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Beating the British Floods

10 October 2008




After a 2007 of flooding, death and damage, Gareth Evans looks at the latest recommendations to beating the summer washouts.


Last summer’s devastating floods exacted a heavy price on people and property, claiming 13 lives, flooding 55,000 houses and driving thousands from their homes. They also forced about 7,000 to be rescued and left some £3bn-worth of damage in their wake.

A year on, thousands have yet to return home.

After an in-depth independent investigation into the events of 2007 when Britain experienced the wettest ever May-to-July period since records began, Sir Michael Pitt concluded that the country was ill prepared for the scale of the damage and disruption that ensued.

His review also revealed a series of systemic problems, including a lack of clarity in inter-agency responsibility and inadequate safeguards for key sites and critical infrastructure – 150,000 homes lost their potable supply when flood waters inundated Tewksbury’s Mythe works.

Clearly the lessons of 2007 need to be learnt, particularly because evidence shows that Britain’s weather and rainfall patterns are shifting, making the likelihood of flooding – and, paradoxically, drought – much greater. According to the Department for Environment Food and Rural Affair (DEFRA)’s Future Water report, published in February 2008, 25% wetter winters, 40% drier summers and an increase in both the intensity and incidence of high temperatures and heavy rains await the UK by mid-century.

As Dan McCarthy, president and CEO of Black & Veatch’s global water business, says: "This is a challenge that no single agency – the water companies included – can be reasonably expected to meet in isolation."

While the inevitable political, practical and commercial elements that must feature in the overall response will, of necessity, take their time to implement fully, there may be the opportunity for fast-developing technologies to make a more immediate difference.

Making drainage sustainable

The perennial problem of inadequate drainage is an area that the Pitt review highlighted and the growing sector of Sustainable Urban Drainage Systems (SUDS) has the potential to address it. Alongside the often discussed problems of developments on flood plains, the widespread use of impermeable surface materials – shortly to come under stricter control – predisposes many areas to flood.

With adequately designed SUDS in place, surface run-off can be reduced, off-flow velocity lessened and the flow itself diverted to beneficial use, mitigating the immediate onsite effect and reducing the demands made of drainage and discharge systems. In addition, SUDS technology can also be used to help improve water quality – an obvious win-win for developers and regulators.

However, the issue is not entirely problem free and, particularly in England, anecdotal evidence suggests that the approach is not always well understood by local planning departments. Moreover, in 2005 a survey of insurance companies revealed concern over "haphazard" implementation – with a significant number of the respondents indicating that risks in areas served by poorly designed drainage schemes could well be declined.

In some respects, insurers may become the unexpected drivers of change. The EU Solvency II reform – widely tipped to set new global insurance standards – forces insurers to reduce their exposure in flood-prone areas.

Accordingly, as insurance companies increasingly make use of high-resolution geological information such as Permanent Scatterer Synthetic Aperture Radar Interferometry data from the likes of the Envisat and Radarsat satellites, their perception of risk will undoubtedly alter.

Mapping flood risk

Good geophysical data-sets are likely to form the keystone in any serious attempt at pre-emptive strategies to deal with future floods. The Pitt review called for the production of electronic maps detailing all the rivers, ditches, drains and other significant features around areas prone to flooding and in July 2008, the EA unveiled its third set of flood maps.

What sets these apart from their 2000 and 2004 antecedents is the level of detail they contain – made possible by sophisticated new three-dimensional laser-mapping tools, which accurately depict previously overlooked landscape features with excellent resolution.

Flood modelling has taken giant leaps forward in recent years, now enabling flow propagation over the complex urban landscape in particular to be simulated with a far higher degree of relevance and reliability than ever before. Conventional approaches have given way to the development of comprehensive, depth-averaged models, while computational advances have opened up the option of entire system simulation in real time.

In the past decade, the science of water modelling has advanced to a stage where its multi-user/multi-functionality allows the dream of fully integrated models to start to become reality. As a result, refining the all-in-one model is today’s cutting-edge modelling trend.

This offers the promise of full across-the-network applicability, and second-generation modelling is expected to combine multiple networks and encompass the assets and infrastructure of all relevant stakeholders and key players.

Pulling together

The development of these new technologies makes ever more comprehensive and detailed data available – and at increasingly exacting standards of resolution, which allows for better prediction, prevention and mitigation of flood events. The more detailed the available information, the more directed the strategic planning can be and the more tailored and effective the response.

In this respect, the rise of real-time simulation is particularly important, since it holds the promise of rapid stakeholder access to an unprecedented level of dynamic system modelling.

"Insurers may become the unexpected drivers of change."

The main message that emerges from the Pitt report is the need for enhanced integration and co-operation. Achieving this means that some practical hurdles must be overcome, not least how the technical capacity within local authorities can be augmented. There also needs to be clarification of the roles and responsibilities of various stakeholders, and greater information sharing between them.

Enhanced data acquisition and modelling technology alone will not provide all the answers. However, it may well hold the key when it comes to empowering water companies, local government, statutory agencies and others to make more informed decisions about a range of flood-risk and flood-prevention matters.

As a result, it seems likely that such innovations will play an increasingly critical role in meeting – and beating – the flooding challenges that lie ahead.

Flood defences at the bottom of Clementhorpe, York, UK.
A composite interferogram created using pairs of images taken by Synthetic Aperture Radar (SAR). Similar technology could hold the key to increasingly accurate flood-risk assessment.
ITV News reporting from a flooded pub car park in Upton-upon-Severn.
A reminder of events three summers earlier, when the Cornish town of Boscastle was devastated by sudden flooding.
CAAD image of part of a proposed new development: advances in computer modelling of complex urban landscape elements will play their part in meeting future flood challenges.