type of habitat, with Zone 1 being a drier meadow and Zones 2

and 3 becoming progressively wetter meadows and deeper marshes.

As Figure 2.21 shows, each zone also has its own planting lists which

are designed to be tolerant of their designated flooding depths and

contain plants particularly suited to bioremediation. The different zones

will allow infiltration and sedimentation of solids and water soluble

pollutants, especially heavy metals and PCBs. Due to the highly

polluted, heavy metal- and petrochemical-rich soil in the area, specific

plants have been chosen for breaking down this type of pollution.

Figure 2.20Axonometric of Street End Sponge Park. Showing Street planters, bioremediation wetlands, suspended esplanade and storage cisterns.(source: Dlandstudio, 2008)


Figure 2.21Note the coloured circles which correspond to the zones in Figure 2.19 and those plants that have either the gold or silver dots next to them, indicating their ability to remediate pollution.(source: Dlandstudio, 2008)


2�9 In Conclusion

The Gowanus Canal Conservancy (2008) is a non-profit organisation that

has dedicated itself to the restoration of the canal and its surrounding

area. It has gained the support of the local community and all relevant

city agencies, such as planning, transport and environmental agencies.

Legislatively, cooperation between all these parties has meant very

little opposition to the implementation of the plans, in theory. In reality,

the funds, resources and opportunities for any work to go ahead come

in small chunks. In order to make this project achievable Dlandstudio

supplied a masterplan that can be implemented in stages:

“The strength of the Sponge Park plan lies in the clarity of the idea and

the flexibility of the framework to maintain a unified design in the face

of disparate agency jurisdictions and private development projects.

The potential for incremental development will enable sections of the

design to be developed as prototypes over the next two to five years.”

(Drake and Kim, 2009)

This project recognises that problems cannot be completely or

instantaneously solved. No viable scheme can immediately turn around

a century of pollution and ill-advised drainage infrastructure. It does,

however, attempt to remediate the problem, by providing a scheme that

is well suited to the area and acceptable to most parties involved. It is

part of a wider plan, and facilitates gradual implementation in itself. It

can solve multiple issues, with solutions such as SUDS, providing both

public and community amenity and connecting the neighbourhood

back to the water.


3.0 SUDS on the StreetDealing with rainwater runoff on the street is very important within the

urban realm. As discussed in Section 1.1, it is a place where lots of

pollutants and silt can accumulate and the hard tarmac collects water

and washes this all this into a drain quickly. Often water is collected from

properties that line up along side of it and this can add to the problem.

There are, however, several SUDS solutions that can reduce remediate

these problems, and green the street providing more pleasant roads in

our cities.

As the EA (n.d.) inform us, by allowing untreated runoff into our sewers

and watercourses we are causing many problems. The silt and litter

from our streets is washed off into local watercourses, or, more likely in

the dense urban realm, into sewers and here it needs to be dealt with.

The traditional method of doing this is either unblocking or cleaning

out specialist silt traps, both of which require expensive and specialist

skills and equipment.

The roads are hard impervious surfaces and a lot of the time must

remain so. As discussed, One of the principles of SUDS is to maximise

the chance of infiltration, but it seems that on most roads, permeable

paving is not an option. As Greenroads (2011) state “Permeable

pavements may not be suitable for high volume traffic loads or

arterials. However, shoulder areas and sidewalks may be appropriate

applications to consider.” They go on to say, and are supported by

other publications, including RBA (2010) and Concretethinker (2011),

that they are suitable for residential roads, alleys, and driveways.

Permeable pavements will be discussed more later in Section 4.2.

There are alternatives to permeable surfaces however, by having SUDS

systems close by we can reduce the peak flow and the amount of

water, silt and litter entering the sewer system. A separate storm drain

and wastewater drain is always preferable as well, but many towns and


cities there is already a combined sewer system in place (RBA, 2010,

DEFRA, 2008). It would be a massive undertaking to change this but

there are ideas and technology to address the problems associated

with a combined system with out doing this.

Roads can act as huge, hard lined drainage channels (see Figure

3.1) and many drives and front yards draining onto the street. This is a

problem that has been addressed in London (CIRIA, 2009), by reducing

the amount of extra water flowing onto the street. By by dealing with it

at source and not allowing water to flow out on to the street thereby

reducing the amount of runoff (CIRIA, 2009).

So by applying the aims of SUDS: implementing source control, allowing

infiltration, filtering and attenuating water flow, we can improve our city

streets. A lot of the time this can involve the greening of our streets,

which improves the appearance of the street and even the air quality.

3�1 The aligning properties

The research mainly concentrates on residential properties, but what is

stated can also be applied to any road side properties.

As mentioned, there is legislation in place in London to ensure that

anyone wishing to pave over their front garden with hard surfaces must

apply for planning permission. As Vidal (2011) observes, there has

been a trend for turning the front gardens of many London properties

into car parking (Figure 3.2), and CIRIA (2009) ascribe a noticeable

increase in street water to this increase in hard surfacing. In Portland

there has been increased efforts to encourage local residents to help

remedy this problem.

As Green Streets (2011) inform us, the local councils there encourage

residents to install rain gardens in their front yards to help alleviate

the flooding. As discussed in Section 2.3, the idea aligns itself with

the SUDS concept that many small source control measures make a

Figure 3.1Flooding on the streets of Brooklyn due to impervious surfaces.(source: GCC, n.d.)

Figure 3.2Front dives being paved for off-street parking.(source: Vidal, 2011)


larger overall difference. GreenTreks Network (2011) describe the rain

gardens of the residents of Portland and we can see how the design

and plant selection has become interesting in itself. Its seems that the

careful selection of plants that are tolerant of variable conditions is

just the start, and with thought being given to ornamentals plants and

edible plants, its more than just a SUDS scheme.

Green Streets (2011) describe other measures, such as stormwater

street planters which are sited on the sidewalk and have in and out

flows on road level and sit flush with side walk (Figure 3.3). They can

collect water from both the sidewalk and the street and are able to

attenuate and allow infiltration as well as greening the street.

As Stovin and Digman (2011) illustrate in Figure 3.4, in this tight inner-

city terraced street, as you can see from the photo on the left, that there

is not a huge amount of space, either on the road or on the sidewalk.

Lack of off-street parking requires cars to be parked on the road and

the houses on the left abut the street meaning that there are no front

gardens to take up any excess water. But the conceptual sketch on the

right illustrates the possibilities even with this little space:

Figure 3.3Right: Attractive street planters sunk below street level.Below: Runoff flowing from street into planter to infiltrate or attenuate.(source: Green Streets, 2006)


On the left, narrow flow-through planters intercept roof water that

would otherwise flow into the streets or down sewers. By collecting this

rainfall we can filter out any pollutants that may have settled on the roof

and attenuate flow further down the system. As Figure 3.5 illustrates

the water is collected and allowed to filter down through the growing

medium and then exits through the outflow. The advantage of this

system is that it can be retrofitted as it can sit on top of any surface. The

outflow in this example still runs on to the street and will be intercepted

by the kerb extensions. But as the flow exits at ground level it can be

directed either underground or to another surface water feature.

The front gardens on the right have also been converted to intercept

runoff preventing further accumulation on the road surface. There is also

the option of disconnecting down pipes from sewers and redirecting

this water. As well as the flow-through planters, by simple greening of

the property, we can facilitate infiltration, reducing the flow on to the

road. The road has kerb extensions that allow infiltration, attenuation

and filtration, they green street and act as traffic calming measures

while still allowing space for on-street parking.

Figure 3.4Stovin and Digman (2011) illustrating potential measures that could be retrofitted to a narrow urban street.(source: Stovin and Digman, 2011)

Figure 3.5Flow-through planter. Allows for runoff attenuation and filtration. Can be easily retrofitted and water still remains on the surface.(source: CPBES, 2010)


3�2 Kerb Extensions

Despite the problems faced, there is still opportunity for SUDS

measures on the road itself. One way is through the use of extended

kerbs, which can act as both infiltration ditches, street greening and

traffic control. These have been used to great effect in Portland, as

Green Street (2011) explain. Green Streets (2011) describe how they

collect the gutter water and allow it to flow into and through the kerb

extension (Figures 3.6, 3.7 and 3.8). This water is then slowed, filtered

and given a chance to infiltrate and any water remaining will flow out

of the other end toward the sewer system. As they explain, the water

leaving the vegetated kerb extensions may still enter the sewer system,

but in smaller quantities, at a slower rate and much cleaner.

As Green Streets(2011) go on to say, kerb extensions are also useful

as street greening and as traffic calming, providing crossing points

for pedestrians and cyclists The only restriction on the planting is that

it is resistant to the regular flooding and the airborne and water born

pollutants that flow into it.

The City of Portland - Bureau of Environmental Services (CPBES)

Figure 3.6Kerb extension section. Note the level that has dropped below street level to allow flood storage and the dropped kerb to allow in and out flow.(source: AW, 2011)


(2004a) have done extensive testing on kerb extensions to test their

efficiency and performance. This report is also supported by similar

more general report from CPBES (2010) from across the whole city.

