Översvämningsanpassade samhällen med grön infrastruktur – ett behov i framtiden? En förändringsanalys av grönytor och översvämningsrisk i Källby, Lund

Sammanfattning: The consequences of climate change affect our environment as well as humanity all over the world. For the city of Lund in southern Sweden, climate change consequences are seen as an increase of both intensity and frequency of extreme rain events, which causes an extensive risk for pluvial flooding. Simultaneously, the population and need for housing are growing. When building new districts, the permeable green surfaces, that can infiltrate surface runoff water, are often converted into impermeable surfaces. This enhances the runoff water and the risk of flooding, which may have devastating social, economic and health related consequences. In this bachelor thesis, the connection between green surfaces and flood risk has been studied for the area of Källby in Lund municipality. Källby is a focal district for future development plans and is therefore of high interest. Change analysis of green infrastructure was done over the years 1940-2019, using GIS and remote sensing. From this, the hydrological model TFM-DYN (Pilesjö and Hasan 2014; Nilsson 2017) was used to model the risk of flooding with the change of green infrastructure over time. The model is based on infiltration values, surface friction values, a digital elevation model and rain intensity for a 100-year rain event. Future risk of flooding has also been modeled using a future climate scenario. The results show that the extent of potentially flooded areas does not change with a reduction of green surfaces over time. However, high-risk areas and maximum water depth will increase as green surfaces decrease in extent. For a future scenario, the magnitude of all these factors will increase even further in addition to an increase in the total flood extent. The results of this analysis also indicate the importance of flood adaptation strategies in city planning for sustainable management and development. General recommendations on how this can be implemented are given in this study and can be used both in the area of Källby where the study was conducted, but are also of relevance for other areas.