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5.0 Case Studies

Barnes Wetland Centre Chapter 5 - 111

Case study index

The case studies below offer local and London under 500m² London over 0.2ha strategic SuDS examples to demonstrate the versatility of sustainable drainage in various 5.1 Priory Common 85 m² 5.14 Queen Caroline Estate 0.23ha contexts. Many are examples from London, 5.2 Dale Court 90m² 5.15 Australia Road 0.26ha but there are also studies from elsewhere, that 5.3 Museum of London 100m² 5.16 Crown Woods Way 0.26ha are exemplars applicable to the Capital. They 5.4 Upminster Bridge swale 400 m² 5.17 Hackbridge 0.27ha are described and ordered by size. 5.5 Kenmont Gardens 435m² 5.18 Goldhawk Road 0.27ha 5.19 Firs Farm 0.48ha 5.20 Salmons Brook 0.77ha London under 2000m² 5.21 Richmond Park 1ha 5.22 Coulsden Bypass 34ha 5.6 Central Hill 640m² 5.23 Dagenham SIP 142ha 5.7 Derbyshire Street 765m² 5.24 LuL depot roof, Middlesex 125m² 5.8 Renfrew Close 900m² 5.9 Islington Town Hall 1000m² National & International 5.10 Rectory Gardens 1000m² 5.11 Hollickwood School 1100 m² 5.25 Clay Farm, Cambridge 109ha 5.12 Talgarth Road 1200m² 5.26 Alnarp, Sweden 0.37ha 5.13 Mile End Green Bridge 2000m² 5.27 Benthemplein, Netherlands 0.95ha 5.28 Rue Garibaldi, Lyon, France 15ha 5.29 Bo01, Malmo, Sweden 85ha 5.30 Augustenborg, Sweden 320ha SuDS In London: A Design Guide Chapter 5 - 112

5.1 Priory Common rain meadow

Location Priory Common Objectives London Borough of Haringey • Intercept road runoff pollutants at source Extent 85m² and use the existing landscape to allow Cost £48,000 (Construction only) ‘interception loss’ (ie, prevent water from Date 2016 reaching the ground) for everyday rainfall Credits London Borough of Haringey • Clean and cool run-off during summer Thames21 when the watercourse is most susceptible Robert Bray Associates to the effects of pollution and water temperature increases (which inhibits the SuDS Components ability of water to carry dissolved oxygen) • Filter strip • Infiltration basin • Channels Actions and results • Runoff is diverted at the surface into a gully Summary in Redston Road and collected in a five-sett Green space enhancement and re-purposing channel that directs water onto the grass for surface water interception and infiltration. verge along Priory Road • Verge re-profiling carries water for its full Project Description length until it reaches the sewer Next to Priory Road is a linear green space • Early observations indicate that water with mature plane trees planted along the flows quickly into the rain meadow but roadside. The verge is about 75 metres long slows as it travels through the grass, and was highlighted as a site to deal with soaking into the tree-lined verge before surface runoff from the road, via a sewer reaching the letterbox outfall to a road gully. connection directly to the River Moselle. This Performance will improve as the meadow project is part of a suite of SuDS schemes grows locally that will cumulatively improve water quality. Image courtesy Robert Bray Associates

Priory Common after installation Chapter 5 - 113

Benefits • This simple SuDS retrofit shows how an existing urban green space can bring significant benefits to unprotected urban watercourses • Surface collection of runoff avoids any significant excavation or spoil for removal • Surface dressing with topsoil and low earth banks (bunds) have minimum impact on the trees with simple wildflower meadow seeding for open soil areas • Trees will be watered in times of water- stress, base flows in the soil will be Love the Lea campaign, Thames 21 enhanced and the River Moselle will be protected from urban runoff • High intensity summer storms will be diverted from the sewer and cooled before release to the river • Monitoring will show the extent of interception loss and the protection offered to the River Moselle

Lessons Learned • Importance of contractor selection • The value of expert supervision • How sites, that might otherwise be considered unsuitable for SuDS, can provide benefits with minimum intervention • The client partnership with Thames21 Images courtesy of Robert Bray Associates and Haringey Council are considering monitoring opportunities Conveyance of water through the scheme SuDS In London: A Design Guide Chapter 5 - 114

5.2 Dale Court

Location Hornsey Actions and Results London Borough of Haringey • Rainwater from the roof of the building Extent 90m² is re-routed away from the drainage Cost £20,000 (Construction only) network following rainfall by disconnected Date 2016 downpipes. The flow is diverted into two Credits London Borough of Haringey detention basins created within the existing Homes for Haringey lawn area, designed to accommodate one Thames 21 in 100 year rainfall Greysmith Associates • Rainwater is allowed to infiltrate the ground, but also return to the existing drainage SuDS Components network via buried outlet pipes. This • Bioretention basins process reduces peak flow. The wildflower • Downpipe disconnection turf also takes up water as it infiltrates into the ground Before Summary • Maintenance is carried out by the existing Transformation of amenity lawn to biodiverse grounds maintenance team and has been community asset. reduced as the mowing regime for the wildflower turf is less than that for the Project Description former amenity lawn Dale Court is a small block of flats with an area of lawn between the building and the street. It Benefits is enclosed by a low brick wall and features a • Inhibits the flow of storm water runoff into number of trees and a perimeter rose bed. the combined sewer system • Creation of a small area of wildflower Objectives meadow that improves biodiversity and is • Reduce flash flooding within the catchment more attractive of the culverted River Moselle, a tributary of • Water capacity of the SuDS system can the River Lea to. This was part of a plan to withstand a one in 100 year rain fall event Images courtesy of Greysmith Associates deliver a number of local SuDS projects in this catchment. Visualisation Chapter 5 - 115

Lessons Learned • Active engagement and discussion with residents has raised awareness of the issues • The scheme makes good use of an otherwise unremarkable and unused area of lawn • Small scale interventions make a difference as part of a strategic network of projects • The effectiveness of the SuDS scheme has been demonstrated by the amount of rainwater draining into the rain gardens. The scheme has been designed to allow for flow-monitoring equipment to be installed later if required

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5.3 Museum of London

Location London Wall City of London Objectives

Extent 100m² • Improve attenuation of rainfall and reduce

Cost - runoff entering the storm drain system Water attenuation performance of the Museum of

London green roof Date 2011 • Improve biodiversity Credits University of East London

GLA Drain London Programme Actions and Results • Bauder were commissioned to design and SuDS Components install living roof at the northwest corner of • Living roof the museum • The roof area was divided into two by an Summary impermeable barrier, creating two separate Living roof source control and monitoring hydrological units (sub-catchments). This provided an ideal location for comparative Project Description rainfall runoff measurements on the green As part of a sustainability initiative at the roof and the existing control roof Museum of London, a series of living roofs • A range of roofs, from biodiverse systems were installed across the museum’s roof during with topographical interest, to wildflower a programme of waterproofing renewal. and sedum mat systems, was used. This Supported by the Greater London Authority’s variety, in terms of their scale, levels, Drain London programme, this installation shading, and aspect, created an important included a range of roofs from biodiverse biodiverse urban habitat systems with topographical interest to • To monitor the water attenuation wildflower and sedum mat systems. The performance of the living and control roofs, complexity of roof systems at the Museum of it was necessary to quantify the volume London meant a variety of living roofs could and rate of rain falling onto the roof and the be installed in terms of scale, levels, shading volume and rate of rainfall runoff entering and aspect, thus creating an important urban the storm drain system of the museum resource for a range of biodiversity supported • The living roof was established in 2011 and University of East London Assessment by the living roof habitat. Chapter 5 - 117

monitoring began in 2014 Benefits • Living roof outperformed control grey roof in terms of rainfall attenuation • Reduced peak flow and amount of rain discharging from the roof

Lessons Learned • Much of the rainfall on the roof and subsequent runoff was within the lowest range of the v-notch gauge, where the flow rate could not be captured accurately

