Knowledge gain based on the pilot project Bad Deutsch-Altenburg at the Danube River for navigation, ecology and hydraulic engineering | Erkenntnisse aus dem Pilotprojekt Bad Deutsch-Altenburg an der Donau für Schifffahrt, Ökologie und Wasserbau

This paper summarizes the knowledge increase based on the results of the pilot project Bad Deutsch-Altenburg (BDA) for navigation, ecology and hydraulic engineering in the Austrian Danube River. Concerning the various stakeholders and thematic fields it could be shown that the pilot project led to several changes, additionally to a significant knowledge gain: Navigation is confronted with intensified sedimentation in the ford section BDA but also with positive effects like decreased flow velocities along the groyne heads and a slightly increased fairway width. The ecological conditions improved by a restoration of river banks and rheophilisation of river shoreline zones (bank-near habitats) and the Johler sidearm. Positive effects were found regarding an expansion of biota indicating dynamic and riverine conditions (e.g. diatoms and pioneer vegetation) and regarding a major increase of young-of-the-year fish in reconstructed areas. Regarding hydraulic engineering, measures could be optimised that contribute to river bed stabilisation (granulometric bed improvement and groyne reshaping). Water levels at low flow conditions were slightly increased by means of the measures (also based on the aggradation within the area), having positive ecological effects for the National Park Donauauen. At the same time high water levels were slightly decreased, improving the situation during floods. A combination of optimized hydraulic engineering structures and bedload management based on the results of the pilot project should allow a sustainable improvement for navigation conditions, a stop or minimisation of river bed degradation and an improvement of the ecological situation. By integrating abiotic and biotic investigations the effects of river engineering measures can be better analysed and the gained knowledge forms the basis for future planning.