Bishop Hill On the floods in Cumbria
Dec 7, 2015 Climate: Statistics Climate: WG2 Environment Agency ;)
The floods in Cumbria are obviously attracting a lot of attention this morning. A couple of things are exercising my mind.
Firstly, as readers are pointing out, the claim that 340mm of rain fell in 24 hours seems suspect. Nobody seems quite sure where it came from. I have seen it suggested that this was the amount that fell over two days and in Unthreaded, Mike Post wonders if it is actually the November rainfall total.
Secondly, how do we know what the 100-year flood is in any given river basin? The process looks less than straightforward and involves a wealth of assumptions.
The first assumption is often but not always valid and should be tested on a case by case basis. The second assumption is often valid if the extreme events are observed under similar climate conditions. For example, if the extreme events on record all come from late summer thunder storms (as is the case in the southwest U.S.), or from snow pack melting (as is the case in north-central U.S.), then this assumption should be valid. If, however, there are some extreme events taken from thunder storms, others from snow pack melting, and others from hurricanes, then this assumption is most likely not valid. The third assumption is only a problem when trying to forecast a low, but maximum flow event (for example, an event smaller than a 2-year flood). Since this is not typically a goal in extreme analysis, or in civil engineering design, then the situation rarely presents itself. The final assumption about stationarity is difficult to test from data for a single site because of the large uncertainties in even the longest flood records[3] (see next section). More broadly, substantial evidence of climate change strongly suggests that the probability distribution is also changing[7] and that managing flood risks in the future will become even more difficult.[8] The simplest implication of this is that not all of the historical data are, or can be, considered valid as input into the extreme event analysis.
Lots to dig into.
Bishop Hill
On Twitter, Derek Sorensen tracks it down to Honister.
Reader Comments (73)
Do we know how this flood compared to that of 1898 as shown here
http://www.waymarking.com/waymarks/WM3G68_Historic_Flood_Levels_Kendal_Cumbria_UK
Interesting book here, Bish, "An Account of the Great Floods in the Rivers Tyne, Tees, Wear, Eden, &c. in 1771 and 1815" https://books.google.co.uk/books?id=gjguAAAAMAAJ&dq
Shukman: “Scientists always shy away from blaming any particular weather event on climate change. But they also point to a basic physical property of the atmosphere: that warmer air can hold more moisture”.
True, but extreme weather events, including rainfall, are caused by the TEMPERATURE DIFFERENCE between two mixing air masses. Under global warming (if there is any at the moment) the temperature of each of those air masses increases by the same degree. Therefore, the temperature difference is unaffected. Shukman’s moisture stays aloft.
340mm rainfall is the 'wet equivalence' of 36.7 degrees C measured at Heathrow this year. Irrelevant and misleading. But the damage has been done - metaphorically - and the figures 'stand' as testament to worsening climate.
As far as Harrabin et al at the BBC are concerned, this flooding is excellent news, coinciding with the Paris party, as it has otherwise been overshadowed by more newsworthy events.
It is really fortunate that hospitals had reliable diesel generators to rely on for emergency power.
Clearly, in this case, over a short time period, water ran onto the land quicker than it ran off. So it needs help in running off in the future. How about helping it, by building dam big ditches. The land contour maps will show the obvious routes. Be a huge investment in the future The major problem will be nimbyists, and claims about damage to the countryside and threats to snails or something. But what a wonderful investment in the future!
GC: "It is really fortunate that hospitals had reliable diesel generators to rely on"
Except that they are not that reliable. As I commented on unthreaded yesterday, the hospitals in the area that are on backup power are unable to conduct MRI or CT scans because their generators are "unable to support this equipment". This means that anyone needing a scan, including acute trauma cases needs to be moved to another acute case facility outside the area PDQ. You cannot run these scanners on backup generators.
Don't forget what 17 senior IPCC scientists said in a major paper last year:
"Blaming climate change for flood losses makes flood losses a global issue that appears to be out of the control of regional or national institutions. The scientific community needs to emphasize that the problem of flood losses is mostly about what we do on or to the landscape and that will be the case for decades to come."
http://www.tandfonline.com/doi/full/10.1080/02626667.2013.857411
"Now the Met Office told me today that it's very difficult to connect a single flooding event like this one in Cumbria to climate change, but, from what they know about the atmosphere and their detailed models of weather systems that there should be an extremely strong link. Now for the rest of us that means we should assume there is a link between these events and climate change, and therefore we have to plan accordingly"
Alok Jha- ITN Science Correspondent (ITV 6.30 News) Formerly of The Guardian. Note how he reports caution from the 'experts' to assumption 'from the rest of us' in one easy sound bite. Frightening, and an utter disgrace.
Mind you, last week he actually uttered the cultist mantra "the science is settled" during another climate change report.
Harrabin will want to sign him up pronto.
Salopian.
Further to that, I have lived in more than one or two towns in Britain and visited a few score others over the years. My being interested in the local architecture and siting of old towns etc. It would seem to me and this is a purely personal observation [ie anecdotal] these old towns and buildings seem not to suffer too much damage because, mostly our far more canny [maybe] forebears knew how to judge where and how extreme stream flow heights could be assessed and then promptly built their houses and churches above the nicks of the highest known flood events - I mean you would, wouldn't you?
