Just or Unjust: Assessment of rainfall-related flood damage in a Swedish context

Bidragets översatta titel : Just or Unjust: Assessment of rainfall-related flood damage in a Swedish context

Forskningsoutput: AvhandlingDoktorsavhandling (sammanläggning)


Climate change has led to an increase in heavy summer rainfalls, and climate projections for Sweden indicate that there will be more sudden rainfall in the future. While the exact locations and time for this rainfall are unknown, it is known that there will be damages to buildings, cars, and people when the rainfall occurs. It is thus important to evaluate past events to understand the resulting flood damage, with an emphasis on the people who suffer from it, and the procedures for damage claims. Moreover, with more and more people living in cites, there is also an increasing diversity in the socioeconomic conditions that determine residents’ capacity to manage losses.
This thesis examines flood damage claims for 1992-2019 in Malmö, Sweden in detail, including the extreme cloudburst event on 31 August 2014. In terms of population, Malmö is Sweden’s third largest city, and historically, there have been recurring problems with rainfall-related flooding there. The socioeconomic conditions of Malmö’s residents are diverse, making it an interesting and important case for the study of urban flood damage management. This requires an analysis of both the technical aspects of the flooding process and of how different groups are affected. Key aspects for evaluating this in this thesis are residents’ coping capacity for flood damage costs; how damage claims compensation is handled; and an evaluation of equity in flood damage management.
The majority of homeowners in Sweden have home insurance, and there is no separate flood insurance. Therefore, some part of the damage cost is usually covered by the insurance company, but homeowners' losses also comprise their deductible portion as well as the reductions that are not covered by the insurance companies. The impact of these costs on residents will differ based on the resident’s socioeconomic conditions. This thesis investigates the effect of income, education, and immigration status on flood vulnerability in different neighbourhoods in Malmö. A main result is that flood damage costs are higher in low-income neighbourhoods in which there are high rates of immigrants and lower levels of education.
A natural and technical explanation for the differences in outcome between residents lies in what causes flood damage and why some areas are more prone to flood damage. One main risk factor is the difference between combined and separated sewer system connections. Houses connected to a combined sewer system are at a higher risk of basement flooding each time the rainfall exceeds the capacity of the sewer pipe. The results showed that, historically, there are more and repeated flood damage claims for houses connected to combined than separated sewer systems. It was also found that a higher percentage of homes connected to separated sewer systems received compensation compared to homes connected to combined systems.
The current legal practice in Sweden entails that the water and wastewater utility must assume full responsibility for homes in which basements have been flooded via sewer overflow and that are connected to separated sewer systems. On the other hand, the water and wastewater utility has only a partial responsibility for homes connected to combined sewer systems; in these cases, the municipality must investigate the capacity of the pipeline in question to decide where the responsibility lies. This explains why there was a high percentage of rejected flood damage claims in this category during the August 2014 event. Ironically however, all houses connected to combined sewer systems are at greater risk of flooding, as the system collects both rainfall and wastewater. This means that people in areas with combined sewer systems are both more exposed to flood damage and not compensated to the same degree for their damage claims as people whose houses are connected to separate sewer systems.
Based on the results, the equity of damage compensation from the water and wastewater utility in the Swedish system is questioned. Why is flood damage liability based on the type of sewer system, and why does the system favour owners of buildings that already have a lower risk of flooding? The results in this thesis show that there is a need for an assessment of inequities in the Swedish urban flood management system under the present laws and regulations. The next step should be to investigate how support can be strengthened for those who suffer the most from flood damage. There are many potential systems for dealing with compensation to houseowners that are affected by urban flooding. Irrespective of the compensation system, it is important to consider the consequences on different groups and use that information to develop systems based on a perspective of justice.
Bidragets översatta titel Just or Unjust: Assessment of rainfall-related flood damage in a Swedish context
Tilldelande institution
  • Avdelningen för Teknisk vattenresurslära
  • Larsson, Rolf, handledare
  • Nilsson, Erik, Biträdande handledare
  • Berndtsson, Ronny, Biträdande handledare
Tilldelningsdatum2021 dec. 1
ISBN (tryckt)978-91-8039-079-8
ISBN (elektroniskt)978-91-8039-080-4
StatusPublished - 2021

Bibliografisk information

Defence details
Date: 2021-12-01
Time: 10:15
Place: Lecture Hall V:A, building V, John Ericssons väg 1, Faculty of Engineering LTH, Lund University, Lund.
External reviewer(s)
Name: Priest, Sally
Title: Associate Prof.
Affiliation: Middlesex University, United Kingdom.

Ämnesklassifikation (UKÄ)

  • Vattenteknik
  • Tvärvetenskapliga studier


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