Conservation by restoration: the management concept for a river-floodplain system on the Danube River in Austria

One of the last remnants of a functional alluvial landscape on the Danube extends from Vienna to the Slovakian frontier. It is recognized as an ecosystem extremely worthy of protection and therefore has been designated as a National Park (‘Alluvial Zone National Park’). 2. However, surface connectivity has been reduced and floodplain habits have been fragmented. At present, lateral exchange processes of matter are restricted to short-term flood pulses, while most of the year backwater processes are de-coupled from the river system. 3. A very high species diversity is recorded for this section, with a high proportion of endangered species in all groups, ranging from 16% for riparian vascular plants to 100% for amphibians and reptiles. High diversity is mainly a result of the remaining spatial array of water bodies of different age across the river-floodplain complex (between-channel diversity). 4. A successful conservation strategy for this floodplain area requires a management scheme based on a solid conceptual foundation of the key processes in river-floodplain systems. Re-establishing hydrological dynamics is recognized as the most vital step, because other processes are influenced by the flow regime and resulting connectivity. Therefore, a large-scale pilot project has been developed for a segment of the free-flowing section to restore gradually the hydrological connectivity between the river and its floodplain. 5. The side-arm system will be reconnected to the main channel by lowering parts of the riverside embankments. After implementation, the side-arm system will be integrated with the flow regime of the river for more than half of an average year (at present: <8 days per year). 6. A key challenge in the evaluation of the effects of restoration is the development and testing of an appropriate monitoring scheme, which has to include a wide range of physical, chemical, geomorphic, and ecological parameters.