Sustainable drainage systems (SuDS) - what's next?
Sustainable drainage systems (SuDS) are both a practical part of urban planning and an aspiration for a greener approach to construction
and living. They’re designed to manage the flood and pollution risks resulting from urban runoff and to contribute wherever possible to environmental enhancement and place-making.
To achieve this effectively, engineers, landscape architects, urban designers, local authorities, water companies and developers need to work together to get the best out of every site, in terms of water quantity, water quality, amenities and biodiversity benefits. Early engagement is crucial to a cost-effective solution, underlining the importance of embedding SuDS into site planning from the start. This early engagement can also help settle the issue of ongoing maintenance responsibilities, making sure SuDS schemes are adopted by whatever body, or combination of bodies, is best placed to manage them.
“To manage surface water, all the relevant authorities and contractors have to work in partnership - you cannot work in isolation.” Ian Titherington, Lead Officer, City of Cardiff Council
Today, SuDS is moving into a new, exciting phase of development. Recent shifts in government approach, environmental and cost factors, as well as societal expectations, have prepared the ground for change.
Already, use cases for fresh SuDS approaches are up and running, giving insight into what the future will look like. But this growth in SuDS is currently outpacing the pool of experts available to support the projects, creating a skills gap and this makes it all the more important that, as an industry, we share expertise freely and widely.
“The construction and water industries are beginning to realise that SuDS can not only help anage local flood risk and deliver greater resilience, but can also deliver multiple benefits that improve the quality of our places and spaces. They see that SuDS also deliver on a number of other policy drivers like reducing carbon, and improving the health of our rivers and local communities.” Paul Shaffer, Director of Innovation and Delivery, CIWEM
As a result, in this whitepaper we will:
• explore how SuDS have reached this tipping point
• examine the specific shifts that are prompting change
• evaluate the future of SuDS, based on use cases
Download the SuDS whitepaper as a PDF
“We need to keep the momentum of SuDS going. We want to be actively involved in this conversation and align ourselves with the future of SuDS - blue green infrastructure that will be delivered and managed in a holistic way.” Martin Lambley, Product Manager, Wavin
Sustainable drainage systems in brief
What are SuDS?
In essence, an effective SuDS (Sustainable drainage system) solution enables a developed site to handle rainfall and surface water runoff as it would have done as a greenfield site. SuDS are designed to mimic natural drainage by managing surface water runoff as close to the source and surface as possible, creating opportunities for runoff to naturally soak into the ground (infiltration), evaporate from surface water and provide transpiration from vegetation (evapotranspiration).
“Well planned SuDs with effective stakeholder collaboration and the engagement of communities can overcome challenges and deliver other opportunities.” Paul Shaffer, Director of Innovation and Delivery, CIWEM
A complex operating environment
Water management solutions, like SuDS, can operate in a complex environment where competing factors can pull decision-making in different directions. Pioneering research by the EU identified key challenges that can complicate responses:
• Climate change
Bringing increased intensity of rainfall and localised flooding, plus an increase in wider flooding events
• Intensifying urbanisation
High-density living leads to a loss of green space and natural water management capabilities
• Governance and policies
New institutional frameworks and legislation, plus changes in political direction, can make longer-term planning difficult
• Deterioration of infrastructure systems
A lack of investment and ageing systems can increase pipe breakages, leading to increased water losses and wastewater leakage
• Changes in public priorities
In times of economic hardship, the focus can shift away from investing in environmental priorities. Alternatively, a sustainability drive can influence spending towards environmental projects
• Increasing complexity in the operating environment
As dependencies on IT systems and interlinkages between the water, energy and transport sectors grow, water management gets more difficult
Today, the stand out factors influencing SuDS development are urbanisation and climate change.
As the urban population keeps growing, so too does the importance of urban water management. It’s predicted that the urban population will be about 60% of the total global population by 2030. An environment with little natural green space, combined with the rise of intense rainfall incidents, makes sustainable drainage systems critical in controlling surface water quantity and water quality to mitigate flooding and the risk of pollution.
“When you get it right, it’s brilliant. It works better than people realise. But design has to be right for the location and the installation has to be absolutely spot on.” Ian Titherington, Lead Officer, City of Cardiff Council
What makes an outstanding Sustainable drainage system?
