Showing papers by "Zbigniew W. Kundzewicz published in 2005"

Summer Floods in Central Europe – Climate Change Track?

Abstract: In Central Europe, river flooding has been recently recognized as a major hazard, in particular after the 1997 Odra /Oder flood, the 2001 Vistula flood, and the most destructive 2002 deluge on the Labe/Elbe. Major recent floods in central Europe are put in perspective and their common elements are identified. Having observed that flood risk and vulnerability are likely to have grown in many areas, one is curious to understand the reasons for growth. These can be sought in socio-economic domain (humans encroaching into floodplain areas), terrestrial systems (land-cover changes – urbanization, deforestation, reduction of wetlands, river regulation), and climate system. The atmospheric capacity to absorb moisture, its potential water content, and thus potential for intense precipitation, are likely to increase in a warmer climate. The changes in intense precipitation and high flows are examined, based on observations and projections. Study of projected changes in intense precipitation, using climate models, for several areas of central Europe, and in particular, for drainage basins of the upper Labe/Elbe, Odra/Oder, and Vistula is reported. Significant changes have been identified between future projections and the reference period, of relevance to flood hazard in areas, which have experienced severe recent floodings.

Trend detection in river flow series: 1. Annual maximum flow

Abstract: Les resultats d'une etude de detection de changements dans des series temporelles hydrologiques de debits fluviaux maximum annuels sont presentes. Un jeu de donnees mondial, constitue de 195 longues series de debits moyens journaliers, a ete selectionne parmi plus de mille series temporelles longues fournies par le Centre Mondial de Donnees sur l'Ecoulement (GRDC) de Coblence en Allemagne. La selection verifie d'une part certains criteres comme la longueur de la serie, l'actualite, l'absence de lacunes durables et ponctuelles et une distribution geographique adequate, et d'autre part une priorite aux plus petits bassins versants. L'analyse des debits maximum annuels ne verifie pas l'hypothese d'une augmentation generalisee des forts debits. Bien que 27 cas d'augmentation forte et statistiquement significative aient ete identifies grâce au test de Mann-Kendall, 31 cas de diminution ont egalement ete identifies, tandis que la plupart (137) des series temporelles ne presente aucun changement significatif (au niveau 10%). La prudence est preconisee dans l'interpretation de ces resultats, dans la mesure ou la crue est un phenomene complexe, cause par de nombreux facteurs qui relevent de processus climatiques locaux, regionaux et hemispheriques. De plus, le debit fluvial a une forte variabilite naturelle et presente une persistance a long terme qui peuvent perturber les resultats des tests de tendance et de signification.

Natural flood reduction strategies – a challenge

Abstract: Flood hazard and vulnerability to floods tend to increase in many areas, due to changes in socio‐economic, and physical – especially climatic – systems. Therefore, increasing attention is being paid to upgrading flood protection systems. As in many vulnerable areas sufficient flood protection cannot be reached with the help of structural means only, further flood damage reduction via non‐structural measures is advisable. The most essential principles in natural flood reduction strategies are illustrated by the slogans “keep water where it falls” and “give rivers their floodplains back”, both being widely discussed in Germany, especially after the destructive flooding of August 2002. Examples of implementation of natural flood reduction strategies are presented.