Rossatz Flood Defences

In September 2010 the bidding consortium of PORR Technobau und Umwelt AG, TEERAG-ASDAG GmbH and PORR Bau GmbH was awarded the tender to build the Rossatz flood defences for the towns of Rührsdorf and Oberarnsdorf, which lie on the right bank of the River Danube.

The consortium built effective underground sealing and a reinforced concrete wall above the sealed base. The wall is designed so that mobile flood protection elements can additionally be mounted on top of it in emergency situations, along with a drainage system on the landward side of the wall base.

Multifaceted services
The total length of the defences was 1,350m in Rührsdorf and 890m in Oberarnsdorf. The underground sealing was realised with concrete piles and jet grouting lamella and piles in between, a thin diaphragm wall or with injection sealing, depending on the properties of the soil. When integrated into the stevedore, these reach depths of around 13m.

The flood defences were built in-situ as a reinforced concrete wall. Here a total of around 6,500m³ of concrete and 700t steel was installed. Challenges in terms of both logistics and mechanics arose from the narrow space restrictions as a result of the historic settlement structure.

A pipe system for seepage and drainage was used to drain the hinterland (total length 3,440m with DN 300-800), and a spillway and overflow structure was built in the sewer system along with a pumping station. 

The bank was protected using stone pitching along with the access roads and steps leading up to the water level.

The structures were designed in such a way as to ensure that the flood defences were integrated into the townscape as effectively as possible and various road and urban development measures were also carried out to this end.