Images courtesy of University of East London

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5.4 Upminster Bridge swale

Location Upminster Bridge A London Underground Power Upgrade London Borough of Havering Project, involving the construction of new Extent 400m² substation, presented the opportunity to trial Cost Trial scheme an experimental SuDS scheme. This included Date 2015 two swales with associated tanks and v-notch Credits London Underground weirs. One receives water from the new sub- Environment Agency station roof, the other from adjacent London Green Infrastructure Agency Underground tracks. Funding was provided Environmental Scientifics Group by the Environment Agency with London Environmental Protection Group Underground Limited contribution in kind. SEL Environmental ITM Monitoring Objectives • Better manage water quality by improving SuDS Components remediation capabilities • Swale • Mitigate rail infrastructure flood risk • Outfall/runoff interception • Enhance local biodiversity No disruption to service during construction Summary Actions and Results Swale construction for increased on site • Surface water from the railway lines and attenuation and water treatment from the outflows of the sub-station roof was attenuated. This enhanced the site’s Project Description flood resilience and reduced saturation Upminster Bridge Station serves the District of the soil on the slopes by the River Line and is 3.5km west of the M25. The Ingrebourne. Slope stability improved as a River Ingrebourne is vulnerable to flooding result and has been deemed an at-risk river by the • Monthly remote monitoring provides Environment Agency. The river is within the data on water quantity. Data loggers are sub-catchment area of the line and to a lesser attached to sampling chambers. These extent, nearby roads, with implications for both contain water chambers which house pollution and bank stabilisation of the River water level sensors 400m2 swale under construction Ingrebourne and reliability of the line. Chapter 5 - 119

• Plant establishment is also being monitored • Water quality is being sampled monthly from five locations and analysed. The data will be available in 2016

CRUSHED BRICK Benefits BENTONITE SEAM Ø225MM DRAINAGE PIPE • Improved water quality Depth varies 0.87-1.00m

• Ability to withstand a 1 in 100 year flood RAMP APRON event of 59L/sec • Reduced waste from building demolition EXISTING CONCRETE SLAB through the reuse of waste rubble for swale construction • Any outflow from the scheme is conveyed to River Ingrebourne, not to rail SECTION BB infrastructure • Enhancement of outlook over rail Ø450MM DRAINAGE PIPE infrastructure from residential areas Depth varies 0.87-1.00m BENTONITE SEAM (FUTURE CONNECTION TO TRACK DRAINAGE) • Enhanced local biodiversity

Lessons Learned EXISTING CONCRETE SLAB • Design required interface with conventional drainage systems

Images courtesy of LU Infrastructure Protection

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5.5 Kenmont Gardens

Location Kensal Green The project is a Neighbourhood and Corridor London Borough of Scheme, developed to incorporate SuDS. Hammersmith & Fulham It is funded through a combination of TfL Extent 435m² LIP Funding and Lead Local Flood Authority Cost £300,000 (total scheme) Funding. Date 2015 Credits London Borough of Objectives Hammersmith & Fulham • Improve an under-used area through public Project Centre Ltd realm works, including planting, paving and FM Conway lighting improvements Green Blue Urban • Incorporate SuDS features within the design SuDS Components • Retrofit SuDS to the existing drainage • Permeable paving system of a deep combined storm and foul • Rain gardens sewer, fed by gullies that were formerly in • Geo-cellular storage the carriageway • Tree planting Actions and Results Summary • Surface flow is directed towards rain Transformation of highway to neighbourhood gardens and trees garden • Trees are planted in linked trenches that incorporate below-ground attenuation Project Description • Water flow is held and slowed within the The garden was previously road carriageway attenuation before passing through control that had been pedestrianised. The carriageway chambers and into the existing drainage was still in existence but had been closed off system with bollards. The area had been raised and • Permeable paving partially landscaped, with three trees planted, • Community involvement throughout the Images courtesy of George Warren but was a fairly low grade landscaped area. project, with concept designs sent out for Community planting workshop public consultation in September 2014, from which a positive response was Chapter 5 - 121

received and a preferred option selected. A dialogue was maintained with College Park Residents Association (CoPRA) and Kenmont Primary School throughout the process

Benefits • The design restricts runoff to greenfield rate for events up to the one in 10 year average recurrence interval (ARI) with exceedance routes • CoPRA and Kenmont Primary School were heavily involved in the latter stages, with pupils of the school creating clay tiles under the supervision of a professional potter, which were then installed in the new space • Engagement throughout the process and a planting event ensured community buy-in

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5.6 Central Hill

Location Upper Norwood This section of Central Hill falls within a London Borough of Lambeth Critical Drainage Area (CDA) identified within Extent 640m² Lambeth’s Surface Water Management Plan Cost £30,000 (total scheme) (SWMP). There is no historical evidence of Date 2012 properties flooding, however, surface water Credits London Borough of Lambeth runoff and significant highway ponding occurs FM Conway at the bottom of the hill.

SuDS Components it was decided that the build-out at the junction • De-pave of Central Hill and Elder Road would form part of the adjacent footway works proposed for Summary Central Hill. Before De-paving as part of highway maintenance to address ponding Objectives • Replace standard paving with SuDS as part Project Description of footway works Central Hill is part of the Principle Road • Cost to not exceed traditional like-for-like Network (PRN). it is a main east-west route footway maintenance (the A214) linking Streatham and Crystal Palace. The road is, therefore, heavily trafficked Actions and Results with two bus routes. Central Hill starts at its • Increased permeability and a reduction in junction with Elder Road, and heads east uphill the amount of surface water runoff entering to Crystal Palace. Elder Road is the lowest the drainage system point of Central Hill on the original route of • A grass verge introduced into the footway the River Effra which rose in Upper Norwood. was constructed lower than the footway. Within Lambeth there are also three known This captured surface water runoff, natural springs that appear along the 85m preventing it from draining into the highway contour, one of these springs is at the junction • The cross-fall of the footway was changed, of Central Hill and Salters Hill. where possible, to drain into the adjacent Images courtesy of Owen Davies park. Where levels would not allow the fall After to be changed, the footway was graded to Chapter 5 - 123

drain into the grass verge footway • The build-out was changed to grass with • Check dams and a cut-off drain installed the same detail as the verge in the verge would have enhanced its performance Benefits • Unidentified groundwater drain systems • The footway works enhanced the public not noted at the outset of the project could realm by extending the park into the road have been incorporated within the scheme • The grass verge has been incorporated into had this information been available at the Lambeth’s existing grounds maintenance start contract • After construction, it became apparent that • Although the grass verge was introduced vehicular over-run was an issue during the and the cross-fall changed, it is accepted school run. Initial reaction was to install that this scheme alone will have a minimal either bollards or a post and rail system; impact for the CDA as a whole however, it was decided not to introduce • This scheme shows positive results and street furniture as this would negate the will, with other future projects, have a objective of de-cluttering. The verge is cumulative impact on improving the surface being monitored for excessive damage. water runoff across the CDA Should this happen, planting low level • One of the principles of these works has shrubs will be considered as a mitigation been to show that the cost of a grass verge measure would not be any greater than paving • For future designs, consideration will be • The verge design is a standard, repeatable given to raising kerb heights to between design 150-200mm to deter vehicle over-run

Lessons Learned • Using asset costings and the actual invoiced cost for the works, the project demonstrated that the footway works were £8m² cheaper than traditional like-for-like

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5.7 Derbyshire Street Pocket Park

Location Bethnal Green, Project Description London Borough of Tower Derbyshire Street is located in a densely Hamlets populated part of east London, next to a park Extent 765m² and the Oxford House community and arts Cost £120,000 (total scheme exc. centre. Before the redesign, the street was officer time) a dead-end with parking issues, anti-social Date 2014 behaviour and fly-tipping. Credits London Borough of Tower Hamlets The potential of the site’s south-facing aspect, Greysmith Associates existing trees and community involvement Oxford House helped develop a consensus for streetscape Mayor of London’s improvement. A key aspect of delivery was the Pocket Park Initiative partnership between local highway authority, JB Riney flood management teams and the community. The Grass Roof Company This grassroots approach enabled funding Thames Water Utilities from the Mayor of London’s Pocket Park RBMP initiative.

