Author(s): Helmut Scheuerlein
Linked Author(s):
Keywords: Upper Danube river; Fluvial processes; Hydroprojects; Navigation; Bed degradation; Bed stabilization; Ecological constraints
Abstract: Up to the 19 th century the Danube in Germany and Austria was a braided river subject to morphodynamic changes during flood season. As human settlements along the river were growing continuously in number and size, flood control measures had to be given prime attention. Furthermore, prospering trade centers along the river started to promote inland navigation for commercial exchange. The existing braided river characteristics were rather unfortunate for both, flood protection and navigation. Thus, extensive river regulation works were carried out in order to convert the braided river into one single concise channel. The concentration of the flow in one single channel and the increase of the energy gradient resulted in an undesired side-effect: the degradation of the river bed. In the 20 th century the upper Danube and its tributaries were soon recognized as excellent locations for hydropower generation. At first the tributaries were tackled preferably due to their potential of pressure height and storage capacity. The standard solution was to construct a storage dam rather high up in the mountains associated with a high head power plant for peak energy followed by a consecutive chain of run-of-river (low head) power plants along the river. The hydropower plants in the tributaries and in the Danube itself (all together around 60 in the upper catchment) signified a considerable interference with the sediment budget of the whole river system. In the backwater reaches upstream of the barrages most of the coarse material (bedload) and an unknown portion of fine material (suspended load) settled down. In the remaining free surface flow reaches the sediment deficit resulted in an increase of the already existing tendency of bed degradation caused by the historical river training works of the past. In some of the free flowing reaches of the upper Danube the continuous bed degradation has by now reached a stage where further erosion can no longer be tolerated. The paper reports on the various alternative proposals presently up for discussion in Germany and Austria and on the present stage of the struggle for a commonly acceptable solution.
Year: 2004