LMNH Unit

Luc Feyen & Ad de Roo

With contributions of:Jose Barredo, Rutger Dankers, Katalin Bodis, Carlo Lavalle,

EFAS teamDG Joint Research Centre

European Commission

Assessing Future Flood Risk in Europe:advances in climate change scenario development -

progress in model predictions -research challenges

Working Group F – Workshop on Climate Change and FloodsKarlstad, 8 September 2009

LMNH Unit

source pathway receptor consequence

� extreme precipitation� prolonged wet period� rapid snowmelt

� overtopping, overflow� flood defence� floodplain

� people� property� environment

� loss of life� economic impact� environmental damage

FLOOD HAZARD FLOOD RISK

Assessment of flood risk

LMNH Unit

source pathway receptor consequence

� extreme precipitation� prolonged wet period� rapid snowmelt

� overtopping, overflow� flood defence� floodplain

� people� property� environment

� loss of life� economic impact� environmental damage

socio-economic system

climate

emissions

FLOOD HAZARD FLOOD RISK

terrestrial system

Assessment of future flood risk

LMNH Unit

Return period (years)

hydrologicalhydrologicalhydrologicalhydrological modelmodelmodelmodelextreme extreme extreme extreme valuevaluevaluevalue analysisanalysisanalysisanalysis

Assessment of future flood hazard

climateclimateclimateclimate modelsmodelsmodelsmodels

sociosociosociosocio----economic economic economic economic scenariosscenariosscenariosscenarios

highhighhighhigh----resolutionresolutionresolutionresolution

climateclimateclimateclimate scenariosscenariosscenariosscenarios

LMNH Unit

� capturing fine-scale climatic structures induced by complextopography or land use patterns is essential

� RCM runs at increasing horizontal resolution

� PRUDENCE, ENSEMBLES, CECILIA, CLAVIER, nationalclimate scenarios (e.g., UKCP09, KNMI'06)

� development of a set of “Representative ConcentrationPathways ” (RCPs)

Climate scenario development

LMNH Unit

� relatively few studies have considered extreme river flows

� focus on catchments rather than regional/continental analyses

� geographical preference for catchments in the UK, Benelux, Germany, Central Europa and Scandinavia

� several studies project an increase in flood hazard …

� … others project a decreasing trend

� application of different scenarios, driving climate models, downscaling techniques and hydrological models

Model predictions of changes in floods

� Overall situation in Europe??

LMNH Unit

Relative change in 100-year return level of river discharge between scenario (2071-2100) and control period (1961-1990) – ensemble run

Dankers, R., and L. Feyen, 2009. Flood hazard in Europe in an ensemble of regional climate scenarios, J. Geophys. Res., doi:10.1029/2008JD011523.

Model predictions of changes in floods

ECHAM4/OPYC3 HadAM3HHIRHAM & RCAO

LMNH Unit

Climate change effect on extremes:change of max 5 day Q and mean

annual min 7 day Q

-> increase extremes everywhere

except Scandinavia and Portugal

LMNH Unit

Number of scenarios (out of total eight experiments) showing a decrease (plot a) or increase (b) in Q100 of more than 5% in the scenario period

Dankers, R., and L. Feyen, 2009. Flood hazard in Europe in an ensemble of regional climate scenarios, J. Geophys. Res., doi:10.1029/2008JD011523.

Model predictions of changes in floods

LMNH Unit

� monetary assessments of climate change impacts on floods are poorly covered

� few studies in UK (e.g., Foresight, 2004; Hall et al., 2005;� Mokrech et al., 2008), showing large increases in flood risk, but� strongly dependent on scenario of economic growth

� studies exclusively account for direct tangible damages

� psychological effects� inconvenience of post-� flood recovery

� loss industrial production� traffic disruption

� emergency costsIndirect

� loss of life � health effects � loss ecosystem services

� damage to buildings� damage to infrastructure � damage to contents

Direct

IntangibleTangible

Predictions of changes in flood risk

LMNH Unit

From flood hazard to flood risk

� convert hazard into damage based on static land use� classification and flood depth damage functions

