Temporal dynamic vulnerability - Impact of antecedent events on residential building losses to wind storm events in Germany

Severe storm events are one of Central Europe's most damaging natural hazards, thereby under particular focus on disaster risk management. One key element for risk reduction is vulnerability. Risk assessments often assume vulnerability as constant, leading to an overestimation of risk in the future. This work aims to quantify the temporal dynamics of vulnerability to assess future risks more precisely. An essential factor for the dynamics of vulnerability is the hazard itself. Extreme events destroy the most vulnerable elements, which are rebuilt or repaired in a less vulnerable way. Therefore, the intensity of the previous events and the resulting damage is a decisive factor in reducing vulnerability. A second important factor is the period between events. If the next event occurs during the reconstruction phase, vulnerability is higher than when the reconstruction phase is completed.

We analyze the impact of previous storm events on the vulnerability of residential buildings. For this purpose, generalized additive models are implemented to estimate vulnerability curves, which are set as a function of the intensity of the previous event and the duration between the events. The damage is extracted from a 23-year-long data set of the daily storm and hail damages for insured residential buildings in Germany on the county level provided by the German Insurance Association, and the hazard component is described by the daily maximum wind load calculated from the ERA5 reanalysis. The results show a negative relationship between the previous event's intensity and the current event's damage. The duration between two events shows a significant reduction of the damage for events occurring one or more winter seasons ago compared to events occurring within the same season. On a daily scale, the first seven days are especially crucial for vulnerability reduction.