Effects of river restoration at the river Lech - Comparison and change of hydrodynamic processes and vegetation composition at the Weißenbacher Au with a focus on Myricaria germanica

The River Lech in Tyrol is one of the last wild riverine landscapes in the alpine region and is therefore often named in literature as one of the last natural and pristine rivers in Austria. The widespread accumulation areas with the indicator species German Tamarisk (Myricaria germanica) and the high bedload regime with diverse riparian floodplain forests are typical for alpine riverine landscapes like the River Lech. But also this river with its strongly braided course in the upper reaches was partly straightened by regulation measurements. The anthropogenic inventions led to negative ecological effects due to accelerated discharge in combination with less bed load input. River and floodplain habitats were divided functionally and dynamic processes were limited to the deeper river course. The creation of the Natura 2000 site for the Lech Valley followed by the Life-Nature Project „Wild riverine landscape of the Tyrolean Lech“, was the result of a rethinking process of the last decades. In addition to preserve the remaining natural and dynamic river sections another aim of the project was to stop riverbed degradation and restore river sections where anthropogenic inventions were done in the past. ... mehrThis Master Thesis intends to show the short- and intermediate-term effects of the Life-Nature Project measures regarding both the change of vegetation composition as well as the change of hydrodynamic processes at the Weißenbacher Au with a focus on the distribution of Myricaria germanica in the study area as a reference site in comparison with the distribution of the species within the cut off floodplain forests where the plant still occurs after 50 years with no dynamic river processes.