Urban stormwater management : a case study of the Deichman’s street pilot project for low impact development (LID) stormwater management in Oslo, Norway

Abstract

One of the predicted impacts of global climate change in Norway is more frequent and heavier rains. The country is set to receive ‘wetter and wilder’ seasons, and experience damaging floods as a result. Sea levels will continue to rise, and warmer temperatures will cause precipitation that would normally fall as snow to be rain instead. At the same time, 82% of Norway’s population live in urban settlements, and the country’s cities are expected to experience continued growth. Increased urbanization leads to a reduction in permeable surfaces, which leads to more urban runoff. Lastly, the water and sewerage networks in Norway are in a state of disrepair, with dimensions for handling waste and urban runoff from a century ago. These three factors - climate change, urbanization and pressed sewerage systems, are creating a negative aggregate effect on the quality of life, private and public property and critical infrastructure in Norway’s cities. Low Impact Development (LID) comprises a series of measures for stormwater management that mimic natural hydrological processes and can be adapted to a built environment, as well as work with existing sewerage systems. This thesis seeks to examine how LID can more effectively be implemented in future stormwater management projects in urban settlements in Norway, and reviews relevant literature and frameworks, as well as a pilot project for urban LID stormwater management in Norway’s capitol city Oslo. The Deichman’s street project, which opened in 2016, is now in its fourth year of operations. This pilot project for climate change relief in urban settlements was a collaboration between the Agency for Water and Wastewater Services in Oslo, the Urban Environment Agency and Asplan Viak, a consultancy company for engineering and architecture. project uses a number of LID measures, including rain gardens and permeable surfaces, to handle stormwater locally and delay water surges to the sewerage system. It also provides access to green spaces for residents, and demonstrates how ‘blue-green’ surface solutions, can be multifunctional. The answer to handling increased amounts of rain is not an either-or solution. Modern grey solutions, in terms of improved sewerage systems and water management are still needed, but should aim to work with LID solutions that offer flexibility and provide more services to the people and environment they are placed in. By evaluating the Deichman’s street project, looking to other reference projects for rain gardens and LID stormwater management, and analyzing a selection of existing literature, this thesis seeks to translate findings into actionable measures for urban LID implementation in a Norwegian climate. The case study evaluates several aspects of the project, from design to performance and public perception. The research data were collected from June to July of 2019 on behalf of the Agency for Water and Wastewater Services in Oslo. The findings are then translated into a list of actionable measures that landscape architects, planners and other relevant parties involved in planning and designing future LID stormwater management projects can use.