River floods

Indicator Assessment
Prod-ID: IND-104-en
Also known as: CLIM 017
Created 22 Nov 2019 Last modified 04 Dec 2019
17 min read

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River floods increased in north-western and parts of central Europe but decreased in southern and north-eastern Europe over the period 1960-2010 because of climate change. Climate change is projected to increase the occurrence and frequency of river floods in most regions of Europe, with the exception of north-eastern Europe and the southern Iberian Peninsula. Pluvial floods and flash floods, which are triggered by intense local precipitation events, are likely to become more frequent throughout Europe. River floods are among the most damaging extreme climate events in Europe. Under a high-emissions scenario, climate change could triple the direct damages from river floods during the 21st century in the absence of additional adaptation measures.

This indicator will be updated in December 2019

Key messages

  • River floods increased in north-western and parts of central Europe but decreased in southern and north-eastern Europe over the period 1960-2010 because of climate change.
  • Climate change is projected to increase the occurrence and frequency of river floods in most regions of Europe, with the exception of north-eastern Europe and the southern Iberian Peninsula. Pluvial floods and flash floods, which are triggered by intense local precipitation events, are likely to become more frequent throughout Europe.
  • River floods are among the most damaging extreme climate events in Europe. Under a high-emissions scenario, climate change could triple the direct damages from river floods during the 21st century in the absence of additional adaptation measures.

What is the trend in river floods across Europe?

Projected change in river floods with a return period of 100 years

Note: 100-year daily peak flow (Q100). Relative change for the time slices 2006-2035, 2036-2065 and 2066–2095 compared to the ensemble mean of the baseline (1976–2005), based on an ensemble of EURO-CORDEX RCP8.5 scenarios. Data points with CV>1 are greyed out. (CV = coefficient of variation)

Data source:
Downloads and more info

Past trends

Fig. 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 [i]. The figure and the underlying analysis show that climate change has both increased and decreased river floods in Europe. Specifically, river floods increased in north-western and parts of central Europe because of increasing autumn and winter rainfall; decreased in southern Europe because of decreasing precipitation and increasing evaporation; and decreased in north-eastern Europe because of 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 indicate that climate change has been the main driver of the changes shown in Fig. 1.

Note that Fig. 1 covers floods mostly 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 warmer climates. This means that, in the Mediterranean, floods in small catchments may have increased even though those in medium and large catchments have decreased [ii].

Climate change has also affected the timing of annual floods; these changes include spring snowmelt floods in north-eastern 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, because of 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, various neighbouring river basins are flooded at the same time more often now than in the past, which can create new challenges for flood risk management [iv].

Although Fig. 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 decays the limited length of homogenous time series. However, another recent study based on the European Flood Database found that trends in the 100-year 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 (Bertola et al., 2019). Therefore, the trends shown in Fig. 1 are a reasonable proxy for trends in more extreme flood events. Some recent flood events have been so much stronger than previous events that they have led to significant changes in flood risk estimation methods for that region [v].

The previous version of this indicator focused on the number of severe floods in Europe based on the European past floods data set. However, this data set has not been updated since 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 inter-annual variability [vi].

Flood events resulted in over 4 300 fatalities and caused direct economic losses of more than EUR 170 billion (based on 2017 values) in European Environment Agency (EEA) member countries over the period 1980-2017. These losses account for almost one third of those caused by all natural hazards, and less than a quarter of them were insured [vii]. A shift from purely technically oriented flood defences towards a more integrated flood risk management system that also considers non-structural measures to minimise the adverse effects of flooding has led to more effective flood management and meant that substantially less damage was caused by the 2013 floods in Germany than had been by the 2002 floods [viii].

Projections

Fig. 2 shows the change in the discharge of one-in-a-century (Q100) river floods between the reference period (1981-2010) and the end of the century (2071-2100) for a medium-emissions scenario (RCP4.5) based on the hydrological model Lisiflood and an ensemble of climate models, assuming that non-climatic factors remain the same. Blue rivers indicate an increase in flood discharge and red rivers indicate a decrease. The greatest increase in Q100 floods is projected for the British Isles, north-west and south-east France, northern Italy and some regions in south-east Spain, the Balkans and the Carpathians. Mild increases are projected for central Europe, the upper section of the Danube and its main tributaries. In contrast, decreases in Q100 floods are projected for large parts of north-eastern Europe (owing to a reduction in snow accumulation, and hence melt-associated floods) and the southern part of the Iberian Peninsula (because of a reduction in rainfall) [ix]. The results in Fig. 2 are generally consistent with other recent studies [x].