SuDS Components Objectives • Permeable paving • Improve facilities for community use • Bioretention basins • Onsite water management through SuDS • Green roofs • Tree pits Actions and Results • Green roofs on bike sheds and a bin Summary store increases the attenuation storage Transformation from roadway into community capacity, improving the streetscape’s ability shared space to mitigate impacts during high and/or prolonged peak flow events Images courtesy of Greysmith Associates • Disconnecting downpipes on Oxford House

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increased attenuation storage capacity by Lessons Learned redirecting water away from the combined • Active engagement between the sewer overflow and conveying it into community and local authority has social bioretention basins and a new swale and economic value • Permeable paving, allows water to seep • SuDS can help define and enhance into the ground. During high and/or public realm improvements that relate to prolonged peak flows, additional runoff pedestrian and cycle routes is attenuated by the surrounding SuDS • Permeable block paving is susceptible to scheme gathering litter fragments, so the jointing of • A network of rain gardens, swales and paving systems needs consideration engineered tree pits has increased the • Connectivity with Weavers Field could have attenuation storage capacity of the further enhanced the scheme streetscape • A bespoke information board communicates the streetscape and community benefits of the scheme leading to continued community buy-in to the maintenance and monitoring of the scheme

Benefits • Inhibits the flow of storm water runoff into the combined sewer system • Community partnerships have safeguarded future management and maintenance • Creation of a community resource • Native and edible plants promote biodiversity and a community ethos • Able to withstand a one in 100 year rainfall event

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5.8 Renfrew Close

Location Beckton Objectives London Borough of Newham • Provide a sustainable drainage function and Extent 900m² alleviate flooding Cost £43,000 (construction only) • The rain gardens should create attractive, Date 2015 productive and biodiverse green spaces for Credits Groundwork the residents Environment Agency Robert Bray Associates Actions and Results Greatford Garden Services • Bioretention basins designed to take road and roof runoff SuDS Components • Downpipes and rainwater conveyed to • Detention basins swales and bioretention basins • Bioretention basins • Swale network to accommodate different • Tree planting sized rainfall events • Channels • Rain gardens are attractive • Downpipe disconnection • Swales Benefits • Can withstand one in 100 year + 30 per Summary cent storm event Transformation of green space to multi- • Runoff from 750m² of roof and 165m² from functional green infrastructure for the estate roads are attenuated in the scheme • 12-hour delay between rainfall event and Project Description pressure recording in the basin An existing communal green space between • 16-hour delay between peak rainfall and residential blocks was retrofitted with a SuDS scheme. The rain gardens receive water from hard surfaces at roof and ground level and Images courtesy Robert Bray Associates from soft surfaces at ground level. After Chapter 5 - 127

peak pressure in rainfall basin for first event Lessons Learned • Monitoring system by UoEL installed and used to support design of future SuDS • Future retrofit projects should try to direct flows from known problem areas into bioretention basins to prevent all surface flooding • Maintenance agreements need to be in place along with a clear method of reporting

Images courtesy of Robert Bray Associates

Channel detail Channel outflow into swale and bioretention basin SuDS In London: A Design Guide Chapter 5 - 128

5.9 Islington Town Hall

Location Upper Street This was coupled with recognition of the poor London Borough of Islington presentation of the building to the street. These Extent 1,000m² were key factors in the project gaining support. Cost £100,000 Date 2011 It shows how small public realm projects can Credits London Borough of Islington address car parking issues and storm water J&L Gibbons runoff, while transforming a space into a focal point for community life. SuDS Components • Permeable paving • Large specie tree planting Objectives Before • De-paving • Enhance the town hall’s setting as a key civic location Summary • Provide a high quality public realm on Transformation of a car park into a green Upper Street public space for community and ceremonial • Resolve car parking issues while events maintaining suitability for ceremonial events • Plant large species trees for long-term Project Description benefit Islington Town Hall is on the A1 Upper Street which is populated by shops, bars and Actions and Results cafes and attracts heavy footfall. Before the • Permeable paving surfaces allow water to redesign, the forecourt of the town hall was seep directly into the sub-base, thereby a car park with impermeable surfaces. This redirecting excess and polluted water away had implications for the management of storm from the combined sewer water runoff onto Upper Street’s carriageway • Trees and planting provide canopy cover, and for combined sewer overflow. increasing the interception of rainwater and enhancing biodiversity A political incentive to ‘green’ the town hall • De-paved and planted surfaces increases forecourt initiated the scheme as part of attenuation storage capacity by maximising After Islington’s sustainable agenda. sites for infiltration Chapter 5 - 129

Benefits • Increased attenuation storage capacity • Improved water quality • Enhanced public realm and green infrastructure • Enhanced civic function of the forecourt • Tree-planting for improved air quality

Lessons Learned • Permeable surface treatments can successfully address shared space requirements • An integrated SuDS scheme can have environmental and economic benefit

Images courtesy of J & L Gibbons

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5.10 Rectory Gardens

Location Hornsey, London Borough of SuDS aspiration of ‘managing quality and Haringey quantity aspects of runoff whilst delivering Extent 1000m amenity and biodiversity benefits’ can be Cost £80,000 met in an existing urban park setting Date 2016 Credits Haringey Council Actions and Results Robert Bray Associates • Runoff from the road is collected in three Thames21 bespoke, cast iron inlets that replace Hugh Pearl (Land Drainage) Ltd gully pots and perform like chute gullies, delivering the dirty surface water into two SuDS Components SuDS management drains • Retention basins • System A to the west, delivers runoff to a • Detention basins silt interception forebay basin • Planted channels • In System B, runoff travels along a grass channel, which is planted so that oils and Summary silts are concealed but is easily accessible Retrofit and transform green space to manage to remove solids road runoff • The ‘source control’ features are followed by wildflower meadow basins that can hold Project Description lots of reasonably clean runoff to the one in Runoff flows directly to the River Moselle via a 10 year return period surface water sewer connection. • An under-drain below the basins ensures water drains down in a matter of hours, An existing local park was identified for leaving the site at greenfield rate of runoff, accommodating SuDS components that through a protected orifice control chamber enhanced amenity and biodiversity value. • In larger storms, up to the one in 100 year return period, with a 30 per cent allowance Objectives for climate change, these basins overflow Images courtesy of Robert Bray Associates • The project aims to collect the whole into further grass storage basins. The volume of runoff from a defined road second basins are managed as amenity After catchment and demonstrate how the full grass so are accessible most of the time Chapter 5 - 131

• The wildflower meadow basins have Lessons Learned balance beams so that even when wet • The project was undertaken in tandem or filled with water they can be used for with the Priory Common rain meadow adventure play (case study 7.17) and therefore benefited from sharing expert site supervision and a Benefits knowledgeable contractor • Retrofit demonstrates how polluted runoff • Protecting planted channels where water can be practically managed in an existing entered the SuDS and the relatively flat local park or urban green space, while basins reduced erosion to a minimum enhancing amenity and biodiversity • Physical protection of the basins was • The small interception forebays provide considered but not used for reasons a simple way of trapping and removing including visual quality, risk of vandalism pollutants such as silt and heavy oils and cost. It may be necessary to overseed • The changes of level in the park landscape the basins when germination of the enhance the quality of the space, while wildflower seed is inspected defining the SuDS and biodiversity features • The client partnership (Thames21 and Swale • The under-drain ensures the basins are dry Haringey Council) are currently considering most of the time, but the rainwater irrigates monitoring opportunities both trees and the meadow, particularly • It would be useful to estimate natural in summer when many urban park losses at different times of year in different landscapes suffer drought weather conditions • Water-play in a safe place helps the • The quality of runoff should be easy to community relate positively to normal assess by collecting it as it passes through rainfall and to appreciate the impact of the control chambers heavy storms in summer when the basins fill • Signs to inform the public about SuDS and the community benefit

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5.11 Hollickwood Primary School

Location Sydney Road and low attenuation storage capacity of the London Borough of Barnet site. Extent 1,100m² Cost £18,000 (construction only) Objectives Date 2013 • Alleviate surface water flooding, focusing Credits Hollickwood Primary School on the Pymmes Brook catchment Environment Agency • Provide a wetland and wildlife educational Thames Water resource for the school Wetlands and Wildlife Trust • Improve management of storm water runoff London Borough of Barnet in the surrounding area • Improve water quality leaving the site SuDS Components • Swales Actions and results • Bioretention basin • Green roof installation increased the volume • Detention basin of rainwater intercepted by the SuDS scheme and slowed the flow of rainwater Summary throughout the system, improving its Transformation of the school fields to an effectiveness during peak flow events educational resource • A network of swales has increased the attenuation storage capacity. Monitoring by Project Description Thames Water confirms that outflow was Hollickwood Primary School is on a residential successfully controlled following a rainfall street just south of the North Circular. The in December 2013 that caused localised school playing fields were either paved, had flooding low permeability surfaces or compacted • Bioretention and detention basins have ground, with minimal grass cover. increased the attenuation storage capacity of the scheme and slowed the flow of These conditions meant surface runoff water through the system. The detention Images courtesy of WWT from paved surfaces and the school’s roofs basin is the final component of the SuDS inundated the playing fields during prolonged After and/or peak rainfall due to the low permeability Chapter 5 - 133

scheme and is significant during prolonged and/or high peak rainfall events • The bioretention basin and detention basin both act as educational focal points in school learning

Benefits • Probability of on-site flooding has decreased • Improved quality of play areas, including the addition of a valuable educational resource

Lessons Learned • School-wide engagement has demonstrated that project objectives can be met with limited resources and minimal disruption, particularly with the assistance of large organisations. Engagement has also contributed to the ongoing maintenance of the scheme

Data courtesy of Thames Water

Monitoring data shows the success of the scheme SuDS In London: A Design Guide Chapter 5 - 134