1. Managing water quantity
This is all about the volume and flow rate of surface water runoff, and using attenuation to reduce the rate of runoff to that of an equivalent greenfield site. Restricting the flow of surface water and slowing its movement to the next stage of the system tackles the impact of everyday rainfall and high-intensity storms.
2. Managing water quality
Surface water comes into contact with a variety of pollutants, particularly from roads and the vehicles that run on them. SuDS work to remove pollution from entering the natural environment and to improve the quality of water entering combined sewers.
3. Creating amenity
An effective SuDS project will improve the quality, character or overall enjoyment of an area. This could include, for example, providing green places within an urban environment, improving the air quality, or enhancing a streetscape.
4. Creating a habitat for biodiversity
Increasing urbanisation has disrupted natural wildlife habitats and ecosystems. Sustainable drainage can seek to replicate what would have existed in a greenfield site, benefiting water quality and urban wildlife.
A wide range of sustainable options
As Sustainable drainage systems gain momentum, the ways to achieve these four pillars are expanding, with SuDS development options including:
•soakaways simple/advanced rainwater harvesting
• infiltration trenches
• filter strips
• constructed wetland
• retention (wet) ponds
• detention basins
• underground attenuation tanks and storage.
• green roofs
• rain gardens
• tree pits
• permeable paving
• filter drain/perforated pipes
• infiltration basins
Milestones leading to SuDS today
Starting from a two-speed uptake in the UK
Commercial developments have historically embraced SuDS to a far greater extent than residential developments have. Often not obvious to the casual observer, commercial sites frequently incorporate SuDS into their design via implementations such as porous parking areas, green strips between parking bays, living roofs and gravelled areas. There’s an easy fit between commercial landscaping and SuDS, along with intensive planning procedures and resources for SuDS ownership, so take-up has been high. In the residential sector, SuDS have traditionally taken the form of feeding water into an underground plastic tank or poorly designed pond at the end of the site, a so-called ‘end of pipe’ SuDS solution that doesn’t meet all four SuDS pillars. However, this is slowly changing, prompted by the events we take you through here.
The pain point of the 2007 floods
The summer of 2007 was the wettest on record. There was 414mm of rainfall across England and Wales from May to July - more than in any period since records began in 1766. The government’s best estimate of the overall cost of the 2007 floods is £3.2 billion. Excessive runoff in residential areas overwhelmed the drainage system and the rivers the pipes discharged into, a situation that wider use of SuDS could have mitigated. The scale of the flooding raised the issue of water management in the public consciousness and led to the commissioning of the Pitt Review.
The 2008 Pitt Review
The review focused on flood risk management, the resilience and vulnerability of critical infrastructure, the emergency response, emergency planning and the recovery phase. With reference to SuDS, it recommended: • adopting a long-term approach to flood risk management, with priority given to adaptation and mitigation • preventing householders from laying impermeable surfaces on front gardens • removing the automatic right to connect surface water drainage from new developments to the sewerage system.
The 2010 Flood and Water Management Act
This Act was a direct result of the Pitt Review, passed with the intention of providing a more comprehensive management of flood risk for people, homes and businesses, protecting water supplies to the consumer and helping to safeguard community groups from unaffordable rises in surface water drainage charges.Schedule 3 of the Act proposed changes with far-reaching consequences for SuDS:
• Mandatory rather than preferred
SuDS would become a legal requirement for any development over 100sq/m and would have to be implemented at the design stage of development.
• Greater powers for local authorities
It would remove the automatic right of developers to connect drainage systems to public sewers, designating the local authority the SuDS Approving Body (SAB), able to deny connections.
• Designated ongoing responsibilities for SuDS
It would require the SAB to adopt and maintain approved drainage systems that served more than one property and were not part of the public highway.
There are a significant number of policy and regulatory documents relevant to the delivery of sustainable drainage. For a full list and links please see appendix in downloadable whitepaper here.Divergence over Schedule 3
Implementation of Schedule 3 varied across England and the devolved governments of Scotland and Wales. Their very different approaches highlight how the take up of SuDS is influenced by governance and legislation.