CPBES (2004a) simulated a 25 year storm by pumping known quantities

and rates of water towards the kerb extensions on Siskiyou Street in

Portland (see Figure 3.8). They did it this way so they could isolate

the individual kerb extension and used a water meter to control the

exact amount and exact rate of water entering the device. From this

simulated 25 year storm, the device dealt with 84% of the volume of

water and reduced the Peak flow by 88%. This Council report states

in its conclusions “Infiltration rates at this facility were excellent, even

during saturated conditions. This ensures that the facility will be ready

for subsequent storms”.

CPBES (2010) list the results of tests form all over the city form kerb

extensions and rain gardens, listing flow reductions from 78%- 100%

and an average of 90% and various volume retention Figures at

averaging 73% and 93%. CPBES (2010) also point out that basement

flooding, which was a major issue and a main driver behind the Green

Streets programme, has been virtually completely eradicated from

these areas that have taken up the scheme.

On a more general note, these reports and results indicate the high

levels of efficiency you can achieve form a well designed SUDS

schemes and the benefits form just a number of smaller interventions.

3�3 Street Trees

By planting street trees and a well designed subsurface drainage

system it is possible to solve the problem of both irrigation of the trees

and vegetation as well as the flooding and pollution(Ferguson, 2011).

As illustrated in 3.9, by providing permeable concrete for infiltration

and a profile that encourages ground water to flow away from the

buildings and towards a buried trench you can plant trees on a busy

Figure 3.8A kerb extension in action during a flow and infiltration test.(source: CPBES, 2004a)

Figure 3.7Kerb extensions. Very similar to street planters in Figure 3.3 but have additional traffic calming and pedestrian safety benefits.(source: Green Streets, 2006)


urban street. Ferguson (2011) goes on to say that as long as there is

enough room for the root system trees can provide certain benefits that

a planter cannot.

He explains by saying that trees can provide shade, air-cooling and air

quality improvements. These are generally not things that are listed as

major benefits for SUDS. With the planting of street trees rather than

planters, it is also possible to utilise the spaces between the trunks,

while the permeable paving allows water to infiltrate and either be taken

up by the tree or conveyed by the buried drainage trench (Figure 3.10).

3�4 Permeable Paved Streets

Some times it may be possible to have whole roads paved with

impermeable surfaces as demonstrated by these projects in Figure

3.11, in Portland (Green Streets 2006). In some streets its may also be

possible to have hybrid surfacing, combining strong durable tarmacked

Figure 3.9Correct profiling for street trees allows permeable paving across the whole sidewalk, and the use of impervious materials below ground will draw water away from the buildings and towards the tree pits.(source: Ferguson, 2011)

Figure 3.10Street trees and permeable surfacing ‘bridging’ the infiltration and storage underneath.(source: Ferguson, 2011)


roads with the infiltration properties of permeable paving. There may

not be room for kerb extensions in some situations, but there might be

the opportunity for a strip of permeable paving down each side of the

road. As illustrated in Figure 3.12 a strip of permeable paving down the

side of the road allows for the benefits of infiltration but by doing this

you can still drive over the infiltration area without causing damage. It is

worth remembering too the sidewalk can also be a permeable surface.

More will be said on permeable surfaces in Section 4.2.

The streetscape can account for a large surface area of the watershed.

While it is possible to allow either infiltration on the road surfaces

themselves or direct the runoff to large roadside SUDS there is a

middle ground. On small streets, decentralised interventions work

best, assimilating roles of street greening and traffic safety or making

use of small, unneeded bits of roadside land.

Figure 3.11Entire Streets with permeable paving.(source: Green Streets, 2006)

Figure 3.12Permeable paving strips along the edge of roads. Allows infiltration as well as being durable to allow vehicles to drive over them.(source (left): Nowell, 2009. source (right): Ferguson, 2011)


3.5 Case Study: Learning From Portland

This Case study focuses on its implementation and regional strategy.

Information on the SUDS features mentioned (Raingardens, street

planters and kerb extensions) can be found in Sections 2.5, 3.1 and 3.2.

Portland are leaders in implementing SUDS as a citywide strategy- as

Green Streets (2011) attest, they have performance and success. A

key point fundamental to this success is legislation; the city has been

encouraging the uptake of small stormwater management facilities

for a while now. As CIRIA (2009) indicate, while it may fall to the

individual stakeholders in the city to make things happen in their own

neighbourhood it is important that it all falls under a regional strategy

so that it all works as a system.

Portland’s successes seem to stem from their public awareness

programme and full council involvement. They have really been pushing

for lots of small-scale additions to their stormwater management, and

they see this as part of the wider city strategy:

Green Streets (2011) state: “In Portland, urban design, multi-modal

transportation systems, watershed health, parks, open spaces, and

infrastructure systems are all enhanced by integrated planning, design,

and budgeting.”

3�6 Green Streets

Their ‘Green Streets’ Initiative, led by Portland City Council, aims at

using “vegetated facilities to manage stormwater runoff at its source”.

Its goals are exactly aligned with that of SUDS with an additional focus

on public well-being. Among its core Green Streets strategies, it lists:

Figure 3.13Screen grab of the Green Streets website.(source: Green Streets, 2011)


• Improve pedestrian and bicycle safety;

• Improve air quality and reduce air temperatures;

• Address requirements of federal and state regulations to protect

public health and restore and protect watershed health; and

• Increase opportunities for industry professionals.

So as well as achieving the core environmental aims of stormwater

management, they also aim to improve public health, safety and way

of life. Portland City Council have made it key legislation that the

implementation of ‘Green Streets’ is a major priority citywide. As Greens

Streets (2011) illustrate in Portland’s Green Streets Resolution, the city

see the need to “improve the function of the right of way” by providing

improved connectivity and livability for both humans and nature.

Their ‘Resolution’ Document estimates that 60%-70% of the volume of

storm water is attributed to run off from streets and from private property

on to the streets. It aims to remove 60 million gallons of stormwater from

combined city sewers by 2011 and clearly states that vegetation and

infiltration are central to achieving this. They have therefore made it key

policy to ensure this happens.

As Green Streets demonstrates, they have a very transparent out look

to it and publish the results of constant tests and appraisals on the

systems in place. There is information on what Green Streets are and

how to plan and implement them in your area, as well providing the

necessary legal and fiscal information as well. It is also the focus they

have on implementing citywide programme of ‘Green Streets’ meaning

a regional strategy connecting small, decentralised interventions,

which as Dreiseitl (2007) illustrates for Singapore is important.

It may even be this focus on street interventions like extended kerbs

and stormwater street planters that make it so successful. Rather than

pushing SUDS in general and releasing comprehensive design guides,

Green Streets have kept it simple. The planters and extended kerbs S U S T A I N A B L E S T O R W A T E R M A N A G E M E N TGreen Street Projects (Built)

NE Sandy Facilities

NE Fremont & 131st

SE 45th and AnkenySE 21st and Tibbets (People’s Co-op)

SW 12th and Montgomery

SE 21st and Tibbets (People’s Co-op)

NE 35th and Siskiyou

Glencoe Elementary School

SW Headwaters Project

N Willamette and Denver Ave.

SE Rex Pervious Pavers

N Gay Ave. Pervious Concrete

SE 57th and Pine

New Columbia

Figure 3.14Part of a poster illustrating the variety of projects already completed by the Green Streets programme(source: Green Streets, 2011)


do the job as the documentation shows and they also demonstrate

and employ most SUDS principles. They are easy to understand and

their benefits are clear. So convincing people and demonstrating the

benefits of SUDS is achieved and it puts SUDS techniques in the public

spotlight, paving the way for widespread use of SUDS to be more

readily accepted.

The programme focuses its main efforts on streets, having recognised

that this is where the majority of stormwater collects. This is the place

where SUDS interventions can be most efficient and most visible,

hopefully educating and inspiring the public. In fact, as Green Streets

(2011) illustrate, they also encourage residents to build rain gardens in

their front yards to add more SUDS features to the streets.

They even facilitate neighbourhood ownership of these schemes by

asking for local volunteers to maintain the planting. This will also reduce

the cost to the city for sending teams round to these small planters,

making them more sustainable in terms of city finances. Furthermore, by

encouraging the public to request them and suggest sites, they again

raise awareness in the local districts and raise a sense of ownership.

Rather than being a faceless man at City Hall sending men out to put

them in, the local residents can make their own decisions.

So while lots of small source control measures are better than one large

regional control, it is important that these are part of a wider strategy.

Portland have concentrated on implementing as many of these small

measures as possible on the street, to get the greatest impact from

their stormwater control.

Figure 3.15Part of one of many reports on the performance of Green Street interventions.(source: CPBES, 2004a)


4.0 SUDS In DevelopmentRoofs, roads, front drives, playgrounds, pathways; these all gather

water and due to their surroundings there is often little option where

the water can go. As discussed, the traditional method is to put the

runoff in to the drains to save space. Many developments take place on

previously developed land, and the natural flow routes may have been

destroyed (RBA, 2010). There can be many demands on the space that

multifunction becomes paramount here.

