The retention area located to the west of the A5 freeway in the north of the city of Karlsruhe serves to retain floodwater from the Pfinzentlastungskanal. The planning for its rehabilitation, which has now been completed and submitted, is being examined by the planning approval authority of the city of Karlsruhe.
The main components of the plan are the construction of a new combined intake and discharge structure to replace the 800-meter-long intake gap in the dam of the Pfinzentlastungskanal (spillway) and the renovation of the existing dams that define the retention area over a length of approximately 3.7 kilometers. Other planned measures include the replacement of the outlet structure in the north of the retention area, the lowering of two paths through which the retention area is filled in the event of an emergency, and the raising of the terrain along the Gießbach stream.
With the newly built intake structure as a controlled hose weir, a controlled filling of the retention area and thus an optimized use of the available retention volume will be possible after the implementation of the measure and thus the degree of protection of the system will be significantly increased.
The planning of the engineering structures was carried out in close cooperation with the nature conservation planning. During the planning process, a wide range of options for minimizing the impact were developed and intensively discussed in the project advisory group set up for this purpose, so that the valuable gallery forest along the Pfinz and extensive tree stands in the retention area could be preserved on the basis of the submitted document. Unavoidable interventions will be compensated for by compensatory measures. For example, it is planned to hang nesting boxes for bats and to enhance other areas in terms of nature conservation.
In the meantime, the accompanying physial model test (a video of which is available here abrufbar) has been completed. According to the client, construction is not expected to start before 2023.
Matthias Höhne – Freiburg i. Br.