The ensemble mean presented in Fig. 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 Lisiflood 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 [xi]. Similarly, floods in smaller rivers in southern Europe may increase because of an increase in convective rainfall [xii].

Changes in flood frequencies 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. events 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 [xiii].

Model studies of the socio-economic impacts of river floods conducted by the Joint Research Centre (JRC) suggest that future climate change will increase the population affected and economic damages from floods in almost all 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 north-eastern Europe, the average change in flood risk is smaller and the agreement between different studies is poorer. A high-emissions climate change scenario (RCP8.5) could increase the socio-economic impact of floods in Europe by more than three fold by the end of the 21st century. Modelled flood impacts would increase further if socio-economic developments or indirect damages were considered whereas additional adaptation measures for flood risk reduction could significantly decrease impacts [xiv].


[i] Hall, J. et al., 2015, ‘A European flood database: Facilitating comprehensive flood research beyond administrative boundaries’, Proceedings of the International Association of Hydrological Sciences 370, pp. 89-95, https://doi.org/10.5194/piahs-370-89-2015.

[ii] Blöschl et al., ‘Changing climate both increases and decreases European river floods’.

[iii] Blöschl, G. et al., 2017, ‘Changing climate shifts timing of European floods’, Science 357(6351), pp. 588-590, https://doi.org/10.1126/science.aan2506.

[iv] Berghuijs, W. R. et al., 2019, ‘Growing spatial scales of synchronous river flooding in Europe’, Geophysical Research Letters 46(3), pp. 1423-1428, https://doi.org/10.1029/2018GL081883.

[v] For examples from the United Kingdom, see Miller, J. D. et al., 2013, ‘A hydrological assessment of the November 2009 floods in Cumbria, UK’, Hydrology Research 44(1), 180, https://doi.org/10.2166/nh.2012.076; Schaller, N. et al., 2016, ‘Human influence on climate in the 2014 southern England winter floods and their impacts’, Nature Climate Change 6, pp. 627-634, https://doi.org/10.1038/nclimate2927.

[vi] Kundzewicz, Z. W., Pińskwar, I. and Brakenridge, G. R., 2018, ‘Changes in river flood hazard in Europe: A review’, Hydrology Research 49(2), pp. 294-302, https://doi.org/10.2166/nh.2017.016.

[vii] EEA, 2019, ‘Economic losses from climate-related extremes in Europe’, Indicator Assessment, European Environment Agency, https://www.eea.europa.eu/ds_resolveuid/IND-182-en.

[viii] Thieken, A. H. et al., 2016, ‘Review of the flood risk management system in Germany after the major flood in 2013’, Ecology and Society 21(2), 51, https://doi.org/10.5751/ES-08547-210251.

[ix] Adapted from Alfieri, L. et al., 2015, ‘Global warming increases the frequency of river floods in Europe’, Hydrology and Earth System Sciences 19(5), pp. 2247-2260, https://doi.org/10.5194/hess-19-2247-2015; Alfieri, Dottori, and Feyen, ‘JRC Peseta III Project. Task 7 — River Floods’; Dottori et al., ‘Adapting to rising river flood risk in the EU under climate change’.

[x] Kundzewicz, Z. W. et al., 2016, ‘Differences in flood hazard projections in Europe — Their causes and consequences for decision making’, Hydrological Sciences Journal, 02626667.2016.1241398, https://doi.org/10.1080/02626667.2016.1241398; Roudier, P. et al., 2016, ‘Projections of future floods and hydrological droughts in Europe under a +2 °C global warming’, Climatic Change 135(2), pp. 341-355, https://doi.org/10.1007/s10584-015-1570-4; Donnelly, C. et al., 2017, ‘Impacts of climate change on European hydrology at 1.5, 2 and 3 degrees mean global warming above preindustrial level’, Climatic Change 143(1-2), pp. 13-26, https://doi.org/10.1007/s10584-017-1971-7; Thober, S. et al., 2018, ‘Multi-model ensemble projections of European river floods and high flows at 1.5, 2 and 3 degrees global warming’, Environmental Research Letters 13(1), 014003, https://doi.org/10.1088/1748-9326/aa9e35.

[xi] Vormoor, K. et al., 2016, ‘Evidence for changes in the magnitude and frequency of observed rainfall vs. snowmelt driven floods in Norway’, Journal of Hydrology 538, pp. 33-48, https://doi.org/10.1016/j.jhydrol.2016.03.066.

[xii] Ban, N. et al., 2015, ‘Heavy precipitation in a changing climate: Does short-term summer precipitation increase faster?’, Geophysical Research Letters 42(4), pp. 1165-1172, https://doi.org/10.1002/2014GL062588.

