USING PALEOFLOOD HYDROLOGY FOR THE RECONSTRUCTION OF PALEOCLIMATE IN EUROPE

In a specific drainage basin paleoflood research enables understanding of the long-term flood occurrences. Combining paleoflood records from several basins within a hydroclimatic region promotes understanding of regional climate variations in terms of the occurrences of extreme storms. Records from wider climatic zones may be helpful in constructing the larger paleoclimate. An attempt to reconstruct a regional paleoflood chronology was initiated in the southern Massif Central, France. It reveals a consistency in flood occurrences in the Ardèche and the Gardon Rivers (2450 km² and 1900 km², respectively). These rivers drain the Cévennes region of the Massif Central and are confluences of the Rhöne River. Their largest floods occur during the autumn from storms associated with moisture transported to the north from the Mediterranean. When compared with earlier and later times, more frequent large/extreme floods characterized the Little Ice Age (LIA). During the ~2000 years preceding the LIA there were no extreme floods in the Ardèche River. This 2000 years long gap followed by a frequency increase of large floods during the LIA was also identified in paleohydrological studies in the eastern Spanish Pyrenees and in Italy; all affected by the same flood producing mechanism. This temporal pattern over such a wide region may indicate that flood occurrences are not merely random in time, but follow trends controlled by the larger climate. Expanding such studies in space and time may provide a better understanding of the extremes embedded in paleoclimates.