5.12 Talgarth Road

Location Talgarth Road Objectives London Borough of • Improved air quality with integrating SuDS Hammersmith & Fulham • Planting Miscanthus to act as a filter to Extent 1200m² traffic emissions. This grass grows to Cost £240,000 (total scheme) 1.8 metres and provides a soft, visibly Date 2016 permeable border, to ensure a sense of Credits London Borough of safety Hammersmith & Fulham FM Conway Actions and Results • Some trees along this stretch were in a SuDS Components poor state and need to be replaced; others • Bioretention basin need to be removed to allow a bicycle path • Tree planting to be repositioned • A 26 metre-long section of the roadside Summary planting has been designed to accept Green infrastructure enhancements on the runoff from the highways and footway, highway to improve air quality thus reducing the surface water flow to the combined sewer and providing additional Project Description capacity within the Counters Creek The project includes the installation of green Catchment infrastructure along a stretch of shared space • The bioretention basin will be deeper than along Talgarth Road between Butterwick and the other stretches of planting to provide Shortlands to the north of the Hammersmith below ground attenuation for the surface Flyover. The project intends to reduce the water flows, with a controlled release to the exposure of pedestrians and cyclists to the sewer poor air quality in Hammersmith town centre, • Exceedance flows, during extreme events, while incorporating SuDS and providing a safe are directed towards the existing road gully and secure setting. The aim is to replicate this • Roadside bioretention basins incorporate Images courtesy of George Warren approach elsewhere in the borough. bespoke roadside inlets

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• A border of herbaceous groundcover will Lessons Learned be planted between the Miscanthus and • The bioretention basin will include the the bicycle path same plant species as the rest of the roadside planted areas to test how these Benefits species perform when experiencing runoff • Air quality monitors, placed on either side from the surrounding area, compared to of the grass, measure particulate matter conventional planting beds and nitrogen dioxide levels to demonstrate • Should the species thrive in this the extent of air quality benefits from the environment, the aim is to repeat this greening along other stretches of highway within the borough to help tackle air quality and flooding issues

Under construction SuDS In London: A Design Guide Chapter 5 - 136

5.13 Mile End Green Bridge

Location Mile End Road The proposals had to consider the London Borough of Tower requirements of the A11 below. Traffic flows Hamlets on this part of the TfL road network could not Extent 2000m² be impeded during the works or maintenance Cost £75,000 operations once planting was established. Date 2010 Credits Design for London Objectives London Borough of Tower • Enhance park connectivity Hamlets • Increase the impact of the planting from the Mile End Park road below and the parkland above muf architecture | art • Enhance soil infiltration Tim O’Hare Associates • Enhance biodiversity J & L Gibbons

SuDS Components Actions and Results Before • Green roof/bridge • The soil required de-compacting and • Tree planting amelioration to increase its capacity to • Soil amelioration retain water Summary • Soil depths were increased by 250mm to Green bridge reinstatement of soils and allow for greater root-zone and better plant planting establishment • Trees were planted at a high density to Project Description improve their resilience to shallow soil The bridge provides a key connection within profile Mile End Park by spanning the A11, Mile End • The central median was removed to create Road. greater openness

As part of High Street 2012 works, the existing green bridge was rejuvenated to incorporate more planting. After Chapter 5 - 137

Benefits • The young plant stock established faster than previous semi-mature tree planting • The dense blocks of planting and mix of species provide increased biodiversity • The planting had immediate impact due to its density and educational interest as an emerging ‘upland’ ecology • The bridge is more successfully integrated into the park landscape. • The planting creates a distinctive feature and is more visible from the A11 below

Lessons Learned • Stability of high level planting, achieved through young stock able to adapt rooting structure to specific soil depths • Parapet planting proposals have to take into account the restricted access for planting and maintenance • Early engagement with TfL necessary to prevent contract delays • Early engagement of soil scientist to avoid delays due to soil testing

Images courtesy of J & L Gibbons

Green Bridge from the A11 SuDS In London: A Design Guide Chapter 5 - 138

5.14 Queen Caroline Estate

Location Hammersmith identified areas of improvement including the London Borough of management of water. Hammersmith & Fulham The challenges of the site made it an Extent 0.23ha appropriate development for the LIFE+ Cost £226,000 (total scheme) Climate proofing social housing project that Date 2015 provides low-cost, retrofitted SuDS to improve Credits Groundwork community resilience to climate change. London Borough of Hammersmith & Fulham Objectives Greater London Authority • Reduce surface water flood risk and EU LIFE+ Programme frequency • Improve the condition of the estate’s After SuDS Components infrastructure • Green roofs • Address deprivation and vulnerability to • Bioretention basin climate change on the estate • Detention basin • Permeable paving Actions and Results • Green roofs were installed to increase Summary attenuation storage capacity where it Estate regeneration through integrated SuDS has not been possible to disconnect design downpipes that run internally. • Green roofs were installed on bin stores Project Description and pram sheds; these are visible at Queen Caroline Estate is bound by the River ground level and from above Thames and the Hammersmith Flyover. The • A bioretention basin was built to r estate is a mixture of paved carriageway attenuate rainwater. This flow comes from surfaces for access and parking and grassed surrounding impermeable surfaces and areas. Council data on surface water flood risk, from the roof of an adjacent building Images courtesy of Groundwork site surveys to map existing vegetation and • Permeable paving has increased the drainage patterns, plus resident engagement, volume and rate of infiltration into the Garage green roof Chapter 5 - 139

subsurface, helping to maintain the effectiveness of bioretention and detention basins by limiting the water flowing to them

Benefits • The works were delivered at the same cost as conventional landscape improvement when compared to other housing estate works • Landscape has been transformed into multi-functional space • 142m² of green roof has been installed, improving biodiversity • Run off from 900m² of impermeable surface has been conveyed into a SuDS system • A community growing area of 32m² has been created

Lessons Learned • Engaging residents in the development of proposals ensured a detailed understanding of how the streetscape functioned, thereby maximising the reach of project benefits • Despite CAT and radar scans, some below ground services were not identified and required designs to be revised to accommodate them

Bioretention basin outside homes Permeable paving strip SuDS In London: A Design Guide Chapter 5 - 140

5.15 Bridget Joyce Square, Australia Road

Location White City This stretch of Australia Road has a school London Borough of on one side and playgrounds on the other – Hammersmith & Fulham potentially hazardous for children crossing the Extent 0.26ha road between parked cars. Cost £950,000 (total scheme) Date 2015 The street lies within the Counters Creek Credits London Borough of Sewer catchment, which is exceeding its Hammersmith & Fulham capacity, resulting in the flooding of properties Robert Bray Associates downstream. Hydrological modelling of the Thames Water borough has also shown that this stretch of TfL Australia Road is susceptible to significant GLA surface water flood risk. McCloy Consulting Before F M Conway Objectives • Create a landscape that serves a vital SuDS Components drainage function in providing flood • Permeable paving resilience against surface water and sewer • Bioretention basins flooding issues and that provides climate • Rills change adaption benefits • Raingardens • Instill a sense of pride within the local • Tree planting community • Downpipe disconnection • Provide a multi-functional space that could be used for a variety of events Summary • Provide educational potential, while being Transformation of the road into a shared ‘urban safe for the children who use the site on a oasis’ for pedestrians and cyclists. daily basis

Project Description Actions and Results Australia Road is in the heart of the White City • Permeable block paving (1,320m²) allowed Housing Estate, in the northern section of retention of existing site levels, negating After Shepherds Bush, south of the A40 Westway. the need to excavate the existing concrete Chapter 5 - 141

road slab. The 180mm permeable • Annual flow volumes into the combined pavement depth can cater for heavy loads sewer overflow have been reduced by 50 • The permeable paving and the per cent disconnected downpipes from the • The attenuation of water and its associated surrounding school and playground vegetation have contributed to air quality buildings direct rainwater to heavily (principally NOx and PM) and water quality planted bioretention basins and rain (hydrocarbons and total suspended solids) gardens, providing over 55m³ of additional • The ecological considerations (hydrological attenuation and vegetative) have provided a site for • Flow controls are designed to restrict biodiversity that will increase as the scheme flows to below 1 l/s (less than the 5 l/s matures, while providing an educational generally adopted by industry) and retain resource and community buy-in to flows onsite for longer. This is achieved, monitoring and maintenance in part, by designing drainage outlets that minimise the risk of blockage, yet ensure Lessons Learned easy access and safety for council staff to • Supervision of SuDS construction by inspect and maintain designers was essential to successful • The scheme uses sculpture to replace delivery traditional downpipes to make the scheme • Involvement of the construction contractors distinctive. The sculpture also provides an early in the design process ensures the important security deterrent against those best outcome trying to access the school roof • Interpretation boards explain the design; monitoring equipment provides performance evidence

