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News Release from: Chartered Institute of Building [CIOB] | Subject: Watertight conference
Edited by the Buildingtalk Editorial
Team on 21 March 2006
2m homes and businesses at risk from
flooding
BRE working on innovative design and build approach for flood risk areas
The recent Watertight conference at the Building Research Establishment was organised against the background, according to the latest Development and Flood Risk report from the United Kingdom's Environment Agency, that over five million people and two million homes and businesses in England and Wales are currently at risk from flooding Some 200,000 of these are said to be at very high risk
This article was originally published on Buildingtalk on 12 Mar 2004 at 8.00am (UK)
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The implications of these figures are of major significance for house builders and the industry generally.
The estimates cover the flooding risks to which 10 per cent of homes in the U.K.
are subject: this includes both maritime and fluvial flooding (coasts and rivers), supplemented from time to time by failures in public water supply and drainage systems.
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The subject was introduced by Darren Johnson, chair of the London Assembly's environment committee, which last October produced a report on the state of London's flood defences.
This came a few weeks after the New Orleans catastrophe, a tragic reminder of the threat under which cities lie from water allowed to rampage uncontrolled through densely occupied urban areas.
In the executive summary of its report, the committee pointed out that 1.25 million people are already at risk from flooding by the Thames, and that a major flood in the Thames Gateway growth area could cost as much as £12 billion in reconstruction and repairs.
The Thames Estuary 2100 project, led by the Environment Agency on behalf of the Government, is working with partners to identify the range of solutions necessary to reduce this risk and the impact of any flood that occurs.
The London committee welcomed the approach of this project, but is concerned that the deadline for proposing options may slip, and has called for any options to be accompanied by clear funding mechanisms.
It also welcomed plans to create a Green Grid in East London consisting of areas which could be sacrificed to flooding when necessary, but insists that this scheme needs to progress rapidly to ensure that the idea does not get lost due to the speed of new development.
Considering the speed of development in the Thames Gateway, the committee thinks the plans for the Green Grid are progressing too slowly and is asking the Office of the Deputy Prime Minister and the London Development Agency to fund the work necessary to identify sites based on the Strategic Flooding Risk Assessment.
In response, the Environment Agency, acknowledging the report as a valuable contribution to the debate on this critically important issue, said that Londoners could be reassured that the city's flood defences are in good shape, offering a high level of protection and due to be improved to the extent of £300 million investment over the next 15 years.
But the London Assembly is concerned that the impact of floods may worsen due to the new developments planned within the Thames floodplain.
They quoted the Association of British Insurers report of February 2005 as pointing out that more than 90 per cent of the new homes in the Thames Gateway and one million square metres of commercial property are likely to be located in the floodplain, albeit relatively well protected.
"Whilst we were pleased to hear that most tidal defences in East London are well-maintained, we are very concerned that not all defences are in good condition.
In early 2004, we were told by the Environment Agency that 19 km of the 223 km of tidal flood defences are in less-than-satisfactory condition, about eight per cent of the defences.
According to recent evidence there has been an improvement, but not all defences are yet in a satisfactory condition." 'No room for complacency'.
Perhaps more shocking, the report added, was the fact that outside the London area, the condition of 65 per cent of the defences are not known.
If a defence fails due to pressure from flood water, said the report, the repercussions could be catastrophic.
There were other parts of the Gateway where there was no readily available information about the condition of the defences.
The committee commented: "We recognise that lack of knowledge does not mean that the defences are necessarily in bad condition.
However there is clearly no room for complacency, when we take into account that flood defences were only breached in three places during the flooding in New Orleans." The committee has asked the Environment Agency to identify the lessons that should be learnt from New Orleans.
It has also recommended a survey of all Thames Estuary defences, not just tidal ones, and by the end of this year believes a plan should be developed for repair of any sub-standard defences.
Surface water and sewerage flooding becoming more common in London, says the report, due in part to increased frequency of intense rainstorms and the increase in hard surfaces which reduce the time that water takes to hit the drains and increases the amount of water as less is absorbed or evaporates.
Other factors are inadequate maintenance of drains and their inadequate capacity to deal with the increase of run-off.
"An additional problem in London is sewerage flooding.
Apart from where sewers break, these floods are normally caused by the overflow of 'combined sewerage overflows' which are common across London.
These carry both sewerage and surface run-off.
Their existing capacity is failing to meet growing needs of run-off and the increase of sewage as we use more water in our homes." The committee is also very concerned about the number of bodies which produce policy and guidance relevant to the Thames Gateway.
"Different sites will be subject to different master plans and local development frameworks, and will be subject to a number of strategies which often overlap.
It can therefore be hard to determine what status and weight should be given to the different forms of guidance.
"This is causing difficulty for developers and architects because they are unsure of what standards are needed or who should be consulted in advance of planning applications." 'Organisational effectiveness is critical'.
Confusion of this order was mentioned in the report by the American Society of Civil Engineers in its external review document on the hurricane protection system in the New Orleans metropolitan area.
"The External Review Panel sees clearly that organisational complexities and the ways in which decisions are made are among the most important factors that influenced the performance of the hurricane protection system.
Organisational effectiveness has been and will continue to be questioned, with justification.
It is impossible for the ERP to conceive a mechanism through which the levee system can be rebuilt and operated effectively and efficiently with such organisational discontinuity and chaos.
The ERP recommends than organisational issues be assessed critically and thoroughly as soon as possible." The situation in London may not be as bad as that, but it is important that there should be a co-ordinated source of design and build information for developers and planners, particularly in relation to flood risk and the work that has been done on flood resilient building.
This sounds like the job for which BRE is presently equipping itself.
The establishment has already done a lot of work on flood resistant structures in collaboration with the Association of British Insurers.
The objectives at present are identifying design solutions that meet the needs of all key stakeholders; building working partnerships to apply the lessons learned to real developments; promoting innovative approaches to refurbishment and renewal work; and raising awareness of work on flood resilience being done elsewhere in Europe and beyond.
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