Aalborg municipality wanted to relocate an existing canal and culverted section of the Østerå river to become an open green watercourse. Currently the lower part of the river is culverted, which prevents fish from migrating from the Limfjord and up into the watercourse. This impacts the fish has a negative impact on the ecological condition of the river as a whole and means that the river system in its current state cannot meet the its goal of Good Ecological Status within the EU Water Framework Directive.
Ramboll has together with SLA as a subconsultant prepared an outline proposal and project description for the restoration of the Østerå. The project contributes natural areas and paths to the ongoing urban transformation and development along the entire approx. 3 km course, with climate adaptation and cloudburst protection an important aim of the project.
Climate adaptation and cloudbursts
By creating greater capacity for the drainage of rainwater throughout the Østerå’s catchment area, the project helps to make Aalborg more resilient to extreme rain events.
A key part of the project is adapting the Østerå’s culverted course to become an open watercourse with a double profile, so that paths and slopes can become a pool to help manage extreme weather events in the catchment area.
The water environment in the entire Østerå system is improved with the opening of the watercourse through the city, as the overflow to the river is reduced.
Improving the ecology of a river
The project is part of Aalborg municipality's water planning, so that a good ecological condition can be achieved in the watercourse according to EU Water Framework Directive.
A key parameter for a successful project is that the watercourse must be fully ecologically functional while also being able to handle extreme rain events. Ramboll has handled this through the hydraulic calculations and the design of solutions that can be used to direct the water, for example by using the existing canal as relief in case of major cloudburst situation with an extreme discharge from the catchment area.
Ramboll undertakes together with SLA the assessment of the aquatic environment in the reopened and restored river, including plant selection and general flora and fauna, so that water and natural quality live up to a good aquatic environment.