“In Urban Areas, particularly in very dense development (…) every

hard surface becomes a rain water collector and the constructions

profile must be considered for runoff management” (RBA, 2010)

We have to be more imaginative about what we do with water and how

we use it in the urban realm. The more dense the area, the more open

it may be to the pollutants and problems. As discussed in Section 1.1,

airborne pollutants settle on hard surfaces that cannot break them

down and are then washed from them to spread through the area.

Pollutants can originate from commercial, industrial and residential

sources which are closer together and therefore these pollutants will

more concentrated.

So space needs to be used as efficiently as possible and the

effectiveness of the SUDS should be maximised too. We need to be

a bit more innovative in our thinking about natural processes and

placement of the systems.


4�1 The Ray and Maria Stata Centre

The Ray and Maria Stata Centre at MIT in Boston has a very advanced

and integrated system that combines high technology with natural

processes (Zheng, 2007). The Building itself contains vegetated

terraces on upper levels and roof gardens. As a redevelopment on

a previously urbanised site, the building and landscape has created

its own topography. Described by Zheng (2007) and Figure 4.1, the

system drains first through a “water quality inlet”, where heavy metals,

free oils and nutrients introduced via urbanisation are filtered. Then it

is pumped into the large “Outwash Basin”, the most visual part where

natural processes take over. Bioremediation and natural filtration take

part in a naturalised basin based on the local glacial landscape of New

England. This water is then stored and recycled for flushing toilets,

where it is passed through a sand filter and UV sterilisation to control

bio-growth. It is also used for irrigation in and around the site. There

are a number of tanks and pumps powered by photovoltaics in place

to refill toilet-flushing system or remove excess storm water in severe

storm events.

This system employs a number of hi tech and naturalised systems, and

a combination like this is important where space is tight. It is missing

any natural infiltration systems, but in an already urbanised site in the

middle of Boston, this may not have been possible. However it does

ensure that water is clean and filtered and runoff is attenuated on site.

In this case holding it for use on site and the vegetation on site allows

for a certain amount of evapotranspiration.

Figure 4.1Diagram describing the collection, flow, filtration and use of the collected on site stormwater.(source: Zheng, 2007)

Figure 4.2The outwash basin based on the local glacial landscape.(source: Zheng, 2007)


However, as Zheng (2007) explains, it does use natural processes as

much as possible, even using the natural local glacial landscape as

a concept for the outwash basin and choosing native species (Figure

4.2). The outdoor spaces have been designed to fully maximise the

usability of the out door space. Being an educational institution, the

staff and students were very keen to have space out side to sit, relax,

read and study (Figure 4.3). So the water management system is fully

integrated with building and its external areas, creating sun traps and

evapotranspiration cooled vegetated areas.

4�2 Permeable Surfaces

While SUDS features with enough space aim to keep the water above

ground or infiltrating into it, in the dense urban realm we may need

to allow storage underground. This may take the form of permeable

paving on car parks with cavities underneath for attenuation or

infiltration. Although the water is underground, it is not being moved

swiftly off site,as in pipes, but remains in the structure and if it releases,

it does so slowly.

“The use of permeable surfaces in urban SUDS design is critical

because space is at a premium and permeable pavement, along with

green roofs, are the only SUDS techniques that require no additional

land take to function effectively.” (RBA, 2010)

As discussed in Sections 3.0 and 3.4, while they may not be suitable

for arterial roads, they are suitable for residential roads, alleys, and

driveways. Which means that they are perfectly suited to building

developments. As Figure 4.4 illustrates and Interpave (2008) state

permeable paving can be used for a wide variety of residential,

commercial and industrial applications.

Figure 4.3Outside space to sit, relax, read and study.(source: Zheng, 2007)

Figure 4.4 Different situations for use of permeable paving.(source: Interpave, 2008)


As the following data shows, permeable paving is effective in terms of

infiltration and attenuation rates as well as removing large amounts of

suspended solids and pollutants (Wilson and De Rosa, 2011, Interpave,

2008, DEFRA, 2004b):

Percentage Removal of Pollutants

Total suspended solids 60-95%

Hydrocarbons 70-90%

Total phosphorus 50-80%

Total nitrogen 65-80%

Heavy metals 60-95%

(original source: CIRIA C609, 2004)

Water Quality Treatment Potential

Removal of total suspended solids High

Removal of heavy metals High

Removal of nutrients (phosphorus, nitrogen) High

Removal of bacteria High

Treatment of suspended sediments &

Dissolved pollutants High

(original source: CIRIA C697, 2007)

(Source: Interpave, 2008)

Permeable paving does not take up any space from areas that require

hard surfacing, such as parking, playgrounds or footpaths. It comes in

all sorts of varieties, like tarmac, clay pavers or more open reinforced

grass (see Figure 4.5). As RBA (2010) point out, they can turn play

surfaces or open plazas into retention areas with out affecting the look

of the space. As described in Section 2.5, they predominantly work by

use of an open grade substrate that allows water to percolate through

the voids between granules. These voids provide both a filtration

function and a storage function to varying extents, depending on the

requirements.

Figure 4.5Some of the various forms permeable paving can come in.(source: Tensar, 2011)


Interpave (2008) explain further the versatility of permeable paving;

as Figure 4.6 illustrates, there can be full, partial or no groundwater

infiltration with excess water being conveyed in perforated pipes, but

they still perform filtration functions (Figure 4.7). Maintenance is also

not an issue: as Wilson and De Rosa (2011) explain, “The reduced

infiltration rates of most pervious surfaces are so much greater than

rainfall intensity that even when left unmaintained the pavements

continue to function.”

Figure 4.6Top: Full infiltration. The water percolates through the filtration layers and eventually enters the Sub grade

Middle: Partial Infiltration. To allow faster drainage, a perforated pipe is laid in the sub base to allow water flow away more freely

Bottom: No Infiltration. If it is undesirable for water to soak into the ground then an impermeable membrane can be laid so that all water enters the drainage pipe.

(source: Interpave, 2008)

Figure 4.7Any sediment and oil sits on the surface until washed through. The sediments are trapped in the upper laying course or geo-textile and the oils are trapped and biodegraded in the pavement.(source: Interpave, 2008)


4�3 Hazeley School, Milton Keynes

As Figure 4.8 shows, Interpave (2008) illustrate how permeable paving

can perform a central role a SUDS system. They describe the system

in place at Hazeley School in Milton Keynes. It is a two-phase system

that firstly collects water from car parks and footpaths and other paved

areas that enter a series of “compartments” that control the flow of

infiltrated water and allow extensive treatment of pollutants. The water

then enters one of two retention basins, home to protected wildlife,

which illustrates the high standards to which these systems have to

work.

Phase two collects rainwater, playground runoff and rain falling directly

on to permeable in to a geo-cellular storage box. This is then used for

toilet flushing on site, while an overflow device delivers excess water

back in to the phase one system.

These geo-cellular devices are sometimes used in collaboration with

permeable paving, as it is also possible to provide cavities under

hard paving as well. As Interpave (2008) illustrate this takes the form

of space formed by an engineered supporting structure that allows

temporary water storage for infiltration and attenuation or for rainwater

harvesting.

4�4 Large Scale Stormwater Storage

As described in Section 2.5, sometimes storage cisterns are used, like

those at Potsdamer Platz in Berlin. These can capture the water for use

in and around the site for things such as irrigation. As space is severely

lacking they have built massive underground storage tanks that collect

the water for use around the site or for storage to control the flow in to

Figure 4.8SUDS system at Hazeley School.(source: Interpave, 2008)


the neighbouring water bodies.

Dreiseitl and Grau (2005) explain how the ING headquarters in

Amsterdam provides a stormwater management system comprising

of a green roof, a water basin and underground storage system. The

system is fully integrated into the design of the building and the storage

basin is also aesthetically very important to the building design. The

green roof slows runoff rate and acts a pre-filter before draining in to

the basin. In this basin they have cleansing biotopes to ensure that any

water leaving the basin to the Spoorlagsloot canal is clean. The basin

also has a built in buffer volume to attenuate flow into the canal during

storm events. The underground storage system is in place to top up

the basin during periods of low water. Car parking is underneath the

visible water basin, raising the public profile of the importance of water

management in this state-of-the-art building.

It appears that by building up and thereby reducing the footprint of the

building they are allowing more space for water management. Similarly,

as Dreiseitl and Grau (2005) illustrate, the DWR headquarters (also in

Amsterdam) stands in a large retention pond edged with cleansing

biotopes. The pond, many times the size of the building foot print, is

an important advert for this dyke control and sewerage utility company.

