Abstract
Abstract. Rainstorm damage caused by the malfunction of urban drainage systems and water intrusion due to defects in the building envelope can be considerable. Little research on this topic focused on the collection of damage data, the understanding of damage mechanisms and the deepening of data analysis methods. In this paper, the relative contribution of different failure mechanisms to the occurrence of rainstorm damage is investigated, as well as the extent to which these mechanisms relate to weather variables. For a case study in Rotterdam, the Netherlands, a property level home insurance database of around 3100 water-related damage claims was analysed. The records include comprehensive transcripts of communication between insurer, insured and damage assessment experts, which allowed claims to be classified according to their actual damage cause. The results show that roof and wall leakage is the most frequent failure mechanism causing precipitation-related claims, followed by blocked roof gutters, melting snow and sewer flooding. Claims related to sewer flooding were less present in the data, but are associated with significantly larger claim sizes than claims in the majority class, i.e. roof and wall leakages. Rare events logistic regression analysis revealed that maximum rainfall intensity and rainfall volume are significant predictors for the occurrence probability of precipitation-related claims. Moreover, it was found that claims associated with rainfall intensities smaller than 7–8 mm in a 60-min window are mainly related to failure processes in the private domain, such as roof and wall leakages. For rainfall events that exceed the 7–8 mm h−1 threshold, the failure of systems in the public domain, such as sewer systems, start to contribute considerably to the overall occurrence probability of claims. The communication transcripts, however, lacked information to be conclusive about to which extent sewer-related claims were caused by overloading of sewer systems or failure of system components.
Highlights
Heavy rainfall causes considerable damage to building structure and content all over the world
Claims related to sewer flooding were less present in the data, they are associated with significantly larger claim sizes (EUR 1150–3160, based on the 95 % confidence interval around the median in Fig. 4) than claims generated by roof and wall leakages (EUR 680–840), the majority class
The main goal of the current study was to investigate the relative contributions of different failure mechanisms to the occurrence of rainstorm damage to building structure and content, as well as the extent to which the probability of occurrence of these failure mechanisms relate to weather variables
Summary
Heavy rainfall causes considerable damage to building structure and content all over the world. Research on this topic has mainly concentrated on the adverse consequences of river flooding (Douglas et al, 2010; Jongman et al, 2012). Danish insurers received more than 90 000 claims and paid out more than EUR 800 million (2011 value) in compensation (Garne et al, 2013) Another example is the heavy rainfall event of autumn 1998 in the Netherlands, which was associated with a return period of about 125 years and caused around EUR 410 million (1998 value) worth of damage to private buildings and agriculture (Jak and Kok, 2000). The cumulative damage of minor rainfall events can be considerable in the long run due to their high frequency of occurrence (Ten Veldhuis, 2011)
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