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

• Introduction to CEH

• Natural hazards and floods research

• Past events

• The future: Is flooding the new normal?

Structure

©The Guardian

Meeting the Challenges of Environmental Change

• Securing the Value of Nature

• Building Resilience toEnvironmental Hazards

• Managing Environmental Change

CEH Strategy 2014 – 2019

Delivering our Strategy

CEH Science and Impact• Excellent

• Distinctive

• Relevant

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

Flooding

Non-native invasives Wildfires

Drought

Volcanic eruptions

Pathogens

Flooding at Wallingford Bridge, January 2014

Centre for Ecology and Hydrology

Recent events – winter 2013-14

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

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

• 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)

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. 

Persistence of high flows

River flows: 30 day annual maxima

Beware of trends in short records

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

Increased variability?

England and Wales National Runoff Series, 2012

Calderdale, Jun/July N. Wales, Nov NE Scotland, Dec

All photos © bbc

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

Changing floods: the evidence

http://www.lwec.org.uk/resources/report-cards/water

Future flood risk

Percentage change in 20-year river flow by the 2080s

Change %

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.

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

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

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%

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

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)

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)

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?

Thank you!

Nick Reynard – Science Area Lead for Natural Hazards researchCentre for Ecology & Hydrology, Wallingford

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