Wales’s approach to Schedule 3
Schedule 3 came into effect in Wales in January 2019, and requires new developments over 100sq/m to include SuDS that comply with mandatory Welsh national standards. SABs in Wales oversee a process that puts the onus on developers to demonstrate their compliance in their planning application. The SAB must approve the surface water drainage design, and it then monitors the installation phase. Upon completion and sign off, the surface water drainage system is adopted by the relevant local authority.
This approach gives the body that will ultimately be responsible for the SuDS control over their design and implementation.
“Ultimately, the local authority are the biggest stakeholders so why shouldn’t they have management of it? Local flood risk management is the responsibility of the local authority, so this gives them the power to make sure it’s done properly and then gives them control over it in the end.” Martin Lambley, Product Manager, Wavin
Scotland’s approach to Schedule 3
Scotland hasn’t adopted Schedule 3, having long built a SuDS policy into local planning laws. It takes guidance from the Water Environment and Water Services (Scotland) Act 2003 which makes specific provision for promoting sustainable water use, ensuring the progressive reduction of pollution of groundwater, and mitigating the effects of floods. The Scottish Environment Protection Agency (SEPA) holds responsibility for the protection of the water environment and stipulates that SuDS are built into new developments. SEPA also extracts guarantees of adoption of SuDS that lie beyond the boundaries of a private property by Scottish Water, the local authority or a public body. If a developer constructs SuDS to Scottish Water’s standards, Scottish Water has a duty to adopt and become responsible for the SuDS, should the developer request it.
This approach achieves the aims of Schedule 3 via an alternative legislative route.
“Wales and Scotland have got this right; they’re leading the way in terms of SuDS and have taken different approaches that England should consider.” .Martin Lambley, Product Manager, Wavin
England's approach to schedule 3
England hasn’t adopted Schedule 3, choosing instead to make amendments to the National Planning Policy Framework. Section 14 sets out policy to make sure flood risk is taken into account at all stages of the planning process, and that development avoids areas at the highest risk of flooding. It states that developments should only be allowed in areas of flood risk if they incorporate SuDS, unless there is clear evidence that SuDS would be inappropriate.
The Framework stipulates that SuDS should be incorporated into developments of 10 dwellings or larger (or equivalent non-residential developments), unless demonstrated to be inappropriate by the developer.
The Local Planning Authority and the Lead Local Flood Authority (LLFA) must approve drainage schemes and make sure they are appropriately maintained, although the onus is on the developer to explore adoption and ownership possibilities as there is no single adoption route.
This approach made SuDS a mandatory part of planning, but allowed developers to object to SuDS if their inclusion compromised the ability to fully develop the site.
“The biggest difference is the lack of statutory or mandatory standards for SuDS. The non-statutory SuDS standards that are available primarily focus on managing the volume and flows of runoff and do not support the delivery of the four pillars of SuDS or multiple benefits.” Paul Shaffer, Director of Innovation and Delivery, CIWEM
In 2018, the government published a review of the effectiveness of planning policy for SuDS. It revealed that planning policy was driving the
implementation of SuDS in new developments, but that only 30% of local authorities check whether implementation happens once planning is granted, and that 70% of applications had no provision for maintenance. The report also found that the majority of objections developers raised to avoid implementing SuDS revolved around land-take or economic reasons. LLFAs and Local Planning Authorities commented in the report that developers weren’t including SuDS in their planning proposals because of concerns about adoption and the cost of maintenance.
This divergence over the implementation of Schedule 3 meant that Wales and Scotland pulled ahead of England in terms of incorporating SuDS into the built landscape. This continued as the status quo until pressures for change in England intensified from 2020 onwards.
Catalysts for change in England
Catalyst #1 – DEFRA’s 2021 reports into SuDS
DEFRA’s report, ‘Assessment of how strategic surface water management informs Sustainable Drainage Systems (SuDS) delivery through the planning system’, put the question of SuDS implementation firmly back on the development agenda. The report investigated the relationship between strategic surface water management activity and the planning system, including the opportunities for improvement. Its aim was to explore the potential to contribute to strategic (catchment or sub-catchment) surface water management through the planning system. The five recommendations that emerged were strongly in favour of greater use of SuDS in England:
1. Data and data sharing
This aimed to create a shared body of comprehensive and consistent data that could be used to develop a strategic approach to surface
water management. The standardisation of metrics and methods of measurement would help bodies share experience and insight of flood events and SuDS outcomes. It would also bring information held by large private landowners in the public realm.
