Dynamic Vulnerability of residential buildings - Quantifying the effect of previous storm events on damages

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 for risk reduction is the vulnerability. Risk assessments often assume vulnerability as constant which lead to an overestimation of risk in the future. The aim of this work is to quantify the dynamics of vulnerability in order to better assess future risk.

An important factor for the dynamics of vulnerability is the hazard itself. Extreme events destroy the most vulnerable elements, which are rebuild or repaired in a less vulnerable way. The intensity of the previous events and the resulting damage is therefore a decisive factor in the extent to which vulnerability is reduced. A second important factor is the period between events, which can be called the reconstruction phase. If the next event occurs during the reconstruction phase, vulnerability is higher than when the reconstruction phase is completed.

In this work, the impact of previous storm events on the vulnerability of residential buildings is analysed. For this purpose, generalised 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 yearlong data set of daily storm and hail damages for insured residential buildings in Germany on county level provided by the German Insurance Association and the hazard compoment is described by the daily maximum wind gust calculated from the ERA5 reanalysis.

First results show a negative linear relationship between the intensity of the previous event and the damage of the current event. The duration between two events shows a significant reduction of the damage for events that have a summer season between the events and hardly any difference when the storm events occur within a winter season.