SUDS in the City by Robert Norris

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

Contents

Abstract �� 5 Introduction �� 6 1.0 SUDS Introduced �� 9

1.1 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 �� 22 1.9 The Main elements and the roles they fulfil ��24 1.10 Summary ��26

2.0 SUDS in the City �� 27 2.1 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 �� 42 Solutions ��43 2.8 Sponge Park Stormwater management ��46 2.9 In Conclusion ��49

3.0 SUDS on the Street �� 50 3.1 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 �� 58 3.6 Green Streets ��58

4.0 SUDS In Development �� 61 4.1 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

4.9 Case Study: Ekostaden Augustenborg, Malmö. �� 72 4.10 Community Involvement ��74 4.11 Well designed SUDS Built around Community ��75

5.0 SUDS at the Park �� 78 5.1 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. �� 93 5.12 A Classic Example ��94 5.13Summary ��97

Conclusion �� 99 References �� 100

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

SUDS in the CIty-MA Landscape Architecture

“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

Abstract Sustainable 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.

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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.

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â&#x20AC;˘

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. â&#x20AC;˘

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.

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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.

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

SUDS in the CIty-MA Landscape Architecture

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

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

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

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

“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

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

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

Figure 1.6 Combined 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)

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).

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

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:

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

“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.”

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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 It 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 1.9). 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)

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Water butts

Green Roof

Filter strips stop sediment from entering swales

Reed beds Swale Treatment pond

River

Permable paving

Inﬁltration

Rainwater Harvesting

Swale Inﬁltration Inﬁltration

Figure 1.10 Diagram 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)

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.

SUDS in the CIty-MA Landscape Architecture

1.3 The Management Train This 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 Figure 1.11 Showing 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)

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.

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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. â&#x20AC;&#x153;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 costsâ&#x20AC;? (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.).

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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 Figure 1.12 A 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)

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.

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

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,

SUDS in the CIty-MA Landscape Architecture

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 1.14 Graph 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 1.15 Graph showing the comparative reduction in volume of pollutants washed from impermeable surfaces between traditional drainage and SUDS. The â&#x20AC;&#x153;first flushâ&#x20AC;? is the peak. (source: SNIFFER, 2004)

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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.

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•

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)

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Figure 1.16 Linburn 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 â&#x20AC;&#x153;slowly conveying waterâ&#x20AC;? not being achieved. (source: SNIFFER, 2004)

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.

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

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 Agencyâ&#x20AC;&#x2122;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

Figure 1.17 Top, 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.)

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.

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

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Figure 1.19 One 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.)

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 Figure 1.20 The 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.)

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

Figure 1.21 The 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.)

(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 â&#x20AC;&#x2DC;normalâ&#x20AC;&#x2122; pollutants like road dust, and drinks spills. This is often the first stage of the cleaning

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Figure 1.22 Interception 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.).

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.

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

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.

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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 subcatchments 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.

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2.0 SUDS in the City While 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

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

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. Figure 2.2 Parc 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 SĂ¸rensen, 2011)

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.

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

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 â&#x20AC;&#x2DC;making room for waterâ&#x20AC;&#x2122;. When we have the opportunity to, we should build floodplains and Figure 2.3 (previous page Different ways in which hard surfaces public space can be used to temporarily store storm water. (source: Boer, Jorritsma and van Peijpe, 2010)

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.

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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 Figure 2.5 Using 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 multiuse 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)

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

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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 â&#x20AC;&#x153;collaborative effort is considered to be more cost effective and beneficial than stakeholders acting individuallyâ&#x20AC;? (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

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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)

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Figure 2.6 Potential 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)

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-bystep 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

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Figure 2.7 Left: 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)

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 Portlandâ&#x20AC;&#x2122;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.

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

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

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

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

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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 donâ&#x20AC;&#x2122;t hold water on the Figure 2.10 Filter 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)

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.

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

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

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Figure 2.12 Illustration 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)

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 2.13 A 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)

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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.

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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.

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

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 Figure 2.15 The 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.)

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.

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

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.

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

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 waterâ&#x20AC;&#x2122;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 farmersâ&#x20AC;&#x2122; 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)

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Figure 2.18 Controlled street measures and zonal2.8 Sponge Park Stormwater management flooding in average and heavy rain falls. As shown in Figure 2.18, water from the rainfall will flow down the street (source: Dlandstudio, 2008)

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

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

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Figure 2.21 Note 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)

SUDS in the CIty-MA Landscape Architecture

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: â&#x20AC;&#x153;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.â&#x20AC;? (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.

