Yet more unacceptable delays to the implementation of long-awaited legislation to make Sustainable Drainage Systems (SuDS) compulsory for new developments in England and Wales have been exacerbated by an "overly-idealistic" interpretation of SuDS as natural above-ground drainage features, experts have warned.

“It’s time to get real about the principles and practice we need for surface water drainage not just for new development but also for much-needed improvements to the existing surface water drainage infrastructure. This will be essential not only to combat flooding, but also to tackle pollution of our rivers and watercourses,” said Alex Stephenson, chair of the British Water Sustainable Water Management (SuWM) Focus Group and Director of Hydro International’s UK Stormwater division.

Despite another period of devastating flooding, Defra has confirmed that plans to make SuDS compulsory for developments over one property in April 2014 have been delayed again to take account of the outcomes of consultations with industry stakeholders. A new date for implementation has yet to be confirmed.  The new regulations as part of the Flood and Water Management Act will make sustainable drainage systems subject to approval by new local authority SuDS Approving Bodies, who will then be responsible for adopting and maintaining the SuDS.

Part of the ongoing delay centres around housebuilders and developers concerns’ about the costly loss of land required to build space-hungry above-ground ‘natural’ features such as ponds, wetlands and swales.  There are also questions surrounding the proper funding for local authorities to maintain SuDS effectively.

Alex Stephenson commented:

“It’s not that housebuilders are anti-SuDS –  many have been installing good SuDS schemes for the past 10 years or more and these issues are not new to our industry.   The question is, why are they the focus of attention now?”

“I believe a significant contributory factor is a tendency to interpret SuDS too rigidly as  ‘natural’ or above ground drainage features and this is what threatens to hold back progress.”

“It’s time to go back to the first principles of what we are trying to achieve in sustainable surface water control as well as treatment of pollutants from runoff, in particular from highways.”

The key principle of SuDS is to mimic natural drainage paths and processes and to deal with rainwater as close as possible to where it falls – by infiltration where possible.  By doing so, the unsustainable outcome of directing surface water into the over-burdened sewer network is avoided.

Innovative technologies are already available to reduce the amount of space needed for surface water features.  Proprietary solutions can also help to deliver predictable and repeatable maintenance schedules that local authorities can effectively cost.  Technologies such as vortex flow controls, underground storage/infiltration systems and treatment devices are available to use alongside, or instead of natural features.

Alex Stephenson continued:

“It’s vital that Defra gets the all-important design guidance that will accompany the legislation absolutely right.  It’s essential that this, and future, design guidance for SuDS takes full account of the toolbox of well-proven technologies available to support natural design features.”

 “A pragmatic approach is essential if we are to realise the full potential of sustainable drainage systems.  It was 2007 when devastating surface water flooding first prompted the Pitt Review which led to the Flood and Water Management Act.  Six years later, after persistent delays and repeated calls for action by politicians on the Efra committee, it seems unbelievable that we are still waiting.  Technologies are already available that can deliver a satisfactory compromise.”