High sea levels and flooding - Assessment of the consequences of events occurring in Sweden 1980 - 2017

At a global level, flooding is one of the types of natural disasters that causes the most deaths and economic damage. The likelihood of flooding along coasts is particularly affected by high water levels. In the predicted future climate, the sea level rises, which among other things means that higher extreme sea levels can occur. Flooding will hence become worse. Future changes in the frequency and magnitude of storms can also contribute to changes in extreme sea levels. Research on future storms is however still contradictory. Already today buildings near coasts may be at risk of direct flooding in high-water situations. Sweden so far has been relatively spared from major floods and their worst consequences. Nevertheless, the material damage and costs to the society caused by floods can be significant. In Sweden, 36% of the population live within 5 km of the coastline. If the coast zone is extended to 10 km, the number is up to 49%. The consequences of extreme sea levels however vary depending on the location and the size, the depth and duration of the flood, as well as the vulnerability and significance of the affected natural and built environment. The Swedish Civil Contingencies Agency (MSB) commissioned FOI to perform this study. In the study the impact of record high sea levels and floods in Sweden is analysed on human health, the society and economic activities, the environment and cultural. The 14 instances of highest levels between 1980 to January 2017 are included in the study. These events were observed on the measurement stations provided by SMHI when the study began in November 2016. A discussion about the management of the events has also been included, as well as assessments of the potential consequences of similar contemporary events. The analysis laid out in this report is delimited to effects along the coastline that is approximately represented by the respective measurement station. The main method of the study has been a media survey of newspapers, interviews and a literature study. The result will be used as a basis for flood protection work under the Flood Risk Regulation (SFS 2009: 956), conducted by MSB. The purpose of this work is to reduce the negative impact of floods, thus safeguarding human health, the environment, cultural heritage, and economic activity.