I'd also like to know, since 05 and 09 - if the EA had allowed, ordered dredging [particularly of the Eden*] of the lower reaches of the river systems of the bigger rivers running off towards the coast and if not, then why not? Plus, some of the older bridges - spanning the larger river courses. needed to be replaced/re-engineered .....did it happen?
Does anyone know or, what did they spend the £48 mil' on?
* and a tidal river, which at peak times hardly helps matters.
@ SuffolkBoy Dec 7, 2015 at 4:45 PM
"The Cumbrians are extremely used to having bridges swept away and needing to rebuild them."
Not really. Braithwaite Bridge, which as you point out was rebuilt in 2010, was built in the 19th Century and lost in the 2009 floods. Navvies Bridge in Workington (and on which we used to clamber outside the footway as kids for a dare) was built in 1878, also lost in 2009. Northside Bridge, where Bill Barker died, was built in 1904. Pooley Bridge, lost this weekend, was built in the 1700s. These are structures which had stood for a century or more; we're not "used to bridges being swept away" at all.
There is an implication floating around that, since Pooley Bridge was built in 1764, the 2015 peak flow on the River Eamont was the largest for at least 250 years. That is not necessarily the case. Most bridge failures during flood events are caused by scour of the foundations. It is apparent from photographs of the failed bridge that one of the in-river piers of the bridge collapsed and foundation failure is the most likely cause. Progressive scour over the centuries could have weakened the foundations with the 2015 flood being the final straw. Other bridges could have failed because of erosion of the abutments with progressive bank erosion a common phenomenon. Without an analysis of the mechanism of failure of bridges in 2015, we have to be cautious about ascribing historic significance to the 2015 floods.
Salopian,
This is scary:
"Except that they are not that reliable. As I commented on unthreaded yesterday, the hospitals in the area that are on backup power are unable to conduct MRI or CT scans because their generators are "unable to support this equipment". This means that anyone needing a scan, including acute trauma cases needs to be moved to another acute case facility outside the area PDQ. You cannot run these scanners on backup generators."
I need both in the next few weeks. Glad I'm not in the UK.
Good to see Dr Richard Betts stepping up to the plate to defend Dame Julia. Chapeau, Dr Betts!
A rare plaudit from me: The BBC's favourite, a George Monbiot, spoke very good sense on the Today program this morning on the subject of the Great Cumbrian Floods, opining that the problems and solutions lie upstream. I am sure he is correct, and we need major policy change over land draining of the uplands and permitting flooding of farmland to lessen the chances of catastrophic damage to conurbations. Mind you, I have been hearing this argument from many true experts over the past 40 years, but nothing serious is ever done. Flood defences in towns will often fail in the end.
(I should add that my commendation of Monbiot does not extend to his stance on AGW!)
Dec 7, 2015 at 10:32 PM | Peter Melia
Flood drainage canals ! - a far better idea than building dams that eventually hold the water IN, as they are now.
However, the country(file) set would be up in arms for anything so ugly spoling their views and harming tourism.
Salopian thanks for the update on emergency reliable power. I would guess that diesel generators are not sized to cope with total loads. Can anyone advise further?
jazznick, flood drainage canals can prevent flooding in one area, but they just move the problem downstream even quicker.
This morning I heard the BBC quote the following that also appeared on the Daily Mail website:
Perhaps they should also stop to consider that the floods in Keswick, Cockermouth and Carlisle are also consistent with an act of God. So do we now have conclusive proof of the existence of God?
It is important to remember in times like this that you are able to get help from qualified professionals when your home has been flooded. I recommend Public Loss Adjusters, because they have a reputation for looking after their clients properly and arranging emergency accommodation.
Floods can be exacerbated by Increased flood prevention measures upstream that channel more water downstream.
..hmm interesting thing worth thinking about eh EA.
thinkingscientist says
"Environment Secretary claims ‘unprecedented weather’ is consistent with ‘trends we’re seeing of climate change’
and Jeremy Corbyn ’"..... ditto
A few years back we had a series of below average temperature winters which did not fit in with the runaway global warming narrative.
The BBC would host various 'climate scientists' who would opine knowingly, informing us that this is WEATHER not CLIMATE and we should wait 30 or even 100 years before identifying a new climate trend.
Further the same 'scientists' said that British winters were going to be dryer! and water meters would be obligatory.
It just goes to show that anything is compatible with 'climate science'.
The purveyors of such junk are not scientists at all.
Is their a relationship between the lack of Atlantic hurricanes, and the weather we see after the hurricane season is over. These storms are heat pumps pulling heat from the ocean to the air, if the Atlantic/Gulf of Mexico storms for whatever reason aren't powerful is the heat that is not removed moving further North and adding to the potency of our Atlantic storms. I think 1929 showed a similar pattern.
Paul Homewood's piece has an interesting link in a comment concerning the floods in Kendal, for which there is a large marker, showing previous record levels. I wonder how the current one compares with 1898?
Look at the pictures in the media. All the stuff piled outside the houses, and the flooded vehicles, is stuff which would not have existed 60 or more years ago. If you look into local history these flood events happened, a day or two of water in the ground floor simply wasn't a big issue.
As to the bridges, they were a lot newer and probably better maintained the last time this sort of thing was common. Most of our rural road network has not been significantly maintained or improved since the 30s.