Closing the flood gates with SUDS

Though the government's water and flood bill is being developed, Alex Stephenson, director of Hydro International UK and chair of the British Water SUDS Group, is concerned the measures will not go far enough

The floods of summer 2007 highlighted major shortcomings in the UK’s water control and management strategies and practice. More than 50,000 properties were affected and the final bill is expected to reach £3B.

Since then, a number of seminal government reviews and policy statements have paved the way for new legislation and a water and floods bill is expected in spring. New policies have been shaped against the background of Defra’s Future Water strategy for England and Making Space for Water. However, as a result of the floods, the government commissioned Michael Pitt to conduct a thorough and independent review in May 2008. The Environment Secretary Hilary Benn responded formally to the Pitt Review in Parliament at the end of December and laid the way forward for new legislation.

The review contains many recommendations for emergency response mechanisms to deal with flooding once it occurs. But two thirds of the 2007 floods were the result of surface water drainage. The long-term measures to ensure an effective drainage network are of the most concern to the water industry. Particularly welcome are plans to clarify the roles and responsibilities of the various agencies responsible for management of flood risk and “ownership” of the drainage infrastructure. Confusion over who “owned” some drains and sewers was said to have contributed to last year’s flooding.

Local authorities are to be given new powers to assess and manage flood risk from all sources, including surface water. While most agree this is the right way forward, there is concern that the move will be ineffective unless local authorities are given more than the £15M promised by Hilary Benn for flood engineers.

While local authorities are keen to embrace the opportunity for stronger leadership, they are concerned that they will not have sufficient resources, in money or staff, to do so. Building adequate technical knowledge and engineering expertise will take time, recruitment, practical guidance and a significant amount of education.

It is critical that work starts now to prepare for these changes, rather than waiting for the bill to become law. It is hoped that the new bill will set out in more detail the practical steps to be taken to establish the new responsibilities and how they can be made to be effective.

The government has put its wholehearted support behind Pitt’s recommendations to increase the use of sustainable drainage systems (SUDS) and it is clear that championing SUDS will be a key part of the local authority portfolio. It has been very encouraging to see the growth of support for SUDS principles since the early days and see it now adopted as a first-choice option by the government. But we need to be realistic about what must still be done to ensure its proper adoption – and that means tackling some serious misperceptions.

One of the guiding principles is to replicate the pre-developed site runoff hydrograph and deal with surface water as close as possible to the point of falling (the source). But the speed of uptake of SUDS has been hampered, in part, by the definition of a sewer and the inability of most water companies to adopt many sustainable drainage techniques as they are not classed as sewers. So far, Welsh Water is arguably the only water company that has readily embraced such systems, facilitated by the nature of its not-for-profit business model. Unfortunately, some planners, developers and even some water companies are losing their way with the concept of sustainable drainage.

Toolbox of technology

Just when SUDS is beginning to become a more recognised term, it has become bogged down by association in some minds with soft concepts such as swales and ponds. The government itself, in its official response to Pitt, puts forward the Elvetham Heath housing development as a shining SUDS example – and indeed it truly is.

But the report highlights its soakaways, detention basins, ponds and swales and crucially fails to point out that the scheme was only made possible with the engineered technology of 18 Hydro-Brake flow control attenuation devices.

In fact, a mixed engineered and natural approach is an excellent way forward. A best-management approach is required using the full SUDS toolbox of techniques; selecting the most appropriate for both new and retrofit applications, using both natural methods and proprietary technologies, including underground infiltration, storage/attenuation and treatment devices. New developments like the government proposed 3M new homes, create more areas of land impermeable to rainwater and, with it, the need to avoid potential flooding events from runoff.

Of particular concern is the government’s indication that it is considering abolishing developers’ automatic right to connect to the public sewers. This might appear to protect the sewerage system downstream from overburdening, but the proposal could turn out to be impractical.

Using infiltration and soakaways is simply out of the question for many ground conditions. At worst, the move could simply outlaw the already perfectly sustainable at-source discharge limit solutions, which are currently being achieved through restricted outflow and onsite drainage techniques to meet local planning requirements.

But the disconnection issue needs to be carefully thought through and managed. If withdrawal means that more developers have to demonstrate very clearly their SUDS friendly measures, well and good. If it results in a cowboy attitude with developers finding any discharge point or ditch and just connecting up, the measure will be counter-productive.

The proposals need to embody the use of appropriate storage and attenuation technologies, either to slow flood waters down before they enter the sewers, or to deal with increased loads of stormwater locally.

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