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SuDS come up to date

By Paul Shaffer
CIRIA’s new SuDS Manual deals with creating better places and spaces, managing floods and delivering multiple benefits

The new SuDS Manual, launched at the House of Commons in November 2015, is the most comprehensive sustainable drainage systems (SuDS) guidance available in the UK. It is more of a re-write than a simple update to the first SuDS Manual (C697) that was published by CIRIA back in 2007.

At over 900 pages, two years in the making and with a collaborative project team incorporating more than 70 experts in various advisory capacities, the publication marks a step-change in progress not just for those involved, but also for the wider community that will undoubtedly benefit from this new guidance, including landscape architects, engineers, planners, designers and developers.

Back in 2007 information on SuDS was sparse, spread across multiple publications and not widely applied in the UK. Things have moved on a great deal since then and SuDS implementation in the UK has significantly increased, as has the technical knowledge and the number of case studies that can be drawn on. This has been further supported by a Government announcement in early 2015 that it expects that sustainable drainage systems will be provided in new major developments ‘wherever this is appropriate’. Although the true impact of the policy, remains yet to be seen!

For those not familiar with SuDS, sustainable drainage systems slow the rate of surface water run-off and improve infiltration, by mimicking natural drainage. This reduces the risk of ‘flash-flooding’ which occurs when rainwater rapidly flows into the public sewerage and drainage systems. As those closely involved will tell you though, it is not just about managing floods through controlling surface water flows and volumes. SuDS also contribute to improving water quality, local amenity, and habitats for increased biodiversity as well as improving health and wellbeing and air quality.

So what has changed in the new manual and why should this matter to landscape professionals? The short answer is that the new SuDS Manual (again, published by CIRIA) not only updates the extensive technical information; there is also new guidance to improve the design approach including sections on designing SuDS for urban areas, roads and highways, biodiversity, amenity, and overcoming challenges with specific site conditions. Information on SuDS components has also been updated with additional information on using trees to manage surface water runoff.

The overriding message from the manual is that through effective and early engagement SuDS can be delivered on any site and the best schemes are likely to be delivered by interdisciplinary teams. The new manual suggests that SuDS isn’t just for engineers, it’s also a design process recognising the role of different disciplines, encouraging an interdisciplinary approach to SuDS design (particularly between landscape architects and drainage engineers). The SuDS Manual stresses that surface waters should be used as an asset and viewed as an opportunity to deliver multiple benefits for schemes.

The manual’s revision complements CIRIA’s BeST (Benefits of SuDS tool) project – aimed at strengthening the business case for SuDS. As previously hinted, SuDS can cost-effectively deliver multiple benefits and BeST provides a structured approach to evaluating a range of wider benefits, often based upon the overall drainage scheme. When evaluating SuDS the cost is only one side of the equation, and to make an informed decision an understanding of other benefits needs to be realised and compared to the likely cost – in other words viability and an economic justification for SuDS needs to articulate more than just costs, by presenting and valuing the multiple benefits.

The entire manual should be of interest to the landscape profession depending on what level of master planning, design and construction they are involved in. The early part of the manual provides an overall philosophy of SuDSm recognising that the types of benefit that can be achieved by SuDS will be site dependent. The manual considers four categories: water quantity, water quality, amenity and biodiversity, also referred to as the four pillars of SuDS design. Each pillar has a design objective and associated criteria. The early chapters lead the designer into increasing detail from the application of the philosophy, through to the technical detail and good practice. Chapters on biodiversity and amenity will be of particular interest to landscape professionals; both include detailed information on design criteria and example indicators to maximise the value of SuDS for both the development and the wider community. Further chapters examine how and when to apply these criteria.

The SuDS Manual is primarily aimed at UK applications, though it will be of interest to all engaged in sustainable drainage work globally.

It recognises the need for better information and engagement for those involved in the development process and it is structured in a way that allows easy access and navigation, whether that is for high level appreciation of the concepts only, or for detailed design guidance.

The SuDS Manual (C753) can be downloaded for free from the CIRIA website (www.CIRIA.org) (where printed versions can also be purchased) and further information on both SuDS and BeST can be found on the susdrain website (www.susdrain.org).

Amenity design criteria and example indicators as featured in Chapter 5: Designing for Amenity

Amenity design criteria
Example indicators
1. Maximise multi-functionality
The number, variety and quality of additional and multi-functional uses for SuDS, such as recreational areas, car parking or traffic management
2. Enhance visual character
The proportion of the drainage system that is designed to be visually attractive, adds visual value to the development, supports local heritage and landscape character and integrates appropriately with the surrounding area
3. Deliver safe surface water management systems
The consideration of public safety within the design of each SuDS component (related to the “use” of the system as an amenity feature)
4. Support development resilience/adaptability to future change
The proportion of the drainage system that is designed with an allowance for future climate change or development change
The proportion of the drainage system that will contribute to the development’s climate resilience, such as reducing the heating/cooling needs of buildings or through shade provision
5. Maximise legibility
The proportion of the system that is visible
6. Support community environmental learning
The extent of community awareness strategies, school involvement, community education strategies, visitor provision etc


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