4�5 Important Aesthetics

It is an important consideration that SUDS should look attractive,

especially in the urban realm. Dreiseitl and Grau 2005 explain how

they always put the value of aesthetic design along side the efficiency

of a SUDS scheme. Whether inserting ecological wetlands into sharp

modernist squares like Potsdamer Platz or providing large naturalistic

wetlands in a redeveloped urban area, such as Tanner Springs Park

the system is attractive, evident and observable. Public perception of

SUDS features is critical to their implementation and acceptance and it

is important that the public sees things such as ponds as a worthwhile

part of their residential estate (Heal, 2011). Kazmierczak and Carter


(2010) state in their study of the SUDS in Augustenborg, “Aesthetics

were more important to many residents than the functioning of the

system.”

4�6 Making the Most of Space

As is discussed in Section 5.6 and illustrated by The City of Malmo

(n.d.) in Section 4.9, it is important that the public can see these things

happening and notice a change in the landscape when they do (see

Figure 4.9). It is important to improve and maintain high quality public

space.

Making the most of available space is important, as you can see from

Figure 4.10,for example. There is sometimes little space between

buildings to provide fully natural SUDS features but here it has been

achieved in an attractive manner. By water proofing the base, for

example, water can’t seep into the buildings foundations, and adding

vegetation will attenuate flow rate and purify the water before it flows

further down the system. In this case the addition of a filter strip of grass

aids the effectiveness of this system. The scheme has also allowed for

fluctuating water levels and the hard steps mean that bare mud isn’t

exposed when this happens.

Figure 4.9A conveyance channel filling up in Augustenborg.(source: Brattli and Sørensen, 2011)

Figure 4.10An urban wetland right up against a building.(source: RBA 2010)


As the EA (2011) encourage, the installation of rainwater harvesting

and grey-water reuse systems can dramatically reduce water use, and

its inherent energy use. As been discussed throughout, water can be

stored for irrigation and water use in and around the building and the

site.

RBA (2010) suggest a number of things especially suited when space

is low in urban developments and courtyards: Under-drained filter

strips, permeable paving, rain-gardens and bio-retention features

that use planting areas as drainage structures, below-surface water

storage devices or urban wetlands and ponds. These all share the

same characteristic of following SUDS principles but in a compact

manner.

4�7 Green Roofs

Green roof technology is well established and its efficiency is well

proven. The City of Malmo (n.d.), estimate that 50% of rainwater is

dealt with by the thin sedum roofs in Augustenborg. RBA (2010) put

the performance at 40%-60% reductions in runoff. They also state it

is possible to add an additional rain storage box if ground level or

underground attenuation devices are not possible.

Green roofs (Figure 4.11) work by planting into a thin layer of growing

medium, these can be soil or specially engineered growing mats.

Green roofs are beneficial because they replace, to a certain extent,

the vegetated permeable ground that was lost when a building went

up. The City of Malmo (n.d.) list the advantages of green roofs:

•Take the pressure off the stormwater system as the plants and

substrate absorb the rainwater

•Provide a better microclimate.

•Protect the underlying roof material

•Enhance biodiversity

•Are beautiful to look at


•Act as noise reduction

•Can minimise building heat in the summer

As RBA (2010) and The City of Malmo (n.d.) attest, green roofs not

only remediate flow but also send any water down from the roofs clean.

Airborne pollutants can accumulate of roofs and so you may get a

‘first flush’ of pollutants washing down the drainpipe in to the sewers.

By fitting a green roof, any pollutants are trapped and absorbed by

the vegetation. They improve air quality and ensure clean water flows

down from the roof, which can be redirected for use on site.

As RBA conclude, green roof technology can prove to be especially

important where buildings account for large proportions of land take.

Like permeable pavements, green roofs are critical because they

require no extra land take to function effectively.

4.8 Retrofitting SUDS

We obviously can’t knock everything down to rebuild them with

sustainable technologies so we have to turn to retrofits. Reuse and

retrofit can save us money and reduce energy use and waste involved

in rebuild and new build.

Cott (2010) makes some convincing arguments on Retrofitting Buildings

in general. He claims that by effectively retrofitting the US building stock,

a 40% reduction in energy use could be achieved. Adding on top of

this the waste and embodied energy in demolition, waste disposal and

rebuild, he claims the justification of new builds becomes increasingly

difficult.

Figure 4.11Showing the basic components of a green roof along with the additional storage box for extra attenuation.(source: RBA, 2010)


Retrofitting green roofs to a building can not only reduce the stormwater

runoff and improve quality, but can also improve insulation, reducing

energy and costs for heating and cooling. As livingroofs (2011) show, an

industrial plant in Frankfurt which had a green roof installed recovered

the cost of the green roof in 2-3 years through the savings in heating

and cooling costs.

RBA (2010) points out that many housing estates in Britain have green

public spaces that can easily altered to contain SUDS features, such

as infiltration swales and retention ponds, without losing their primary

functions. Many of these spaces could be improved by the introduction

of bio-diverse SUDS features, like that which has been done in

Augustenborg (see case study 4) that can benefit the whole area.

As most of the SUDS features that have been discussed are surface

devices, retrofitting should be a fairly straightforward procedure,

especially compared to the installation of traditional subterranean

drainage. RBA point out that just a simple diversion of the downpipes

of building can be of great benefit. By Redirecting the downpipes away

from the drains and diverting roof water into the SUDS interventions

can prevent a lot of unwanted and unneeded stormwater entering and

overflowing the sewers. They also mention that this can be seen in

the Augustenborg where they have disconnected downpipes and kerb

crossings, diverting water into the public landscape. The resulting

attractive public space also functions to take the peak out of storm

events and can clearly be seen doing their job by the change in the

appearance of the channels and attenuation devices.


4.9 Case Study: Ekostaden Augustenborg, Malmö.

Augustenborg is a housing development in the city of Malmö, Sweden,

finished in the early 1950’s. As The City of Malmo (n.d.) explain, as the

first public housing area in Malmö, it was seen as a fine place to live,

high end and well designed, even using unique “Sun studies” to get

the most out of outdoor space. But by the end of the 80’s it had become

run down, a victim of the economic decline of Malmö’s industries (The

City of Malmo, n.d., Kazmierczak and Carter, 2010)

Kazmierczak and Carter (2010) describe how the aging buildings were

falling prey to deterioration with damp, insufficient insulation and poor

appearance being major problems. Also that lack of capacity in the

combined sewer system was causing major flooding and all sorts of

problems came along with that. Flooding was damaging underground

garages and basements, there was restricted access to roads and

footpaths and the overflow from sewers meant untreated sewage was

entering the watercourses.

In 1997 work began to try to regenerate this area with collaboration of

the Malmo city council. The City of Malmo (n.d.) state that the Malmo

municipal housing company set up some key aims for the project. They

wanted to create a more socially, economically and environmentally

sustainable neighbourhood, and in line with Malmo city policy, they

wanted full involvement of the residents. Kazmierczak and Carter

(2010) state that the cities initial focus was on combatting flooding,

waste management and enhancing biodiversity.

So Ekostaden Augustenborg (literally Eco-town Augustenborg) was

implemented and they set about improving the area. A major part of

all of its success was the SUDS approach and the interrelated systems

and benefits that are connected with it.


As Kazmierczak and Carter (2010) and The City of Malmo (n.d.)

illustrate, SUDS played a central role on all of this. The outdoor areas

were designed around stormwater management and the increase in

biodiversity is due in a large part to the botanical green roof. The SUDS

seem to be successful, partly through their biological nature, but also

their efficiency and their aesthetic nature. They have attempted to

integrate all features into the fabric of the area and enhance the urban

realm.

The City of Malmo (n.d.) explain that two of the individuals who really

got this project moving wanted to base their approach on how mother

nature solves the problems of floods. They have employed standard

SUDS techniques of wetlands, ponds, dry drainage ditches, but

they have also had to consider other options due to the dense urban

environment that is prone to flooding. One issue that they had to deal

with was that of avoiding damage to the buildings by water, which meant

they could not allow deep groundwater infiltration. So, as Kazmierczak

and Carter (2010) explain, all the SUDS features had to be underlain

with geo-textile to prevent this, and all water that leaves the site has to

go down the combined sewerage system. This requires giving even

more consideration to retaining water and allowing evapotranspiration

from the SUDS scheme.

Figure 4.12Botanical Green Roof.(source: City of Malmo, n.d.)


As Kazmierczak and Carter (2010) state, one of the issues that came

from the community consultation was their concern that they would lose

courtyard space to areas of unusable open water. So total area of pond

was reduced to increase the amount of public recreational space. As

The City of Malmo (n.d.) note, there was also a desire to keep the new

interventions in keeping with the original 1950’s style of the housing

development so a lot of the SUDS features are concrete channels that

become design features in them selves (Figure 4.15). In fact a lot of

the channels have a specially designed rain drop motif in the bottom to

optimise water flow (Figure 4.14).

