Summer 2007 floods: a very singular event

11 March 2008

A new scientific study of the wet summer of 2007 confirms that the floods were a very singular event and does not support the idea that the exceptional river flooding was linked to climate change. This conclusion is contained within a comprehensive hydrological appraisal of the summer 2007 floods carried out by scientists from the Centre for Ecology & Hydrology.

The new report, The summer 2007 floods in England & Wales - a hydrological appraisal, brings together both flood and meteorological data and systematically breaks down the series of events leading to extensive river flooding, which had no close modern parallel for the June-August period across the UK.

Lead author Terry Marsh comments, "The river floods of summer 2007 were a very singular episode, which does not form part of any clear historical trend or show consistency with currently favoured climate change scenarios."

Mr Marsh adds, "The exceptional river flooding last summer fuelled speculation that flood risk is increasing due to global warming. Due to the inherent variability of the UK climate, any extreme hydrological event cannot readily be linked directly to climate change."

The new report recognises that the 2007 flooding was remarkable in its extent and severity and truly outstanding for a summer event. River flows in many areas exceeded the design limits of many flood alleviation schemes. Rainfall amounts and intensities led to urban drainage systems being overwhelmed in a number of areas. This underlines the UK's continuing vulnerability to climatic extremes, but long-term rainfall and river flow records confirm the exceptional rarity of the hydrological conditions experienced in 2007.

The report complements a recent paper on flood trends in the UK, which was led by Jamie Hannaford at the Centre for Ecology & Hydrology and published in the International Journal of Climatology late in 2007. The paper found that trends over the last 30-40 years can be identified, but that there is little compelling evidence over the long term to suggest that flood magnitude is increasing.

Mr Marsh continues, "Extreme flooding in the UK is historically rare but vulnerability to flooding has increased markedly as a consequence of floodplain development. This is despite increased resilience to flood risk through improved flood alleviation strategies and more sophisticated flood warning capabilities."

The new study is an output from the National Hydrological Monitoring Programme (NHMP), operated jointly by the Centre for Ecology & Hydrology and the British Geological Survey.

Further information

Barnaby Smith
CEH Press Office
Mob: 07920 295 384

NERC Press Office
Natural Environment Research Council
Polaris House, North Star Avenue
Swindon, SN2 1EU
Tel: 01793 411561
Mob: 07917 557215

Notes

1. A copy of the report (11·6MB PDF file) is available on the Centre for Ecology & Hydrology website.

2. The analyses in the new report was carried out by independent scientists from the Centre for Ecology & Hydrology (CEH), the UK's centre of excellence for research in the land and freshwater environmental sciences. Funding was provided by the Natural Environment Research Council (NERC).

3. The new report is an output from the National Hydrological Monitoring Programme (NHMP), operated jointly by CEH and the British Geological Survey (BGS). The hydrometric data analysed in this report were provided primarily by the UK hydrometric measuring authorities (the Environment Agency, Scottish Environment Protection Agency and, in the Northern Ireland, the Rivers Agency); a substantial proportion of the meteorological data used was provided by the Met Office.

4. The NHMP was set up in 1988 to document hydrological and water resources variability across the UK. The measuring authorities, together with Defra and OFWAT, provide financial support to the NHMP for the production of monthly Hydrological Summaries for the UK. These are available via the Water Watch pages of the CEH website.

5. Short synopsis of the events surrounding the summer 2007 floods:
The May to July 2007 rainfall was the highest for England and Wales since 1766. The concentration of exceptional river runoff into several major basins caused extensive flooding. Parts of the lower Severn basin, Thames tributaries and rivers in Yorkshire and Humberside saw peak river flows exceeding previous record highs by wide margins. Total river outflows for England Wales during June and July was well over three times the long-term average and nearly twice the previous maximum (1968). In some of the worst affected areas flooding was more extreme than the benchmark event of March 1947. However, in marked contrast to 2007, the 1947 flood was caused by a rapid thaw following severe blizzards. An unusual, and very significant, feature of the summer flooding was the high proportion of damage not attributable to fluvial (river) flooding. Around two-thirds of the properties affected, more than 8,000 in Hull alone, were inundated by pluvial flooding (flash flooding) affecting urban areas.

6. The Centre for Ecology & Hydrology is the UK's Centre of Excellence for research in the land and freshwater environmental sciences. CEH is a wholly-owned research centre of the Natural Environment Research Council and employs around 500 staff at six major sites in England, Scotland and Wales with an overall budget of about £35m. CEH science covers three core areas of expertise, Biodiversity, Water and Biogeochemistry with a major cross-cutting activity focusing on Environmental Informatics. CEH tackles complex environmental challenges through integrated research, aiming to deliver practicable solutions to help preserve our environment for future generations.

7. The Natural Environment Research Council funds world-class science, in universities and its own research centres, that increases knowledge and understanding of the natural world. It is tackling major environmental issues such as climate change, biodiversity and natural hazards. NERC receives around £400m a year from the government's science budget, which is used to provide independent research and training in the environmental sciences.

Summer 2007 floods: a very singular event

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