Truly exceptional weather conditions have been experienced across some areas of the UK during the last week leading to severe flooding in Cumbria and several other parts of England, Wales and Scotland.
The Environment Agency has stated that rainfall in Cumbria reached record levels with one site, Seawaite Farm, recording a provisional total of 314.4mm (12.3 inches) in 24 hours, a UK record for 24-hour rainfall.
CEH staff have prepared a briefing note on the recent flooding, placing the provisional data into a historical context.
Jamie Hannaford from the Centre for Ecology & Hydrology said the flooding reflected a combination of circumstances which had led to elevated flood risk.
"Whilst October rainfall was below average in most of the affected areas, there has recently been some very wet weather in the north and west of the UK. River catchments were therefore already saturated, and levels in many rivers were already high." he explained.
"A persistent sub-tropical south westerly airstream has occurred, over oceans which are still very warm, meaning the air mass has been holding exceptional amounts of moisture. As this air has encountered mountainous areas in the west of the British Isles, orographic enhancement has occurred (ie the air has risen and become even wetter). This combination of factors has led to the exceptional rainfall totals which have been observed in recent days.”
Hannaford said the flood-affected areas were some of the wettest parts of the British Isles, and had seen some notable rainfall totals in the past. However, the recent rainfall in the north-west had eclipsed previous records by some margin, provisionally establishing a new 24-hour rainfall total for the UK.
He added, "The extreme rainfalls are broadly consistent with recent observations that suggest the north and west of the UK have become wetter and have experienced higher daily rainfalls and more protracted high river flows in the recent past. However, long-term river flow records indicate there is little compelling evidence for any trend towards increased flooding in the UK."
Chris Huntingford, a climate modeller with the Centre for Ecology & Hydrology, said, "It is certainly not possible to link any specific extreme rainfall event with climate change. However, researchers are getting very near to assessing whether the overall chances of major storms occurring are changing due to higher levels of carbon dioxide in the atmosphere."
"There is evidence that, for some parts of the world, storm patterns and frequency may change," he said.
The Centre for Ecology & Hydrology jointly operates the National Hydrological Monitoring Programme in conjunction with with the British Geological Survey. NHMP scientists produce the UK Monthly Hydrological Summary which assesses rainfall, river flows, groundwater and reservoir levels. They also operate the National River Flow archive. The NHMP also has a remit to analyse major flood and drought events in the UK and analyse long term trends in UK hydrological data.
Media enquiries on the current flooding situation should be directed to the CEH Press Officer, Barnaby Smith (mobile 07920 295384).
Our scientists can provide explanation and analysis of historic flooding patterns, possible future scenarios under climate change and scientific understanding of the current flooding situation. We are not able to comment on immediate operational issues.
The UK Monthly Hydrological Summary is a water resource assessment produced by the National Hydrological Monitoring Programme operated jointly by the Centre for Ecology & Hydrology and the British Geological Survey. The National Hydrological Monitoring Programme was set up in 1988: the programme relies on the active co-operation of measuring authorities throughout the UK
Related CEH links and news stories
Latest monthly hydrological summary for the UK - October 2009 [PDF] [NEED NEW INTERNAL LINK]
National River Flow Archive [NEED NEW INTERNAL LINK]
National Hydrological Monitoring Programme [NEED NEW INTERNAL LINK]
Recent scientific paper by Hannaford and Marsh: High-flow and flood trends in a network of undisturbed catchments in the UK (subscription required)
Summer 2007 Floods: A Very Singular Event - 11 March 2008
Understanding Floods - CEH Information Leaflet (PDF) [NEED NEW INTERNAL LINK]