The City of Malmo (n.d.) highlight the fact that Augustenborg also has

within its boundaries a world leader in research and demonstration

of Green Roof technology. On the roof of an old industrial warehouse

is the world’s first botanical green roof, installed as part of the initial

stages of the project in 2001. Along with the other 30 green roofs in the

area, which are cared for by the staff of the botanical green roof, they

account for 50% of the rain fall in the area, which is a huge load off the

stormwater system.

4�10 Community Involvement

As The City of Malmo (n.d.) illustrate, one of the key reasons for its

success was community involvement from the beginning with full support

of the city council. The community had a very strong engagement from

the out set, through the design stage and beyond and this has been

Figure 4.13Hard edge retention pond. Designed to be in keeping with the original 50’s styling.(source: Nowell, 2009)

Figure 4.14Raindrop motif in drainage channels that help optimise flow.(source City of Malmo, n.d.)


very important for the smooth running of the project. By addressing

the needs and desires of the residents and keeping them involved and

informed along the way, it has meant there has been little opposition.

It has also meant that they have begun to get very involved with the

community itself.

It goes on to say that community groups and initiatives has seen an

increase in popularity and since the project opened in 2001 vast

improvements in the areas socio-economic status. Unemployment is

down, education figures have improved and the number of inhabitants

has risen and they are staying around. There is also an increase in

biodiversity, flooding is virtually nonexistent and heat and hot water

consumption has dropped.

The City of Malmo (n.d.) indicate this is in some part due to the community

involvement, partly due to the SUDS approach to landscape design and

partly due the educational side and effect of the project process. Even

the school has all these processes going on in around its premises and

fully involves the kids and teaches them, which will be discussed further

in Section 5.7. They say that now the main regeneration of the area

is complete, the next phase is ensuring that community involvement

continues. A major focus of this phase is educating new residents to

the area about why the area is laid out as it is, how it works and getting

them involved in this tight-knit community.

4�11 Well designed SUDS Built around Community

It is this happy coexistence of community involvement, well-designed

SUDS features and other natural features and aesthetically-pleasing

feel that makes such a successful SUDS project. The performance of

Figure 4.15A drainage channel filling up, highlighting the surface drainage systems to the public. (source: Nowell, 2009)


the features is well proven, having coped with a 50 year storm in 2007,

when many parts of Malmo suffered (Kazmierczak and Carter, 2010).

The City of Malmo (n.d.) state it has suffered very little flooding and this

is almost entire due to attenuation, slowing down the water, indicating

the effectiveness of the scheme.

As infiltration is not possible here, all water that leaves the site

must either flow in to the sewers, be evaporated or leave via

evapotranspiration. However, Kazmierczak and Carter (2010) go on to

say that the implementation of this open stormwater system means that

stormwater entering the sewer system is now negligible. They attribute

this firstly to the water retention and attenuation of the whole site and

evapotranspiration from channels and ponds between rainfall events.

And secondly they attribute it to the green roofs which more than make

up for the shortfall in ground level SUDS when the residents requested

more recreational space.

They continue by stating that even though the SUDS have been to

some extent compromised by the need to adjust the design to suit the

residents’ needs, they still work very efficiently. They have managed to

address the issues of community, amenity, biodiversity and stormwater

management without one sacrificing the impact of the others.

Kazmierczak and Carter (2010) go on to note that “there is a range of

benefits additional to adaptation to more extreme rainfall events that

stem from the comprehensive regeneration of the Augustenborg area:

• Reconfiguration of public spaces between housing blocks has

given residents opportunities to grow their own food in small allotments,

and has created places for leisure and attractive areas for children to

play.

• Biodiversity in the area has increased by 50%. The green roofs,

predominantly the Botanical Roof Garden, have attracted birds and

insects, and the open storm water system provides better environment

for the local plants and wildlife. In addition, flowering perennials,


native trees and fruit trees were planted, and bat and bird boxes were

installed.

• The environmental impact of the area (measured as carbon

emissions and waste generation) decreased by 20%.

• The participatory character of the project sparked interest in

renewable energy and in sustainable transport among residents, after

they heard about similar plans for other areas.

• Between 1998 and 2002 the following social changes have

occurred:

o Turnover of tenancies decreased by 50%; Unemployment

fell from 30% to 6% (to Malmö’s average);

o Participation in elections increased from 54 % to 79%.

• As a direct result of the project, three new local companies have

started: Watreco AB (set up by local resident and amateur water

enthusiast), the Green Roof Institute, and the car pool established in

2000, which uses ethanol hybrid cars to further reduce environmental

impacts.

(Kazmierczak and Carter, 2010)

The Scheme at Augustenborg handles stormwater and flooding, it

provides amenity along side its function as a SUDS device, provides

space for and encourages biodiversity and it is an aesthetically-

pleasing space. Even though it is one of the original large development

SUDS schemes as The City of Malmo (n.d.) point out, it still attracts a

lot of visitors both nationally and internationally to attend regular hosted

tours of the site and is often sited as an exemplar of SUDS.

Figure 4.15Retention pond in one of the courtyards of Augustenborg.(source Kazmierczak and Carter, 2010)


5.0 SUDS at the ParkIt is preferable to deal with the stormwater at source (DEFRA, 2004a,

AW, 2011), but this may not always be possible. So following the

management train set forth by SUDS manuals (DEFRA, 2004a, AW,

2011), once source control and site control and been considered, we

must start looking at regional control.

As these manuals set forward (DEFRA, 2004a, AW, 2011), regional

control often involves the collection of water from several catchments

and sub catchments and it requires a big intervention, or series of

SUDS measures over a larger area. This can be an open pool or large

wetlands, or a series of these. But as space is what we are lacking in

the dense urban fabric, much if the time the only obvious place for

large regional control in our cities are urban parks.

This chapter will explain how contemporary urban parks are being

used to contain SUDS and how their position as large areas of open

public land in the city can be capitalised on. Also included in this will

be SUDS techniques used in schools and river corridors, as these are

also large potential resources with in our urban fabric.

The examples used are:

-Sherborne Common in Toronto. This is a sharp modern park that

combines hi-tech machines with natural filtering processes to create a

stormwater management system in an urban park

-Point Fraser, in Perth in Western Australia, is a park using fully natural

processes that has been retrofitted to the end of a stormwater drain.

It provides flood alleviation and urban runoff right next to the central

business district.

-Tanner Springs is a park in the centre of a regenerated district in

Portland Oregon. It provides stormwater management on a small city

block in the middle of a built up area.

-Renaissance Park, Chattanooga, Tennessee is a contaminated ex


industrial site that not only remediates the site contamination, but also

deals with the urban runoff from the local neighbourhood

-The Olympic Sculpture Park in Seattle has far more harmful

contamination, but it still manages to incorporate natural SUDS systems

into its stormwater management

-Augustenborg School is an institution that has a fully integrated

approach to stormwater management, dealing with toilet waste,

sustainable technologies and education.

-Mount Tabor Middle school has rain garden that has alleviated

stormwater inundation in the local area and provided many other

benefits to the students and staff.

-Finally is some guidance from the government about the re-

establishment of rivers and watercourses in the urban environment.

5�1 Sherborne common, Toronto

An article by ASLADirt (2011) describes Sherborne Common as

“the future”, a new park opened in 2010 in Toronto that incorporates

stormwater treatment and an ultramodern design. Central to the parks

design is a treatment facility that cleans urban stormwater runoff

before it enters Lake Ontario. It combines UV sterilisation, brand new

technology, and more natural bio-filtration to ensure the water entering

the lake is clean.

ASLADirt (2011) describe the process: “ “Water cleaned with UV light

shimmers as it flows down chain-mail screens – held by curved nine-

metre-high concrete arms – into raised pools that extend generously

to Queens Quay. From there, the water gushes south into long troughs

densely planted with native grasses selected for their ability to help

clean water through bio-remediation. It then flows across the street

toward Lake Ontario, nudging pedestrians to one side, before bursting

above ground in spikes erupting from the splash pad.” During winter,

that “splash pad” will turn into a skating rink framed by “fantastically

frozen fountains.” ” (Rochon, n.d. cited in ASLADirt, 2011)

Figure 5.1Chain mail screens and bioremediation troughs.(source: ASLADirt, 2011)


The UV sterilisation takes place in a series of machines underground,

hidden from the public, but there are clues as to the technology at

work (see Figure 5.2). They do, however criticise the lack of expository

signage, explaining the park and its hidden masterwork, which is

important of the public area going to see this as more than a park. That

said, this is an excellent example of how to combine new technology

and natural processes in a high profile public space.

5�2 Point Fraser

Point Fraser as a space that integrates a fully natural stormwater

management with in a public park. Opened in 2004 and situated on

the edge of the Swan River, the main aim of the park is as a facility

to deal with stormwater runoff from a 16 hectare of the Perth Central

Business District. Its secondary aims are provision of wildlife habitat,

public amenity and car parks (Quinton, 2007).

Previously the site had been a car park and helicopter pad (Sustainable

sites, 2008) and the storm water runoff from the Central Business

District was just deposited through a pipe straight in to the river. This

new wetlands is essentially retrofitted to the end of this pipe so that it

can clean stormwater runoff before it enters the river and slow flow rate

to prevent flooding and bank erosion.