Benefits • Carriageways adaptations have made the use of community assets safer Images courtesy of George Warren • Reduction in local and wider flood risk Before SuDS In London: A Design Guide Chapter 5 - 142

5.16 Crown Woods Way

Location Eltham to improve the function and quality of the London Borough of Greenwich streetscape. Extent 0.26ha Cost £23,000 (Total scheme) Date 2015 Objectives Credits London Borough of Greenwich • Reduce flood risk Trees for Cities • Address concerns about the environmental impact of air and noise pollution SuDS Components • De-paving Actions and results • Kerb drainage • Two rain garden bioretention basins have • Bioretention basins increased the attenuation storage capacity of the streetscape, reducing the likelihood Summary of water being conveyed to the combined Enhanced streetscape and flood risk resilience sewer overflow. This measure allowed 30 through bioretention. per cent more water to infiltrate into the After subsurface, compared with a conventional Project Description grassed area of comparable size Crown Woods Way is a residential street, south • Trees were planted within the de-paved of the A2 East Rochester Way and is within rain garden areas. This addressed the a high flood risk area. Narrow grass verges hydrological balance of the site and and a crematorium next to the site made the impact of noise and air pollution by limited contribution to water management. The providing a physical noise barrier and proximity of a busy carriageway also meant the zone for air exchange and particulate site was subject to high levels of noise and air accumulation. Special consideration was pollution. given to the drainage and growth capacity of each tree The programme to address these conditions was fronted by a partnership between the Royal Borough of Greenwich and Trees for After Cities, who adopted a holistic approach Chapter 5 - 143

Benefits • Reduces street flood risk by increasing attenuation storage capacity • Reduces noise and air pollution • Establishes a new carbon sink through tree planting

Lessons Learned • Modest public realm improvements can promote partnerships between a range of stakeholders

After SuDS In London: A Design Guide Chapter 5 - 144

5.17 Hackbridge

Location Hackbridge Objectives London Borough of Sutton • Reconfigure the streetscape to make it Extent 0.27ha safer and better for pedestrians Cost £920,000 (Total scheme) • Manage water runoff by installing SuDS Date 2014 • Mitigate air and noise pollution Credits London Borough of Sutton Civic Engineers Actions and results Adams & Sutherland • Bioretention basins, including tree planting, provide attenuation for runoff from the SuDS Components reconfigured streetscape • Permeable paving • Rills and filter drains with flow control • Bioretention basins devices control the flow of water into tree- • Tree Planting rooting zones that provide bioretention • Filter drains & rills • Permeable paving allows for water • Downpipe disconnection infiltration into the subsurface, improving capacity during prolonged or high peak Summary flow rainfall events. Up to 40 per cent of Transformation of street function and traffic the carriageway has been reallocated flow with integrated green infrastructure to permeable paving. Reduced traffic speeds have also improved the pedestrian Project Description environment The public realm around the junction of Hackbridge Road and London Road was previously dominated by busy carriageways, with pedestrians confined to narrow footways fronted with shops. Traffic on the carriageway was fast-moving, adding safety concerns to those around noise, air pollution and health and safety. The low-lying topography of the area meant the site was susceptible to surface Tree planting along the carriageway water flooding. Chapter 5 - 145

Benefits • Traffic calming; shop frontage enhancement • Surface water flooding in the area has not been observed since the scheme was installed

Lessons Learned • Detailed surveys of underground services and features are necessary in retrofit situations • A project approach that can adapt to unforeseen constraints makes the construction process more efficient • Crossings and parking bays should be clearly marked

Images courtesy of Civic Engineers

Permeable paving SuDS In London: A Design Guide Chapter 5 - 146

5.18 Goldhawk Road

Location Shepherd’s Bush Actions and Results London Borough of • Each tree is planted within a 1.8 metre x Hammersmith & Fulham 1.8 metre tree pit with tree grille, located Extent 0.27ha within a much larger soil-filled rooting zone Cost £100,000 (construction only) beneath the pavement, aiming to provide Date 2015 between 10-20 metre³ of soil per tree Credits London Borough of • Runoff from the adjacent road and footpath Hammersmith & Fulham flows directly into the tree pit at road level Robert Bray Associates via a custom kerb inlet Plan showing modular soil system McCloy Consulting • The soil level in the tree pit is lower than GreenBlue Urban the road. It is surrounded by a raised FM Conway polypropylene weir to allow initial water storage. This ensures the trees get water SuDS Components every time it rains and allows sediments • Kerb inlets and litter to drop out of the water • Tree pit attenuation • During heavier rainfall, when the tree pit • Flow control fills above the weir level, the water flows into a sub-base replacement layer covering Summary the rooting zone just beneath the paving Tree trench planting for attenuation build-up. This distributes the water over the whole rooting zone, allowing it to infiltrate Project Description into the soil Street tree planting within the pavement on • Specialist soil with a 25 per cent void ratio a busy London high street utilising a modular allows rainwater storage structural tree soil system combined with kerb • Perforated pipes in the base of the inlets and flow-control devices construction collect water and direct it to a flow control chamber, which discharges Images courtesy of LBHF Objectives to the combined sewer. The flow control To provide SuDS functionality and to protect chamber allows water to build up in the Completed scheme the combined sewer. rooting zone when it rains and be released Chapter 5 - 147

slowly once the peak in runoff has passed • Integrated protected overflows ensure the system can discharge freely to the sewer once storage capacity has been reached. Flow rates are designed to reduce the risk of combined sewer overflow events

Benefits • Combines benefits of large tree rooting zones with their ability to store runoff, with little modification • SuDS scheme introduced in a demanding, fully-paved urban location

Lessons Learned • Detailed surveys of underground services and features and careful analysis is essential in retrofit situations

Images courtesy of Robert Bray Associates Image courtesy George Warren

Tree pit details Under construction SuDS In London: A Design Guide Chapter 5 - 148

5.19 Firs Farm Wetlands

Location Winchmore Hill de-culverted and diverted to a series of open London Borough of Enfield watercourses, wetlands and ponds to improve Extent 0.48ha water quality. Cost £900,000 (total scheme) Date 2016 Objectives Credits Enfield Council • Improve water quality alongside flood Environment Agency alleviation, habitat enhancement, Thames Water community space provision and creating TfL cycleway links Sustrans • Provide intensive monitoring programme GLA to be carried out by Thames21/Enfield Thames 21 Council over next two to three years to Friends of Firs Farm determine the impact of wetlands on reducing diffuse urban pollution. This data SuDS Components will be used to optimise future management • Ponds and wetlands of the two sites

Summary Actions and Results Open space transformation with wetland • Northern and southern branches of Moore habitats to improve water quality outflow Brook are diverted from their culverted courses to three combined wetland cells Project Description • Cells channel the water for treatment The main driver for the wetland creation was through flow paths Enfield council’s desire to improve water • A watercourse downstream connects to a quality in Pymmes Park Lake, where Moore fourth cell which is constructed as a pond, Brook outfalls prior to entering Pymmes before continuing further downstream in an Brook. Moore Brook is a lost watercourse open channel to the original culvert within a surface water sewer. Firs Farm was • Surface water is treated at the surface Images courtesy of Graham Campbell identified as a space suitable for the creation before re-entering the culvert downstream, of a wetland scheme. The watercourse was improving the quality of the water which Outlet into wetland area Chapter 5 - 149

outfalls at Pymmes Park Lake Lessons Learned • A further diversion to four more wetland • Importance of working alongside other land cells at Pymmes Park upstream of the lake uses, in this case sports pitches provides further treatment • Pre-treatment measures upstream of the wetland would be beneficial Benefits • Water quality improvements before outfall to river further down the catchment • A surface system allows for issues to be identified and easily dealt with due to the size and location of the SuDS elements • Transformation of a previously underused open space to an area with an enhanced natural habitat and for the local community to focus activities. A local ‘Friends’ group and a waterway charity Thames21 have generated community-based interest in the site. This included help with consultation, volunteers for planting and outdoor learning, and assisting in future funding bids • A range of amenity areas, including seating, an outdoor classroom and dipping ponds • Opportunity for many disciplines to work together across the council and other organisations • Provided opportunities to combine other objectives, such as the provision of cycleway transport infrastructure • Biodiversity enhancements Plan Wetland basins and planting SuDS In London: A Design Guide Chapter 5 - 150