2. Evidence base and strategy
This recommendation focused on strengthening the evidence base for planning policy and pulling that robust information through into a strategy for surface water management. It wanted to create links between evidence and the development of Strategic Flood Risk Assessments (SFRAs) that would support local planning authorities and LLFAs in building costed strategies for surface water interventions.
LLFAs would become integral to the preparation of SFRAs, and drainage and wastewater management plans would take a more central role in planning.
3. Local planning system
This highlighted the importance of making sure that planning policy and development management deliver a strategic approach to surface water management.
The focus here was on giving LLFAs the powers they need to fulfil their statutory duty to manage local flood risk arising from surface water. It would start by upskilling planning officers to manage surface water management issues. Then, mechanisms to bring SuDS schemes into consideration early on in the planning process would be introduced to increase the likelihood that multifunctional SuDS would be incorporated into the built environment. This could include LLFAs being given specific powers to provide and to charge for preapplication advice. Importantly,
LLFAs could become statutory consultees in plan-making.
4. Widening collaboration
This recommendation emphasised the need for partnership working in surface water management to help local planning authorities use information effectively in the planning system.
It called out the role of LLFAs as facilitators of a strategic approach to surface water management, specifically mentioned the need to bring in the highways authorities into the picture and focused on the role of the Environment Agency as a supporting body to the LLFAs. Water and sewerage companies (WaSCs) were also identified as potential statutory consultees on major planning applications, to complete the collaborative circle. Plus, government clarification of the contexts in which the right to connect to a public sewer might reasonably be withheld was requested.
5. National planning policy and guidance
This recommendation was centred around making planning policy and guidance clearer about the role of the planning system in delivering a strategic approach to surface water management.
This aimed to strengthen national planning policy by creating links between SFRAs identifying where reductions in surface water risk are needed, and planning policy powers that could achieve the reductions. It recognised that the national planning policy and guidance may need updating so design codes would specifically reflect the need to deliver a strategic approach to surface water management. The report noted that greater consistency would be needed in the SuDS adoption approach used by different organisations so that this diversity wouldn’t be a barrier to delivering a strategic approach to surface water management.
This report was complemented by DEFRA’s Recommendations to Update Non-Statutory Technical Standards for Sustainable Drainage Systems (SuDS), which aimed to evaluate and update the Non-Statutory Technical Standards (NSTS) in a way that helped provide for multiple benefit SuDS.
At their core, the reports’ recommendations sought to revive Schedule 3 in England to back its guidance with power, and to provide practical recommendations on creating multiple benefits from SuDS.
England needs its own version of Schedule 3, which will be a better version than the Welsh one because England can learn from the Welsh experiences.” Ian Titherington, Lead Officer, City of Cardiff Council
Catalyst #2 – Ofwat Sewerage Sector Guidance 2020
This new guidance allowed England’s nine water and sewerage companies to adopt a wider range of sewer types fulfilling specific design criteria, including those with some SuDS elements. It was an important step towards supporting Ofwat’s decision to require all water and sewerage companies to commit to a single, mandatory national approach to sewer adoption. The Design and Construction Guidance documentation set out that sewer elements in public open spaces will be potentially adoptable by the water and sewerage company if they serve more than one property. Detention basins, swales, rills, under-drained swales, ponds, wetlands, infiltration basins and soakaways are all suitable candidates for adoption. However, ultimately, the water and sewerage company has the power to assess the assets that are being offered for transfer and agree or refuse connection. Currently some water companies are exercising these new rights to adopt SuDS schemes, and some are not.
Catalyst #3 – growing construction industry concern around ground issues
In the face of anecdotal evidence that the smooth flow of development was being affected by conflicting ground-related issues, the NHBC Foundation undertook workshops to look at the situation.