As can be seen in fig 5.3, the stormwater drain entering at the northwest

corner of the site is directed in to the 3 stage wetlands that dominate

the western part of the site. Quinton (2007) states that the bio-filter

is comprised of native reeds, sedges, shrubs, and trees. As dirty

stormwater moves through the wetland, pollutants are absorbed on the

bio-film surfaces of the plants.

He describes the 3 zones like this:

“The Permanent Pond, the Ephemeral Zone, and the Tidal Zone.

Figure 5.2“Light artist Jill Anholt’s use of light to create an “eerie blue aura” helps create the sense that advanced technologies are at work, but when visitors pass by a set of “watery veils,” motion detectors briefly turn the lights green.”(ASLADirt, 2011)(source: ASLADirt, 2011)


“The Permanent Pond includes a bubble-up pit and dense plantings

that reduce water velocity and stimulate chemical sedimentation. Varied

vegetation clears pollutants in the Ephemeral Zone; and the Tidal Zone

aerates out-flowing water. Water entering the river after passing through

the bio-filter is now at least 25 per cent less in nitrogen, 45 per cent less

in phosphorous, and records a 75 per cent sediment reduction.”

To illustrate the effectiveness of this system, he goes on to say that water

entering the river from the system is now cleaner than the river water

itself. But the entire brief required the provision of public amenity and

wildlife habitat that would fulfil the environmental, educational, cultural

and recreational needs of the area. Sustainable sites (2008) point out

its suitability for tourism given the central location in the city. They also

go on to mention the signage and an information centre enabling the

site to function as a dynamic educational and demonstration tool.

The rest of the park isn’t just cosmetic either, as Quinton (2007)

illustrates, the park also provides car parking and play parks which

double as swales. In order to deal with water that falls on the park

itself, these swales are designed as “folds” that divert any floodwater

away from the city and use the swales as conveyance and infiltration

devices. The Gabions that provide the structural integrity to these folds

also act as passive filtration as water passes in and out.

Log-brush barriers and brush mattressing were used to stabilise the

foreshore edge so planting establish there. Reeds replace hard-edged

limestone surfaces that were installed with the car park and helicopter

pad. Point Fraser really manages to integrate amenity, ecology and

SUDS stormwater management into an urban park.

Figure 5.3 Point Fraser. The Water enters the site via the stormwater drain in the northwest of the site and drains in to the wetlands. The carpark swales can be seen on the north and north east and a visitor centre explaining the processes is on the south(source: Quinton, 2007)

Figure 5.4The treatment wetlands as public amenity.(source: Quinton, 2007)


“By applying contemporary ecological urban design principles to

an inner city wetland, Point Fraser formidably suggests that urban

developments do not have to be steel, glass and concrete; urban

development can be ecological too.” (Quinton, 2007)

5�3 Tanner Springs Park, Portland, Oregon

Dreiseitl and Grau (2005) demonstrated with their design for Tanner

Springs Park, opened in 2005, the possibilities for a naturalistic

ecological park in the middle of a fully urban, regenerated ex-industrial

district. They explain how, for the last 30 years this old industrial

neighbourhood, the Pearl District, had been establishing itself as a

progressive community, home to families and businesses. As this new

neighbourhood reached complete adoption of the land, Portland City

council commissioned a new green space, a new park in to this area.

Reflecting, as Dreiseitl and Grau (2005) refer to it, the new efficient

and ecological land use of the area, they have reversed time to create

a park that is like a view port to pre-development days. “The long

forgotten wetland habitat is restored to the full glory of its plants and

animals” (Dreiseitl and Grau, 2005).

Figure 5.5Tanner Springs Park, Portland. A floating boardwalk over the pond and backed by the wall. The site slopes from right to left, allowing a naturalised wet to dry succession and allows water to flow in from the surrounding streets(source: Dreiseitl and Grau, 2005)


Reusing a square city block in the middle of the district, Dreiseitl and

Grau (2005) have peeled back the urban skin to reveal the wetlands the

area was originally built upon. It provides public space and a wetland

ecology that can deal with the stormwater runoff from the surrounding

streets. As Figure 5.6 illustrates, the site slopes from west to east,

collecting stormwater runoff from the surrounding streets and allowing

it to flow and filter through a natural wetlands progression, from high

and dry planting through marginal planting into the sunken wetland

pond, 1.8m below street level. In periods of inundation, water enters an

overflow outflow at the east of the site under the sidewalk.

This site sits well in the urban fabric, providing a fully ecological natural

slice of wetlands where the public can come and relax (Figure 5.7).

The terracing and the wave fence at the sides provide a strong tie and

transition between street and park, and the terraces provide seating for

visitors. As Figure 5.8 shows, the water is crystal clear in this urban park

demonstrating the effectiveness of the natural native wetlands system.

5�4 Renaissance Park, Chattanooga, Tennessee

This park is used as a restorative tool for a contaminated inner-city site

as well as providing SUDS for a 190 hectare area of urban watershed.

Hargreaves and Kelly-Campbell (2007) explain how the city council of

Chattanooga, Tennessee commissioned a park that not only refers to

the history of the region but also deals with storm water management.

Figure 5.6Site plan indicating the water flow and cleaning strategy.(source: Dreiseitl and Grau, 2005)

Figure 5.8When compared to Figure 5.5, which was taken soon after completion, you can see the improvement in water quality.(source: Archlandscapes, 2009)

Figure 5.7Terraces provide a transition between street and park as well as place to sit and relax.(source: Archlandscapes, 2009


Chattanooga.gov (n.d.) describes it as a wetland that collects, cleans

and releases water into the Tennessee River from two sources of

urban pollution: From the 190 hectare urban watershed and from the

contaminated soils beneath the site, by-products of the sites previous

industrial processes.

Hargreaves and Kelly-Campbell (2007) explain how the contaminated

soils have been contained on site in sculpted landform. Figure 5.9

shows the water entering the site in the northeast corner and flowing

into the constructed wetlands where it filters in, through and around

planted gabion fingers that extend into it. This water, once cleaned can

either be pumped in to the river or used on site for irrigation.

Chattnooga.gov (n.d.) also mention the “flooded forest” which sits in the

Tennessee Rivers 10-100 year floodplain and is regularly inundated.

This provides habitat for native flora and fauna, and acts as an important

link in the green ribbon extending along the riverbanks. Looking at the

scale of the park compared to the scale of the Tennessee River, this

flooded forest is unlikely to alleviate river flooding, but as illustrated in

Singapore (Dreiseitl, 2010), one SUDS principle is that small measures,

as part of a larger system, are effective. But more likely is that this

flooded forest is more useful as green link and an educational tool, both

just as important in the wider scope of the park.

Figure 5.9Plan of Renaissance Park showing the water entering in the Northeast corner, flowing into the main basin and circulating around and through the gabion fingers until it is ready to be pumped out through a pipe in the Southwest corner.(source: Hargreaves and Kelly-Campbell, 2007)

Figure 5.10Aerial Photo of Renaissance Park.(source: Hargreaves and Kelly-Campbell, 2007)


5�5 Olympic Sculpture Park

The Olympic Sculpture Park in Seattle deals with a contaminated site

in a different way. Weiss and Manfredi (2007) describe a multi-layered

system where surface water is collected and kept uncontaminated and

separate from the contaminated soil.

Opened in 2007, the site is positioned on the edge of Elliot Bay in

downtown Seattle and Weiss and Manfredi (2007) envision it as a new

urban model for sculpture parks. It was previously an oil transfer facility,

which has left behind highly contaminated soil. The site is sliced into

three by a main road and train line that run along the waterfront. By

reinstating the original topography of the site it will effectively sink the

train line and the road. This will take full advantage of the 12m-grade

change between top and bottom and allow links over the divisions.

They say this will provide long-denied pedestrian access between the

waterfront and downtown Seattle.

Weiss and Manfredi (2007) explain how they have moved as much

of the contaminated soil off site as possible, but there are areas of

contamination left. They need to keep the water on site from getting

polluted by the contaminated soil remaining on site. To achieve this, as

Figure 5.11 illustrates, they installed a cap over the areas of remaining

contamination and built a drainage system to bypass any ground water

past these areas. They also installed a number of monitoring wells

around the site in order to keep ongoing records of the current state.

Figure 5.11 also illustrates that above ground runoff water is allowed

to flow freely in to Elliot Bay. Weiss and Manfredi (2007) describe the

passage of the water through deep-rooted swales, which slow down flow

rate and allow infiltration, percolating through the soil into the drainage

system. They state how the swales provide both bioremediation of

any surface runoff and prevent the erosion of the paths on this steeply

contoured site. The use of this underground drainage system where

water is captured before it gets to the contaminated soils, allows


the use of natural remediation techniques, such as infiltration on a

contaminated site. Allowing the water to run through contaminated

soils would wash the pollutants out and facilitate diffuse pollution of the

groundwater, any aquifers and the water of Elliot Bay.

