The importance of sustainable stormwater management in urban areas - A case study on current and future development in Lerum, Sweden

Examensarbete för masterexamen
Infrastructure and environmental engineering (MPIEE), MSc
Norlén, Karl
Oscarsson, Linda
The risks of pluvial flooding in urban areas are expected to increase due to climate change leading to heavier rainfall events in the future. In addition, urbanisation contributes to impermeable surfaces which further increases the risk of flooding. Sustainable stormwater management that mimics nature based solutions is considered a favourable way to treat urban flooding. The use of sustainable stormwater management also enables incorporation of ecological and social services whilst reducing the impacts of urban flooding. Infiltration and surface roughness are two key parameters in assessing how efficient these sustainable stormwater solutions are. Infiltration has been established to have a large impact on flooding, while more recent studies have shown that surface roughness impacts runoff to a large extent. This project aims to further investigate the impact of infiltration and surface roughness on sustainable stormwater management. To achieve the aim, a case study is performed in the municipality of Lerum, Sweden. The softwares SCALGO Live and MIKE 21 are used to identify current and future infrastructure at risk for flooding in Lerum. Stormwater solutions to manage floods in the area are then implemented in suitable locations into the software SCALGO Live. The model is then imported into MIKE 21 where the solutions’ properties are altered to correspond to permeable or impermeable surfaces to study the effect of infiltration and surface roughness. Thereafter simulations are performed to obtain results on flow speeds and water depths to assess risk levels stemming from the flooding, as well as investigating the impact of the alterations in infiltration and surface roughness. The results are compared and show that stormwater solutions with high surface roughness lowers flow speed and solutions with high infiltration capacity lowers water depths. Both parameters con tribute to lower risk levels, which leads to the conclusion that both parameters are important to manage the runoff by affecting separate aspects of a flooding event.
flood risk levels , infiltration , multifunctionality , pluvial flooding , surface roughness , sustainable stormwater management
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