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UK floods past, present and future
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UK Floods: Past, Present and FutureNick Reynard – Science Area Lead for Natural Hazards researchCentre for Ecology & Hydrology, Wallingford
Thanks to Jamie Hannaford, Bob Moore, Steve Cole, Vicky Bell, Alison Kay
Wallingford, December 2012Maidenhead, January 2014
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• Introduction to CEH
• Natural hazards and floods research
• Past events
• The future: Is flooding the new normal?
Structure
©The Guardian
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Meeting the Challenges of Environmental Change
• Securing the Value of Nature
• Building Resilience toEnvironmental Hazards
• Managing Environmental Change
CEH Strategy 2014 – 2019
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Delivering our Strategy
CEH Science and Impact• Excellent
• Distinctive
• Relevant
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Natural Hazards: Vision
Science to improve the
understanding and prediction of
the threats and impacts posed by
natural hazards, and the
development of management
and resilience strategies.
Understand the threats
Predict and forecast
Manage and
mitigate
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Flooding
Non-native invasives Wildfires
Drought
Volcanic eruptions
Pathogens
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Flooding at Wallingford Bridge, January 2014
Centre for Ecology and Hydrology
Recent events – winter 2013-14
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Are floods the new normal?
Central/Northern England, 2007
England and Wales, 2000
Photos: Environment Agency, NERC, BBC
Cockermouth, Cumbria, Nov 2009
Moorland, Somerset Levels, 2013
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Are floods the new normal? 2000 - 2014
• 2000 extensive autumn floods• 2002/3 winter floods in southern
England • 2004 Boscastle flood• 2005 Flooding in NW England• 2007 summer floods• 2008 flooding in Northern Ireland &
northern Britain• 2009 Floods in Cumbria and eastern
Scotland• 2010-12: from drought to floods• 2013/2014 winter floods
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• 1946 Major floods in central Britain
• March 1947 – most extensive 20thC flooding in E&W
• 1951 Severe groundwater flooding• 1952 Lynmouth Disaster • 1953 Devastating tidal flooding• 1954 Severe flooding in the South• 1955 Martinstown storm (rainfall
record to this day)
Were floods the old normal? 1946 - 1955
(with thanks to Terry Marsh for the history lesson)
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2007
1947
1809
1894
1947
2003, 2007, 2014
Historic flood levels on the Thames, Shillingford
Thames flood record from Kingston, 1883 - 2014
Are floods becoming more severe? The long view
Marsh, Terry and Harvey, Catherine, L. 2012. The Thames flood series: a lack of trend in flood magnitude and a decline in maximum levels. Hydrology Research 43.3, 203-214.
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Persistence of high flows
River flows: 30 day annual maxima
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Beware of trends in short records
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National trends in high flows?
Hannaford, J. and Buys, G. 2012. Trends in seasonal river flow regimes in the UK. Journal of Hydrology, 475, 158 – 174.Hannaford, J. and Marsh, T.J. 2008. High flow and flood trends in a network of undisturbed catchments in the UK. International Journal of Climatology, 28 (10), 1325 – 1338
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Increased variability?
England and Wales National Runoff Series, 2012
Calderdale, Jun/July N. Wales, Nov NE Scotland, Dec
All photos © bbc
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The logical case for increases in flood magnitude/frequency
• The world is getting warmer• Increased winter rainfall across the UK• Some evidence of increased rainfall intensity• Cluster of recent flood episodes• Some consistency with projections based on
climate change scenarios• Natural variability
Future floods: climate change
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Changing floods: the evidence
http://www.lwec.org.uk/resources/report-cards/water
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Future flood risk
Percentage change in 20-year river flow by the 2080s
Change %
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Catchment modelling
Probabilistic projections (box-and-whisker plots):10,000 Sampled Data delta changes100 Weather Generator time-series
Regional Climate Model data (points):11 delta changes (crosses)11 time-series (rectangles)
9 catchments modelledTeme at Tenbury (54008)2080s, Medium emissions
Kay, A.L. and Jones, R.G. (2012). Comparison of the use of alternative UKCP09 products for
modelling the impacts of climate change on flood frequency. Climatic Change, 114(2), 211-230.
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Science for flood management policy
• Communication to potential users
REGIONALISED IMPACTS OF CLIMATE CHANGE ON FLOOD FLOWSIn support of climate change policy and guidelines for flood management
• Investigate the impact of climate change on river flows across Britain to assess the suitability of 20% climate change guidance
• Investigate catchment response to climate change to identify potential similarities such that the Defra nationwide guidance could be regionalised
• Model >150 catchments under 10,000 scenarios of future climate
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1. How appropriate is the national allowance?
Allowance (% change)
% o
f UK
CP
09
scen
ario
s
2. What should the new allowance be?
Welsh region
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Adapting to Climate Change
ADVICE FOR FLOOD AND COASTAL EROSION RISK MANAGEMENT AUTHORITIESEA, AUGUST 2011
Total potential change anticipated for the 2020s
Total potential change anticipated for the 2050s
Total potential change anticipated for the 2080s
Northumbria
Upper estimate 25% 30% 50%
Change factor 10% 15% 20%
Lower estimate 0% 0% 5%
H++ scenario 35% 45% 75%
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Flood Risk is more than just high flows
Risk = probability x consequence
SOURCE
PATHWAY
RECEPTOR“The Battle for Walham Switching Station”, July 2007
Providing power to 500k homes. The fire brigade, Army, Royal Navy, Royal Air Force and the Environment Agency joined forces to save the power station which came within a few cms of flooding
Oxford, July 2007
Wet feet!Providing power to 500k homes
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Historical floods: 1894
‘One of the sad and yet ludicrous features of a visit to the flooded districts was to see, rising through the water in dozens of localities, posts bearing large posters announcing “Eligible building land to let”.
(Symons & Chatterton, QJRMS)
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Historical floods: 1947
‘Many of the complaints of the flooding of houses came from…lands known to have been flooded many times in the past…The restrictions of building on such areas must be encouraged in the future…’
(Howarth, Mowbray et al, JIWE)
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Floods: Past, present and future - Final thoughts
"It is commonly observed, that when two Englishmen meet, their first talk is of the weather; they are in haste to tell each other, what each must already know, that it is hot or cold, bright or cloudy, windy or calm.“
Dr Samuel Johnson
We live on some islands on the margin of the Atlantic Ocean, with a climate which is inherently variable.
Despite widely-held perceptions, there is no compelling evidence to suggest any long-term tendency towards increasing severity or frequency of floods and droughts in the UK
However, recent years have been in the extreme ranges of recorded variability and underlined our vulnerability to both drought and flood.
Recent hydrological volatility may be indicative of anthropogenic climate change, but it could also reflect natural variability; differentiating the two is a major scientific challenge.
Is the past a guide to the future in warming world?
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Thank you!
Nick Reynard – Science Area Lead for Natural Hazards researchCentre for Ecology & Hydrology, Wallingford
© United U
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