[xiii] Alfieri et al., 2015.

[xiv] Alfieri, L. et al., 2015, ‘Ensemble flood risk assessment in Europe under high end climate scenarios’, Global Environmental Change 35, pp. 199-212, https://doi.org/10.1016/j.gloenvcha.2015.09.004; Alfieri, Dottori, and Feyen, ‘JRC Peseta III Project. Task 7 — River Floods’; Alfieri, L. et al., 2018, ‘Multi-model projections of river flood risk in Europe under global warming’, Climate 6(1), 6, https://doi.org/10.3390/cli6010006; Koks, E. E. et al., 2019, ‘The macroeconomic impacts of future river flooding in Europe’, Environmental Research Letters 14(8), 084042, https://doi.org/10.1088/1748-9326/ab3306.

Indicator specification and metadata

Indicator definition

This indicator monitors:

  • observed regional trends in river flood discharges;
  • projected changes in river floods with a return period of 100 years.

Units

  • % change per decade
  • Percentage change (%)

Policy context and targets

Context description

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 documentadaptation 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.

Targets

No targets have been specified.

Related policy documents

  • 7th Environment Action Programme
    DECISION No 1386/2013/EU OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 20 November 2013 on a General Union Environment Action Programme to 2020 ‘Living well, within the limits of our planet’. In November 2013, the European Parliament and the European Council adopted the 7 th EU Environment Action Programme to 2020 ‘Living well, within the limits of our planet’. This programme is intended to help guide EU action on the environment and climate change up to and beyond 2020 based on the following vision: ‘In 2050, we live well, within the planet’s ecological limits. Our prosperity and healthy environment stem from an innovative, circular economy where nothing is wasted and where natural resources are managed sustainably, and biodiversity is protected, valued and restored in ways that enhance our society’s resilience. Our low-carbon growth has long been decoupled from resource use, setting the pace for a safe and sustainable global society.’
  • Climate-ADAPT: Adaptation in EU policy sectors
    Overview of EU sector policies in which mainstreaming of adaptation to climate change is ongoing or explored
  • Climate-ADAPT: Country profiles
    Overview of activities of EEA member countries in preparing, developing and implementing adaptation strategies
  • DG CLIMA: Adaptation to climate change
    Adaptation means anticipating the adverse effects of climate change and taking appropriate action to prevent or minimise the damage they can cause, or taking advantage of opportunities that may arise. It has been shown that well planned, early adaptation action saves money and lives in the future. This web portal provides information on all adaptation activities of the European Commission.
  • Directive 2007/60/EC of the European Parliament and of the Council on the assessment and management of flood risks
    Directive 2007/60/EC of the European Parliament and of the Council of 23 October 2007 on the assessment and management of flood risks (Text with EEA relevance) OJ L 288, 06/11/2007, p. 27–34
  • EU Adaptation Strategy Package
    In April 2013, the European Commission adopted an EU strategy on adaptation to climate change, which has been welcomed by the EU Member States. The strategy aims to make Europe more climate-resilient. By taking a coherent approach and providing for improved coordination, it enhances the preparedness and capacity of all governance levels to respond to the impacts of climate change.
  • Evaluation of the EU Adaptation Strategy Package
    In November 2018, the EC published an evaluation of the EU Adaptation Strategy. The evaluation package comprises a Report on the implementation of the EU Strategy on adaptation to climate change (COM(2018)738), the Evaluation of the EU Strategy on adaptation to climate change (SWD(2018)461), and the Adaptation preparedness scoreboard Country fiches (SWD(2018)460). The evaluation found that the EU Adaptation Strategy has been a reference point to prepare Europe for the climate impacts to come, at all levels. It emphasized that EU policy must seek to create synergies between climate change adaptation, disaster risk reduction efforts and sustainable development to avoid future damage and provide for long-term economic and social welfare in Europe and in partner countries. The evaluation also suggests areas where more work needs to be done to prepare vulnerable regions and sectors.
  • Guidance for Reporting under the Floods Directive (2007/60/EC)
    Guidance Document No. 29 A compilation of reporting sheets adopted by Water Directors Common Implementation Strategy for the Water Framework Directive (2000/60/EC)

Methodology

Methodology for indicator calculation

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).

Methodology for gap filling

Not applicable.

Methodology references

Uncertainties

Methodology uncertainty

Not applicable.

Data sets uncertainty

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.

Rationale uncertainty

No uncertainty has been specified

Data sources

Metadata

Topics:

information.png Tags:
, , , , ,
DPSIR: Impact
Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)

Dates

Frequency of updates

Updates are scheduled every 4 years

EEA Contact Info

Peter Kristensen
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