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BSG press release - Storm Desmond floods - December 2015

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Flooding and Geomorphology - Dr Chris Skinner (University of Hull)  and Dr Lynda Yorke (University of Bangor) on behalf of the British Society for Geomorphology

The past weekend has seen record breaking levels of rainfall fall upon the North-West of England. Storm Desmond, as named by the MetOffice's 'Name our Storms' pilot project (http://www.metoffice.gov.uk/uk-storm-centre), has brought with it scenes of devastation as flood defences overtop and water spilled into people's houses. For the people of Carlisle, this is the third major flood event in a decade, having suffered previously in 2005 and 2009. These floods have been described as a 1 in a 200 year event (www.bbc.co.uk/programmes/p03bd6bd) but of course that only describes the size of such an event. In reality in any one year there is always a 0.5% chance of getting a flood of this size. What appears unusual is that we have seen a number of large floods in such a short space of time!

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Photos courtesy of Mr Abe Butterworth, of Appleby, Cumbria

We are writing this article in our capacity as members of the British Society for Geomorphology (http://www.geomorphology.org.uk/). Geomorphology is the science of how the planet's surface changes, most often by processes due to water, ice or wind, and these processes are all too evident during storms and floods such as the like Desmond has brought us. Yet, the impact of these on people and property is not always at the forefront when considering flood risk.

 Why river geomorphology matters.

Rivers and landscapes change all the time. Their shape and form, or geomorphology, has a profound effect on how and where rainfall in transported over the land into the rivers and out to the coast. We have models that can predict river levels and likely flooding, but very few take into account that our landscape changes. During intense flood periods, rivers can undergo massive changes such as cutting across meanders and changing course, or stripping away the vegetation and cohesive sediments, leaving behind an easily changeable gravel bed. These changes can make the river more likely to flood in the future until it has time to recover its former state.

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Photos courtesy of Mr Abe Butterworth of Appleby, Cumbria

What can geomorphology do to help understand flood risk?

The flood waters have now begun to recede and streets that were flooded are now emerging once again, but left behind on the paths, the roads and in people's houses is a thick layer of mud (http://www.bbc.co.uk/news/uk-35019428). Mixed in the mud is the debris of flooding, bits of trees, buildings and litter. The water will drain away but it leaves behind what it was carrying and this can often be more damaging than the water itself. It also leaves the public wondering why it keeps happening and what can be done about it.

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Photos courtesy of Mr Andrew Wright  (Courtyard Gallery) and Mr Abe Butterworth of Appleby, Cumbria

Understanding how rivers behave now is important but crucially it is their past behaviour that is the major key to help unlock some of the issues surrounding the frequency and size of floods. Rivers have always flooded but our understanding of these flood events are based on more recently gathered records of large river flows during the last 50-60 years. Our concept of flood risk, the ‘one in a 100 year event’ only reflects recent river data. However, if we look at the sediments that have built up our floodplains (again looking to the geomorphology) we are able to unravel a much longer record of flooding, and also to determine the size and extent of those earlier floods.

The future of flood risk management.

Geomorphologists, those of us that study how rivers behave and change, can generate this longer-term flood data, which can be combined with our understanding of how rivers and landscapes change over time. We can start to feed more detailed data into our computer models. These models will then allow government agencies, emergency planners and stakeholders to be better prepared for flooding in the future. 

It is important to remember that whilst we may be experiencing a ‘flood-rich’ period, where large, damaging floods appear to be the norm, our historical data tells us that we have experienced greater, more frequent floods in the past. However, the impacts of today’s flood are much greater because of how and where we live.

The impact of climate change in the UK indicates that we can expect storms like Desmond, and scenes such as those in Keswick, Cockermouth and Carlisle, to happen more often. This means not just more water, but more mud too. It means less time between storms for our rivers and valleys to recover making our landscape much more likely to change, and we need to learn to change with it. It is possible that the age of static defences is at an end and the age of resilience and flexibility is about to begin. Uncomfortable questions such as, what do we actually mean by adaption and resilience, and what does that mean for the people living in flood-affected areas, must be raised and addressed. 

 

For any further information about this press release or the British Society of Geomorphology please contact [email protected].

A PDF version of the BSG's press release on the December 2015 Storm Desmond floods can be downloaded here: http://www.geomorphology.org.uk/publications/bsg-press-release-storm-desmond-floods-december-2015

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