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Indicator Assessment
Occurrence of major floods in Europe
Note: Occurrence of major floods in Europe (1998–2009)
Projected change in river floods with a return period of 100 years
Note: Projected change in the level of a 100-year maximum level of river discharge between the reference period 1961–1990 and the 2020s (left), 2050s (centre) and 2050s (right) based on an ensemble of 12 RCM simulations with LISFLOOD for the SRES A1B scenario.
Past trends
Figure 1 shows the occurrence of flood events in Europe from 1998–2009. This picture is incomplete because events with small spatial extent and/or impact are not included. Nevertheless, it becomes clear that large areas throughout Europe have been affected by flooding over the last decade, many of them even multiple times. Flood losses in Europe have increased substantially over recent decades but this trend is primarily attributable to socio-economic factors, such as increasing wealth located in flood zones. The influence of anthropogenic climate change remains inconclusive [i].
Significant trends in river inundations have been identified in some regional and national studies. For example, significant increases in flood intensities have been identified between 1951 and 2002 in western, southern and central Germany [ii] as well as in upland catchments in the northern and western UK [iii]. A new analysis of the strong UK floods of 2000 suggests that anthropogenic climate change was a contributing factor [iv]. In the Alps [v] and Nordic region [vi], snowmelt floods have occurred earlier because of warmer winters. In contrast, no conclusive evidence was found in an analysis of flood trends in Austria [vii], and an increasing flood trend in Catalonia is attributed to socio-economic factors [viii].
Projections
Changes in future flood hazard in Europe have been simulated by a hydrological model driven by an ensemble of climate simulations [ix]; [x]. An increasing flood hazard is consistently projected for several of Europe’s major rivers across climate models and emissions scenarios [xi].
Figure 2 shows the change in the return period of a 1-in-a-century flood between the reference period and 2050 based on an ensemble of 11 climate and hydrological simulations. Red rivers indicate a decrease in the return period, which implies that floods of this magnitude will occur more frequently in the future. While the ensemble mean presented in Figure 2 provides the best assessment of all model simulations together, individual simulations can show important differences from the ensemble mean for individual catchments, partly due to significant decadal-scale internal variability in the simulated climate [xii]. A decrease in 1-in-a-century floods is projected in large parts of north-eastern Europe due to a reduction in snow accumulation and hence melt-associated floods under milder winter temperatures [xiii]. This projection is consistent with other studies on snow-dominated regions, including parts of Finland [xiv], the Alps and Carpathian Mountains [xv]. Flash floods and pluvial floods, which are triggered by local intense precipitation events, are also likely to become more frequent throughout Europe [xvi]. A regional approach is required for solving pluvial and fluvial flood problems in urban areas [xvii] because regional and local city characteristics are very important in determining the impacts from projected increases in floods and intensive precipitation events. Flood risks in a city can also be strongly influenced by factors outside the city boundaries such as upstream river management.
[i] J.I. Barredo, „Normalised flood losses in Europe: 1970–2006“, Natural Hazards and Earth System Sciences 9 (Februar 9, 2009): 97–104, doi:10.5194/nhess-9-97-2009.
[ii] Theresia Petrow and Bruno Merz, „Trends in flood magnitude, frequency and seasonality in Germany in the period 1951–2002“, Journal of Hydrology 371, Nr. 1–4 (Juni 5, 2009): 129–141, doi:10.1016/j.jhydrol.2009.03.024.
[iii] Jamie Hannaford and Terry J Marsh, „High‐flow and Flood Trends in a Network of Undisturbed Catchments in the UK“, International Journal of Climatology 28, Nr. 10 (August 1, 2008): 1325–1338, doi:10.1002/joc.1643.
[iv] Pardeep Pall et al., „Anthropogenic Greenhouse Gas Contribution to Flood Risk in England and Wales in Autumn 2000“, Nature 470, Nr. 7334 (Februar 16, 2011): 382–385, doi:10.1038/nature09762.
[v] B. Renard et al., „Regional methods for trend detection: Assessing field significance and regional consistency“, Water Resources Research 44 (August 12, 2008): W08419, doi:10.1029/2007WR006268.
[vi] Donna Wilson, Hege Hisdal, and Deborah Lawrence, „Has streamflow changed in the Nordic countries? – Recent trends and comparisons to hydrological projections“, Journal of Hydrology 394, Nr. 3–4 (November 26, 2010): 334–346, doi:10.1016/j.jhydrol.2010.09.010.
[vii] Gabriele Villarini et al., „Analyses of Extreme Flooding in Austria over the Period 1951–2006“, International Journal of Climatology 32, Nr. 8 (2012): 1178–1192, doi:10.1002/joc.2331.
[viii] M. Barnolas and M.C. Llasat, „A flood geodatabase and its climatological applications: the case of Catalonia for the last century“, Natural Hazards and Earth System Sciences 7, Nr. 2 (April 5, 2007): 271–281, doi:10.5194/nhess-7-271-2007.
[ix] Rutger Dankers and Luc Feyen, „Flood hazard in Europe in an ensemble of regional climate scenarios“, Journal of Geophysical Research 114, Nr. D16 (August 27, 2009), doi:10.1029/2008JD011523.
[x] Martina Flörke et al., Climate Adaptation – modelling water scenarios and sectoral impacts. Final Report Contract N° DG ENV.D.2/SER/2009/0034 (Kassel, Germany: Center for Environmental Systems Research, University of Kassel, Oktober 28, 2011), http://circa.europa.eu/Public/irc/env/wfd/library?l=/framework_directive/climate_adaptation/climwatadapt_report.
[xi] Luc Feyen et al., „Fluvial flood risk in Europe in present and future climates“, Climatic Change 112, Nr. 1 (November 23, 2011): 47–62, doi:10.1007/s10584-011-0339-7.