CORINE Land Cover 2000 (EEA, 2000)

Huizinga (2007)

LMNH Unit

Change in flood risk by 2080s in Europe

� change in Expected Annual Damage (averaged over NUTS2)

A2 B2

EAD of EU27, currently €6.5 billion, is projected to rise to €18 billion (A2) and €14 billion (B2)

PESETA study

LMNH Unit

1 10 100 1000protection ctrl (rp in yrs)

0

50

100

150

200

250

exp

an

n d

am (

bill

ion

€) A2

scenario

control

A2, EU27

∆damage = € 31 billion∆damage = +75%∆damage = € 31 billion∆damage = +75%

↑ protectionrp = 10 → 26 y↑ protectionrp = 10 → 26 y

potentialbenefitscost of adaptation

potentialbenefitscost of adaptation

Potential benefits of flood mitigation

LMNH Unit

1 10 100 1000protection ctrl (rp in yrs)

0

50

100

150

200

250

exp

an

n d

am (

bill

ion

€) A2

scenario

control

∆damage = € 11 billion∆damage = +294%

A2, EU27

potentialbenefitscost of adaptation

potentialbenefitscost of adaptation

↑ protectionrp = 100 → 400 y

Potential benefits of flood mitigation

LMNH Unit

1 10 100 1000protection ctrl (rp in yrs)

0

2

4

6

exp

an

n d

am (

bill

ion

€) A2, Danube in RO

control

scenario

1 10 100 1000protection ctrl (rp in yrs)

0

1

2

3

4

exp

an

n d

am (

bill

ion

€) A2, Danube in CZ

scenario

scenario

1 10 100 1000

protection ctrl (rp in yrs)

0

4

8

12

16

exp

an

n d

am (

bill

ion

€) A2, Danube in AT

scenario

scenario

1 10 100 1000protection ctrl (rp in yrs)

0

10

20

30

40

50

exp

an

n d

am (

bill

ion

€) A2, Danube

scenario

control

Potential benefits of flood mitigation

LMNH Unit

Key Research Challenges

• Major research advances are needed in climatology, hydrology, land-use planning, socio-economic sciences and multi-objective decision-making under uncertainty

• need for sustained, high-quality observations & data sets– E.g. at European scale / transnational river basins, good meteo datasets allowing

downscaling & bias correction are hardly available

• advance scientific understanding of the mechanisms that trigger, and alter the probabilities of, extreme events

– e.g. Vb conditions triggering 2002 Elbe floods

• interaction/feedback between land-use and climate change and variability– Consequences of land use change hardly taken into account in GCM & RCM’s

• interaction/feedback between hydrological cycle and climate– e.g. extreme frequency of thunderstorms in Italy in 2009 <> relation to wet topsoil

conditions?

• improve capabilities of regional climate models to represent and predict variability and extremes at regional and local scale

LMNH Unit

� better quantification of (intangible) damages

� better quantification of cost/benefits of adaptation options

� better quantification of current and future vulnerabilityand of the reliability of protection measures

� formal treatment of uncertainty in the chain “emissions – climate – extreme flows – inundation – damage”

� flood risk mapping and management in the face of these uncertainties

Key Research Challenges

LMNH Unit

Conclusions• Even when scenario results are variable, there are some

emerging trends:– Increase of 100yr flood in several large EU rivers (Danube,

Rhone, Po, Loire, Garonne)– Decrease in snowmelt 100yr floods in parts of Scandinavia– Even with strong decrease in annual rainfall in the

Mediterranean, still substantial or higher flood risk

• Methodology for cost-benefit analysis for flood protection at large scales– Refinements needed & ongoing:

• New RCMs, multi-ensembles, multi-model approaches• Etc etc

• A large number of (research) challenges remain

LMNH Unit

http://floods.jrc.ec.europa.eu Thanks for your attention!