Funktionalität der getesteten flussbaulichen Maßnahmen im Pilotprojekt Bad Deutsch-Altenburg

Abstract

A comprehensive monitoring program was compiled in order to observe all measures at the Danube River within the pilot project Bad Deutsch-Altenburg also during the implementation phase. Especially bathymetry analyses, Freeze Core samples and pebble tracers provided insights into the functionality of the measure “granulometric bed improvement (GBI)”. Furthermore the monitoring showed first reactions regarding the reconstruction of the low flow river regulation and the reconnection of the Johler sidearm. The effectiveness of the GBI regarding its aim to stop river bed degradation was not as high as predicted during the planning phase and physical model studies, however the coarser grain sized had an important impact on bed stability. The effect of the new groyne shapes was higher than expected before construction and led—in some parts—to a reversal in trend, resulting in an aggradation process necessitating an optimisation of the measure. River bank restoration led to banks of gentle slopes with open gravel bars and due to side erosion and river widening, there was a visible effect on bed stability. However more dynamic conditions and lower water ages can be encountered in bank near habitats and in the side arm leading to a shift towards the natural conditions corresponding to the “Leitbild” theory with anticipated positive effects on the ecology within the national park.