[xii] Feyen et al., „Fluvial flood risk in Europe in present and future climates“.
[xiii] Dankers and Feyen, „Flood hazard in Europe in an ensemble of regional climate scenarios“.
[xiv] Noora Veijalainen et al., „National scale assessment of climate change impacts on flooding in Finland“, Journal of Hydrology 391, Nr. 3–4 (September 24, 2010): 333–350, doi:10.1016/j.jhydrol.2010.07.035.
[xv] EEA, Regional climate change and adaptation — The Alps facing the challenge of changing water resources EEA Report (Copenhagen, September 9, 2009), http://www.eea.europa.eu/publications/alps-climate-change-and-adaptation-2009.
[xvi] J. H Christensen and Ole B. Christensen, „Severe summertime flooding in Europe“, Nature 421 (Februar 20, 2002): 805–806; Zbigniew W. Kundzewicz, Maciej Radziejewski, and Iwona Pínskwar, „Precipitation extremes in the changing climate of Europe“, Climate Research 31 (Juni 26, 2006): 51–58, doi:10.3354/cr031051.
[xvii] EEA, Urban adaptation to climate change in Europe - Challenges and opportunities for cities together with supportive national and European policies EEA Report (Copenhagen: European Environment Agency, 2012), http://www.eea.europa.eu/publications/urban-adaptation-to-climate-change.
In April 2013 the European Commission presented the EU Adaptation Strategy Package (http://ec.europa.eu/clima/policies/adaptation/what/documentation_en.htm). This package consists of the EU Strategy on adaptation to climate change /* COM/2013/0216 final */ and a number of supporting documents. One of the objectives of the EU Adaptation Strategy is Better informed decision-making, which should occur through Bridging the knowledge gap and Further developing Climate-ADAPT as the ‘one-stop shop’ for adaptation information in Europe. Further objectives include Promoting action by Member States and Climate-proofing EU action: promoting adaptation in key vulnerable sectors. Many EU Member States have already taken action, such as by adopting national adaptation strategies, and several have also prepared action plans on climate change adaptation.
The European Commission and the European Environment Agency have developed the European Climate Adaptation Platform (Climate-ADAPT, http://climate-adapt.eea.europa.eu/) to share knowledge on observed and projected climate change and its impacts on environmental and social systems and on human health; on relevant research; on EU, national and subnational adaptation strategies and plans; and on adaptation case studies.
No targets have been specified.
The occurrence of flood events in Europe from 1998–2009 is based on data of the Dartmouth Flood Observatory. This picture is incomplete because events with small spatial extent and/or impact are not included.
Projected change in the level of a 100-year maximum level of river discharge between the reference period 1961–1990 and the 2020s (left), 2050s (centre) and the 2080s (right) are based on an ensemble of 12 RCM simulations with LISFLOOD for the SRES A1B scenario.
Not applicable
Not applicable
Detailed data on water quantity is often difficult to assess, and homogeneous time series are generally shorter than those for meteorological data. It may, therefore, require substantially more time before statistically significant changes in hydrological variables can be observed than for meteorological variables, especially with respect to extreme events (floods and droughts). Quantitative projections of changes in precipitation and river flows at the basin scale remain highly uncertain due to the limitations of climate models and to scaling issues between climate and hydrological models.
The main data sources for European-wide studies of extreme hydrological events and their changes are global databases for natural disasters. These include general impact-oriented disaster databases such as EM-DAT ([1]) maintained by the Centre for Research on the Epidemiology of Disasters (CRED) and the NatCatService ([2]) maintained by Munich Re, as well as specific mostly event-oriented databases, such as the Dartmouth Flood Observatory ([3]). Some of the limitations of these databases included the use of thresholds for inclusion of an event, which may exclude smaller events with a significant regional impact, changes over time in the comprehensiveness of the coverage (see below), and privacy issues related to detailed data collected by the insurance industry. Improvements of these datasets are planned in coming years. The available data is currently evaluated, for example in the ongoing emBRACE project ([4]). A more detailed and comprehensive event-oriented database that also includes events without any (major) damages would be needed to separate the effect of climate change from socio-economic changes.
The reporting of flood and drought events has generally improved during the past few decades as a result of improvements in data collection and flows of information. As a result, it is often difficult to identify whether an increase in reported flood events (or their impacts) over time is due mostly to improvements in data collection or to actual changes in these events. Furthermore, river flood records are usually sourced from different institutions and often collected using a wide range of different assessment methods and rationales, which may have changed over time. This multitude of sources limits the comparability of key attributes associated with such events (e.g. economic losses, human casualties) across space and time.
As part of the preliminary flood risk assessment for the European directive on the assessment and management of flood risks (2007/60/EC) ([5]), EU Member States will give an overview of significant past floods. In addition, a European flood impact database could bring together publicly available inventories of flood events. At the national/regional level, such an inventory would be particularly useful to provide accurate data and assessments which would serve as a basis for disaster prevention. At the European level, these inventories could assist in tracking the trends in flood-disaster losses, and in mitigation programmes monitoring and obtaining a clearer picture of the linkages between climate change and floods and flood losses.
Further information on uncertainties is provided in Section 1.7 of the EEA report on Climate change, impacts, and vulnerability in Europe 2012 (http://www.eea.europa.eu/publications/climate-impacts-and-vulnerability-2012/)
[1] See http://www.emdat.be online.
[2] See http://www.munichre.com/geo online.
[3] See http://floodobservatory.colorado.edu/ online.
[4] See http://embrace-eu.org/ online.
[5] See http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2007:288:0027:0034:EN:PDF online.
No uncertainty has been specified
For references, please go to https://www.eea.europa.eu/data-and-maps/indicators/river-floods-1/assessment or scan the QR code.
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