Depending on the levels and type of contamination, it may not always

be possible or appropriate to remediate existing site pollution using

SUDS techniques. However, the Sculpture Park demonstrates that it is

still possible to use SUDS techniques to deal with urban runoff within

a contaminated site. It utilises them to filter and attenuate stormwater

on a sloping urban site and provide public amenity and connections.

5�6 SUDS in School

Schools are often public owned institutions that, like parks, occupy

large areas in our urban fabric and hold the potential to collect large

volumes of storm water from a large area of hard surfaces. They also

hold great potential for the remediation of storm water problems and

provision of SUDS that can benefit a neighbourhood. They can house

green roofs, and often have areas of vegetation as well as areas of

hard surfacing, like playgrounds and car parks, that can be covered in

permeable paving.

Figure 5.11Seattle Olympic Sculpture Park. Top: The blue indicates the flow of water through the site, and in green the underground drainage.Bottom: Showing the cap on top, the contamination sites shown in coloured planes and the monitoring points as vertical pointers(source: Weiss and Manfredi 2007)

Figure 5.12Aerial view of the Olympic Sculpture Park showing the road and train lines slicing the park in to threes, the slope of the site and the sites proximity to downtown Seattle.(source: Weiss and Manfredi 2007)


The Document “Promoting Sustainable Drainage Systems: Design

Guidance for Islington” written by Robert Bray Associates (2010)

encourages the use of SUDS in schools. It strongly promotes the use

of storage under the hard surfaces, even if the whole surface can’t be

permeable. Car parks are usually the most polluted areas of a school,

so permeable paving here is ideal, especially where open SUDS are

difficult to provide. They say the same is also true of hard surfaced

play area where voided crushed stone substrate can be considered for

storage opportunities.

RBA (2010) go on to explain how these large features can be linked

together by surface conveyance and SUDS features, such as rills,

channels, swales and filter strips. There is also the possibility of

interaction and education; Waterspouts and rain chutes can be diverted

from roof runoff, and SUDS features can be ponds and wetlands that

provide play and learning for children, who may not otherwise have

much contact with the water cycle.

Schools can be a great place to put in SUDS, with nearly every area of

the grounds appropriate for some kind of SUDS intervention. We can

see how they can be fully integrated into the wider SUDS strategy and

even provide space for SUDS that can serve the whole neighbourhood.

5�7 Augustenborg School

The School in Augustenborg, Malmo is a fantastic example of

incorporating SUDS and water management techniques into the school

and the teaching. It is important that SUDS are visible and accessible

and that the children understand about them. The City of Malmo (n.d.)

Brochure on Augustenborg explains how the children’s education and

school environment introduces them to the idea of water management.

Figure 5.13Children playing in detention basin and swale maze, Red Hill School, Worcester.(source: RBA, 2010)

Figure 5.14Rainslides as part of SUDS at newly completed Fort Royal School, Worcester(source: RBA, 2010)

Figure 5.15Green roofs and permeable play surfaces as part of SUDS, Exwick Heights School, Exeter(source: RBA, 2010)


The City of Malmo (n.d.) go on to explain that the School site used to be

covered in asphalt, but now has new trees, an outdoor playground and

water channels that become rushing torrents in the rain. The students

have even participated in the change by being involved in the design

after inspirational study visits.

The City of Malmo (n.d.) also tells us how the whole site is very eco-

friendly and involves or guides the children through how it all works.

The school contains green roofs, an eco-pavilion made of a recyclable

material and a facility to compost all human waste from the school,

which is then used for garden fertiliser.

The school has open stormwater ditches and SUDS systems running

through and around the whole school which then connects and runs

into the rest of the area. As we can see in Figure 5.16, in the school

playground there is an amphitheatre that doubles as a 1 in 10 year

storm attenuation basin, and in the park adjacent to the school, where

they play are stormwater channels and swales.

The children are close to this SUDS infrastructure, actively learning

about it and from it, and see it change as the conditions change. It is

important that these initiatives are put in place, but that the effects are

seen too.

5�8 Mount Tabor Middle School Rain Garden, Portland, Oregon

Schools are one of the best places to incorporate a SUDS scheme

that will benefit the whole neighbourhood. In 2007 ASLA awarded

the Mount Tabor Middle School Rain Garden in Portland, Oregon the

General Design Honor award. The ASLA (2007) website stated among

its reasons the educational benefits and the positive effect it had on the

neighbourhood combined sewer system. It has severely reduced the

Figure 5.16Augustenborg School, Malmo. Left: a 1 in 10 year storage basin that functions as an amphitheatre in the school yard.Right: an open public space, adjacent to the school that functions as a main storage space.(source: Nowell, 2009)


stormwater runoff from the site to virtually nothing, saving an estimated

$100,000 in sewer upgrades for the city.

Built in the summer of 2006, ASLA (2007) explains that this project was

successful in three key ways. Firstly, it has taken an under used section

of school parking lot and turned it into a usable green space, that

provides student seating, bike parking and created a new entrance

plaza to the school. Secondly it alleviates a serious localised urban

heat island; the students and staff have all complained how even on

mild days the heat generated from the asphalt parking lot would send

the temperature within their classrooms soaring.

Finally and most importantly it has, along with other measures in the

school grounds, helped to solve a massive local problem of basement

flooding. As ASLA (2007) explain, the 80-year-old combined sewer

system does not have adequate capacity to deal with the pure

volume of runoff from the huge amounts of impervious surfaces in

the neighbourhood today. During intense rainfall events, the extra

stormwater entering the sewer system will back up into the basements

of local residences, causing flooding.

Figure 5.17The Rain garden at Mount Tabor Middle school collects stormwater form the site and stores it in an 8 inch deep vegetated basin for infiltration. There is an overflow incase of inundation, but so far that has hardly been used.(source: ASLA, 2007)


This is a very impressive list of achievements considering the simplicity

of the concept. ASLA (2007) describe how just by redirecting the flow

from approximately 30,000 square feet of asphalt and roof tops away

from the sewer system and towards this 4,000 square foot intervention,

the rain garden is able to deal with large amounts of stormwater runoff.

As it flows in, water is allowed to spread and infiltrate through out the

rain garden (Figures 5.17 and 5.19) and once it reaches its designed

depth of 8 inches, it will overflow into the local combined sewer system.

The infiltration rate of 2-4 inches per hour means that water is sat there

for only a few hours after the storm has finished.

ASLA (2007) go on to say that the educational benefits this scheme has

been widely felt too, with study trips from other schools also visiting to

learn from it. It has also been very efficient; in its first year of operation,

it did not have to overflow into the sewer system once and infiltrated

500,000 gallons of stormwater runoff. It is an effective, low cost, low

maintenance feature that benefits the whole neighbourhood in a wide

variety of ways.

5�9 SUDS on the River

Rivers are often poor and neglected with in our urban realm, more often

than not they are concrete channels, fenced off and hidden (Figure

5.20). Yet they hold the potential for providing similar benefits to parks,

a public amenity that provides important stormwater management.

The London City council and Environment Agency guide (LC and EA),

‘River Restoration’ (2001) states quite clearly that urban development

and traditional flood defence strategy involved canalising the rivers. It

Figure 5.18 Showing the garden in the dry(source: ASLA, 2007)

Figure 5.19Illustrating the use of the gravel distribution channel. Filling and spreading the water evenly over the whole raingarden.(source: ASLA, 2007)


goes on to say that many rivers are lost completely; rivers such as the

Fleet, Tyburn and Effra have been pushed completely underground

and become part of the sewer system. In doing this we have the lost

natural habitat and wildlife associated with rivers and streams, the

public amenity that comes with them and the flood control benefits.

LC and EA (2001) says that removing the high concrete walls of these

channels and reinstating the flood plain can potentially have many

benefits. It increases the flood storage capacity and reduces peak flow

volume and velocity. It helps to protect wildlife habitat by ensuring that

no high powerful water flows erode the banks and bottom. It also states

that wetlands and marginal planting will intercept runoff and filter out

pollutants. Providing a soft edge will also mean that water entering the

river will do so more uniformly along the river and it will not all enter it at

one particular point, such as from an overflow pipe.

The Environment Agency (n.d.) describes the regeneration of the River

Ravensbourne in East London (Figure 5.21). It demonstrates how

recreating a meandering river course can aid habitat restoration and

slow flow rate. It also says that using vegetation can trap pollutants,

and increase the water quality further down stream. It is also worth

noting the importance of rivers as green corridors and parks for both

Human amenity and the well being of wildlife corridors. LC and EA

(2001) states how important both these benefits are to improving the

health of a city and its green connections.

5�10 Summary

As seen we can use parks to provide us with space that we would

otherwise be lacking in the urban realm, but it is possible to do even

more with it. We can use high-tech approaches, such as Sherborne

Common or fully naturalised approaches, like Tanner Park and Point

Fraser. But what is common in all of these in the multifunctionality of

them all. They are not exclusively SUDS but rather SUDS are a part of

them.

