Troubling Waters Ahead – an Evaluation of Coastal Flooding in Stockholm

Sammanfattning: The increasing rate of global sea mean level rise, one of many effects of climate change, will most likelyproduce heightened risk of coastal flooding. Cities located along coastlines have to adapt to thesecircumstances that otherwise will increase the magnitude and frequency of coastal flooding. The purposeof this study is to evaluate the current and future risk of coastal flooding in central Stockholm in relationto global sea level rise. The overall coastal flood risk of central Stockholm is assessed using the currentsea level as well as with possible future sea level rise. Wave modelling is carried out in Saltsjön toestimate the possible addition to extreme sea levels from wave action. The wave characteristics isdetermined according to the physical properties of inner Saltsjön and local meteorological conditions.In-depth case studies regarding flood risk and flood prevention measures are carried out on Stadsholmenand Hammarby Sjöstad, two areas with very different physical characteristics. Areas most prone toflooding in these districts are identified using flood vulnerability maps. Suggestions for flood defencemeasures for the identified vulnerable areas are presented. It is evident that implementation of flooddefence should be adapted after the physical and social properties of the locality. Results of this studycorrelates with well with similar research claiming that there is a small risk of significant coastalflooding in central Stockholm. The flood risk will not increase significantly in the near future, primarilydue to the effect of regional uplift counteracting the global sea level rise. The accelerating rate of globalsea level rise in combination with possible trend changes of meteorological extremes will however mostlikely generate larger problems with coastal flooding in a longer time span.