Analysis Of Winter Extreme Rainfall
By Paul Homewood
Is climate change making winter floods getting worse in England?
This is a question that is often posed. There are many reasons why river levels may be reaching higher levels than in the past, including the concreting over of upstream drainage areas and flood defences which often simply transfer the problem downstream.
But is rainfall now more extreme? There is no evidence of this in monthly or daily totals. But often the key factor in fluvial flooding is the accumulation of rain over a period of time, rather than one big storm.
The European Climate Assessment & Dataset (ECA&D) provides some good tools for analysing rainfall data, in particular the Highest 5-Day Rainfall total for each year.
I have used this to analyse rainfall during the winter-half year, October to March, for most of the long running stations in England.
https://www.ecad.eu/indicesextremes/customquerytimeseriesplots.php
Trends are either flat or even decreasing.
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NOT A LOT OF PEOPLE KNOW THAT 
Well done Paul for some good evidence. This evidence is the complete opposite of everything you hear on the BBC about rainfall. If the BBC says the weather is becoming wetter then you can bet it is getting drier.
From my time with the Environment agency due to EU directives the EA simply wouldn’t clear many watercourses, the water from surface drainage often went straight into rivers due to hard surfaces and first and foremost councils insisted on giving planning permission for expensive developments on flood plains. any mitigation then sent water into other peoples houses.
Why did the Somerset levels flood… EU directive to stop dredging, well, well surprised, of course not, but oh no its climate ch…..!!!
Agreed, in particular, the lack of proper maintenance of our rivers and watercourses (right down to simple roadside ditches) for more than half a century is a national scandal.
It goes without saying (I have a small river – which feeds the Avon – at the bottom of my garden) that the EA seem to have abandoned riverbank maintenance on the principle that they can justify it on the effects of CC. How sad that our civic infrastructure support systems have been usurped by the nonsense of those who would see this country fail.
It is a fact Harry that riparian landowners were paid by the EU to leave two meters of each bank untouched to facilitate the habitat and breeding of aquatic mammals and birds.
The real reason of course was to heap even more subsidies on the landowners and agribusinesses beloved by the House of Lords.
Landowners even profit from the widows mites that they invest in the National lottery – it took them less than ten years to inveigle themselves into the list of “good causes” that Major with barely concealed duplicity promulgated when he set it up and it continues to be a good little earner today.
Maintenance of waterways, building on flood planes, and paving over gardens about covers it.
Plains. Cutting down trees upstream doesn’t help, either.
Yes, and the BBC did not disappoint today.
Some time after 8.00 am a scientist was wheeled out on the Today programme and asked what steps could be taken to reduce the effect of flooding on the river Severn. Our learned friend preferred to go back of the cause of the flooding — many which we are already quite familiar – and not suggest any remedies .
Strange that such academics should be unwilling to address the question and the BBC be unable to repeat it in the hope of getting a relevant answer. The closing remarks relied on the usual arguments about habitat depletion and the effect of dredging on the hydromorphology — again a favourite defensive position of the Environment Agency.
Paul, timely research, thank you. My own research (with valuable comments from others) regarding what I believe to be inaccurate claims of increased rainfall and flooding in Wales can be found here:
The red lines may be misleading, it looks to me that there are no trends at all, with Southampton having a step down around 1960, which may be due to rain shadow from a new nearby building, or a relocation to a more sheltered position. There is no sign of a similar step down in the data from “nearby” Eastbourne.
I think the same. And some of the red lines don’t look quite right – dipping when they ought to rise.
These are just averages of highly variable data I’m not sure a similar graph of dice throws wouldn’t show such “trends”?
Here is HadUKP data for South-West England, highest 5-day rain totals in each winter (DJF), no sign of any trend:
A number of commentators here query why new developments are allowed on flood plains.
The purpose of the National Planning Process is to allow development on floodplains, not stop or control development on floodplains.
The process is based on the “Flood Map for Planning” Zones 3 and 2 which is a rather outdated static data set, and is prone to error due to the limited resolution of when the aerial surveys were completed. For most of the country’s flood zones there are no gauging stations, no measurements, no historical flood outlines, no comparison of model flood extents to actual etc etc. All that is required of a developer is he completes a “flood risk assessment” and as long as it says “flood risk assessment” on the front it will be accepted by the planning authority. The EA rarely get involved in the detail of each development and just take a strategic overview, local councils have little or no expert resources and national government instruct planning authorities not to impose onerous conditions. I have yet to read a “flood risk assessment” that says “don’t build here!”