Figure 5.21The restoration of the River Ravensbourne. Before (top) and after (bottom).(source: LC and EA, 2001)

Figure 5.20Poor and neglected urban rivers.(source: LC and EA, 2001)


Education is a big theme among these projects, especially in the

schools, but also in the parks where signage is erected to explain the

processes at work. It is important that SUDS are employed but that

people also understand what is happening. Public space is a good

place to do this as lots of people visit them and experience them.

Urban runoff may contain pollutants and sediments that need to be

removed but often, when developing in the urban realm, we are using

brownfield sites that may contain pollutants in the soil. So it is important,

as we have seen in Chattanooga and Seattle, to either remediate the

problem or ensure that this pollution does not leave the site.

There is quite often in the urban realm little chance to incorporate larger

SUDS features, but when that chance occurs, it is possible maximise

the efficiency and effectiveness of them. Fully naturalised systems can

and do have a place in our dense urban realm.


5.11 Case study: Watersquare, Rotterdam.

The Dutch are no strangers when it comes to dealing with water and

flooding. With large areas of the country under sea level and even more

of it recovered from marshy low lying land, they have been addressing

flooding for centuries.

As one of the designers of the Watersquares, Boer (2010) says that

currently the city of Rotterdam’s sewer system cannot cope with

sudden volumes of water. The city is prone to severe flooding and

this can cause an inundated sewer system that overflows. This can

cause severe problems and damage to the public domain and private

properties.

Boer (2010) explains that the watersquare concept was developed in

2005 and In 2007 it became part of official Rotterdam water management

policy. Boer, Jorritsma and Peijpe (2010) describe the how they

developed a concept that is intended to provide water storage during

heavy storm events in unison with improved public space. It Acts as a

SUDS by retaining water for short periods then releasing it slowly back

into the system to avoid peak flows. More is said in Section 2.1, but

explained here, as Boer, Jorritsma and Peijpe (2010) state “a classic

example of what a watersquare can look like and how it could function”.

Rotterdam has many problems facing it, as Boer (2010) points out. The

older parts of the city are very dense so they do not have a lot of room

for more standard SUDS techniques. Additionally, as the city is below

sea level, there is also virtually no scope for infiltration. As a result water

collected in these neighbourhoods will have to be stored temporarily

and the slowly released. The water may have to enter the existing sewer

system eventually, although preferably a separate system from that of

the wastewater.


As Boer (2010) goes on, large basins will be required to hold the water,

but these will be empty for 90% of the year. So therefore money that is

used for creating infrastructure to alleviate flooding can also be used

for civil improvements in the dense urban realm.

5�12 A Classic Example

As Figure 5.22 illustrates, the design for the Watersquares pilot scheme

is a play area split into two areas. A flat area for ball games sunken into

the ground by a meter and surrounded by steps, which can double

as seating. The second area is a hilly, featured surface containing a

playground, also sunken, which contains areas at different levels for

different activities.

This is more than a sunken playground however, as there is careful

contouring going on. The provision of interest, changing play

opportunities and the retention of other play opportunities has been

incorporated in the design, as Figures 2.23 and 5.24 shows. The

playground is at a lower level to that of the sports pitch and fills up

first. The playground has channels and islands at different heights built

into it so as it fills up the channels become fuller and then the islands

become surrounded by water. As Boer, Jorritsma and Peijpe (2010)

states, the level of the water is inversely proportional to the frequency

of the storm events and so when a certain level is achieved the sports

pitch becomes flooded. There are however still play opportunities in

the playground for the hardy and brave.

Figure 5.22Concept and model for this Watersquare (source: Boer, Jorritsma and Van Peijpe, 2010)


This site can be used as a recreation area for most of the year and

becomes an attenuation basin in storm events. It has seen the

opportunity and interest in highlighting the changes that occur when it

rains. It has made the stormwater management system not only visible,

but interactive as well, an integral part of educating the public about

SUDS.

Figure 5.23The flow rate increasing as the down pour increases.(source: Boer, Jorritsma and Van Peijpe, 2010)

Figure 5.24Top: In the dryMiddle: Light rainBottom: Heavy rainIllustrating the changing character and opportunities as the water square fills up.(source: Boer, Jorritsma and Van Peijpe, 2010)


Hygiene is an important consideration here too, so only rainwater is

collected from the neighbourhood, its roads, public spaces and roofs.

As Figure 5.25 illustrates, the rainwater is sent to a water chamber where

it is filtered before running into the square. Boer (2010) explains that

this is done to ensure that only clean water enters the square because

when the square starts to fill up, children are still encouraged to use it.

To avoid collecting water that may bypass the filtering system from the

adjacent streets, there is a vegetated buffer surrounding the square

that catches and filters any water.

In this pilot scheme the water held will be able to discharge its water

slowly into a nearby waterbody. As Boer (2010) mentions, not only is

it clean filtered water discharging, but as the water does not inundate

the sewer, there is no overflow of wastewater, thus improving the water

quality of the cities water bodies in two ways. Boer, Jorritsma and Peijpe

(2010) adds that the system is specially designed to retain water until

the level in the canal or receiving water body has returned to normal.

Figure 5.25The flow routes (top) gathering water from the street into a water chamber, where it is filtered and allowed to flow into the watersquare. It will sit here until the canal is sufficiently drained to accept this water(source: Boer, Jorritsma and Van Peijpe, 2010)


Water never sits in the square for too long, Boer, Jorritsma and Peijpe

(2010) stating a maximum time period of 36 hours, so water doesn’t

become stagnant or become a health hazard

When the water leaves the watersquare, there may be dirt and debris

left behind. To ensure that this doesn’t become an unsightly hazard

Boer (2010) explains that ease of cleaning has been designed into it.

The use of a hard material such as concrete is ideal as it is durable

and smooth allowing for a simple hose down to remove the debris.

To aid this hose down, smooth corners, slopes and an in built hose

connection to the water chamber are part of the design.

5�13Summary

Demonstrated here is attention to maintenance methods and the

avoidance of possible health and safety issues. Ease of maintenance

and cleaning is important for retaining a high quality appearance,

especially when it gets inundated with water that can leave dirt and

debris behind. It can potentially be dangerous, and definitely be

unattractive if litter and sediment are left behind, so the facility to

remove them easily needs to be present.

Ideally, we want as natural a system as possible in the urban framework

but this is not always possible. Here they have had to use a technical

solution to clean the water, but have created a park with a greater

Figure 5.26The frequency of a storm event is inversely proportional to the volume. De Urbanisten have therefore allowed areas to fill up in sequence, rather than a small amount everywhere.(source: Boer, Jorritsma and Van Peijpe, 2010)


degree of multifunctionality compared to other sites. It is a well-crafted

imaginative neighbourhood park, and by lowering it they have created

space for water. They have even enhanced its quality by giving it a

changeable character when it floods to different levels. As Boer,

Jorritsma and Peijpe (2010) illustrate, they have even created the

opportunity for other activities: flooding it and letting it freeze for ice

skating in the winter or becoming a paddling pool in the summer.

It is a multifunctional space that serves the needs of the neighbourhood

and provides a functioning water management scheme. It has

managed to make the most out of restrictive conditions and address

the requirements of SUDS. While it may appear to lack any major SUDS

features,it does, like a good SUDS scheme, retain water to prevent it

from flooding down stream and it filters and cleans it so that the public

may interact with it It provides high- tech stormwater management and

public amenity in a dense urban environment.

Figure 5.27It could even be flooded and frozen for use as a skating rink.(source: Boer, Jorritsma and Van Peijpe, 2010)


ConclusionSustainable Urban Drainage Systems (SUDS) offer multiple benefits:

in the country, in the suburbs or in the city. Beyond providing

stormwater management and pollution remediation, they enhance

and create public amenity, create and restore wildlife habitat and

encourage biodiversity. They can educate and facilitate community

cohesion and can save money both in installation costs and in

maintenance costs.

In the dense urban realm, they have been used to solve the major

problems of flood risk and prevent pollutants and sewage finding

their way out into natural water bodies. Examples and case studies

shown illustrate the success and resilience of SUDS schemes in

the city and their proven benefits. There is increasing evidence that

SUDS schemes can be adapted to almost any type of situation, and

regardless of how far away from being a natural system some of them

get, they always adhere to the principles of attenuation, remediation

and multifunction.

All the ideas and schemes prevent water from being channelled on

too quickly down stream, they all, in some way, filter or clean the water

and they all offer some other function beyond water management.

What is clear is that the more we understand how natural drainage,

flood remediation and bioremediation work, the more we can adapt

these processes to the urban realm. Although these schemes may

require specialist technical knowledge, the information is there.

None of this is new technology, it is all adapting existing technology

to a given situation. SUDS can play a central role in the regeneration

and enhancement of our communities, neighbourhoods, towns

and cities. This study shows there will always be an opportunity to

implement a SUDS scheme in the city and it will always benefit the

landscape.


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