Will UK Floods Get Worse?
By Paul Homewood
DEFRA have just published their Climate Risk Assessment Report for the UK. It seems that the main environmental risk to the UK is increased flooding:-
But the main risk is that global warming will cause flooding that could cost up to £12 billion every year because of heavy rainfall in the winter and rising sea levels, affecting up to 3.6 million people by 2050.
As we all know, floods in recent years have been exacerbated by non-climatic factors, such as building on flood plains, loss of water meadows and the concreting over of many riverside areas. But is there any evidence that precipitation patterns have changed in the last few decades?
Not according to Met Office figures. Annual rainfall data for England shows virtually no trend over the last 100 years :-
http://www.metoffice.gov.uk/climate/uk/actualmonthly/
What about winter, which the report seems particularly worried about?
Again nothing much seems to be happening here.
Of course annual, or even seasonal, figures can hide peaks and troughs, or regional variations. Let’s then have a look at peak rainfall months at four sites, which give a good geographical sample across the country :-
London – South East
Shawbury – Midlands
Bradford – North
Aberporth – Wales and the West
The next graph shows the number of months in each decade since 1951 for each site where monthly rainfall exceeds 100mm :-
And again, for monthly rainfall over 150mm :-
http://www.metoffice.gov.uk/climate/uk/stationdata/
There is no sign that rainfall is becoming more extreme.
Whatever DEFRA’s computer models show, they do not seem to bear much resemblance with reality.
Comments are closed.
NOT A LOT OF PEOPLE KNOW THAT 
It’s high amounts in one day or so that cause floods. Warm air can hold more moisture which can come down at once.
Sometimes, with flash floods, but most floods result from a steady build up of water, with the ground becoming saturated.
USHCN provide much more detail than the Met Office do in this respect, and in the US it is easy to prove that there has been no increase in “extreme rain” days,
e.g. in Texas
The biggest problem with these sort of flash floods is when the weather front gets stuck in one place for a length of time, as happened at Boscombe a few years ago. This resulted in the worst floods in that part of the world since Lynmouth in 1952, which was caused by exactly the same phenomenon.
Rather than the annual rainfall the maximum rainfall for a 24 hour period would be a better indicator of floods. As we know it can bucket down in a mountainous area and the rivers and streams cope due to the slow run-off from forests and farmland. A town that has grown to cover the previous watershed with houses and factories will create a greater run-off over a small period of time, this being the biggest contributor increased stream flood levels.
Yes, I am working on some daily data and will post up today.