With the Somerset Levels still flooded and the Thames Valley drying out, it is time to try and consolidate the evidence for the underlying causes of these events that are a catastrophe for those affected.
4 factors underpin the recent floods. Anthropogenic global warming is not one of them.
- Flood management engineering
- Heavy sustained rainfall
- Natural climate variability
- Exceptional tides
Figure 1 Composite image of the River Parrett in Burrowbridge in the early 1960′s (top left) when dredging was carried out on a regular basis, a recent picture before the current flooding event showing the encroaching river banks (bottom left) and during the recent flooding. Caption and Photo from Wattsupwiththat based on a comment originally posted on Bishophill.
Flood management and engineering
I am dealing with flood management and engineering first since without the floods the winter storms of 2014 would have received significantly less media and political attention. There are three main affected areas 1) the Somerset Levels, 2) the Thames Valley downstream from Windsor and 3) coastal areas of SW England. The possible exacerbation of coastal flooding by exceptional high tides is dealt with in the final section.
The Somerset Levels
The Somerset levels are areas of low lying land that have been recovered from a coastal marsh by enhanced drainage and water management that according to Wikipedia began in the Middle Ages. In keeping with all recovered land, continuous maintenance is required or the land will revert to its intended state, i.e bog or shallow lakes.
Reports on a number of blogs all seem to concur that a lack of dredging in the last decade is a major cause of the current flooding. Wattsupwiththat carried an intriguing story posted originally by an anonymous commenter on Bishophill. In 1939 the Ministry of Defence (the MOD) built a munitions factory, ROF Bridgewater, by the Somerset Levels. The MOD then proceeded with some river engineering to get water to the factory and effectively assumed responsibility for water management of The Levels until 2008 when the factory was finally closed. It is claimed that the MOD understood the consequences of their withdrawal and attempted to pass this responsibility to The Environment Agency who failed in their duty to assume it. A few years later, The Levels are flooded and many lives severely disrupted if not ruined.
This story requires corroboration, but if true, then heads must surely roll at The Environment Agency.
The Thames Valley
The badly flooded part of the Thames Valley, downstream from Eton, was probably more severely flooded owing to river engineering works designed to reduce flood risks upstream.
Figure 2 The River Thames and the Jubilee River at Windsor.
This from Wikipedia:
The Jubilee River is a hydraulic channel in southern England. It is 11.6 km (7.2 mi) long and is on average 45 metres (148 feet) wide. It was constructed in the late 1990s and early 2000s to take overflow from the River Thames and so alleviate flooding to areas in and around the towns of Maidenhead, Windsor, and Eton in the counties of Berkshire and Buckinghamshire. It achieves this by taking water from the left (eastern) bank of the Thames upstream of Boulter’s Lock near Maidenhead and returning it downstream of Eton.
The Environment Agency commissioned the design and construction of the river which cost £110 million. When it was formed, the channel was the largest man-made river project ever undertaken in Britain, and the second largest in Europe.
Whilst it would be wrong to blame the flooding on the Jubilee River it will most certainly have made things worse in the affected areas whilst reducing or preventing flooding in the areas upstream from Eton as it was designed to do.
In summary, the flooding in Somerset and the Thames Valley has been caused or made worse by The Environment Agency.
Heavy sustained rainfall
The main cause of the flooding was of course heavy sustained rainfall. It was not the result of a single “catastrophic event” but the cumulative impact of successive storms brought in by a fast moving jet stream that was further south than “normal”. The reason for this is dealt with in the next section.
Statistics for “heavy sustained rainfall” can be sliced and diced in a number of ways. The most readily accessible statistic is monthly rainfall for England and Wales (Figure 3). These show that January 2014 was very wet, up there with wettest months on record, but in no way exceptional or unprecedented. But this can mask important local and temporal variations. For example a couple of counties may have had exceptional rainfall over a week or two. But this can hardly be used as evidence for Global Warming.
Figure 3 Rainfall for England and Wales (CET data?). Provenance of chart unknown.
Had exceptional rainfall caused flooding in the Midlands, the North of England or Scotland it would not have mattered. But flooding of the Home Counties is different. This caused David Cameron to cancel a visit to The Middle East to take command of a situation that his inept Green government and its agencies are to a large extent responsible for creating.
Natural Climate Variability
A cornerstone of the climate sceptic argument that sets it apart from the IPCC global warming dogma is that sceptics assert (based on evidence) that Earth’s climate is variable at many scales. IPCC global warming orthodoxy on the other hand has managed to foster the extraordinary view that Holocene climate everywhere should somehow be uniform, unvarying. And so, when there is any deviation from that normality its is attributed to “climate change”. The term “climate change” has been adopted since the troposphere stopped warming rendering the term global warming obsolete. But here the whole debate runs into trouble since attributing the recent storms to “climate change” may in fact be correct, it is just that this climate change is natural and most probably has nothing to do with Human induced global warming.
So what are the natural forces at work? It is possible to identify symptoms of the unusually stormy period January / early February 2014 but far more difficult to pin down the physical underlying cause – especially for a solitary blogger. This should be the job of the UK Met Office Hadley Centre and other esteemed UK climate research institutes who should be sallying forth asking the question “what was the underlying physical cause of the winter 2014 storms?” One has to be concerned, however, that the Met Office will go out and try to find ways of proving that the storms were caused by global warming. Even though they dumped a mass of snow on Scotland.
The simple explanation for the UK 2014 winter storms is that a very fast moving jet stream spawned one cyclone after another off the E coast of Canada and sent them on a route along the jet stream to the UK and western Europe. And though fast moving, the jet stream trajectory was “frozen” resulting in a monotonous repetition of events.
This sequence appears to be linked to the active polar vortex that was over Canada and the USA but has since moved over Greenland. The active polar vortex appears to be linked to a cold polar stratosphere which is tempting to link to The Sun, but I have been told from an authority that this is unlikely and that stratosphere temperatures in any given year are more likely controlled by dynamic (i.e. circulation) than radiative variations. Thus a physical explanation for the root cause of the January storms remains elusive. However, it seems likely that a similar climatic sequence of events has happened many times before in which case there is no real reason to go hunting for a human cause other than to scapegoat government ineptitude and to excuse their risible energy policies. Paul Holmwood has numerous stories covering historic flooding events in Britain if anyone needs convincing that this has all happened before and does not require a super natural explanation.
Clive Best has been having a close look at combined lunar and solar tidal variations and had this to say:
Now consider the coastal flooding this winter which has mainly effected western coastal regions of the UK. The main reason for this are the unusually strong spring tides rather than global warming. These storms have tended to coincide with unusually extreme tides. Next winter such flooding is unlikely to re-occur.
Figure 4 Exceptional high Spring tides in early and late January will have added to storm surges for a few days either side of the peaks. Chart from Clive Best.
Clive sent the chart above by email and points out that the high tides at the beginning and end of January are extreme high tides perhaps 1.25 m higher than the ordinary high tide. This is linked to both Sun and Moon approaching their closest point to Earth in their respective elliptical orbits.
At the beginning and end of January therefore, and a few days either side, exceptional high tides combined with storm surge (low pressure), high winds and large waves to flood coastal areas. It is also possible that surges from storms at these times dumped sediment into the rivers draining the Somerset levels, raising the base level and thus hindering subsequent drainage.
The main human impact on recent flooding is UK government incompetence. It is not possible to exclude or include a Human caused warming component to the 2014 winter storms at this point.
I began writing this post on Monday but have been teaching at The University all week, so its taken more time to complete than planned. The Met Office has since published their own post-mortem (hat tip Burnsider) that I hope to find time to dissect in the next few days.