physical model test of the river Gail from Koetschach-Mauthen to Gundersheim - approximation to reference river morphology

The Gail river suffers from bed degradation. In addition, the morphological quality is low, which also has a negative impact on the ecological status of the river. The water authorithy of Carinthia intends to widen the Gail river in several sections in order to improve both the bed stability and the morphology and thus also the ecology. The widening should be predominantly self-dynamic and only supported by initial measures where absolutely necessary. Furthermore, the development ov the river bed should only be limited with bank protection measures where the natural dynamics would exceed the available areas. As there is still little general knowledge about the processes of self-dynamic river widenings and the associated possibilities but also risks, it is planned to investigate the planned widening in the Würmlach area over a distance of approx. 900 m in a physwical model test. The Würmlach widening begins with an outer bend, which can be expected to have good inherent dynamics, but it is also questionable whether the inherent dynamics will remain limited and whether there is a risk of the river shifting beyond the available areas. The following research questions will be addressed 1. what is the course of the river's own dynamic development after removal of the bank protections, assuming average hydrology (widening of the river, development of the bed heights and the morphological shape, also with regard to the aquatic ecology)? 2. are additional initial measures required to promote self-dynamic widening? If so, which measures are suitable? 3. is there a maximum development width or is migration of the river course to be expected? 4. which bank protection measures can be used to limit the development of the course if necessary? 5. what influence does bed load input have on morphological development? (What effect does a significantly reduced bed load input have?)