The 2011 report, ‘Ground-related requirements for new housing: workshops to examine the issues faced by the industry’, highlighted how SuDS had become a key issue and that rationalisation of guidance and policy would be helpful if the industry was to move forward.
Key stats from the workshops show the general confusion and dissatisfaction amongst developers around SuDS:
• over 90% didn’t believe that skills and experience for taking responsibility for SuDS existed in local authorities and SABs
• 80% believed WaSCs should remain responsible
• over 70% felt that more than a third of their sites would fall to orphaned surface sewers, with significant concerns about their future maintenance
• 70% were aware of the forthcoming legislative changes around sewers, but almost all believe these have not been effectively communicated and there was a lack of confidence about implementing them in their businesses.
Developers wanted clarification on the following key points:
• how to resolve the different requirements for sewage and surface infrastructure, and the inconsistent interpretation of different standards
• the impact of SuDS design standards on smaller sites and the possible withdrawal of underground storage which some developers wrongly believe makes brownfield and non-porous sites undevelopable
• how to navigate the complexity of the proposed changes and interaction with the numbers of WaSCs, highway authorities and SABs
• the future maintenance of SuDS and issues affecting shared drainage, with concerns that responsibilities would remain with developers
• how likely open drainage design approaches would result in health and safety liabilities for developers. Developers are looking for regulatory action to clarify their obligations around SuDS.Catalysts for change in England
“Some of the concerns raised in the report can be overcome with good practice guidance like the 2015 SuDS Manual.” Paul Shaffer, Director of Innovation and Delivery, CIWEM
Catalyst #4 – new information about the costs of SuDS
Defra sponsored comparative studies on the costs and benefits of traditional drainage and SuDS, and these showed that the inclusion of SuDS was cheaper than a traditional drainage system, particularly in terms of lifetime costs.
Looking at quantification, one example in Cambridge suggested around a 10% saving on capital costs with the SuDS scheme. Potentially, the savings could have been greater if the SuDS layout had been considered earlier in the development process.
In pursuing these cost savings, developers are turning towards using numerous smaller water tanks dotted below ground around the site, rather than using one big tank. These smaller tanks are hidden under ponds and play areas, combining valuable biodiversity improvement with the reassurance of future-proofing the site against one-in-30-year and one-in-100-year storms and rainfall events.
Now SuDS can prove to be cheaper to install and maintain, developers are more interested in including them in their sites.
Catalyst #5 – climate emergency and increasing sustainability awareness
The Met Office reports clear evidence that climate breakdown is impacting rainfall and flooding events. It projects warmer and wetter winters, because warmer air can hold more water, so rainfall is becoming more extreme and variable across the world. Since 1998, the UK has seen six of the ten wettest years on record. The winter storms in 2015 were at least 40% more likely because of climate change. Shorter, more intense rain events are becoming the norm in the UK.Flooding is also more likely when heavy rainfall overwhelms drainage systems or burst river banks. Heavily concreted urban areas will be particularly affected because the water cannot soak directly into the soil. Developers are increasingly aware of these factors and the need to adapt construction approaches to take intense rain events and surface flooding into account.Catalysts for change in England
“If you install and design SuDS properly, they work really well. And because of climate change, because of the levels of pollution we’re seeing in urban areas, SuDS shouldn’t be the exception, SuDS have to be the norm.” Ian Titherington, Lead Officer, Cardiff City Council
Catalyst #6 – increasing consumer demand for more sustainable housing set in green environments
Established research from the ONS confirms that home buyers will pay more for houses and flats near green spaces. It found that houses and flats within 100 meters of green space cost 1.1% more than similar properties further away, and that being within 100 metres of a public green space attracted the highest premium for detached homes, adding 1.9% to the price.
This is even more true today, where green space is at a premium in high density housing developments. In response, developers are more interested in improving the amenity of an area with green spaces, trees, ponds and children’s playgrounds that incorporate SuDS.
At the same time, 74% of UK consumers arelooking at their homes differently from how they did pre-pandemic, looking for increased sustainability. Almost four in every five people (79%) are considering how environmentally friendly their property is before deciding where to live, increasing the importance for developers to provide sustainability credentials. Aspirations for sustainable housing aren’t just about minimising the impact of development on a green or brownfield site. Biodiversity Net Gain is set to become an increasingly important concept, one that describes a development that leaves biodiversity in a better state than before – and there’s already a range of guidance available on how to achieve this.
