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Indicator Assessment
Observed regional trends in annual river flood discharges in Europe (1960–2010)
Note: This maps show the linear trend in the annual maximum of daily river discharge over the period 1960-2010. Blue indicates increasing flood discharges and red denotes decreasing flood discharges (in per cent change of the mean annual flood discharge per decade).
Projected change in maximum 100-year daily river discharge for two global warming levels
Note: These maps show the relative change in maximum 100-year daily river discharge for two scenarios of global warming(1.5 °C and 3 °C)
Past trends
Figure 1 shows observed trends in mean annual river flood discharge in medium and large catchments in Europe over the period 1960–2010. The analysis is based on the European Flood Database, which is the most complete database on flooding available for Europe so far [i]. The figure and the underlying analysis shows that climate change has both increased and decreased river floods in Europe. Specifically, river floods increased in northwestern and parts of central Europe, caused by increasing autumn and winter rainfall; decreased in southern Europe, caused by decreasing precipitation and increasing evaporation; and decreased in northeastern Europe, caused by decreasing snow cover and snowmelt. Trends in Fenno-Scandinavia are less pronounced. While individual catchments can be strongly influenced by changes in land use or other factors, the general homogeneity of the changes in large regions and the fact that they can be explained by observed changes in climate variables indicates that climate change has been the main driver of the changes shown in Figure 1.
Note that Figure 1 covers mostly floods in medium and large catchments, which are caused by long-duration synoptic storms. In contrast, floods in small basins are typically caused by local convective storms, which are increasing in a warmer climate. This means that in the Mediterranean, small floods may have increased even though medium and large floods have decreased [ii].
Climate change has also affected the timing of annual floods; these changes include spring snowmelt floods in northeastern Europe occurring earlier, winter floods around the North Sea and parts of the Mediterranean coast occurring later owing to delayed winter storms, and winter floods in western Europe occurring earlier caused by earlier soil moisture maxima [iii]. Another analysis using the same flood database suggests that the distance over which floods affecting different river basins occur near-synchronously has grown from about 80 km in 1960 to 130 km in 2010 in Europe on average. In other words, it now happens more often that various neighbouring river basins are flooded at the same time, which can create new challenges for flood risk management [iv].
Whereas Figure 1 shows changes in annual flood levels, the largest damages are caused by more extreme flood events. Trends in rare flood events are more difficult to detect in observational records because of the limited length of homogenous time series. However, another recent study based on the European Flood Database found that trends in the once-in-a-century flood in Europe show a similar geographical pattern as trends in mean floods over the period 1960–2010, with some variations depending on the region and the size of the catchment area[v]. Therefore, the trends shown in Figure 1 are a reasonable proxy for trends in more extreme floods. Some recent flood events have been so much stronger than previous events that they have led to significant changes in flood risk estimation methods in the affected regions [vi].
The previous version of this indicator focussed on the number of severe floods in Europe based on the European past flood dataset. However, this dataset has not been updated after 2010. A recent independent analysis suggests that the number of very severe flood events in Europe increased over the period 1985–2016, but with large interannual variability [vii].
Flood events have resulted in over 4 300 fatalities and caused direct economic losses of more than EUR 170 billion (based on 2017 values) in EEA member countries over the period 1980–2017. These losses are almost one-third of the damage caused by all natural hazards; less than a quarter of them were covered by insurance [viii]. A shift from a purely technically oriented flood defence toward a more integrated flood risk management system that also considers non-structural measures to minimize adverse effects of flooding has led to more effective flood management and to a substantial reduction of the damage caused by the 2013 floods in Germany, compared to the 2002 floods [ix].
Projections
Figure 2 shows the projected changes in the discharge of a once-in-a-century (Q100) river flood between the reference period (1981–2010) and two levels of global warming (1.5 and 3 °C). The projections are based on the hydrological model LISFLOOD and an ensemble of climate models, assuming that non-climatic factors remain the same. Q100 floods are projected to increase in most European regions, with the greatest increases projected for central and central-eastern Europe. In contrast, decreases in Q100 floods are projected for parts of northern Europe (owing to a reduction in snow accumulation, and hence melt-associated floods) and for southern Spain and Turkey (due to a reduction in rainfall). The projected changes are considerable larger for high than for low warming levels [x]. The results in Figure 2 are generally consistent with those of other recent studies [xi].
The ensemble mean presented in Figure 2 provides the best assessment of all model simulations together, but individual simulations can show important differences from the ensemble mean for individual catchments. Furthermore, the LISFLOOD analysis is restricted to the larger rivers in Europe, which may not be representative of a whole country or region. For example, floods in smaller rivers in northern Europe may increase because of projected increases in precipitation amounts, even where snowmelt-dominated floods in large rivers are projected to decrease [xii]. Similarly, floods in smaller rivers in southern Europe may increase due to an increase in convective rainfall [xiii].
