The Met Office and the Centre for Ecology & Hydrology recently published a report on the recent storms and floods in the UK.
The report documents the record-breaking weather and flooding, considers the potential drivers and discusses whether climate change contributed to the severity of the weather and its impacts.
CEH’s input to the report relates to the major flooding that has been experienced in many areas of the country over the last eight weeks.
Key messages on flooding in the report include:
With catchments across most of the UK saturated by mid-December, the full gamut of flood manifestations – tidal, pluvial (flash), fluvial and groundwater – has been experienced over the ensuing seven to eight weeks.
Estimated outflows (total river flows) from Great Britain remained close to the highest ever recorded during late December and, subsequently, throughout most of January across large parts of England and Wales.
The cluster of drought and flood events through the early years of the 21st century and the recent runoff and recharge patterns, are near to the extreme range of historical variability, and therefore also raise the question that they may reflect anthropogenic climate change. It is important to note, however, that differing flood types may be expected to respond differently to increasing temperatures. Tidal flood risk is increasing as sea levels rise but the outlook is more complex in relation to fluvial flooding.
As yet, there is no definitive answer on the possible contribution of climate change in the recent storminess, rainfall amounts and the consequent flooding. This is in part due to the highly variable nature of UK weather and climate.
The floodplain inundations have caused major disruption to transport, agriculture and restricted sporting and recreational activities, and resulted in severe difficulties for some low-lying hamlets (most notably in the Somerset Levels). However, given the overall volume of runoff, the amount of property flooding at the national scale to date, has been relatively modest; a tribute to the general effectiveness of flood defences.
The report also has some detailed analysis for the River Thames:
During the last two months, In a series from 1883, flow rates on the River Thames have remained exceptionally high for longer than in any previous flood episode. Correspondingly, floodplain inundations on the Thames and in many other areas have been extensive and protracted.
A preliminary analysis suggest that outflows (total river flows) for the River Thames at Kingston aggregated over six weeks were the greatest since the 1947 floods. The 1947 event was the most extensive in England & Wales during the 20th century.
Generally, however, the peak flows registered during the recent flooding were not extreme. On the River Thames the highest flow in 2014 (up to end January 2014) has been exceeded during 14 earlier floods (most prior to 1950).