Ensemble flood risk assessment and adaptation strategies in Europe at 4ºC global warming Lorenzo Alfieri, Luc Feyen, Alessandra Bianchi, Francesco Dottori, and Giuliano Di Baldassarre Climate Risk Management Unit Institute for Environment and Sustainability European Commission - Joint Research Centre Rotterdam, 10 May 2016 1 Floods in Europe: An increasing trend Population affected by water related natural hazards (Alfieri et al., Environmental Science & Policy, 2012) Increase in damage caused by floods over the last decades: Socio-Economic changes are the main driver Climate change will most likely increase damages in the future Increased need for early warning systems and flood risk assessment tools 2 1
Workflow Future flood hazard in Europe Flood inundation maps for the current climate Future flood risk in Europe under high-end climate scenario Flood hazard mapping in Europe Simulation area: 5 million km 2 500 Mpixel (Alfieri et al., Hydrological Processes, 2014) 4 2
Potential impact of floods Population density Land use Depth-damage functions Maps of potential damage and population affected are defined for return periods of 10, 20, 50, 100, 200 and 500 years, by combining flood hazard maps with exposure and vulnerability layers Potential population affected Potential damage 5 Projections of the future streamflow climatology Alfieri et al., HESS (2015) Ensemble of 7 regional climate models Baseline scenario (1970-2005) Future scenario (2006-2100) with RCP 8.5 W/m 2 Droughts Water resources Floods Decrease of discharge peaks More intense streamflow droughts Decreasing average discharge Increasing average discharge General increase in discharge extremes in Central Europe, though with variable local patterns 6 3
Future flood risk in Europe under high-end climate scenarios Damage 1990 2020 Population affected 1990 2020 2050 2080 2050 2080 Alfieri et al. GEC (2015) 7 Adaptation measures for flood risk reduction 1. Reduction of the peak flow (Haz) 2. Increase of flood protection levels (Vul) 3. Reduction of vulnerability (Vul) 4. Relocation (Exp) IPCC (2012) Alfieri et al., Climatic Change (2016) 8 4
Post-event adaptation Alfieri et al., Climatic Change (2016) After each flood event, post-event protections are set to match the return period of the flood flow of the event occurred Average percent reduction in population affected, through post-event adaptation 9 Sensitivity analysis of adaptation strategies Population affected by river floods in Europe, for different adaptation measures and degree of risk reduction 10 5
Sensitivity analysis of adaptation strategies Population affected Germany Damage Germany United Kingdom United Kingdom 11 Residual risk Population affected Germany Damage Germany Hungary Austria 12 6
Conclusions We present a framework to model the socio-economic impact of river floods in Europe in the current century and the benefits of implementing four adaptation options Current flood impact levels can be retained or decreased in the future decades, if coordinated and effective adaptation plans are promptly prepared and put into action Adaptation efforts should target the impact reduction, rather than the frequency reduction of flood events Relocation and vulnerability reduction measures should be further explored for their key features of: 1. Strengthening the resilience of societies by reducing the impacts of all floods without reducing their frequency 2. Risk reduction rates are ~independent on the uncertainty of climate projections 13 More details in: Alfieri, L., Feyen, L., Salamon, P., Burek, P., and Thielen, J.: Modelling the socio-economic impact of river floods in Europe, Nat. Hazards Earth Syst. Sci. Discuss., doi:10.5194/nhess-2015-347, in review, 2016. Alfieri, L., Feyen, L. and Di Baldassarre, G. : Increasing flood risk under climate change: a pan- European assessment of the benefits of four adaptation strategies, Climatic Change, 1 15, doi:10.1007/s10584-016-1641-1, 2016. Alfieri, L., Feyen, L., Dottori, F. and Bianchi, A.: Ensemble flood risk assessment in Europe under high end climate scenarios, Global Environmental Change, 35, 199 212, doi:10.1016/j.gloenvcha.2015.09.004, 2015. Alfieri, L., Burek, P., Feyen, L. and Forzieri, G.: Global warming increases the frequency of river floods in Europe, Hydrol Earth Syst Sci Discuss, 12(1), 1119 1152, doi:10.5194/hessd-12-1119-2015, 2015. Alfieri, L., Salamon, P., Bianchi, A., Neal, J., Bates, P. and Feyen, L.: Advances in pan-european flood hazard mapping, Hydrol. Process., 28(13), 4067 4077, doi:10.1002/hyp.9947, 2014. Lorenzo.Alfieri@jrc.ec.europa.eu Thank you! 14 7
Estimating the average flood impact in Europe (1990-2013) Comparison with reported figures 1998-2009 Simulated Direct damage [B /year] Population affected [pp/year] Reported EEA(2010) 5.38 >5 220,000 262,000 15 Event-based impact assessment Alfieri et al., NHESS (in review) Estimated flood impact in Central Europe between 25 May and 10 June 2013. Simulated vs. reported damage in Europe (1990-2013) Key features Assessment of annual flood impact Impact assessment for selected events Flood impact forecasting applications (EFAS) Along with the hazard, also exposure and vulnerability can change in time 16 8