Original paper

Clusters of extreme floods; their role in the transformation of fluvial systems

Starkel, Leszek


Besides catastrophic events, the higher frequency and/or clustered incidences of heavy rainfall events and floods play a leading role in affecting fluvial regime as well as the morphogenesis of fluvial systems. The duration and intensity of heavy rainfall and river discharges may fluctuate from minutes to hours or even days. Furthermore, their configuration in clusters may vary from days to years, decades and even centuries. On longer time scales we observe clusters of years with higher river activity that are separated by intervals of several years duration when relaxation and stabilization of channels as well as re-vegetation of bars and river banks take place. Particular floods and their clusters may lead to avulsions of river channels. The analysis of the Holocene generations of alluvial fills helps to reconstruct longer phases of clustering, and then to suggest climatic variations. The notable acceleration in formation of clusters of heavy floods is connected with destruction of a natural vegetation cover. Even in young mountains, progressive aggradation may occur instead of the natural trend towards channel downcutting.


extreme floodsfluvial systemclusters of eventsheavy rainfall events