Flooding due to extreme rain events in urban environments is a problem and a growing concern. When the stormwater systems design return period are greatly exceeded during extreme rain events, flooding is inevitable. However, the flood consequences can be mitigated by surface water management. A Swedish methodology, Plan B, is developed for investigation and planning of extreme rain events by means of flood simulation models. This thesis had its starting point in the Plan B methodology which was further developed through a case study by testing two assessment methods that provide information on the efficiency of surface water measures. The two methods were a key figure assessment and a more comprehensive cost-benefit analysis assessment. It was found that the key figure assessment was easiest to use and that it would be a useful tool for decision makers, but also that it still need some improvements for being reliable. The cost-benefit analysis assessment demands much resource to set up and is tedious to manage and was consequently not recommended for smaller surface water investigations. The case study also contributes with experience on relatively new methodologies and therefore also gives other insights. The most important was that a surface water planning strategy, overarching different departments within the municipalities, is required to mitigate flood consequences.

Author names: 
Larsson, J.

Larsson, J. (2012). Assessment of flood mitigation measures. Further development of a proactive methodology applied in a suburban area in Gothenburg. Master of Science Thesis in Master’s Programme Geo and Water Engineering. Gothenburg: Chalmers University of Technology.

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