Author(s): G. Krapesch; H. Habersack

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Abstract: In this study the morphological effects of extreme (～ HQ1000) floods were analyzed and parameters to describe the morphological spatial demand of alpine rivers were derived. The research was conducted on basis of vertical aerial photos of the rivers before and after the floods, hydrodynamic numerical models, cross sections and grain sizes of the rivers. Average widening factors were calculated. The widening factor describes the width change due to the morphological processes during the flood. Depending on the boundary conditions of the river environment a widening factor between 1.12 (Lech River), 1.35 (Bregenzerach River) to 3.45 (Trisanna River) was observed. Parameters which could quantify the width changes due to lateral erosion, cut-offs or partially braiding were then analyzed based on a hydrodynamic numerical model. Different parameters were correlated with the change of the river width which occurred during the extreme flood. The specific stream power could best approximate width changes of the river during the flood. Further hydraulic parameters (shear stress, specific stream power, flow area) which describe morphological changes were found. This should be a basis to asses the morphological spatial demand of rivers for future flood events.

DOI:

Year: 2009