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Britain's floods

27 July 2007

Why is Britain suffering from severe floods this summer? Will climate change bring more frequent and intense storms in the future?

The Natural Environment Research Council is funding scientists in universities and its own research centres, who are currently carrying out research to provide answers to these questions. The research data they produce helps to underpin many of the flood forecasts and defence mechanisms provided by organisations such as the Environment Agency.

This briefing note is to provide information about some of the work that NERC scientists are carrying out in response to these extreme events and provide some contact points for more information. Scientists who have provided information included here will be available to give interviews.

Centre for Ecology & Hydrology (CEH)

CEH carries out research aimed at improving understanding both of the environment as we see it today and the natural processes that underlie the Earth's support systems - for example climate & water resources. Its researchers are particularly interested in the impacts of human activity on natural environments. CEH compiles the monthly Hydrological Summary for the UK and has produced the Flood Estimation Handbook, which provides a way to estimate flood frequency.

CEH has carried out a preliminary assessment of the reasons behind the exceptional flooding we are currently experiencing.

Photograph: Flooding in Oxford

It appears there has been a combination of contributory factors – the jet stream (which influences the paths taken by weather systems in the North Atlantic) has followed a route further south than usual, and the high-pressure cell coming from the Azores (which brings settled weather conditions across Europe in the summer) has bypassed Britain. In addition, a sustained sequence of low-pressure systems over the past 12 weeks has produced exceptionally high rainfall levels. So while Britain suffers grey skies and prolonged flooding most of Europe basks in sunshine and high temperatures, which bring their own problems.

Professor Alan Jenkins, Director of the CEH Water Science Programme, said, "The combined May and June rainfall total is the highest on record for the UK, by a considerable margin. Flood risk during the summer is usually diminished because the ground is dry. This year, because of the record rainfall in the late spring and early summer, accompanied by widespread flooding in June, the soils were so wet they couldn't cope with the heavy rain in July. Added to that, the intense rainfall overwhelmed many urban drainage systems, causing localised flash floods."

An indication of the rarity of the hydrological conditions experienced this summer is provided by the recent increases in groundwater levels in some parts of eastern and southern England. Usually groundwater levels decline between May and September because there is less rainfall to replenish them. But this year groundwater levels in the Cotswolds rose rapidly and by 24 July stood above normal winter levels.

Professor Jenkins said, "The July 2007 flooding is clearly an extreme event and, as such, difficult to link it with any trends in observational records or predictions associated with favoured climate scenarios. It does serve to underline our vulnerability to very exceptional summer rainfall and the, as yet poorly understood, changes in the position of the jet stream."

The full analysis is available on the CEH website.

CEH is leading a major consortium proposal to study the past and future global water cycle under a number of climate change scenarios. The WATCH Integrated Project is to be funded under the "Global Change and Ecosystems" sub-priority of the European Commission's 6th Framework Programme and will run for four years. The WATCH initiative brings together 25 partner institutes across Europe, with an EU contribution of €10m.

For further information, please contact:

Barnaby Smith
CEH Press Officer
Mob: 07920 295384

The meteorological context of the UK flooding in June and July 2007

There is also a useful briefing on the meteorological context of the UK flooding in June and July 2007, from scientists at the Walker Institute, University of Reading. NERC funding is also involved in this work.

British Geological Survey (BGS)

BGS carries out a wide range of environmental research, including flooding and the impacts of climate change. BGS provides information to the government, industry and private individuals to help them make decisions related to environmental hazards. Two sets of information are especially relevant to flooding: 'Geological indicators of flooding' and 'Groundwater flooding'.

A low resolution version of the Geological indicators of flooding data-set is now available through the BGS GeoIndex free of charge.

As part of the NERC response to the flooding, BGS has photographed flooded areas from the air and comparing the images with their new Geological Indicators of Flooding Map. The flight took place just a few weeks after making a similar flight over South and East Yorkshire and North Nottinghamshire, Dr John Carney and scientific photographer Paul Witney once again took to the air in a light aeroplane. Flying at a low altitude of 600m (2000ft) they observed and recorded flooding in the worst-affected areas around Oxford, Gloucester and Tewkesbury.

Photograph/image: Comparing aerial photographs with images taken from the new Geological Indicators of Flooding Map.

Dr Carney and Marieta Garcia-Bajo of the Geological Indicators of Flooding Team have been busy comparing photographs and video footage of the flight with the Geological Indicators of Flooding Map.

The map shows where floods have occurred in the past few thousand years. The map will be a useful guide to where future floods are likely to occur.

Marieta Garcia-Bajo from the Geological Indicators of Flooding Team, BGS said "This summer, flooding has affected a great many people. Collecting information when rivers flood means that we can improve our understanding of ancient floods, shown on geological maps, and help homeowners and planners to manage floods in the future."

