The river continuously transports bedload, which is eroded at one location and deposited at others on the riverbed and along the riverbanks. This natural dynamic is interrupted by numerous embankments and transverse structures, such as power plants. In some areas this leads to a bedload deficit and subsequently to a gradual erosion of the riverbed.
The related lowering of the ground water level is especially critical for the National Park Donauauen (east of Vienna) and appropriate countermeasures have to be taken in order to preserve the ecological functionality and the unique character of the Donauauen.
Therefore, a pilot project was implemented in the river section east of Vienna in 2015. In the course of the project gravel, which had to be removed from shallow river sections as part of regular maintenance dredging works, was transported as far upstream as possible (about 18 km) and then deposited in the river. As a result, the bedload remains in the river system for much longer and works against a negative bedload balance and the involved deepening of the riverbed. In the past, the material dredged was deposited at the nearest low point (average 3-4 km upstream).
The main objective of the pilot was to obtain information for the development of a bedload management system. The analysis took into account the effects on the riverbed as well as constructional considerations. The findings gained from the results help improve the ongoing bedload management and allow for the use of synergies between maintenance dredging and bedload management measures.
- preparation and planning of the pilot project (concept development)
- tendering of the dredging works at two critical ford areas
- dredging of both ford areas, including quality checks by the local building inspectorate and complemented by more frequent riverbed surveys in the dredging and dumping areas as well as the river section inbetween
- analysis of the results
- elaboration of a report on the findings of the pilot project bedload management
The pilot project is already concluded. The results facilitate the continued improvement of the waterway management, taking into account ecological as well as nautical requirements.