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Denmark

River floods

Vulnerabilities Denmark - Present river flood risk

In Denmark, the annual mean runoff in most of the Danish streams shows an increasing trend over the observation period starting around 1917. Also for the annual maximum and minimum runoff the trends are predominantly increasing (21). An increasing trend in streamflow magnitude and a trend in the timing of floods have been detected in annual and seasonal flows in near-natural catchments in Denmark, Finland, Norway and Sweden, given that they tend to arrive earlier in spring (29). Overview studies covering many Scandinavian rivers show no statistically significant trend in river peak discharge over the last century (30)

Vulnerabilities Denmark - Future river flood risk

Changes in dry and wet spell characteristics in Europe have been projected for 2021–2050 compared with 1961–1990, based on Regional Climate Model simulations under the A1B emission scenario. From the results it can be concluded that significant changes in dry and wet event characteristics are expected with high confidence in the southernmost (mainly France, Italy, and Spain) and northernmost (mainly Iceland and Scandinavia) regions of Europe, respectively. Southern Europe is most probably facing an increased risk of longer, more frequent, severe, and widespread droughts, while northern Europe is facing increased risk of intensified wet events. For precipitation, the most pronounced changes are found for the Iberian Peninsula in summer (−17.2%) and for Scandinavia in winter (+14.6%) (28).

Europe: casualties in the past

The annual number of reported flood disasters in Europe increased considerably in 1973-2002 (1). A disaster was defined here as causing the death of at least ten people, or affecting seriously at least 100 people, or requiring immediate emergency assistance. The total number of reported victims was 2626 during the whole period, the most deadly floods occurred in Spain in 1973 (272 victims), in Italy in 1998 (147 victims) and in Russia in 1993 (125 victims) (2).


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Europe: flood losses in the past

The reported damages also increased. Three countries had damages in excess of €10 billion (Italy, Spain, Germany), three in excess of 5 billion (United Kingdom, Poland, France) (2).


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Europe: flood frequency trends in the past

In 2012 the IPCC concluded that there is limited to medium evidence available to assess climate-driven observed changes in the magnitude and frequency of floods at a regional scale because the available instrumental records of floods at gauge stations are limited in space and time, and because of confounding effects of changes in land use and engineering. Furthermore, there is low agreement in this evidence, and thus overall low confidence at the global scale regarding even the sign of these changes. There is low confidence (due to limited evidence) that anthropogenic climate change has affected the magnitude or frequency of floods, though it has detectably influenced several components of the hydrological cycle such as precipitation and snowmelt (medium confidence to high confidence), which may impact flood trends (26).

Despite the considerable rise in the number of reported major flood events and economic losses caused by floods in Europe over recent decades, no significant general climate‑related trend in extreme high river flows that induce floods has yet been detected (7).


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Europe: projections for the future

IPCC conclusions

In 2012 the IPCC concluded that considerable uncertainty remains in the projections of flood changes, especially regarding their magnitude and frequency. They concluded, therefore, that there is low confidence (due to limited evidence) in future changes in flood magnitude and frequency derived from river discharge simulations. Projected precipitation and temperature changes imply possible changes in floods, although overall there is low confidence in projections of changes in fluvial floods. Confidence is low due to limited evidence and because the causes of regional changes are complex, although there are exceptions to this statement. There is medium confidence (based on physical reasoning) that projected increases in heavy rainfall would contribute to increases in rain-generated local flooding, in some catchments or regions. Earlier spring peak flows in snowmelt- and glacier-fed rivers are very likely, but there is low confidence in their projected magnitude (26).

More frequent flash floods

Although there is as yet no proof that the extreme flood events of recent years are a direct consequence of climate change, they may give an indication of what can be expected: the frequency and intensity of floods in large parts of Europe is projected to increase (14). In particular, flash and urban floods, triggered by local intense precipitation events, are likely to be more frequent throughout Europe (15).