Here at Wavin, we believe there’s a role for a water equivalent to an Energy Performance Certificate to provide key information about the sustainability credentials of a site to potential buyers, particularly relevant for new build housing.
Catalyst #7 – strengthening planning policy
As cities increasingly recognise that their ageing drains and sewers are struggling to cope with growing populations and shrinking green surfaces, they’re taking action. They’re realising that they need to change how their drainage systems operate if they’re to manage the increased risk of flooding, and are embedding the need forsustainable drainage into their planning systems. The London Sustainable Drainage Action Plan, for example, addresses a specific need to promote the awareness, and the retrofitting, of sustainable drainage systems right across London.
London – an extreme case in point
The surface water runoff challenge in London is two-fold, combining the more frequent and intense storms the whole of the UK is experiencing, with managing pressure on a 150-year-old sewer and drain network built for a smaller city that is at, or near, capacity in many areas. Existing high-density housing and continual pressure to find more sites for development in the capital mean that there is little or no capacity to free-up the land space that SuDS require.
SuDS in London need to maximise use of the existing streetscape while, where possible, improving the public realm. Bodies such as local authorities and Transport for London are increasingly defining and implementing cross-London flood and drainage strategies to promote the use of SuDS.
There’s a city-wide focus on preserving the 47% of green space and 22% of tree canopy cover London’s green infrastructure provides. There’s also a coordinated SuDS development process that includes consulting utility providers to make sure existing assets aren’t damaged by new SuDS schemes.
“London’s flood board became very practical and forward thinking. A number of organisations in London with responsibilities for flooding and drainage began to collaborate and work together to develop and implement a cross-London strategy where all boroughs were working from the same page and working together to ease flooding across Greater London. The Greater London Authority made this a focus issue because flooding has been so significant, particularly in vulnerable boroughs like Hammersmith and Fulham where a huge amount of the surface water they deal with is coming in from adjacent boroughs.” Martin Lambley, Product Manager, Wavin
Here are some examples of SuDS in action in London:
• a green roof initiative
Provision of green roofs and walls are particularly important in Islington due to its high-density urban pattern of development with relatively few green and open spaces. The council specifies that “developments should maximise the provision of green roofs and the greening of vertical surfaces as far as reasonably possible”. Green roof systems and biodiverse surface finishes meet the four pillars of SuDS and achieve an environmental rating of BREEAM Excellent
• creating rain meadow spaces
This involves re-purposing existing green spaces for surface water interception and infiltration by directing road runoff to the meadow, reducing the volume of water that drains from the grass to the nearby road gully• adapting pedestrianised carriagewaysIn these projects, surface water flow is directed towards rain gardens and trees, trees are planted in linked trenches that incorporate below-ground attenuation and permeable paving allows infiltration
• enhancement of cycle paths
Planting is designed to accept runoff from the highways and footway, reducing surface water flow to the combined sewer, and a deep bioretention basin provides underground attenuation. Porous cycle surfaces also draw surface water away from the existing highway gully
• retrofitting SuDS in a housing estate environment
This includes combining visual improvements to the green areas with incorporating green roofs, a bioretention basin, a detention basin, and permeable paved road surfaces to regenerate the estate through integrated SuDS design
As a high-density urban area, London is an ideal testbed for the effectiveness of SuDS in city environments – if it can work in London, it’s likely to be applicable in other UK cities. London is a prime example of what England can achieve in the SuDS arena – England now just needs the appropriate legislation to make London’s achievements the norm, rather than the exception.
The future of SuDS
Understandably, the conventional, historic approach to water management has been to do whatever’s necessary to meet supply, so citizens can turn on a tap and be guaranteed a flow of clean water. The overall goal for water supply in a city is to provide a safe, reliable and affordable supply in sufficient quantities for all.
However, the sustainability of the technologies and methods used are in many cases questionable, particularly when it comes to reusing water. The Sustainable Water Management in the City of the Future (SWITCH) project carried out pioneering work to drive more sustainable urban water management. It revealed that a conventional approach to the management of stormwater was unfit for the needs of the urban environments ofthe future.