SUDS in the CIty-MA Landscape Architecture

3.0 SUDS on the Street Dealing 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 â&#x20AC;&#x153;Permeable pavements may not be suitable for high volume traffic loads or arterials. However, shoulder areas and sidewalks may be appropriate applications to consider.â&#x20AC;? 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

SUDS in the CIty-MA Landscape Architecture

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

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

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

SUDS in the CIty-MA Landscape Architecture

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

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 innercity 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:

SUDS in the CIty-MA Landscape Architecture

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

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

SUDS in the CIty-MA Landscape Architecture

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 Figure 3.6 Kerb 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)

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)

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(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 â&#x20AC;&#x153;Infiltration rates at this facility were excellent, even during saturated conditions. This ensures that the facility will be ready Figure 3.7 Kerb extensions. Very similar to street planters in Figure 3.3 but have additional traffic calming and pedestrian safety benefits. (source: Green Streets, 2006)

for subsequent stormsâ&#x20AC;?. 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

Figure 3.8 A kerb extension in action during a flow and infiltration test. (source: CPBES, 2004a)

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

SUDS in the CIty-MA Landscape Architecture

Figure 3.9 Correct 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)

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 Figure 3.10 Street trees and permeable surfacing â&#x20AC;&#x2DC;bridgingâ&#x20AC;&#x2122; the infiltration and storage underneath. (source: Ferguson, 2011)

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

SUDS in the CIty-MA Landscape Architecture

Figure 3.11 Entire Streets with permeable paving. (source: Green Streets, 2006)

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

Figure 3.12 Permeable 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)

use of small, unneeded bits of roadside land.

SUDS in the CIty-MA Landscape Architecture

Figure 3.13 Screen grab of the Green Streets website. (source: Green Streets, 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:

SUDS in the CIty-MA Landscape Architecture

Figure 3.14 Part of a poster illustrating the variety of projects already completed by the Green Streets programme (source: Green Streets, 2011)

New Columbia

•

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 for industry professionals. SE 57thopportunities and Pine

So as well as achieving the core environmental aims of stormwater management, they also aim to improve public health, safety and way NE Fremont & 131st

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. SE 45th and Ankeny

SE 21st and Tibbets (People’s Co-op)

Their ‘Resolution’ Document estimates that 60%-70% of the volume of storm water is attributed to run off from streets and from private property SE 21st and Tibbets (People’s Co-op)

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 SW 12th and Montgomery 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 SE Rex Pervious Pavers

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 N Gay Ave. Pervious Concrete

and stormwater street planters that make it so successful. Rather than

Green Street Projects (Built)

pushing SUDS in general and releasing comprehensive design guides,

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 EGreen NT Streets have kept it simple. The planters and extended kerbs

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Figure 3.15 Part of one of many reports on the performance of Green Street interventions. (source: CPBES, 2004a)

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.

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4.0 SUDS In Development Roofs, 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. â&#x20AC;&#x153;In Urban Areas, particularly in very dense development (â&#x20AC;Ś) every hard surface becomes a rain water collector and the constructions profile must be considered for runoff managementâ&#x20AC;? (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.

SUDS in the CIty-MA Landscape Architecture

Figure 4.1 4.1 The Ray and Maria Stata Centre Diagram describing the collection, flow, filtration and use of the collected on site stormwater. The Ray and Maria Stata Centre at MIT in Boston has a very advanced (source: Zheng, 2007)

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. Figure 4.2 The outwash basin based on the local glacial landscape. (source: Zheng, 2007)

In this case holding it for use on site and the vegetation on site allows for a certain amount of evapotranspiration.

SUDS in the CIty-MA Landscape Architecture

Figure 4.3 Outside space to sit, relax, read and study. (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. â&#x20AC;&#x153;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.â&#x20AC;? (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 Figure 4.4 Different situations for use of permeable paving. (source: Interpave, 2008)

permeable paving can be used for a wide variety of residential, commercial and industrial applications.

SUDS in the CIty-MA Landscape Architecture

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 Figure 4.5 Some of the various forms permeable paving can come in. (source: Tensar, 2011)

(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.

SUDS in the CIty-MA Landscape Architecture

Figure 4.6 Top: 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)

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, â&#x20AC;&#x153;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.â&#x20AC;?

Figure 4.7 Any 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)

SUDS in the CIty-MA Landscape Architecture

Figure 4.8 SUDS system at Hazeley School. (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 â&#x20AC;&#x153;compartmentsâ&#x20AC;? 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

SUDS in the CIty-MA Landscape Architecture

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

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(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 Figure 4.9 A conveyance channel filling up in Augustenborg. (source: Brattli and Sørensen, 2011)

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

Figure 4.10 An urban wetland right up against a building. (source: RBA 2010)

fluctuating water levels and the hard steps mean that bare mud isn’t exposed when this happens.

SUDS in the CIty-MA Landscape Architecture

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

SUDS in the CIty-MA Landscape Architecture

Figure 4.11 Showing the basic components of a green roof along with the additional storage box for extra attenuation. (source: RBA, 2010)

•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.

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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.

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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.

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Figure 4.12 Botanical Green Roof. (source: City of Malmo, n.d.)

