Climate change, impacts and vulnerability in Europe ... - MemoFin.fr

Climate impacts on environmental systems3.3.3 River floodsRelevanceThere are many different types of floods. They canbe distinguished based on the source of flooding(e.g. rivers and lakes, urban storm water andcombined sewage overflow, or sea water), themechanism of flooding (e.g. natural exceedance,defence or infrastructural failure, or blockage) andother characteristics (e.g. flash flooding, snowmeltflood, or debris flow).River floods are a common natural disaster inEurope, and — along with storms — the mostimportant natural hazard in Europe in termsof economic damage. They are mainly causedby prolonged or heavy precipitation events orsnowmelt. River floods can result in huge economiclosses due to damage to infrastructure, property andagricultural land, and indirect losses in or beyondthe flooded areas, such as production losses causedby damaged transport or energy infrastructure.They can also lead to loss of life, especially in thecase of flash floods, and displacement of people,and can have adverse effects on human health, theenvironment and cultural heritage.Past trendsMore than 325 major river floods (including flashfloods) have been reported for Europe since 1980, ofwhich more than 200 have been reported since 2000(EM-DAT, 2012). The rise in the reported numberof flood events in the recent decade results mainlyfrom better reporting and from land-use changes.Floods have resulted in more than 2 500 fatalitiesand have affected more than 5.5 million peoplein the period from 1980 to 2011. Direct economiclosses over this same period amounted to more thanEUR 90 billion (based on 2009 values).Map 3.7 shows the occurrence of flood events inEurope from 1998–2009. This picture is incompletebecause events with small spatial extent and/orimpact are not included. Nevertheless, it becomesclear that large areas throughout Europe have beenaffected by flooding over the last decade, many ofthem even multiple times. Flood losses in Europehave increased substantially over recent decades butthis trend is primarily attributable to socio‐economicfactors, such as increasing wealth located in floodzones. The influence of anthropogenic climatechange remains inconclusive (Barredo, 2009).Significant trends in river inundations have beenidentified in some regional and national studies. Forexample, significant increases in flood intensitieshave been identified between 1951 and 2002 inwestern, southern and central Germany (Petrow andMerz, 2009) as well as in upland catchments in thenorthern and western United Kingdom (Hannafordand Marsh, 2008). A new analysis of the strong UKfloods of 2000 suggests that anthropogenic climatechange was a contributing factor (Pall et al., 2011).In the Alps (Renard et al., 2008) and Nordic region(Wilson et al., 2010), snowmelt floods have occurredearlier because of warmer winters. In contrast, noconclusive evidence was found in an analysis offlood trends in Austria (Villarini et al., 2012), and anincreasing flood trend in Catalonia is attributed tosocio‐economic factors (Barnolas and Llasat, 2007).ProjectionsChanges in future flood hazard in Europe havebeen simulated by a hydrological model drivenby an ensemble of climate simulations (Dankersand Feyen, 2009; Flörke et al., 2011). An increasingflood hazard is consistently projected for severalof Europe's major rivers across climate models andemissions scenarios (Feyen et al., 2011).Map 3.8 shows the change in the level of aone‐in‐a‐century flood between the referenceKey messages: 3.3.3 River floods• More than 325 major river floods have been reported for Europe since 1980, of which more than 200have been reported since 2000.• The rise in the reported number of flood events over recent decades results mainly from betterreporting and from land-use changes.• Global warming is projected to intensify the hydrological cycle and increase the occurrence andfrequency of flood events in large parts of Europe.• Flash floods and pluvial floods, which are triggered by local intense precipitation events, are likely tobecome more frequent throughout Europe. In regions with projected reduced snow accumulation duringwinter, the risk of early spring flooding could decrease. However, quantitative projections of changes inflood frequency and magnitude remain highly uncertain.118 Climate change, impacts and vulnerability in Europe 2012