The basis of the conventional approach is to move stormwater away from the urban environment as quickly as possible, channelling it into a combined sewer system where the stormwater is mixed with effluent before being treated, or into a surface water system that only handles stormwater and directs it to rivers, usually without treatment. The primary focus is to manage local flooding, and this can often be at the expense of environments downstream.
As intense rain events increase, this conventional approach is creaking under the strain, and isn’t providing opportunities to reuse water:
• rapid removal of rainwater prevents it from being used for non-potable water supply uses and urban landscaping• heavy rainfall causes combined sewers to overflow, pushing untreated water into the environment
• rapid runoff from roads, roofs and car parks sweeps pollutants into receiving water bodies
• rapid runoff from gardens and parks also directs pollutants into receiving waterways
• generally, rapid runoff causes erosion and sedimentation in streams, rivers and estuaries
• increasing impermeable surfaces prevents natural recharging of the water table
• rapid surface water removal reduces evapotranspiration, increasing urban temperatures.
As part of addressing these unsustainable issues, the SWITCH project adopted a ‘grey to green’ approach. This focused on the importance of green infrastructure, such as green spaces and clean rivers, as an essential part of underpinning the functioning of urban communities. Similar to CIRIA guidance on delivering better watermanagement through the planning system, the SWITCH approach emphasised the value of collaborative, cross-agency planning and working to deliver sustainable solutions. It brought together social, economic and environmental aspects within a long-term perspective, considering the interaction between different elements of the urban water system alongside structural and human factors.
Building a Blue Green Infrastructure
SWITCH pointed the way to an urban future that centred on planning and building a Blue Green Infrastructure (BGI).
BGI is defined by the European Commission as a ‘strategically planned network of natural and semi-natural areas with other environmental features designed and managed to deliver a wide range of ecosystem service’.
In essence, it brings together the blue benefits of good water management with green sustainability credentials. BGI occurs where water elements like rivers, canals, ponds, wetlands, floodplains and water treatment facilities work together with the trees, lawns, hedgerows, parks and fields of the green environment.
SuDS are a key part of BGI that address many of the negatives of the conventional approach to surface water management:
• intercepting runoff so combined sewers aren’t overwhelmed• holding runoff so that it can drain back to the water table
• using the natural environment to filter pollutants out from water and to improve the quality of water entering combined sewers
• capturing runoff so it can be managed through evapotranspiration.
“SuDS take pressure off the combined drainage network, green up the environment, take pollutants out of the water and even catch micro-plastics.” Ian Titherington, Lead Officer, Cardiff City Council
Increasingly, as water sustainability moves up the agenda, citizens, local authorities and government will require proof that BGI such as SuDS have been included in a development.
A simple solution would be a water certificate that examines and certifies how a build manages overall water resilience, covering key elements such as:
• is the property on a combined or separate sewer?
• are low water use fittings in place?• what SuDS are on site?
• have low-flush toilets been fitted?
• are rainwater harvesting methods in place?
However, an initiative like this will need cross-agency agreement and will need to be spearheaded by a prominent organisation.
The question today is, who will step forward?
Sustainable drainage systems (SuDS) are both a practical part of urban planning and an aspiration for a greener approach to construction and living. They’re designed to manage the flood and pollution risks resulting from urban runoff and to contribute wherever possible to environmental enhancement and place making.
“A water performance certificate needs to become part of standard house-buying documents. Particularly on new builds. But this needs to be driven nationally.”Martin Lambley, Product Manager, Wavin
SuDS in action
Portland set out to tackle significant levels of river pollution that had been exacerbated by decades of combined sewerage overspills. Alongside new drainage pipes, the city introduced a Green Streets programme that relied heavily on SuDS systems and included rain gardens, roadside swales, surface water street planters, green roofs and an incentivised downspout disconnection programme.
The Bureau of Environmental Services encouraged residential areas around NE to accept kerb extended and multiple benefit surface water planters, and the initiative’s popularity spread.
