Somerset Floods: A Reality Check
There is no evidence that winters are becoming wetter.
As the waters thankfully begin to recede on the Somerset Levels, it is time to take stock of the last three months.
After a drier than normal November, the rain began falling in earnest in the second week of December, and only began to abate in towards the end of February.
Met Office regional statistics for SW England & S Wales extend back to 1910, and according to these, the December to February period just ended recorded the highest precipitation on record, with 670.6mm. However, this does not tell the whole story, since other years have recorded higher 3-month totals, as Table 1 shows.
|Nov 1929 to Jan 1930||812.2|
|Oct 2000 to Dec 2000||700.8|
|Dec 2013 to Feb 2014||670.6|
Altogether, there have been six winters including this one, where precipitation has exceeded 600mm over a 3-month period. As well as the three above, there has also been 1959/60, 1960/61 and 1989/90. It could therefore be argued that what we have seen this year is a once every 15-20 year event.
While this year’s heavy rain was spread over three months, it should be borne in mind that in other years the unusually wet weather extended for four consecutive months.
The average monthly rate from October 1929 to January 1930 was 251mm, which was more than this winter’s three month average of 223mm.
|Oct 1929 to Jan 1930||1005.4|
|Oct 1960 to Jan 1961||778.2|
|Oct 2000 to Jan 2001||820.8|
|Nov 2013 to Feb 2014||777.8|
Long Term Trends
Finally, let’s have a look at the record since 1910, to see if there is any trend towards increasing rainfall during the heaviest rainfall months of September through February.
This year’s total ranks third behind 1929/30 and 2001/01, but the 10-Year trend has actually been falling during the last decade, and at 742mm is close to the mean of 733mm.