Urban flood damage claim analyses for improved flood damage assessment

Abstract

Urban flood damage leads to major costs for private house owners, insurance companies, and water and wastewater utilities. Analysis of flood damage claims can be used to improve the understanding of the details of flood damage characteristics and reasons for drainage system failures. However, few studies have used data of this kind to investigate urban flood characteristics. We examined 3113 damage claim cases over 30 years (1992–2019) for the city of Malmö, Sweden. We quantified the distribution and frequency of both major and minor flood damages over this period. Our analysis showed that most floods occur in August, but we could not find any significant trend in the count of damage claims between 1992 till 2019. The main drivers of flood damages were rainfall and failure mechanisms in the drainage system. In total, 24.5% of properties suffered from repeated flood damages, 44% originating from combined sewer system connection and 17% from the separated sewer system. This highlights the importance of sewer system types in flood damage claims. In addition, there was an uneven claim count between insurance companies and owners per event. About 42% of insurance company claims were not accompanied by the owner's deductible claims. Our results highlight the need to further investigate the reason behind this difference and ways for better future planning to minimize the damage from flood events.