‘Unprecedented’ flooding?

A few weeks back, on 29 February 2016, there was an interesting BBC TV programme on called, ‘Flooding: Are You as Safe as You Think?‘ It focused mainly on Wales and took objection to the use of the word ‘unprecedented’ to describe the recent Boxing Day 2015 floods.

Presenter Tim Rogers has covered UK flood events for over 30 years. He reported on the 2015 Carlisle floods, and reported there a decade earlier after the flooding in 2005. Both times the floods were called ‘unprecedented’.

The 2005 floods were also called a ‘once in a lifetime event’ that would not be allowed to happen again. After these floods, £38 million of defences were built, but sadly did not prevent all the flooding that happened in 2015. Tim Rogers was shown in the programme, stood on top on some of the flood defences built in Carlisle, following the 2005 floods.

I highly recommend the full programme; do go and watch it while it’s still available (note: may not be accessible outside the UK). In a nutshell though it argues much recent UK flooding is – far from being ‘unprecedented’ – quite precedented if you look for flooding records in the right places.

On this, in the programme Tim Rogers met with Professor Mark Macklin from Aberystwyth University. Prof. Macklin said current (Welsh) flood maps underestimated flood risks. Authorities in Wales reportedly rely primarily on datasets from river level monitoring gauges that go back only 55 years. This omits evidence of past flooding, which Prof. Macklin has inferred through geological research that traces flood events back over a period of 3,000 years or more.

Tim Rogers also visited a local library and found a newspaper article from 1879 in the Aberystwyth Observer, describing ‘a storm of unprecedented severity‘ over Aberystwyth. He highlighted this historical use again of the word ‘unprecedented’ whilst also finding a consistent paper trail, from the available newspaper archives, of ‘major flooding between 1840 and 1957‘ in the area. The programme claimed this evidence was not used for flood risk mapping by the relevant Welsh authority, Natural Resources Wales.

Overall I don’t think the use of the word ‘unprecedented’ is that scientific by policymakers and commentators on UK flooding. It’s more a sensitive, emotional term to be alert to likely flooding impacts on people and property, in my view. But any sloppy use of the term could be replaced by a more scientific, evidence-based view of how ‘precedented’ UK flooding events actually are, I believe this programme argued. This would be by developing more accurate flood maps that combine at least:

  • River level monitoring gauge data;
  • Data from geological research; and
  • Newspaper reports of historical flooding.

I recall from my previous research that the Local Climate Impacts Profile (LCLIP) approach for organisations, such as local authorities, to assess their climate-related risks, can include newspaper data. But I’m not sure whether the Environment Agency currently uses such data – or geological evidence – in its flood risk mapping.

Happy to update this post if anyone from the EA could let me know…?

Duncan Thomas

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