July 2007 floods in UK
Why spending on flood defence should be a priority for the UK
Hyder Consulting's Bob Sargent says there is a desperate need for a single drainage authority to provide oversight and a design to manage flood water in our urban centres. The focus on flood risk management, and working with nature rather than against it, is surely the right approach but we need to adapt our organisational structures to enable proper implementation
The flooding over the past summer has once again highlighted the problem of flood risk in the UK and is once again the subject of government review. The scale of flood risk, and the potential losses from flooding, can only increase in coming years due to:
- The increase in quantity and value of home contents and furnishings
- The expected increase in intense rainfall events, increased storminess and rising sea level due to climate change
- Increasing development, increasing the number of properties at risk and the runoff generated.
Government policy towards flood risk management has in recent years moved away from purely flood defence, ie building flood walls etc to prevent flooding, to flood risk management which has complemented flood defence with trying to reduce development in flood prone areas.
But, will these measures be enough to reverse the increase in flood risk? it looks increasingly unlikely. Partly this is because in practice flood risk management has focused on new development, with planning policy aiming to prevent development in high flood risk areas. This does nothing for the large existing exposure to flood losses which will be subject to the increased flood risk. There has also been difficulty in implementing many of the newer ideas to manage flood runoff because of the fragmented and rigid institutional approach to flood management in the UK.
Even with new development it is difficult to avoid flood risk. Just considering the risk of flooding from rivers and the sea – those shown in the EA flood maps – greatly reduces the potential area available for new development. If flooding from other important sources such as heavy rain and surface runoff is included the potential area is reduced further. In addition, many of our towns are in flood prone areas and preventing redevelopment in them may be undesirable as it will lead to decay and planning blight.
So what is the way forward? The focus on flood risk management, and working with nature rather than against it, is surely the right approach but we need to adapt our organisational structures to enable proper implementation.
We must improve the way we design, manage and maintain drainage. At present drainage is the responsibility of a number of authorities – landowners, local authorities, highways authorities, the EA, water companies and also internal drainage boards in some areas. All these authorities have their own interests which are not aligned and no one authority has an overview. In addition, there is no control on runoff from agricultural areas where changes in cropping and land management can have a significant impact on runoff upstream of urban areas.
There is a desperate need for a single drainage authority to provide oversight and a design to manage flood water in our urban centres. There are many opportunities to reduce runoff and store excess within our urban centres, but without such a strategic body they cannot be properly co-ordinated and maintained.
Sustainable drainage systems, for instance, provide a range of opportunities to reduce flooding, and provide water quality and amenity benefits as well. Green roofs, porous pavements, local storage facilities can all contribute. But in the UK at present they are proposed on a piecemeal basis, and arguments about who should be responsible for them have severely curtailed their use. More strategic use of SUDS, and the provision of regional flood attenuation structures, has similarly been hampered by the absence of a strategic view of flooding.
Again, urban design can often accommodate flood water with minimal damage – green spaces, recreational areas and similar low value uses could be allowed to flood in extreme conditions, and non-critical roads can even be designed to convey flood water across the urban landscape to link them together, but this requires an integrated approach that is sadly lacking. Whilst we now have the technical ability to model how flood water moves across whole cities, the institutional arrangements to taking this approach are absent.
Greater integration also needs to be brought into the way we approach technical design standards in the industry. At present new build needs to be designed and protected for a flood risk from rivers and the sea of once in 100 years, with a suitable allowance for expected climate change over the lifetime of the project. Surface water drains however are designed to accommodate a once in five year storm, with no allowance for climate change. Other standards apply to highway drainage, inlet drains and pumping schemes.
We must also start to consider what happens if these design rates are exceeded. Whilst occasional flooding of, say a local park, may be an acceptable consequence of excess water, flooding of nearby housing should not be.
Finally, some building will always be required in flood prone areas. Indeed, waterfront property has often been the driver in recent urban regeneration. For these cases, we are learning how to design buildings to resist floodwater or, if flooding becomes severe, to be more resilient so flood damage is minimised. Making the first floor the first habitable area is often a good start, using flood resilient materials, which are not damaged by submergence, and keeping electrics above the anticipated flood level are all simple steps which can reduce flood damage. If designed in from the start these measures are not prohibitively expensive, and their use to restore flood-damaged property instead of vulnerable plasterboard and chipboard seems common sense but it is rarely done.
There is no one answer to flood risk management, but there are a wide range of options and technical measures which could be used to reduce it. If we had the institutional arrangements to implement these measures in a strategic and holistic way then the steady increase in flood risk might be averted. We must hope that the government review into the summer flooding starts to address this key issue.
Bob Sargent, Water Environment Director, Hyder Consulting