5.20 Salmons Brook Glenbrook Stream

Location Salmons Brook affects the Salmons Brook’s ability alleviate London Borough of Enfield floods to the surrounding streetscape. Extent 0.77ha Cost £15.3m (Total scheme) EU water quality standards were not being Date 2014 achieved so the Environment Agency and Credits Thames 21 Thames21 devised a scheme to improve the Environment Agency watercourse. Enfield Council Robert Bray Associates Objectives Maydencroft • Create a wetland system to treat and remediate polluted water before it enters SuDS Components Salmons Brook • Bioretention basins • Promote change through education about • Kerb Inlets the urban water cycle • Swale • Enable the community to access and • Weirs benefit from their local waterway Image courtesy of Chaoming Li • Assess the impact of the scheme Summary on Salmons Brook and surrounding Swale incorporating existing mature trees Transformation of existing greenspace into infrastructure in the catchment wetlands Actions and Results Project Description • Bioretention basins were integrated and Salmons Brook is a tributary of the River Lea existing features improved. This has that flows through wasteland, industrial parks made the existing wooded landscape and Deepham Sewage Treatment Works. more efficient at attenuating and slowing Salmons Brook receives polluted wastewater the conveyance of water. The wetland from misconnected plumbing and road runoff basins also encourage the growth of plant from residential and industrial sources within and bacterial communities, which helps Image courtesy of Thames 21 the catchment. This jeopardises the quality of remediate polluted water the watercourse and those downstream and Roadside swale at The Spinney Chapter 5 - 151

• Weirs allow control of water flow through • Public awareness of the reality of waste the SuDS scheme and any subsequent and pollution in their environment that discharge into Salmons Brook. might otherwise remain unnoticed • The base level of the area has also been • A sense of ownership has been fostered lifted to further control flow; this also through scrub clearance and wetland increases the effectiveness of the sub- planting days catchment via the wetland bioretention basin system. Lessons Learned • By raising the base level opportunities for • The value of local community involvement stepping stone and weir crossing points • Managing woodland structure is crucial in were created. This has improved access. ensuring that light levels are sufficient for • Swales slow the flow of water through the the establishment of vegetation system and ensure that, with the weirs and wetland bioretention basin, the higher concentrated polluted water is discharged into the wetland, rather than Salmons Brook • Kerb inlets allow rainwater to be conveyed away from the combined sewer overflow and into the swales and through the network of weirs and wetland basins

Benefits • Salmons Brook water quality improved • Flood risk reduced and road runoff management improved • An area of greater recreational value created • Reduction in house insurance costs for Images courtesy of Robert Bray Associates surrounding properties Weir detail at Grovelands Park Treatment wetland at Grovelands Park SuDS In London: A Design Guide Chapter 5 - 152

5.21 Richmond Park Golf Course

Location Richmond Diffuse urban pollution from A3 runoff at London Borough of Richmond Roehampton Hill and surrounding area was Extent 1ha also addressed. The surface water drains from Cost £18,000 (total scheme) the A3 and now discharges into an open ditch Date 2016 network that flows across Richmond Park Golf Credits South East Rivers Trust (SERT) Course before entering Beverley Brook. The Environment Agency The Royal Parks Runoff detrimentally affects the aquatic Richmond Park Golf Course environment through the input of significant Thames Water quantities of sediment bound contaminants. The Friends of Richmond Park These include; Polycyclic Aromatic RM Wetlands and Environment Hydrocarbons (PAHs), hydrocarbons and Auqamaintain heavy metals. Excavator used for swale and wetland build SuDS Components • Wetlands Objectives • Swales • To improve water quality, the project had • Sediment trap two elements: • Adapt the existing ditch network to Summary create a sediment trap pond Create wetland habitat and ditch network. • Modify the existing pond into a Improve water quality to meet regulations. wetland to trap finer sediment and provide treatment of other waterborne Project Description contaminants Significant river restoration work has recently been completed in the park, enhancing 600 metres of channels to promote flow and habitat diversity and to address the water’s Images courtesy of SERT failing status under the Water Framework Directive (2000/60/EC). After Chapter 5 - 153

Actions and Results • An adjustable water level control structure • The ditch network was widened and is located at the outflow of each wetland. deepened over approximately a 22 metre Sediment accumulation reduces the depth length at the upstream end of the golf of the water, so this feature will allow the course to create a sediment trap. This water depth to be incrementally increased, was to reduce flow velocities and promote reducing maintenance costs and enhancing a depositional environment. Calculations the habitat resilience of wetland species suggest that the trap will capture sediment down to 0.1mm Benefits • The ditch enlargement takes a natural • Biodiversity enhancements sinuous form. The existing ditch was used • Water quality improvements in the Beverley as the centre line, so that both inlet and Brook outlet are located centrally within the width • Reduced ditch maintenance requirements of the pond • Landscape improvements Plan showing site condition prior to works • A shallow marginal ledge was incorporated • The sediment trap and spoil arising from along the length of the trap. This was the works have formed features on the golf planted with a mix of wetland plants course to increase the roughness coefficient, promote deposition and enhance treatment of contaminants • The existing pond was altered by converting the island into a spit. This increased the time water spent in the wetland and therefore the treatment capacity. A second, smaller wetland was created and excavated material used in the existing pond to correct its water depth • Over 20 species were planted and the wetland fenced and strung with bird twine to encourage plant growth Proposed plan increasing water capacity SuDS In London: A Design Guide Chapter 5 - 154

5.22 A23 Coulsdon Bypass, Farthing Way

Location Coulsdon Objectives London Borough of Croydon • The drainage design redirects runoff flowing Extent 34ha from the new A23 away from the inner SPZ Cost £33 million (Total scheme) • Attenuation was needed to ensure the Date 2006 area receiving the runoff can cope with the Credits Transport for London volume of water it now receives Atkins Actions and Results SuDS Components • The new A23 is drained, via a piped • Kerb drainage system with kerbs and gullies, into spillage • Soakaways containment devices and a full retention • Filter strip fuel/oil separator, before discharging into • Filter drains soakaways • To the west of the new A23, the existing Summary ground rises steeply; being chalk Highway runoff attenuation downland, there is likely to be significant run off at times of heavy rain. Here a Project Description separate system, not linked to the highway A groundwater extraction borehole at Smitham drainage, is provided which collects this Carriage way filter strip Pumping Station is located in Coulsdon Town run off and discharges it into a series of Centre. The new section of A23 between soakaways Marlpit Lane and Smitham Station passes • Non-piped drainage components within the across the inner Source Protection Zone (SPZ) site principally relate to linear soakaways at for the extraction borehole and has been the bottom of the embankment adjacent designed to direct runoff appropriately. to footways where water is caught at a low point

Filter strip gravel Chapter 5 - 155

Benefits • The design provides for the flow of drains and watercourses affected by the works to be maintained • The design of the drainage components allows them to be maintained in a safe and efficient manner • The design permitted runoff from the works to drain on to adjoining land

Lessons Learned • Localised design changes were carried out to the pipes network due to the unexpected presence of services • The specified kerb drains were reduced in size from standard beany blocks during construction due to the high retaining wall footing and the 600mm wide narrow verge • Deep-bored soakaways were used extensively throughout the project. During the construction of some soakaways, the piling contractor met some obstructions. This was overcome by relocating the soakaways, but only small changes in the positions were needed

Surrounding carriageway context Plan SuDS In London: A Design Guide Chapter 5 - 156

5.23 London Sustainable Industries Park

Location Dagenham The site is south of the A13 and close to London Borough of Barking and Dagenham Dock Railway Station and the Dagenham Barking Reach Power Station. The Gores Extent 142ha Brook also receives outflow from the site Cost £30m (total scheme) that then discharges into the River Thames. Date 2009-10 Consideration of the hydrology of the site was Credits Civic Engineers crucial to achieving a successful scheme. T. R. Collier & Associates Sergison Bates Objectives Vogt Landscape • Install a water management system for the Price & Myers LSIP URS • Transform the existing infrastructure on- Aerial visualisation GHP site to create a self-sustaining exemplar of green infrastructure design and planning SuDS Components • Swales Actions and Results • Managed wetland and woodland • Swales and bioretention basins allow water • Bioretention to be conveyed from roofs, roads and other • Water recycling features into a system of components with a high attenuation storage capacity. This Summary limits the outflow of water into Gores Brook Cross-section An integrated water management and green at a rate of 12 L/sec/ha during prolonged infrastructure for an industrial park. and/or high peak flow rainfall events • Water quality is improved by allowing Project Description suspended solids to settle out and other The London Sustainable Industries Park (LSIP) pollutants, such as hydrocarbons, to be is part of the Thames Gateway regeneration treated or their discharge limited at Dagenham Dock in East London. It is an • Enhanced ecological value international exemplar, created with the goal of • Attenuation tanks allow rainfall to be the Thames Gateway becoming the UK’s first recycled for use by services that use ‘grey’ Eco Region. water Chapter 5 - 157