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.

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Figure 4.13 Hard edge retention pond. Designed to be in keeping with the original 50’s styling. (source: Nowell, 2009)

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. Figure 4.14 Raindrop motif in drainage channels that help optimise flow. 4.10 Community (source City of Malmo, n.d.)

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

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Figure 4.15 A drainage channel filling up, highlighting the surface drainage systems to the public. (source: Nowell, 2009)

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

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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,

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Figure 4.15 Retention pond in one of the courtyards of Augustenborg. (source Kazmierczak and Carter, 2010)

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 aestheticallypleasing 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.

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5.0 SUDS at the Park It 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

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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 reestablishment 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 ninemetre-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 Figure 5.1 Chain mail screens bioremediation troughs. (source: ASLADirt, 2011)

and

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)

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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

Figure 5.2 “Light artist Jill Anholt’s use of light important of the public area going to see this as more than a park. That to create an “eerie blue aura” helps said, this is an excellent example of how to combine new technology create the sense that advanced technologies are at work, but when and natural processes in a high profile public space. visitors pass by a set of “watery veils,” motion detectors briefly turn the lights 5.2 Point Fraser green.”(ASLADirt, 2011) (source: ASLADirt, 2011)

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.

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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)

“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

Figure 5.4 The treatment wetlands as public amenity. (source: Quinton, 2007)

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.

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“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 5.5 Tanner 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)

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Figure 5.6 Site plan indicating the water flow and cleaning strategy. (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

Figure 5.7 Terraces provide a transition between street and park as well as place to sit and relax. (source: Archlandscapes, 2009

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 Figure 5.8 When compared to Figure 5.5, which was taken soon after completion, you can see the improvement in water quality. (source: Archlandscapes, 2009)

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.

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Figure 5.9 Plan 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 KellyCampbell, 2007)

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 â&#x20AC;&#x153;flooded forestâ&#x20AC;? 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 5.10 Aerial Photo of Renaissance Park. (source: Hargreaves and KellyCampbell, 2007)

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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

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Figure 5.11 Seattle 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)

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 Figure 5.12 Aerial 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)

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.

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Figure 5.13 Children playing in detention basin and swale maze, Red Hill School, Worcester. (source: RBA, 2010)

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 Figure 5.14 Rainslides as part of SUDS at newly completed Fort Royal School, Worcester (source: RBA, 2010)

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.) Figure 5.15 Green roofs and permeable play surfaces as part of SUDS, Exwick Heights School, Exeter (source: RBA, 2010)

Brochure on Augustenborg explains how the children’s education and school environment introduces them to the idea of water management.

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The City of Malmo (n.d.) go on to explain that the School site used to be Figure 5.16 Augustenborg 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)

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 ecofriendly 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

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stormwater runoff from the site to virtually nothing, saving an estimated Figure 5.17 The 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)

$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.

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Figure 5.18 Showing the garden in the dry (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 Figure 5.19 Illustrating the use of the gravel distribution channel. Filling and spreading the water evenly over the whole raingarden. (source: ASLA, 2007)

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), â&#x20AC;&#x2DC;River Restorationâ&#x20AC;&#x2122; (2001) states quite clearly that urban development and traditional flood defence strategy involved canalising the rivers. It

SUDS in the CIty-MA Landscape Architecture

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. Figure 5.20 Poor and neglected urban rivers. (source: LC and EA, 2001)

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 Figure 5.21 The restoration of the River Ravensbourne. Before (top) and after (bottom). (source: LC and EA, 2001)

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.

SUDS in the CIty-MA Landscape Architecture

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.

SUDS in the CIty-MA Landscape Architecture

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.

SUDS in the CIty-MA Landscape Architecture

Figure 5.22 Concept and model for this Watersquare (source: Boer, Jorritsma and Van Peijpe, 2010)

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.

SUDS in the CIty-MA Landscape Architecture

Figure 5.23 The flow rate increasing as the down pour increases. (source: Boer, Jorritsma and Van Peijpe, 2010)

Figure 5.24 Top: In the dry Middle: Light rain Bottom: Heavy rain Illustrating the changing character and opportunities as the water square fills up. (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.

SUDS in the CIty-MA Landscape Architecture

Figure 5.25 The 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)

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.

SUDS in the CIty-MA Landscape Architecture

Figure 5.26 The 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)

Water never sits in the square for too long, Boer, Jorritsma and Peijpe (2010) stating a maximum time period of 36 hours, so water doesnâ&#x20AC;&#x2122;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 doesnâ&#x20AC;&#x2122;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

SUDS in the CIty-MA Landscape Architecture

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 5.27 It could even be flooded and frozen for use as a skating rink. (source: Boer, Jorritsma and Van Peijpe, 2010)

SUDS in the CIty-MA Landscape Architecture

Conclusion Sustainable 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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