Author(s): Boris Kozlowski; Peter Ergenzinger
Linked Author(s):
Keywords: Mountain torrent; Roughness; Cluster; Ring structures; Bed stability
Abstract: Typical structures in steep mountain torrents include clusters, berms, step-pool systems and log jams. The existence of these roughness elements is strongly connected with the hydraulic characteristics of the torrent and the availability of sediment and wooden debris. During floods they control the stability of the river bed, the storage of bed material and the sediment output, as a kind of a natural selforganizing system of the river. This system fails during extreme flood events, so that nearly all bed material is mobilized. After an extreme event only some minor floods are required to reestablish the self organized system, based on newly developed roughness structures. By implementing a balloon sensing system it is possible to obtain a more complete photo sequence of the river reaches (Schmiedlaine, 2, 7 km long). A new cluster type was discovered on these photos. The importance of ring structures was confirmed under different hydraulic conditions during the field campaign 1997& 98 and by flume experiments. The stability of the ring structures and their importance for the selfstabilizing system of a mountain torrent is discussed. An estimation of the quantity of stored material and the potential capacity will be considered. Finally a hypothesis for the development of ring structures will be presented.
Year: 1999