Benefits • Negates the need for costly remediation systems, such as petrol interceptors • The volume of low water quality runoff from carriageways and other built infrastructure on the industrial park has been reduced • BREEAM ‘Excellent’ rating achieved (2010) • The cost of utilities and maintenance has been reduced

Lessons Learned • The installation of an adaptable and resilient water drainage network can provide infrastructure for a range of future uses depending on plot uptake and industry requirements

Images courtesy of Civic Engineers

Plan SuDS In London: A Design Guide Chapter 5 - 158

5.24 Green Roofs on Depots; Trial Project

Location Ruislip Depot • Ensure retrofitting on operational railway Middlesex followed the rigorous assurance and safety Extent 125m² procedures of London Underground, Cost £30,000 (trial project) without any interruption of service Date 2012 Credits London Underground Limited Actions and Results GLA • Biodiverse extensive green roofs types, University of East London each 18.5 metres x 3.3 metres, have been GRC installed on a section of flat roof • One section (south) has a drainage SuDS Components board with 65mm of extensive green roof • Greenroofs substrate. The other section (north) uses recycled wool fibre instead of drainage Summary board After installation Retrofit green roof and monitoring of source • Both roofs are vegetated with sedum control cuttings and seeded/planted with annual and perennial wildflowers Project Description • The two trials are separated by an A small-scale trial to allow evaluation of the impermeable barrier to facilitate the effectiveness of green roof, retrofitted for LUL measurement of run off. Total saturated depot environments. From the results it will be loading is less than 100kg/m² ascertained whether LUL could benefit from a • With the assistance of the University of broader application. East London, monitoring devices have been installed in two downpipes of a green Objectives roof and two downpipes of a conventional • Experimenting in environmentally-friendly control roof to measure water attenuation engineering solutions to address runoff • GLA support through Drain London. A from depot roof small fund enables monitoring performance • Achieve low maintenance • Address Mayoral policy for SuDS by Early green roof growth within 6 months installing a green roof source control Chapter 5 - 159

Benefits • LUL will examine the process of installation, maintenance and performance and the cost-benefit analysis in terms of waterproofing performance and drainage control for a larger scale application • In addition, LUL will assess: longevity of the waterproofing layer; improved working ambiance and environment; structure insulation; air quality improvements; biodiversity enhancements • The trial will allow better understanding of the mechanism and potential areas for improvement

Lessons Learned • The use of wool as a recycled drainage material was an important outcome • Monitoring of water attenuation is complete and will inform future green roof schemes • Organic material used as a drainage board has performed consistently better than the conventional plastic one • Maintenance is minimised due to planting selection of wildflowers

Images courtesy of LU Infrastructure Protection

Programme of monitoring SuDS In London: A Design Guide Chapter 5 - 160

5.25 Great Kneighton/Clay Farm

Location Cambridge Project Description Extent 109ha Great Kneighton, previously Clay Farm, is Cost £45 million former green belt land in the 4km south Date Final phase: 2020 of Cambridge. The site is typical for Credits Cambridge City Council Cambridgeshire – flat, low-laying terrain, Countryside Properties crossed with brooks and land drainage Bovis channels. The mixed use development site of Cala Homes Great Kneighton suffered from poorly draining Crest Nicholson clay soils and a high water table, one metre Skanska below ground. The site is within the catchment Aecom of the historic Hobson’s Conduit, which PEP dictated stringent control measures for runoff BBUK Studio from the development. James Blake Associates Environment Agency Cambridge City Council, along with project Hobson’s Conduit Trust partners, wished to install an integrated water management system within a designated SuDS Components strategic open space that forms part of the • Soakaways Cambridge Green Corridor. • Detention basins • Bioretention basins Objectives • Swales • Control outflow into Hobson’s Brook at 2L/ • Rills sec/ha • Permeable paving • Install a SuDS code of conduct across the • Rainwater harvesting development site • Green/brown roofs • Withstand one in 100 year flood event with 30 per cent extra to allow for climate Summary change Image courtesy of Tim Crocker Holistic integration of water management and • Provide amenity and ecological value to development development Completed residential unit Chapter 5 - 161

Actions and Results • Sub-catchments syphons underneath the • Plot-wide rainwater harvesting system brook discharge into a series of ponds and intercepts rain water and reduces the detention ponds amount being conveyed to the subsequent • Pre-cast concrete rills conveys water into stages of the SuDS scheme bioretention basins in the local square • Detention basins increase the attenuation storage capacity of the scheme and slows Benefits Location Hornsey the conveyance of water, particularly during • Impact of development on surrounding LB Haringey prolonged and/or high peak rainfall drainage infrastructure is minimised through Extent 1000m² • Swales increase the attenuation storage the management of water onsite Location Hornsey, capacity of the scheme and provides • Outflow of water quality and volume London Borough of Haringey vegetated landscape of hydrological, controlled Extent 1000m aesthetic and biodiversity value • Can withstand a one in 100 year flood Cost £80,000 • Hydrodynamic vortex separators inhibit the event Date 2016 discharge of sediment and hydrocarbons • Predominantly above-ground nature into the Hobson’s Conduit outflow. This is of the SuDS features contribute to the of particular note due to the downstream recreational and aesthetic value of the function of Hobson’s Conduit in Cambridge development • Bioretention basins allow water to be • 20,000m² of wetland habitat created attenuated on the east side of Hobson’s • Installation of a landscape of multiple conduit, preventing low quality water from benefits discharging into the watercourse. Water is conveyed from the development to the Lessons Learned west, underneath Hobson’s Conduit into • Engaging developers and project teams the bioretention basins, creating a series early in the development process allows of ponds and wetlands of hydrological, the benefits of SuDS to be shared recreational and ecological value • It is necessary to treat each site within the • Permeable paving increases the development individually to capture the permeability on the site, where below- variations in soil type and topography Images courtesy of Simon Bunn ground conditions allow Permeable paving and tree planting SuDS In London: A Design Guide Chapter 5 - 162

5.26 Alnarpsgården Swedish University of Agricultural Sciences (SLU)

Location Alnarp, Sweden Objectives Extent 0.37ha • Slow water runoff from roofs and hard Cost £170,000 (construction only) surfaces of Alnarpsgården Date 1997 • Provide a first step of water cleaning Credits Anders Folkesson, • Aesthetically enrich the yard Landscape Architect LAR/MSA • Demonstrate an open storm water system Vasajorden AB to the landscape architect students of SLU

SuDS Components Actions and Results • Ponds and wetlands • Water from downpipes is collected in • Disconnected downpipes channels running along the facades, then • Permeable paving led to a retention basin (a former manure Image courtesy of Anders Folkesson • Channels & rills container). At the bottom of the concrete • Retention basin basin are ‘seams’ in which aquatic plants Threshold detail Summary grow in a strict pattern. From the retention Campus courtyard redevelopment to focus on basin, water runs in a ditch towards the sustainable drainage while creating a social Öresund coast hub • Grit-jointed granite setts form permeable paving, over-seeded with wildflowers Project Description Alnarpsgården is a rural campus hosting the Benefits Institution of Landscape Architecture, Planning • The courtyard design repurposed existing and Management at the Swedish University of features, such as the old manure container Agricultural Sciences (SLU). Part of a historic and dung grooves, as SuDS features estate, it consists of buildings converted • The redevelopment of the courtyard has from agricultural use and new builds, set created a social hub, well used by students within a forested landscape. The focus of the and visitors campus is the inner courtyard, which has been • The success of the SuDS components redeveloped with SuDS principles in mind. of the courtyard make them a valuable educational tool Wildflower seeded joints Chapter 5 - 163

Lessons Learned • Previously, the yard’s ground was slightly concave, the middle of the yard being slightly lower than the ground along the facades. To channel all the storm water from the yard to the gutters along the facades, the middle of the yard was raised. Adjusting the topography has affected the quality of the space

SuDS pond acting as a central recreational feature SuDS In London: A Design Guide Chapter 5 - 164

5.27 Benthemplein (Water Square)

Location Rotterdam, Netherlands Due to the proximity to areas of flooding and Extent 0.95ha the opportunity for restructuring of space, the Cost £3.175m (Total scheme) City of Rotterdam and stakeholders, including Date 2013 church and student communities, looked to Credits City of Rotterdam reimagine the function of the square, as part of Schieland and Krimpenerwaard the Rotterdam Climate Initiative. Urbanstein Wallaard














ACO Objectives Catchment areas Topcourts • Reduce flood risk • Provide recreational opportunities SuDS Components • Detention basins Actions and Results • Rills • Detention basins increase the attenuation storage capacity of the site to 1,700m³. Summary Uniquely, the three detention basins provide Multi-functional public realm regeneration a recreation space that is transformed as water is attenuated in the basins Project Description • Rills convey water from the surrounding Benthemplein is in central Rotterdam, north- ground surfaces and buildings into the east of Rotterdam Centraal station. It is detention basins. Each basin has its own bounded by major city roads and enclosed by sub-catchment taking runoff from certain medium rise buildings. surfaces and buildings and incorporates waterfalls, fountains and an outside The low permeability paving of the site meant baptistery for use by the church it was not fulfilling its potential of relieving localised flooding in adjacent areas. This put pressure on the combined sewer overflow of the Nieuwe Maas.

