DANUBE

Description of the project area

The project area Danube covers the section of the Upper Danube in Upper Austria, from the border with Bavaria to Grein an der Donau, a river stretch with approximately 122 km (river-kilometre 2079-2201).

The Danube is the second longest river in Europe, with almost all of Austria’s national territory within its river basin. It is an important habitat and waterway for man and nature. From a hydrological point of view, the Danube is an alpine river. The Inn is the most important tributary. Traun and Enns also bring water “from the Alps”.

Summer floods are typical for the Upper Danube. In this section of the Danube the 100-year flood event (HQ100) is 11 200 m³ per second, the mean water discharge is 1 910 m³ per second. Another typical feature of the Upper Danube is the high gradient, which is approx. 37 cm per km. This causes a high bedload transport capacity. Since, however, due to river engineering measures and hydropower use there is hardly any bedload coming from the tributaries above, causing a lack of sediment in the free flowing sections of the Danube and especially in the downstream sections of hydropower plants, which leads to the problem of progressive deepening of the riverbed.

The almost continuous chain of hydropower dams has changed the Danube ecologically as well. Deficits such as the sedimentation of the Danube tributaries and the lack of free flowing sections particularly affect the rheophile, current-loving fish-species.

DANUBE

Description of the project area

The project area Danube covers the section of the Upper Danube in Upper Austria, from the border with Bavaria to Grein an der Donau, a river stretch with approximately 122 km (river-kilometre 2079-2201).

The Danube is the second longest river in Europe, with almost all of Austria’s national territory within its river basin. It is an important habitat and waterway for man and nature. From a hydrological point of view, the Danube is an alpine river. The Inn is the most important tributary. Traun and Enns also bring water “from the Alps”.

Summer floods are typical for the Upper Danube. In this section of the Danube the 100-year flood event (HQ100) is 11 200 m³ per second, the mean water discharge is 1 910 m³ per second. Another typical feature of the Upper Danube is the high gradient, which is approx. 37 cm per km. This causes a high bedload transport capacity. Since, however, due to river engineering measures and hydropower use there is hardly any bedload coming from the tributaries above, causing a lack of sediment in the free flowing sections of the Danube and especially in the downstream sections of hydropower plants, which leads to the problem of progressive deepening of the riverbed.

The almost continuous chain of hydropower dams has changed the Danube ecologically as well. Deficits such as the sedimentation of the Danube tributaries and the lack of free flowing sections particularly affect the rheophile, current-loving fish-species.

Hot Spots & Highlights

The Eferdinger Becken and the Traun-Danube floodplains are Natura 2000 areas close to the Danube. Both have the conservation of natural riverine landscapes as their goal. On the Danube itself, free flowing sections can only be found on a small scale in the downstream sections of the hydropower plants.

Near the Ottensheim hydropower plant, a larger, free-flowing section with dynamic flows has been preserved. This section with natural gravel dynamics has high potential for renaturation measures. On the opposite riverbank are the Ottensheim regatta course, the mouth of the river Rodl and the cycling track Donauradweg.

Need for action

For the Danube in Upper Austria, the main goal is to counteract the ongoing trend of riverbed deepening. From an ecological point of view, the restoration of the Danube’s and its tributaries longitudinal continuity (passability for fish) is also a priority. It is also important to create side waters sheltered from waves as habitat for breeding and juvenile fish.

Gravel islands and -banks, which once characterised the Upper Danube, have virtually disappeared due to the damming of the Danube. They are important nesting areas for gravel breeders who need open gravel areas as breeding grounds. Key habitats such as these must be restored, taking into account the Natura 2000 protected areas.

Goals

In the area of tension between flood protection, hydropower use, shipping and nature conservation, the interests, responsibilities and planning framework conditions on the Danube in Upper Austria are particularly complex. For the first time in the history of the river, the project LIFE IRIS offers the opportunity to develop a joint action plan as result of a GE-RM planning process. Preparatory work for the planning process has been carried out and is now to be integrated – supplemented by further surveys and analyses – into a concept of measures, which is also coordinated and agreed with stakeholders.

Additionally a pilot measure with added value for flood protection and river ecology will be implemented. It is planned to create a gravel island and a side branch in the downstream section of the hydropower plant Ottensheim. By lowering the terrain, pioneer areas for gravel islands and floodplain forest sites will be created and the flood runoff will be improved.

Ausblick und Zeitplan

Bis Ende 2021 wird das „Gewässerentwicklungs- und Risikomanagementkonzept Donau“ erstellt. Anschließend folgt die Ausarbeitung eines Detailprojektes für eine Pilotmaßnahme, die bis Mitte 2024 realisiert werden soll.

Outlook and time plan

The “Danube River Development and Risk Management Concept” will be finalised by the end of 2021. After that, the selected pilot measure will be planned in detail and implemented by mid-2024.

Eine Landkarte mit einer Hervorhebung der Flüsse Donau und Traun