Changes in the frequency of floods below the protection level (e.g. Q100) are expected to have less significant economic effects and affect fewer people than even small changes in the largest events (e.g. with a return period of 500 years). For a number of European river basins, including the Po, Duero, Garonne, Ebro, Loire, Rhine and Rhone, an increase in extreme floods with a return period above 500 years is projected; this includes river basins such as Guadiana and Narva, where the overall frequency of flood events is projected to decline [xiv].
Model studies of the socio-economic impacts of river floods conducted by the Joint Research Centre (JRC) suggest that future climate change will increase population affected and economic damages from floods in almost countries in Europe. The strongest increase in flood risk is projected for countries in western and central Europe, such as Austria, Hungary, Slovakia and Slovenia. In northeastern Europe, the average change in flood risk is smaller and the agreement between different studies is poorer. A high climate change scenario (RCP8.5) could increase the socio-economic impact of floods in Europe more than three-fold by the end of the 21st century. Modelled flood impacts would increase further if socioeconomic developments or indirect damages were considered whereas additional adaptation measures for flood risk reduction could significantly decrease them [xv].
[i] J. Hall et al., ‘A European Flood Database: Facilitating Comprehensive Flood Research beyond Administrative Boundaries’,Proceedings of the International Association of Hydrological Sciences 370 (11 June 2015): 89–95, https://doi.org/10.5194/piahs-370-89-2015.
[ii] Günter Blöschl et al., ‘Changing Climate Both Increases and Decreases European River Floods’,Nature 573, no. 7772 (September 2019): 108–11, https://doi.org/10.1038/s41586-019-1495-6.
[iii] Günter Blöschl et al., ‘Changing Climate Shifts Timing of European Floods’,Science 357, no. 6351 (11 August 2017): 588–90, https://doi.org/10.1126/science.aan2506.
[iv] Wouter R. Berghuijs et al., ‘Growing Spatial Scales of Synchronous River Flooding in Europe’,Geophysical Research Letters 46, no. 3 (16 February 2019): 1423–28, https://doi.org/10.1029/2018GL081883.
[v] Miriam Bertola et al., ‘Flood Trends in Europe: Are Changes in Small and Big Floods Different?’, preprint (Rivers and Lakes/Stochastic approaches, 18 October 2019), https://doi.org/10.5194/hess-2019-523.
[vi] For examples from the United Kingdom, see J. D. Miller et al., ‘A Hydrological Assessment of the November 2009 Floods in Cumbria, UK’,Hydrology Research 44, no. 1 (December 2013): 180, https://doi.org/10.2166/nh.2012.076; Nathalie Schaller et al., ‘Human Influence on Climate in the 2014 Southern England Winter Floods and Their Impacts’,Nature Climate Change 6 (1 February 2016): 627–34, https://doi.org/10.1038/nclimate2927.
[vii] Zbigniew W. Kundzewicz, Iwona Pińskwar, and G. Robert Brakenridge, ‘Changes in River Flood Hazard in Europe: A Review’,Hydrology Research 49, no. 2 (April 2018): 294–302, https://doi.org/10.2166/nh.2017.016.
[viii] EEA, ‘Economic Losses from Climate-Related Extremes in Europe’, Indicator Assessment, 2019, https://www.eea.europa.eu/ds_resolveuid/IND-182-en.
[ix] Annegret H. Thieken et al., ‘Review of the Flood Risk Management System in Germany after the Major Flood in 2013’,Ecology and Society 21, no. 2 (2016): 51, https://doi.org/10.5751/ES-08547-210251.
[x] Adapted from L. Alfieri et al., ‘Global Warming Increases the Frequency of River Floods in Europe’,Hydrology and Earth System Sciences 19, no. 5 (11 May 2015): 2247–60, https://doi.org/10.5194/hess-19-2247-2015; L. Alfieri, F. Dottori, and L. Feyen, ‘JRC PESETA III Project. Task 7 – River Floods’, JRC Technical Reports (European Commission, 2017), https://ec.europa.eu/jrc/en/publication/peseta-iii-task-7-river-floods; F. Dottori et al., ‘Adapting to Rising River Flood Risk in the EU under Climate Change’, JRC Technical Reports (European Commission, forthcoming).
[xi] Z. W. Kundzewicz et al., ‘Differences in Flood Hazard Projections in Europe – Their Causes and Consequences for Decision Making’,Hydrological Sciences Journal, 29 September 2016, 02626667.2016.1241398, https://doi.org/10.1080/02626667.2016.1241398; Philippe Roudier et al., ‘Projections of Future Floods and Hydrological Droughts in Europe under a +2°C Global Warming’,Climatic Change 135, no. 2 (March 2016): 341–55, https://doi.org/10.1007/s10584-015-1570-4; Chantal Donnelly et al., ‘Impacts of Climate Change on European Hydrology at 1.5, 2 and 3 Degrees Mean Global Warming above Preindustrial Level’,Climatic Change 143, no. 1–2 (July 2017): 13–26, https://doi.org/10.1007/s10584-017-1971-7; Stephan Thober et al., ‘Multi-Model Ensemble Projections of European River Floods and High Flows at 1.5, 2, and 3 Degrees Global Warming’,Environmental Research Letters 13, no. 1 (1 January 2018): 014003, https://doi.org/10.1088/1748-9326/aa9e35.
