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Reopening Waterways

Up until the 1980s, the dominating strategy for Oslo’s rivers and streams was to enclose them for practical reasons. Today, the City takes the opposite approach, actively reopening waterways to make them accessible for people, facilitate increased habitat for biodiversity and handle storm water more efficiently.

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. 

Figure 1: The map illustrates open and closed rivers and streams with tributaries in Oslo’s urban zone today, as well as implemented, on-going and planned long-term reopening projects.Figure 1: The map illustrates open and closed rivers and streams with tributaries in Oslo’s urban zone today, as well as implemented, on-going and planned long-term reopening projects.

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.

Figure 2. Teglverksdammen is a large scale reopening of the stream Hovinbekken. Alltogether 650 meters of the stream has been reopened, with sedimentation basins, water rapids, indigenous plant species, a small lake and shallow waters with dense vegetation. Photos: Agency for Urban Environment.Figure 2. Teglverksdammen is a large scale reopening of the stream Hovinbekken. Alltogether 650 meters of the stream has been reopened, with sedimentation basins, water rapids, indigenous plant species, a small lake and shallow waters with dense vegetation. Photos: Agency for Urban Environment.

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. 

Figure 3: In all reopening projects, the City of Oslo strives to create the aquatic habitat and side areas as natural as possible. From top left; natural bottom substratum with large stones as fish hides, adjustments to make sure fish can migrate, combining gravel and soil to facilitate growth of wetland vegetation. From bottom left; transferring wetland and aquatic plants from a nearby overgrown pond, establishing native/resident/indigenous wetland vegetation, storm water from a nearby school is safely led into the newly reopened stream Hovinbekken.Figure 3: In all reopening projects, the City of Oslo strives to create the aquatic habitat and side areas as natural as possible. From top left; natural bottom substratum with large stones as fish hides, adjustments to make sure fish can migrate, combining gravel and soil to facilitate growth of wetland vegetation. From bottom left; transferring wetland and aquatic plants from a nearby overgrown pond, establishing native/resident/indigenous wetland vegetation, storm water from a nearby school is safely led into the newly reopened stream Hovinbekken.