The BERNARD Gruppe was asked by the city of Kufstein to provide detailed and permit application design services for the flood protection of the Inn River’s inflowing streams.

The streams concerned are Kienbach, Kreuzbach and Mitterndorfer Bach, which drain the northern slopes of the Kufstein Stadtberg into the Inn Valley. The numerous documented flood events, especially the most recent one on 17 July, 2021, show that there is a high potential for damage from the three streams. The sediment transport associated with flood discharges and the hazards resulting from blockages at bridges and culverts aggravate the flood discharge situation in Kufstein.

Due to the streams’ inner-city location, an expansion of the channel form to increase runoff capacities can only be realized in specific areas, so that a continuous protection cannot be assured. For this reason, the new construction of two sediment retention basins and one flood retention basin is planned in order to attenuate flood waves in the streams and reduce sediment transport. Particular emphasis has to be given to the fact that the Kienbach flood retention basin is located in a tributary area which bypasses the main connection. This will cap peak flows in the largest of the three watercourses by up to 4.0 m³/s and channel them via an underground pipe transfer into a 25,000 m³ retention basin in dam construction. The water will be retained in the basin until the end of the event and then be discharged into the Mitterndorfer Bach at a reduced rate.

The commissioned engineering services include the optimization of the previous studies, hydraulic and geotechnical dimensioning, project planning as well as the constructive design of all plant components and measures to upgrade the streams’ water ecology. The detailed and permit application design for the flood protection of the city’s inflowing streams is the planning basis for obtaining the official approvals and for preparing the award of contract.

Manuel Plörer, BERNARD Gruppe