Most “main rivers” have more accurate flood modelling and there will be some gauging, measurements and historic flood extents and the EA may choose to get involved. But again government have instructed the EA and local councils that they must not impose onerous conditions or expect detailed evidence based flood modelling.
And at the end of the day, if it all goes tits up they can blame it all on CC – and happily retire on their pensions.
Yep
Building on flood plains.
https://www.msn.com/en-gb/news/uknews/dismay-as-floods-hit-fields-where-dozens-of-new-homes-will-be-controversially-built/ar-AAUacdH?ocid=msedgdhp&pc=U531
And they generally just wall off a former flood plain and push the water elsewhere. This leads to flooding that has never happened before.
It’s not known as “February Fill Dyke” for nothing.
A report from the Institute of hydrology and ecology completely destroys the myth of increase flooding on the Thames:
https://iwaponline.com/hr/article/43/3/203/31252/The-Thames-flood-series-a-lack-of-trend-in-flood
As the worst floods in the Thame’s history were due to snow melt, milder winters have made serious flooding less likely.
‘Is climate change making..?’ such and such happen more often is a nonsense question. The weather has to change before it can be called a climate change.
The alarmists have the idea that warmer air can hold more moisture, so there must be more rainfall and by extension more floods, and/or worse floods. But of course it’s never that simple. Location, river management and other factors play a part.
Imagine buying a property in somewhere called Fishlake…Surely no-one could possibly be that stupid!
https://www.dailymail.co.uk/news/article-7671871/RAF-Chinook-helicopter-works-night-shore-defences-flood-hit-Yorkshire.html
Great analysis Paul. To support your findings showing no increase in 5-day rainfall statistics, the National Research of Canada recently published a guideline on flood control cost benefit analysis that showed no increase in extreme short duration rainfall intensities across Canada – this is a summary: https://www.cityfloodmap.com/2022/02/nrc-national-guidelines-on-flood.html
Could you please show me the details of the steps you took to produce these graphs so I can do the same for Scotland?
Go to this link:
https://www.ecad.eu/indicesextremes/customquerytimeseriesplots.php
Choose UK
Station – Your Choice
Category – rain
Index – RX5-Higest 5-day rain
Season – Your choice
Many thanks, Duncan
Had the misfortune of catching BBC news last night (too tired to turn it off or over) and saw the unchallenged claim being made by both the narrator and a hard-hat wearing Environment agency woman that the recent 3 floods of Bewdley were due to climate change. Nothing to do with the completely normal rain levels nor with her incompetence in maintaining anti-flood measures (dredging and anti-run-off measures upstream).
The greens often use flooding as a climate indicator. It is not, for the reasons PH states in the article – it is as much an indicator of development as anything else. Only on a pristine, continuous river/flood plain would it be meaningful.
As Paul points out, the only climate linked index would be rainfall – by various measures which could include short term rates, or sustained rainfall over a period of time. This would then be a measure of the volume water input to an area over a given time.
But flooding by itself can be made worse or better irrespective of what a changing climate might or might not do. Flooding should always be called out as a nonsense metric, it should always be pointed out that only rainfall can actually change with climate.
Flooding usually occurs because water that has already fallen cannot get away from where it has fallen, at least on the roads…
Or it gets away too quickly from somewhere else and overwhelms downstream storage capacity and/or drainage.
Similar from Wokingham Weather Station
Click to access sum21.pdf
The problem you have is that you only have the facts.
In general people do not respond well to the facts unless the waves are lapping at their own doors. And then we can see them howling. But that time is not today.
Would you be willing to accept the possibility, not to agree with, just to accept the possibility you are taking the wrong approach on this very important thing? More than that, the possibility you are persisting in taking a wrong approach when you know it’s a perpetual failure?
And that a better approach might be available and ready to role, once you have accepted this extraordinarily difficult psychological fact, the hardest kind of all?
If you can do that, I’d say that is science working as it should. letting it lead you wherever it may go, notwithstanding the consequences.
From the US news:
“During an interview with the BBC released on Wednesday prior to Russia’s attack on Ukraine, Special Presidential Envoy for Climate John Kerry expressed concern that a war in Ukraine would have “massive emissions consequences” and divert attention from climate change and stated, “I hope President Putin will help us to stay on track with respect to what we need to do for the climate.”
You really couldn’t make It up!!!