Detention basin Chapter 5 - 165

Benefits • Water management has the added benefit of creating a novel multiple-use public realm space • Approximately 4,000m² of existing parking and street access has been kept to allow space for vehicles • Interventions such as the baptistery, sports goals and shaded seating has allowed for a range of stakeholders’ needs to be addressed

Lessons Learned • Attention to detail during planning and design phases and supervision during construction is crucial in achieving a scheme with complex sub-catchments • By fulfilling city authority climate objectives, it is possible to receive extra funding for similar schemes. Rotterdam raised an additional £700,000

Images courtesy of Urbanstein

Overview of completed scheme SuDS In London: A Design Guide Chapter 5 - 166

5.28 Rue Garibaldi

Location Lyon, France hydrocarbons and total suspended solids). Extent 15ha Runoff into the combined sewer overflow was Cost £19.3m (total scheme 1st high, particularly during heavy or prolonged phase) peak rainfall, considering the sub-catchment Date 1st phase 2014 area of 65,000m². Credits Grand Lyon Atelier des Paysages These conditions, coupled with a carriageway reconfiguration proposal, presented the SuDS Components opportunity to reconsider hydrological • Retention basins management of the 2.6km stretch of highway. • Swales • Soakaways Objectives • Depaving • Minimise runoff into the combined sewer overflow by installing a SuDS scheme Summary • Improve connection between districts Transformation of an urban motorway to a bordering Rue Garibaldi by design and planted boulevard and high quality civic space planning consideration, within the wider green space context of the area Project Description • Reduce maintenance and utility costs by Rue Garibaldi, east of the River Rhône, installing a water recycling system is a north to south six-lane carriageway, • Reconfigure carriageway function by constructed in the late 1960s. It is fronted instating separate carriageways for public with high storey buildings and features that transport, pedestrians, cyclists and other are synonymous with an urban motorway. The vehicles environment for pedestrians and cyclists is • Improve management of water quality and hostile. mitigate urban heat island effect by planting trees and installing a SuDS scheme The configuration and high capacity of the streetscape meant the effects of urban heat island were exacerbated. Air (principally NOx Rill and de-paving and PM) and water quality was low (principally Chapter 5 - 167

Actions and results a separation between carriageways and • Retention basins were created from the enhancing the sense of place. Sensors redesign of an existing underpass. An have been installed to quantify the cooling automated pumping system was installed effect provided by the vegetation to allow water to be recycled for street cleaning vehicles and irrigation for public Benefits realm planting. This has reduced local • Reconfiguration of carriageway to align with authority utilities and maintenance costs Grand Lyon’s sustainability objectives and increased the attenuation storage • Provision of extra parking for taxis, capacity of the streetscape. Water deliveries and public road users treatment capabilities also feature, due to • Creation of new green links through Lyon the oxidative capacity and bacterial activity • Repurposed existing infrastructure of the retention basin • Peak outflow into combined sewer system • Swales with 4,500m³ of vegetation increase is 5Ls-1ha-1 the attenuation storage capacity. These • Monitoring during the first phase of were integrated into the reconfiguration construction has helped inform the of the carriageways to create vegetated development of phases two and three separation between carriageways with • Onsite availability of recycled water for different functions. This has significantly street cleaning enhanced biodiversity in streetscape • Automated irrigation reduces maintenance • Soakaways have increased the infiltration commitment and cost rate by aiding conveyance of water into • Water and air treatment capability the ground, contributing to the 1300m³ attenuation capacity of the scheme Lessons Learned • Trees have mitigated urban heat island • Ensure clear agreement between local effects by increasing the interception authority services for management and of solar radiation and increasing maintenance responsibilities on cyclical and evapotranspiration. Tree planting has periodic regimes also contributed to the effectiveness of the SuDS scheme. They have helped reconfigure the streetscape by creating Integrated cycleway and SuDS SuDS In London: A Design Guide Chapter 5 - 168

5.29 Bo01 Västra Hamnen

Location Malmö, Sweden is in a key strategic location to accommodate Extent 85ha city growth. The site was prone to flooding and Cost £3.3m (landscape construction its soil contaminated. only) The international housing exposition, Bo01, Date 2001 framed the first phase of development and Credits City of Malmö allowed the City of Malmö to instigate an Government of Sweden exemplar in sustainable urban regeneration. Sydkraft AB (E.ON Svergie) The project featured a new housing district Lokala of 500 apartments, with the public realm Investeringsprogram a significant contributor to achieving wide- European Union reaching sustainability goals. Lund University Objectives Permeable shared surface SuDS Components • Manage flood risks with an open storm • Retention ponds water system • Swales • Create exemplar in sustainable urban design • Permeable surfaces • Use a scoring system to achieve balance • Bioretention basin between development demands • Rills • Achieve off-grid sustainable drainage • Downpipe disconnection Actions and Results Summary • Swales and bioretention basins created high Transformation of an industrial site to a attenuation storage capacity and made an neighbourhood with integrated off-grid off-grid drainage system possible. sustainable water management. • The network of swales and basins complement the well-connected streets and Project Description spaces that characterise the foot and cycle The city of Malmö has developed SuDS networks in the area. schemes since the late 1990s. The Västra • Meadows, woodlands, seashore and marine Hamnen area is on a former industrial site and biotopes served hydrological functions Rill Chapter 5 - 169

in relation to the SuDS system and added a variation in site conditions for an abundance of species

Benefits • Off-grid SuDS system • A cross-disciplinary approach during development allowed for the revision of planning tools • Popular contribution to the character and function of the public space • Scheme can be adapted to reflect changes in public use patterns • The scoring system used to quantify green space factors works in a UK context

Lessons Learned • Development-wide consideration for topography crucial to success • Incorporation of water features, such as fountains, can be achieved through the recycling of water collected by SuDS • Using a points system enhances the legibility of ecological and aesthetic considerations across stakeholders • Proactive approach to management is required to maintain maximum efficiency of the SuDS system

Retention pond SuDS In London: A Design Guide Chapter 5 - 170

5.30 Augustenborg

Location Malmö, Sweden infrastructural changes took place, including Extent 320ha the incorporation of a SuDS scheme that Cost £16m (construction only) allowed Augustenborg to be disconnected Date 2001 from the existing combined sewer overflow. Credits VA-Verkaet, Malmö Municipality Anders Folkesson & Christer Objectives Göransson, Mellanrum AB • Reduce flooding • Support the community through integrated SuDS Components green infrastructure planning • Swales • Ponds and wetlands Actions and Results • Green roofs • 6km of swales and rills allow the flow of • Detention basins water to be controlled throughout the • Tree planting system and aid the connectivity of the Rill • Rills public realm • Downpipe disconnection • Ten bioretention basins create a high attenuation storage capacity of the system Summary This has made an off-grid drainage system Regeneration of a neighbourhood with possible by providing sites for swales, rills integrated off-grid sustainable water and bioretention for roof runoff management • Residential courtyard areas can be flooded, this gives the scheme added resilience by Project Description providing an additional basin for short-term Augustenborg has experienced periods of attenuation socio-economic decline in recent decades and frequently suffered from floods. Between 1998 and 2002, the neighbourhood underwent significant regeneration, driven by the difficult social and economic situation and a desire to improve flood risk management, waste Multiple benefits of SuDS management and biodiversity. Significant Chapter 5 - 171

Benefits • Reconfiguration of public spaces has provided recreation and business opportunities for residents • Biodiversity in the area has increased by 50 per cent • Carbon emissions and waste generation has decreased by 20 per cent • Creation of a storm water neutral system

Lessons Learned • The participatory character of the project sparked interest in renewable energy and sustainable transport among residents • The involvement of residents in the design phase meant there was little opposition to the project and resulted in a sense of community ownership and empowerment

Image courtesy of Christer Göransson

Pond wetland