[xii] Klaus Vormoor et al., ‘Evidence for Changes in the Magnitude and Frequency of Observed Rainfall vs. Snowmelt Driven Floods in Norway’,Journal of Hydrology 538 (July 2016): 33–48, https://doi.org/10.1016/j.jhydrol.2016.03.066.
[xiii] Nikolina Ban, Juerg Schmidli, and Christoph Schär, ‘Heavy Precipitation in a Changing Climate: Does Short-Term Summer Precipitation Increase Faster?’,Geophysical Research Letters 42, no. 4 (28 February 2015): 1165–72, https://doi.org/10.1002/2014GL062588.
[xiv] Alfieri et al., ‘Global Warming Increases the Frequency of River Floods in Europe’.
[xv] Lorenzo Alfieri et al., ‘Ensemble Flood Risk Assessment in Europe under High End Climate Scenarios’,Global Environmental Change 35 (November 2015): 199–212, https://doi.org/10.1016/j.gloenvcha.2015.09.004; Alfieri, Dottori, and Feyen, ‘JRC PESETA III Project. Task 7 – River Floods’; Lorenzo Alfieri et al., ‘Multi-Model Projections of River Flood Risk in Europe under Global Warming’,Climate 6, no. 1 (24 January 2018): 6, https://doi.org/10.3390/cli6010006; E E Koks et al., ‘The Macroeconomic Impacts of Future River Flooding in Europe’,Environmental Research Letters 14, no. 8 (12 August 2019): 084042, https://doi.org/10.1088/1748-9326/ab3306.
This indicator monitors:
In April 2013, the European Commission presented the EU adaptation strategy package. This package consists of the EU strategy on adaptation to climate change (COM/2013/216 final) and a number of supporting documents. The overall aim of the EU adaptation strategy is to contribute to a more climate-resilient Europe. One of the objectives of the EU adaptation strategy is to allow 'Better informed decision-making'. This will be achieved by bridging knowledge gaps and further developing the European climate adaptation platform (Climate-ADAPT) as the ‘first-stop shop’ for adaptation information in Europe. Climate-ADAPT has been developed jointly by the European Commission and the European Environment Agency (EEA) to share knowledge on (1) observed and projected climate change and its impacts on environmental and social systems and on human health, (2) relevant research, (3) EU, transnational, national and subnational adaptation strategies and plans, and (4) adaptation case studies. It was relaunched in early 2019 with a new design and updated content. Further objectives include 'Promoting adaptation in key vulnerable sectors through climate-proofing EU sector policies' and 'Promoting action by Member States'.
In November 2018, the Commission published its evaluation of the 2013 EU adaptation strategy. The evaluation package includes a report from the Commission, a Commission staff working document, adaptation preparedness scoreboard country fiches and reports from the JRC Peseta III project. This evaluation includes recommendations for the further development and implementation of adaptation policies at all levels.
In November 2013, the European Parliament and the Council of the European Union adopted the EU's Seventh Environment Action Programme (7th EAP) to 2020, ‘Living well, within the limits of our planet’. The 7th EAP is intended to help guide EU action on environment and climate change up to and beyond 2020. It highlights that ‘Action to mitigate and adapt to climate change will increase the resilience of the Union’s economy and society, while stimulating innovation and protecting the Union’s natural resources.’ Consequently, several priority objectives of the 7th EAP refer to climate change adaptation.
No targets have been specified.
Trends in river floods are calculated based on the annual flood discharge of all rivers included in the European Flood Database.
Future changes in the risk of river floods in Europe have been simulated using the hydrological model Lisiflood, driven by an ensemble of climate simulations. Of particular interest is the frequency analysis of flood peaks above the 100-year flood level, which is the average protection level of the European river network (albeit with significant differences).
Not applicable.
Not applicable.
The data required for the indicator are those on river flow, in particular data on extreme high flows. Time series can be observed or simulated for historical periods and can be projected for future time windows, taking into account climate change and potentially also other drivers of change, such as land use changes.
River flow is influenced by rainfall run-off and by hydromorphological changes of the river bed, e.g. through river engineering. Furthermore, homogeneous time series are generally shorter than those for meteorological data. Therefore, substantially more time may be required before statistically significant changes in hydrological variables can be observed, especially with respect to extreme and exceptional events, such as floods.
Notwithstanding recent improvements of climate models that simulate large-scale patterns of precipitation and extreme events, projections of changes in precipitation extremes at catchment and local scales remain uncertain. Projections of small river floods are plagued by the highest levels of uncertainty, as they often depend on changes in localised extreme events.
No uncertainty has been specified
For references, please go to https://eea.europa.eu./data-and-maps/indicators/river-floods-3/assessment or scan the QR code.
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