The Future of Sustainable Water Management
publication date: Jul 14, 2008
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author/source: David Harris
Following the floods of 2007 which affected 57,000 homes and caused over £3 billion worth of damage, we have been left in no doubt that urban areas now need to cope with changing weather patterns along with more prevalent and extreme weather events.
Climate change is driving the need for innovative solutions and with average UK temperatures expected to rise by as much as 2-3.5°C by 2080, it is expected that the seasonal distribution of rainfall will change significantly.
Looking to the expected change in UK weather patterns, it is possible to estimate that up to 80,000 homes will have a 10% annual chance of suffering surface water flooding, caused partly by the Government’s plans to grant planning permission in floodplain areas, with a subsequent cost of £270 million per year.
Over the past five years, the use of Sustainable Urban Drainage Systems (SUDS) has become more prevalent in response to growing urbanisation coupled with recent changes in rainfall patterns. The use of SUDS systems has enabled surface water run-off to be controlled and managed in a manner that prevents and mitigates flooding and surface water contamination. On an undeveloped site, typically 15 to 20% of the rainwater that falls becomes direct surface run-off which then naturally drains away slowly into the nearest watercourse without any need for additional control. However, in developed catchments direct run-off can be up to 80% of the rainfall volume, impacting dramatically on the existing drainage network.
In February, the Government released its consultation document Future Water designed to improve water quality in the natural environment and promote the use of SUDS for the management of surface water run-off.
This consultation aims to guide the Government’s water management strategy and whilst the sentiment and direction of the document appears to achieve this through the promotion of more sustainable drainage methods, there is the danger that Government has been limited in its appraisal of SUDS.
Future Water focuses predominantly on the use of above ground solutions, such as reed beds, swales and balancing ponds. The main benefit of an above ground solution is the fact that it is a surface feature, providing some level of water treatment and also a visual feature within a development. They do however have a high land take, making them difficult to use in developed areas such as brownfield sites and open bodies of water could cause a potential risk to health and safety.
Although there is good direction and guidance from organisations such as CIRIA, by limiting designers, engineers and planners there is the potential of unearthing gaps within the industry in terms of the experience and expertise to design and build above ground solutions to appropriate standards. Within the UK there aren’t a large number of soft SUDS schemes which is partly as a result of a lack of specialist contractors and groundworkers with the experience to build and maintain these solutions.
In truth, a holistic approach to water management is needed to ensure designers and engineers can implement the most appropriate solution for a particular project. The fact is, if the appropriate solution isn’t implemented this could result in failure of the system, and possible flooding.
The Government’s current stance on sustainable water management strategy appears to rule out below ground drainage solutions in favour of soft SUDS, without taking into consideration its effect on other policies.
Planning Policy Statement 3 focuses on housing densities for new developers. Within this policy, new housing developments should achieve a density rate of 30 dwellings per hectare. In practice, this is in fact difficult to achieve if planners and developers followed the recommendations set by the Government’s Future Water document, due to the land take required for the implementation of an above ground SUDS solution. This apparent disconnect between varying Government legislation could potentially create a degree of uncertainty as to whether an above or below ground solution is appropriate.
Across Europe there is a growing trend to design a holistic solution which integrates both above and below ground drainage solutions, for example by using porous paving connected to an attenuation structure to control high volumes of stormwater.
Whilst soft drainage methods have their place, modern SUDS solutions from Polypipe WMS offer exceptional drainage performance without impeding on the development footprint. Below ground SUDS systems require minimal space requirements and the land above is available for community use, for example as a car park, sports field or recreational ground. They are protected from vandalism and have no health and safety issues, ‘out of sight, out of mind’ and importantly below ground solutions are conducive to use with rainwater recycling, unlike above ground systems.
Polypipe WMS has recently launched its new Ridgistorm-XL range of large diameter pipes for attenuation and specialist pipeline applications. Ridgistorm-XL is available in diameters from 750 to 2100mm and can be installed under trafficked areas such as car parks, without disturbing the aesthetic appeal of the site and taking up valuable land space that could otherwise be developed.