As part of promoting SuDS, Portland created a cycling tour around the city centre that takes in SuDS implementation sites, with explanations of how the techniques work that empower the public in a cost-effective and multiple beneficial way.
Sheffield created a network of green corridors, parks, recreational areas and green spaces within the city to promote the free movement of wildlife, leisure, recreation, walking and cycling.
One element transformed an almost redundant former inner ring road from a barrier to a green corridor with a SuDS system at its heart, including segregated cycle lanes and public art.
The SuDS replaced hard surfaces with meadows, rain gardens and other vegetation, reconnecting the highway surface to its natural catchment, the River Don. Soils and plants filter out pollution before it reaches the river.
“Blue Green Infrastructure is a term we’re going to see more and more.” Martin Lambley, Product Manager, Wavin
By implementing Schedule 3, Wales is leading the way in ‘greenification’ – that is, it’s blazing a trail for SuDS inclusion in ways that support all four SuDS pillars. The Welsh success stems from adopting surface water drainage systems that consider technical elements as well as human nature - ensuring that communities are able to embrace SuDS and that they offer maximum benefits with minimal maintenance. There’s a distinct focus on managing roof, driveway and highway drainage when planning new build developments, alongside a range of strong practices that England could take inspiration from for its own version of Schedule 3. There are also learnings from the Welsh experience that could help England prevent loopholes that have been exploited in Wales.
In Grangetown, Cardiff, for example, a SuDS project set out to remove surface water that entered the combined sewer network from a network of 12 streets. 108 rain gardens and tree pits containing native trees and plants, improved water quality through the physical and biological treatment of surface water runoff before it was discharged into the nearby river. As part of installing permeable paving and combined kerb drainage and channel drainage, the project seized the opportunity to improve amenity by installing a new cycle path, a new footway and 14 safer road junctions.
Moving SuDS forward
SuDS have achieved significant momentum within the urban environment, and it’s now up to every organisation involved in urban planning, maintenance and management to keep it going.
All water management stakeholders must come together to shape legislation and regulations that will deliver a coordinated, effective strategy for surface water. SuDS need to become a mainstream part of surface water management – a compulsory stage in developments and a key consideration in schemes to regenerate or improve existing
We need to actively seek out opportunities to deploy SuDS. Be ingenious. Be creative. Embrace the Blue Green movement.
“With the introduction of Biodiversity Net Gain and the recognised benefits of SuDS, there is growing recognition of the value of SuDS. This, coupled with concerns about nutrient neutrality should mean that the drivers for SuDS will continue to grow. It needs strong local planning policy to be introduced by Local Planning Authorities that include policies and requirements for multi-beneficial SuDS that deliver the four pillars and more.”Paul Shaffer, Director of Innovation and Delivery, CIWEM
Stormwater solutions from Wavin
Wavin manufactures a wide range of plastic rainwater and stormwater harvesting drainage pipe systems for industrial, commercial and residential industries.These include:
Geocellular attenuation tanks
Our geocellular attenuation tank systems can be used to control and manage rainwater surface water runoff either as a soakaway or as a storage tank. Their modular/honeycomb structure means that they can be tailored to suit the specific requirements of any site and can be easily combined with other SuDS methods.
Roof drainage systems
From half-round guttering that integrates seamlessly to residential, commercial and industrial buildings, to roof drainage systems for flat roofs and complex roof areas, we offer a wide range of solutions to capture rainwater.
Our range of channel drains and gullies help you manage surface water efficiently by collecting and transporting excess water on roads, car parks or industrial sites. Products include permeable paving, channel drainage and non-mechanical means of managing stormwater discharge from attenuation tanks for single dwellings.
Our plastic drainage pipes and connection components are designed to optimise rainwater drainage and transport, whatever the volume or flow, to meet the toughest regulatory obligations.
Attenuation and infiltration
Our underground attenuation/infiltration tanks collect all the surface water from your roof guttering, downpipes, surface water gullies and channel drains, storing it until it can naturally soak into the surrounding ground.
Our silt traps help you meet regulatory requirements to remove pollutants from collected rainwater before discharge. We offer both the expert advice and the solutions you need to meet all compliance obligations.
Find out more, or request a consultation to discuss the possibilities for your next project here