Dynamic Vulnerability of built infrastructure - How previous storm events effect the damage of residential buildings in Germany

Severe storm events are one of the most damaging natural hazards in Central Europe and thereby under special focus in disaster risk management. One key element of risk reduction is the vulnerability. While in risk assessments vulnerability is often assumed as constant, in reality different drivers lead to dynamic developments. To take the step from constant to dynamic vulnerability a detailed understanding of the processes and impacts of these influences is necessary. One crucial driver on vulnerability is the hazard itself. In theory vulnerability is likely to increase immediately after an event (De Reiter et al. 2020), whereas on long term the mean vulnerability decreases due to improved reconstruction (UNISDR, 2018).In this study we quantify the effects of storm events on the dynamics of vulnerability, with a focus on the impact of the intensity of previous events as well as the duration between events. In a first step vulnerability curves are derived from the relation of storm events and damage using generalized linear models. For the damage the loss ratio (loss/insured sum), extracted from a 23 yearlong data set of daily storm and hail damages for insured residential buildings in Germany on county level provided by the German Insurance Association, is used. The storm event is described by the three parameter daily maximum wind gust, duration of the storm event and gust factor, all calculated from ERA5 reanalysis. The threshold for the occurrence of an event is the exceedance of the 98th percentile of the wind gust. In the next step the generalized linear model is extended with the storm intensity of the previous event and the duration between two events as additional covariates. First results confirm the thesis of vulnerability decrease due to previous events. In further analyses, the results will be quantified in more detail and key findings of the vulnerability dynamics will be elaborated.