At the Danube section Petronell to Hainburg (Lower Austria), several important renaturation projects have already been implemented in recent years and low water level regulations have been adjusted. With the renaturation measures at ‘Thurnhaufen’ almost 3 km of natural riverbanks were created. The project was implemented in cooperation with Donau-Auen National Park and has also been awarded by the EU as the best LIFE project in 2007/2008.  Another 1.4 km of riverbank were restored between 2012 and 2014. During this time the so called ‘Johler Arm’ – a former side arm - was reconnected to the main stream of the Danube. Professionals from all over the world are still visiting this lighthouse project.
For the time being, the last significant step towards the renaturation of the section was the reconnection of the Spittelauer side arm system, which is situated on the opposite side of the city of Hainburg on the left bank of the Danube (Stream-km 1886-1882, left bank).

Description of measures

The existing inflow opening was lowered to ensure that water can flow into the side arms almost all year long. The existing traverses made from stone blocks were removed. The big traverse at the mouth of the side arm was removed so that water and sediments can flow back into the Danube unhindered. The connection created a tributary about 4,34 km long, which is flowed through almost all year round. In addition, the 550 m long fishermen's ditch was strengthened in the estuary area. The area of  ‘Thurnhaufen’ opposite of the city of Hainburg has become an island that serves as a retreat for alluvial forest residents. In the system, existing bank protections were removed over a total length of 710 meters.

Ongoing activities & Outlook

In December 2019, the necessary clearing was carried out as an essential preparatory measure. The river engineering work to connect the Spittelauer Arm started in January 2020. In the first half of 2020, the "Rauer Wurf" and "Spittelauer Traverse" traverse structures were removed. In the second half of 2020, the connections to the Danube were established by removing the mighty outflow traverse and by creating a generous inflow opening. The breakthrough took place on 10 September 2020. Since then, Danube water can flow through the tributary again. The dismantled stones (riprap) were collected on the Danube bank and will be gradually transported away for reuse in other projects. Even though residual work is still required, the new sidearm is already functional and the former stagnant water is already transforming into a dynamic lifeline for the Danube floodplains.

The construction works are accompanied by an ecological construction supervision and carried out under the highest possible conservation of the protected goods in the national park Donau-Auen.

Insights into the construction work from the perspective of a sea eagle

Get exciting insights into the construction work at Spittelauer side-arm in our short film from the perspective of a sea eagle.