Case for stronger drainage infrastructure

Climate change threat underscores case for stronger drainage infrastructure .

The United Kingdom Government has in its latest climate change programme declared its belief that climate change is the greatest long-term challenge facing the world today.

The construction industry will play its part in implementing the stricter and more comprehensive measures now being introduced to counter the rise in greenhouse gas emissions which is as the programme recognises a global issue.

One country's contribution however effective it may be on the home front must be small in relation to the scale of the overall problem.

The difficulty of gaining control over carbon emissions in an industrialised economy is demonstrated by the fact that the United Kingdom will fall short of reaching its 2010 reduction target.

The Government's newly-published paper compares its intention of cutting carbon emissions to 20 per cent below 1990 levels - well in advance of the basic Kyoto commitment - to what is now expected to be achieved, even with the additional measures being introduced this year.

Currently the reduction of carbon emissions by 2010 is expected to be between 15 and 18 per cent, implying a 25 per cent shortfall from the target at the lower end of achievement, owing partly to higher than anticipated economic growth.

But this kind of movement is bound to occur in any dynamic economy, putting long range forecasting such as 60 per cent by 2050 under question.

What a domestic government has to do is protect its citizens from the consequences of climate change.

One of the areas of vulnerability raised acutely by the creation of England's new growth areas is the risk of flooding.

The Government doesn't say much about this in its latest survey of the climate change challenge, but what it does say is a significant pointer to dangers that lie ahead.

"Without action to reduce greenhouse gas emissions, global temperatures are expected to rise by between 1.4 and 5.8 deg".

"C by 2100 and sea level could also rise between 0.09 and 0.88 metres." At the top end of the range, that would be a rise of almost 900 mm over the next 100 years.

In the light of recent research by the London Climate Change Partnership, that doesn't give us long before sea level in the Thames Estuary reaches a height at which most of the Thames Gateway becomes subject to flooding risk.

Threat to sustainable communities.

This group, which includes the U.K.

Department of the Environment Defra, says that the rise in sea level could be as much as 860 mm by the 2080s, with extreme sea levels being experienced more frequently.

To put it mildly, a community living unprotected under that kind of threat would soon become unsustainable.

The situation in many of the growth areas is fraught as things stand.

The Association of British Insurers' report published early last year found that many of the 120,000 new homes to be located in the Thames Estuary floodplain are potentially vulnerable to a large-scale storm surge event.

It found that Ashford (Kent) and parts of the Milton Keynes and Stansted-Cambridge corridors are vulnerable to inland flooding risk, suggesting that the high housing densities in the growth areas could increase drainage flooding if the capacity of the existing drainage system is compromised.

This is an area of the infrastructure critically important to the success of sustainable communities and requires substantial expenditure.

This issue was raised in the recent report of the London Assembly's environmental committee.

Setting the framework of its inquiry, the committee said: "A substantial part of London is built on the floodplain of the Thames and its tributaries and is prevented from flooding by a complex system of flood defences".

"There are flood defence measures in place against two major kinds of flooding".

"Tidal flooding occurs when high tide and storm surges coincide and fluvial flooding occurs when rivers overflow due to high or intense rainfall".

But there is a third cause of flooding such as occurs in London when the drainage system cannot cope with the speed that cumulative rainfall hits it - surface water and sewerage flooding.

On this, the London Assembly report says that this type of flooding is becoming more common, due to increased frequency of rainstorms, increasing areas of hard surfaces due to the level of development in London, inadequate maintenance and inadequate capacity to deal with the increased run-off.

It is not difficult to foresee that the arrival of 120,000 new homes in the Thames Gateway would greatly increase the area of hard surface.

That increment of run-off could of course be accommodated provided that sufficient capacity was present in the drainage infrastructure.

On that front, things seem to be moving in their customary sluggish fashion.

For example, the environment committee has welcomed the research programme Thames Estuary 2100 commenced by the government's Environment Agency.

This is considering tidal defences in a wider context and seeking to reduce flooding risk by avoiding development in high risk areas".

"We trust", commented the committee, "that this project will have more success in creating the necessary response than have proposals from the Thames Tideway strategy".

"This strategy proposed construction of a major new tunnel and storage system to prevent untreated sewage from being discharged into rivers.

Unfortunately there has yet to be a decision by government on whether this tunnel will be built".

This of course demonstrates the need for improved funding of the infrastructure, and not only in the growth areas.

This too is an issue whose resolution is moving slowly.

But as the committee put it in the form of a recommendation, Defra and the Environment Agency should ensure that funding mechanisms are identified when options on flood protection are put forward next year [as it understood] for the Thames Estuary.

£12 billion flooding risk.

According to the Environment Agency's reply, the draft TE2100 plan will not be completed until 2008.

But its regional strategy manager based in Reading has promised that outputs from the project will be made available as they are completed prior to 2008.

Progress with this particular project, she says, is reported regularly to the Thames Regional Flood Defence Committee.

For its part, the London Assembly's environment committee has welcomed the approach of this project, but is concerned that the deadline for proposing options may slip - as it apparently has.

Its report observes, "1.25 million people are already at risk from flooding by the Thames and a major flood in the Thames Gateway could cost as much as £12 billion".

"According to the recent Association of British Insurers report, climate change could increase fluvial and coastal flood risk by a factor of eight to twelve times." This is the current situation in London as the level of the North Sea rises by millimetres every year according to the climate change experts.

The Environment Agency has assured the London Assembly that around 95 per cent of London's flood defences are in satisfactory condition, indeed the majority are in good condition and some are very good.

The agency did however correct an error copied by CIOB International in an earlier comment on the assembly's report, which occurred due to a statement in the ABI recommendations which implied that the condition of 65 per cent of the Thames Estuary defences was unknown.

This statement, said the agency, came from an incomplete database the ABI used for its report.

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