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Murky waters ahead

Flooding - Planning policy is changing in response to climate change, but there is confusion about how it should be implemented, reports Bernadette Redfern.

Engineers are in the front line when it comes to managing the effects of climate change. It is they who could design and build defences that would preserve the UK's landmass and protect properties in every flood plain against hurricane Katrina type events.

But government has decided that this is not the way that the UK will evolve, a philosophy clearly illustrated by the recent cuts to flood defence budgets (NCE 7 December 2006).

Although some defences are still being constructed, like those at Cleveleys on the north west coast (see feature page 20), the government's general strategy is to head off the need to defend by better managing risk.

And the main tool in adopting this approach is Planning Policy Statement PPS25 which sets out where local authorities can and cannot allow new development.

'The new PPS25 maintains the sequential risk based approach of the previous Planning Policy Guidance PPG25.

It claries the sequential test that matches types of development to degrees of flood risk and strengthens the requirement to include flood risk assessments at all levels of the planning process, ' says the statement's publisher the Department for Communities & Local Government (DCLG).

But what does it actually mean in practice? 'PPS25 introduces the exception test, ' explains Faber Maunsell technical director Clive Mason.

'If a site meets four key criteria, it may still go ahead even if it is in an area of high flood risk. It has to fit into the sustainable communities agenda, be well protected, add to the overall ood risk management of the area and preferably be on browneld land, ' he says.

Arguably that takes care of the Thames Gateway.

'Vulnerability' is another criterion, explains Atkins flood management consultant Toni Lloyd. 'Annex D of the policy explains the different classes of vulnerability. The new guidance is clear. Local authorities must sequentially allocate development to the lowest risk areas first, with most vulnerable developments (homes for the elderly for example) being built in the lowest risk areas.' All of which means that many local authorities must now carry out strategic flood risk assessments (SFRAs). 'SRFAs were not mandatory under PPG25 but they are pretty close to it in PPS25, ' explains Faber Maunsell senior engineer Barry Barton.

With SFRAs, local authorities will have to make their own best flood risk predictions using current data and climate change estimates for the future.

'What is more the assesments have to be kept up to date.

In some areas like Boston in Lincolnshire, another SFRA was needed as techniques have improved.

'Breach analysis has to be done using 2D not 1D hydraulic modelling [as was used in the previous SFRA]. There are also plans to build a tidal barrier at Boston Haven so the impact of that needs to be included.' The basic principles of the policy seem sound, but uncertainty still surrounds actual implementation. Key to application of PPS25 is a practical guide that has still not been issued despite the policy having already been incorporated into the planning system.

DCLG says it will be issued 'very shortly' as a 'living draft', meaning it can be used immediately but can be revised in six months. In the meantime, engineers are left grappling with a policy that fails to tell them how, or for how long, developments facing some flood risk should be defended.

There are also fears that, unless the guide is extremely prescriptive, approval of projects and the ood management techniques incorporated in them will be highly variable.

'It will provide guidance on how to manage residual risks. However, it can't be prescriptive about the ood defence measures to be used, as different measures will be appropriate for different situations. What it will do is set a framework to help planners and developers make the right decisions about what is appropriate in each individual case, ' says DCLG.

But engineers are worried that this does not go far enough.

'Asking for a one in 100 year protection against a fluvial event is in the policy but nowhere does it say what that should be. Some forward thinking developers will come up with a property that can withstand a one in 1,000 year event, but I am worried that the person reviewing the development for the Agency would ignore that and insist on a metre high ood defence wall, ' says one ooding expert.

The Environment Agency is condent that the practical guidance will include standing statements on what it will and won't object to ensure consistency. The Agency now has the power to oppose any development deemed too risky as it is now a statutory consultee for all projects in flood plains.

'The key change is that PPS25 puts flood risk at the strategic level and in the long term it should reduce our case work, ' says Agency head of planning Mark Southgate.

'There is a lot of development we don't want to see. We will have some standard responses for standing advice so it is clear: this is what we do want to see, this is what we don't, ' he says.

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