Tuesday, 18 February 2014

Après le déluge

The rain and wind in the South of Britain this winter seems interminable as storm after storm is blasted towards us by the Jet Stream breaking records of the worst kind (stormiest, wettest, etc). Well over double the seasonal average rainfall in some places, though not here on the NW coast of Scotland where the Jet Stream has almost left us in peace. And as the flooding continues, more people are stranded, more transport is delayed and tempers become frayed; with scenes of anguished people, depressed or angrily seeking someone to blame.

Last week I was crossing the now infamous Somerset Levels in a train with rain lashing on the roof, picking its way along a causeway with vast stretches of flooded land on either side. Now this line too has been closed. A huge tract of wetlands and lowlands has succumbed to rivers, backed up by exceptional tides on their seaward ends, overflowing their banks. And the tabloid newspapers that heralded ‘the storm of the century’ had to announce ‘the even bigger storm of the century’. Moreover, on the TV, everyone can witness the angry exchanges between flood victims and officials powerless to bring a short-term solution to the misery. “Why weren’t the rivers dredged?” they demanded. “Because our budgets were constrained and we had to prioritise” came the honest but unpopular answer.

And just down the coast in Dawlish, a huge storm has washed away the railway line, cutting the vital connection to the South West, bleeding the economy like a severed artery in a leg. The line was constructed on a causeway along the coast over 170 years ago; an unusual but picturesque choice of route chosen – yes – because of budgetary constraints. And the relief route, inland around the North of Dartmoor was closed in 1968 because it was making a loss and there was a perfectly satisfactory main line … along the coast. Winter storms were always a problem along the line and there are classic pictures of steam trains emerging from the spindrift of waves smashing against the breakwaters. But start adding sea level rise to the equation and sooner or later a threshold for collapse would be exceeded (like many other colleagues, I had pointed this out a decade ago but the engineers insisted the line could cope). So the line is closed, the drama continues and the whole country has been gripped by the pictures and reports.

But what are the lessons learned?  

Firstly, with climate change it is easy to hide behind the statistics. An average sea level rise of 4mm a year seems paltry when the tides may rise and fall by as much as one thousand times this twice a day. But 100 years of sea level rise – which may be accelerating – adds at least 40cm, to the baseline ('datum'); a huge increase in hydrostatic pressure and the power of waves as they strike the coast. And a 1 in 100 year extreme event gives the false comfort that it may never occur in our lifetimes. But the frequency of such extreme events may vary in cycles and there is some empirical evidence that they are increasing. Catastrophes happen because of these extremes and they are poorly studied and difficult to predict; we can only say that more of them are likely to occur as a function of human-driven global change.

Secondly, we have to take the long view. On my long and frequently interrupted journey north, I looked up the Somerset Levels on Google Scholar and was surprised by the wealth of articles - many from the 1940s - that examined the issue of inundations in the region. Pollen records in sediments track the length and timing of the floods and the sediments themselves reveal the frequency of flooding. There is a pattern of inundations going back at least 4000 years, with periods when they were more, or less, severe. And communities were built on the knolls that were above usual flood levels (and are temporary islands today). There were big flooding events like that of 30 January 1607, studied in 2006 by Kevin Horsburgh of NOC, Liverpool and Matt Horritt from the University of Bristol (reference below). Dubbed as ‘God’s warning to his people of England’, the flooding killed hundreds of people on the Bristol Channel coast and Somerset Levels. It followed an intense westerly storm at the time of a spring tide and this must have generated a major storm surge. The wind later swung to the East as the storm passed over Britain and pushed a surge into the Wash in East Anglia, causing major flooding there. The loss of life may have been greater than the flooding in 1953. Interestingly, Horsburgh and Horritt point out that the 16th and 17th centuries were exceptionally windy and there were 128 North Sea floods in the 17th century … and that this may have been caused by a southward displacement of the jet stream! What if the same pattern is returning, and coupled with higher sea levels and increased population density?

The third lesson is that we cannot continue to manage our economy as if there is no tomorrow; and by ‘tomorrow’ I don’t mean 2015. We have to take the issue of global change seriously and ‘muddling through’ simply won’t guarantee the resilience that moves ‘sustainable development’ from rhetoric to commitment. We need serious long term planning; a masterplan that spans multiple political terms of office and engages every sector. Either brace yourselves to share the cost of resilience or brace yourselves, and your children to an increasing chain of catastrophes, social and economic setbacks and missed opportunities.


  • Horsburgh, K & Horritt, M (2006) The Bristol Channel floods of 1607–reconstruction and analysis. Weather, 61(10), 272-277.

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