The influence of warmer weather periods on high river episodes in the French Alps: the case of the last flood of the Isère River in Grenoble in 1859
The great 1859 flood at Grenoble in the southeastern France was the last water-level rise of such magnitude for the Isère River, and Grenoble has not been flooded again since that time. However, one can legitimately wonder whether the calm behavior of the Isère during the 20th century was something definitive or whether it was related to climate change. The present study aimed at answering this question, firstly by determining the climatic characteristics of the hydrological episodes in question, while, secondly, using Gumbel's Law to adjust the maximum annual values of accumulated precipitation over a period lasting from one to six consecutive days, in order to assess how exceptional such climatic conditions actually are. The procedure was then repeated by linking daily precipitation to rises in temperature. It is clearly shown that flood episodes follow truly exceptional climatic conditions. Thus, the absence of such severe floods during the 20th century is not statistically surprising, and perhaps should not be seen as a sign of regional or planetary climate change.