Oslo’s uniqueness is, to a large extent, defined by its green and blue qualities – the prominence of vegetation in urban areas and the 10 main waterways (figure 1) running through. The main waterways also have a large number of tributaries. Up until the 1980s, the waterways were considered problematic for the sewage system and an obstacle for efficient exploitation of land. Hence large sections of waterways were put in culverts. However, pipes and culverts have predefined capacities, and with more and heavier rainfall due to climate change, urban flooding is, and will become, a larger challenge because of these predefined capacities.
The City of Oslo has decided to reopen closed rivers and streams wherever it is possible and expedient. In order to formalise and streamline the municipal cooperation regarding reopening projects, the relevant municipal agencies have, in collaboration, developed a management document that outlines the principles for reopening projects including a list of prioritised projects. The list is updated annually.
The “Teglverksdammen” Project
Teglverksdammen (figure 2) is a large reopening project which was completed in August 2015. Approximately 650 meters of the stream Hovinbekken was reopened in this EUR 10 mill project. Teglverksdammen is planned and designed as a natural cleaning system, with several sedimentation basins, stream with water rapids, a small lake and shallow waters with dense vegetation. Importantly, all plant species are indigenous to the Oslo area. As a result, Teglverksdammen cleans water, provides habitat for biodiversity and has become a popular recreation area for people.