"The BGS Geological Flood Indicator data shows many areas that have been flooded in the past. The floods happening today tend to follow the same routes as ancient flows, and these are often shown on geological survey maps."

Dr John Carney, Principal Geologist, BGS said "From the air, I was able to see just how extensive and dramatic the flooding has been around Oxford, Tewkesbury and Gloucester. Our flood maps show that vital installations such as the Mythe water treatment plant could be placed at risk by such extreme events. This modern flood matched long-gone rivers and channels shown on our geological maps."

Dr Andy Gibson, Leader Shallow Geohazards Research, BGS said "Although events like these are very rare, they affect many people, and it is important that we learn from them. Collecting information at the time of the disaster helps us understand how people are affected by geology and how to best manage geohazards in the future."

For more information about the Geological Indicators of Flooding Project please contact Marieta Garcia-Bajo.

For more information about the floods and the BGS flight to assess damage please contact John Carney.

For more information on Shallow Geohazards research or geohazard response at the BGS please contact Andy Gibson.

The BGS flight on 25 July 2007 captured over 250 images and 45 minutes of video coverage of the floods in the areas of Oxford, Gloucester and Tewkesbury. BGS captured similar photography and video footage of flooded areas of Yorkshire, Humberside and Nottinghamshire on 26 June 2007.

For more information, interview requests or to obtain images please contact:

Ellie Steadman
Communications Unit
BGS Keyworth
Nottingham
Tel: 0115 936 3164
Fax: 0115 936 3250
Mob: 07971 714 258

BGS is also carrying out a project on groundwater flooding in Oxford. The project examines factors controlling the occurrence of groundwater flooding in the Oxford valley, as well as assessing the role that groundwater conditions play in flooding direct from rivers. It is linked with the Environment Agency's ongoing Oxford Flood Risk Management Study. The understanding gained from the BGS project will help the Environment Agency plan flood mitigation works.

Proudman Oceanographic Laboratory (POL)

POL in Liverpool is home to several research and monitoring programmes concerned with sea level rise and coastal flooding. One of its major programmes involves continuous monitoring to provide a global data bank of sea and land level changes around Britain's coastline.

POL scientists support the Met Office in their day-to-day operation of the Storm Tide Forecasting Service (STFS) in collaboration with the Environment Agency. The STFS provides the 48-hour warnings that the Environment Agency use to make decisions on when to raise flood defences, such as the Thames Barrier that protects London from major tidal surges.

POL is collaborating with the Met Office Hadley Centre in a project that forms part of the Environment Agency's Thames Estuary 2100 programme. Using computer models the project will address the issue of how to protect the Thames from flooding this century by indicating whether or not extreme water levels will change in the future.

Dr Kevin Horsburgh said, "The Thames Estuary 2100 programme will provide a decision framework for flood defence strategy in the region over the next 100 years. There are obviously many engineering options, and our long term records of sea and land levels are critical to those decisions."

For more information please contact:

Dr Kevin Horsburgh or Professor Philip Woodworth at POL
Tel: 0151 795 4800

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

NERC's Flood Risk from Extreme Events (FREE) programme

The FREE programme aims to improve estimation, prediction and uncertainty of flood risk from extreme events through considering the meteorological, hydrological and coastal oceanographic processes involved.

The British Geological Survey, the Centre for Ecology & Hydrology and the Proudman Oceanographic Laboratory, as well as a number of university-based researchers, have all received funding through the FREE programme.

For example, FREE is addressing the initialisation of Numerical Weather Predictor forecast models by assimilating new types of weather radar data. This will provide probabilistic rainfall forecasts, which can be inserted into a hydrological model to provide probabilistic river flow forecasts. (Prof A J Illingworth, Reading University with CEH partners )

More information can be found on the FREE website or you can contact:

Professor Chris Collier
FREE Science Coordinator
Tel: 0161 295 5465

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

NERC is also provided funding through the FREE programme for a second light aircraft to gather and record data on two of southern England's flooded regions. Flying just below the cloud base at about 2000 ft, researchers surveyed the Severn floodplain and the Avon floodplain. The results of their mission are currently being assessed.

This briefing note is just a flavour of the many programmes and projects that NERC scientists are involved in. Climate change and the forecasting and mitigation of natural hazards are two of the priorities that NERC has identified for its new strategy 'Next generation science for planet Earth', due to be launched in the autumn. To meet the challenges we face today, NERC will fund more research to improve predictions of extreme hydro-meteorological events and their impacts, and enable better predictions of flooding in urban areas to assess the risk posed to people and buildings.

Briefing note: 14/07

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