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Adaptation strategies - Denmark

A special problem is linked to low-lying areas that are exposed to both increases in the sea level and are under pressure from increasing drainage from the land. In particular, many of the coastal towns near estuaries of larger rivers or at the bottom of fjords could have complex problems. Merely building higher dykes, for instance, is not a long-term solution as the problem of backwater flooding will just become greater as a result of river water being unable to flow freely into the sea. A long-term solution requires the involvement of river valleys further inland. There is a need for space for rivers to allow flood plains to flood regularly to take some of the pressure off at river mouths. One of the tools to change land use in river valleys could be through the EU agricultural subsidy schemes, to make river valleys far more multi-functional (22).

Adaptation strategies - General

Non-structural measures are in better agreement with the spirit of sustainable development than structural measures, being more reversible, commonly acceptable, and environment-friendly. Among such measures are source control (watershed/landscape structure management), laws and regulations (including zoning), economic instruments, an efficient flood forecast-warning system, a system of flood risk assessment, awareness raising, flood-related data bases, etc. As flood safety cannot be reached in most vulnerable areas with the help of structural means only, further flood risk reduction via non-structural measures is usually indispensable, and a site-specific mix of structural and non-structural measures seems to be a proper solution. As uncertainty in the assessment of climate change impacts is high, flexibility of adaptation strategies is particularly advantageous (25).

EU Directive on flood risk management

The new EU Directive on flood risk management, which entered into force in November 2006, introduces new instruments to manage risks from flooding, and is thus highly relevant in the context of adaptation to climate change impacts. The Directive introduces a three-step approach (2):

  • Member States have to undertake a preliminary assessment of flood risk in river basins and coastal zones.
  • Where significant risk is identified, flood hazard maps and flood risk maps have to be developed.
  • Flood risk management plans must be developed for these zones. These plans have to include measures that will reduce the potential adverse consequences of flooding for human health, the environment cultural heritage and economic activity, and they should focus on prevention, protection and preparedness.

References

The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for Denmark.

  1. Hoyois and Guha-Sapir (2003), In: Anderson (ed.) (2007)
  2. Anderson (ed.) (2007)
  3. Mitchell (2003)
  4. Barredo (2009)
  5. Höppe and Pielke Jr. (2006); Schiermeier (2006), both in: Barredo (2009)
  6. Höppe and Pielke Jr. (2006), in: Barredo (2009)
  7. Becker and Grunewald (2003); Glaser and Stangl (2003); Mudelsee et al.(2003); Kundzewicz et al.(2005); Pinter et al.(2006); Hisdal et al.(2007); Macklin and Rumsby (2007), all in: EEA, JRC and WHO (2008)
  8. EEA, JRC and WHO (2008)
  9. Wang et al.(2005), in: EEA, JRC and WHO (2008)
  10. Milly et al. (2005), in: EEA, JRC and WHO (2008)
  11. Hisdal et al. (2007), in: EEA, JRC and WHO (2008)
  12. Ramos and Reis (2002), in: EEA, JRC and WHO (2008)
  13. Barnolas and Llasat (2007), in: EEA, JRC and WHO (2008)
  14. Lehner et al.(2006); Dankers and Feyen (2008b), both in: EEA, JRC and WHO (2008)
  15. Christensen and Christensen (2003); Kundzewicz et al.(2006), both in: EEA, JRC and WHO (2008)
  16. Palmer and Räisänen (2002), in: EEA, JRC and WHO (2008)
  17. Kay et al. (2006); Dankers and Feyen (2008), in: EEA, JRC and WHO (2008)
  18. Andréasson, et al. (2004); Jasper et al.(2004); Barnett et al.(2005), all in: EEA (2009)
  19. Arnell (2004); Milly et al. (2005); Alcamo et al. (2007); Environment Agency (2008a), all in: EEA (2009)
  20. Dankers and Feyen (2008), in: EEA (2009)
  21. Ovesen et al. (2000), in: Hyvärinen (2003)
  22. Danish Ministry of the Environment (2005)
  23. Ciscar et al. (2009), in: Behrens et al. (2010)
  24. Kundzewicz (2006)
  25. Kundzewicz (2002)
  26. IPCC (2012)
  27. Feyen et al. (2012)
  28. Heinrich and Gobiet (2012)
  29. Wilson et al. (2010), in: Mediero et al. (2014)
  30. Bering Ovesen et al. (2000); Forland et al. (2000); Hyvarinen (2003); Lindström and Bergström (2004); Thodsen (2007), all in: Kwadijk et al. (2016)

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