River Floods

Submitted by Michael Rastall | published 29th Nov 2012 | last updated 7th Dec 2012


Key Messages

  • Floods already cause major economic costs in Europe. Climate change could increase the magnitude and frequency of these events, leading to higher costs. However, these events need to be seen in the context of other socio-economic drivers.
  • The ClimateCost study has assessed the potential impacts of climate change on river flood damage in Europe, and the costs and benefits of adaptation. The analysis used the LISFLOOD model, and considered future climate and socio-economic change. As floods are probabilistic events, the results are presented as expected annual damage (EAD) costs (undiscounted). It should be noted that the damages reported here only include direct physical losses and could, therefore, be conservative.
  • The study first assessed the number of people potentially affected by river flooding in the EU27. The expected annual people (EAP) flooded in the baseline climate period (1961-1990) was estimated at around 167,000/year.
  • The economic damages from flooding of the residential and other sectors were then assessed. The EAD in the baseline climate period (with current socio-economic conditions) is estimated at around €5.5 billion in the EU27. The analysis then looked at the increase in the EAP and the EAD from future climate change, considering three future time periods (averaged in 30-year periods), for a medium-high emission and mitigation scenario.
  • Under a medium-high emission baseline (A1B), with no mitigation or adaptation, the projected mean EAP affected by flooding in the EU27 is 300,000 by the 2050s (the years 2041-2070), rising to 360,000 by the 2080s (2071-2100). This includes the combined effects of socio-economic change (future population) and climate change.
  • The EAD for the A1B scenario in the EU27 is estimated at €20 billion by the 2020s (2011-2040), €46 billion by the 2050s (2041-2070) and €98 billion by the 2080s (2071-2100) (mean ensemble results, current values, undiscounted). However, a large part of this is due to socio-economic change (population and economic growth).The marginal effect of climate change (alone) is estimated at €9 billion/year by the 2020s, €19 billion/year by the 2050s and €50 billion/year by the 2080s. Analysis at the country level shows high climate-related costs in the UK, Ireland, Italy, the Netherlands and Belgium.
  • There is a very wide range around these central (mean) estimates, representing the range of results from different climate models. The study considered 12 alternative climate outputs (global climate model/ regional climate model combinations). These reveal that the potential costs vary by a factor of two (higher or lower). Differences are even more significant at the country or local level, with some models showing opposite directions of change in flood risk (i.e. some models project relative reductions in future flood risk due to climate change in areas where other models show an increase). This highlights the need to consider this variability (uncertainty) in formulating adaptation strategies.
  • Under an E1 stabilisation scenario, broadly equivalent to the EU 2 degrees target, the EAD is estimated to amount to €15 billion by the 2020s, €42 billion by the 2050s and €68 billion by the 2080s in the EU27 (current values, undiscounted). The marginal impact of climate change alone (i.e. with socio-economic change not included) is estimated at €5 billion/year by the 2020s, €20 billion/year by the 2050s and €30 billion/year by the 2080s -significantly lower than for A1B estimates above, especially towards the end of this century. However, this analysis is built around a limited number of E1 climate data sets, mostly focused on one climate model. Therefore, the lower damages under the stabilisation scenario are more likely to be related to the climate model choice rather than to the effect of mitigation.
  • The study also assessed the costs and benefits of adaptation. The analysis first assessed the benefits of maintaining 1 in 100-year levels of flood protection across Europe in future time periods, set against the projected changes in flood hazard under the A1B scenario. The benefits of these minimum protection levels (i.e. the reduction in damage costs) are estimated at €8 billion/year by the 2020s, €19 billion/year by the 2050s and €50 billion/year by the 2080s for the results (mean ensemble, EU27, climate and socio-economic change current values, undiscounted). It should be noted that the benefits vary with the climate variability, so there is a significant range around these values. There are also significant residual damages in later years under these minimum protection levels. This suggests higher protection levels would be justified.
  • The analysis then assessed the costs of achieving these protection levels. This has transferred information from detailed protection studies to derive indicative costs of adaptation at the European scale. The costs to maintain minimum protection levels are estimated at €1.7 billion/year by the 2020s, €3.4 billion/year by the 2050s and €7.9 billion/year by the 2080s for the EU (mean ensemble, A1B, undiscounted). It should be noted that the costs of adaptation vary significantly with the level of future climate change, the level of acceptable risk protection and the framework of analysis (risks protection versus economic efficiency).
  • The socio-economic uncertainty and climate-model variability make a large difference to the actual adaptation response at a country level. The need to recognise and work with uncertainty – as part of integrated and sustainable policies – requires an iterative and flexible approach.
  • A number of implications arise from the analysis, the most important of which is to start including these issues in policy across Europe.

Citation

Feyen, L. and Watkiss, P. (2011). Technical Policy Briefing Note 3. The Impacts and Economic Costs of River Floods in Europe, and the Costs and Benefits of Adaptation. Results from the EC RTD ClimateCost Project. In Watkiss, P (Editor), 2011. The ClimateCost Project. Final Report. Published by the Stockholm Environment Institute,  Sweden, 2011. ISBN. 978-91-86125-35-6.