Just add water

New Government planning requirements for sustainable drainage systems (SuDS) incorporating techniques such as concrete block permeable paving came into force this April, amidst a growing realisation that they can deliver far more than just drainage as a key part of urban design. Consultant to Interpave Chris Hodson explains

An additional policy now sits alongside the National Planning Policy Framework (NPPF), spelling out “the Government’s expectation … that sustainable drainage systems will be provided in new developments wherever this is appropriate”. This measure must be applied by local planning authorities (LPAs) in England through local policies and plans, as well as application decisions on ‘major developments’ of 10 or more dwellings and equivalent non-residential or mixed developments.

Defining SuDS

Under the new arrangements LPAs must satisfy themselves of minimum operational standards and ensure that maintenance is provided for the lifetime of the development using planning conditions or other obligations such as Section 106 agreements. SuDS designs must also be ‘economically proportionate’ in terms of operation and maintenance. New Government guidance, in the form of ‘Non-statutory Technical Standards for SuDS’, was published in March, albeit with a minimal level of information, and the NPPF Planning Practice Guidance now defines SuDS as:

“Sustainable drainage systems … designed to control surface water run off close to where it falls and mimic natural drainage as closely as possible.

They provide opportunities to:

  • Reduce the causes and impacts of flooding
  • Remove pollutants from urban run-off at source
  • Combine water management with green space with benefits for amenity, recreation and wildlife.”

However, guidance for LPAs and designers, on various aspects of SuDS is already available from a number of sources, including the 2013 Code of Practice BS85823. The Code seeks to integrate SuDS with urban design in delivering amenity and community value as well as enhancing landscape and townscape character, and stresses the importance of linking surface water management and development planning. Interpave will also continue to develop its guidelines on all aspects of using concrete block permeable paving – a key SuDS technique – in urban design.

Designers take the lead

This is a clarion call for architects, master-planners and landscape designers to take the lead in developing multi- functional SuDS as an integral part of place shaping. As the RIBA’s 2014 report Building a Better Britain points out:

“For too long, we have been designing water out of our towns and cities when we should have been designing it in…”

Now is the time for a closer understanding of, and engagement with SuDS by designers and planners. With good design as a priority, drainage engineering becomes simply a supporting function, not an end in itself.

Conceptually, a SuDS scheme comprises a ‘management train’ of interconnected features, each combining water storage, pollution removal and amenity benefits. SuDS replicate the natural drainage from a site before development. But that is not to say that all SuDS features have to be vegetated or that urban projects need to take on a rural character with lower housing densities.

Concrete block permeable paving is uniquely placed to help meet these requirements. In terms of urban design, the growing choice of concrete block permeable paving products available from manufacturers – with numerous shapes, styles, finishes and colours – allows real design freedom. At the same time, it can provide completely level, well-drained, firm and slip- resistance ‘accessible’ surfaces without the need for cross-falls, channels, gulleys or other interruptions. Rainwater ‘ponding’ is eliminated, reducing the risk of ice forming on the surface and preventing splashing from standing water.

Gradual flow of clean water

But the real strength of concrete block permeable paving is an ability to remove water-borne pollution offering the important – and often missed – opportunity of a gradual flow of clean water that can be exploited to enhance landscape design and biodiversity. With concrete block permeable paving, SuDS offer imaginative designers opportunities, rather than technical problems to be solved. Taking a holistic approach, designers should embrace SuDS as one of the central design considerations from the very start of their projects, exploring innovative solutions that form an integral part of urban design.