Loss of residential buildings in the event of a re-awakening of the Laacher See Volcano (Germany)

We estimate damage and loss to the residential building stock from tephra fallout for a re-eruption of the Laacher See Volcano in Germany with similar volcanological features as compared to the 10900BCE eruption (VEI = 6) but current population and wind conditions. This eruption was the largest eruption north of the Alps since the Late Quaternary. It generated several fallout fans with proximal deposits of several meters in height. The main cities that would be affected today are Cologne, Bonn, Koblenz and Frankfurt with a total population of at least 2.2 million people. We derive possible wind fields from an analysis of 44years of radiosonde observations provided by the Deutsche Wetterdienst (DWD). As they vary significantly with season, the loss numbers and patterns reflect this dependency. We use the HAZMAP software to calculate the spatial distribution of tephra. HAZMAP simulates the tephra distribution using a 2D advection-diffusion-sedimentation model. The tephra load as a hazard parameter is used to quantify roof and building damage. As the physical parameter for damage due to snow loads is comparable, we utilise the available knowledge on snow load damage to buildings and derive vulnerability curves that are representative within a geo-cell of 500 × 500m. Available information on the replacement values in each geo-cell are derived and loss estimation is undertaken. Depending on the wind conditions, we calculate a range of 18 to 27 billion Euros for the various scenarios. These absolute numbers translate to Mean Damage Ratios (MDR, ratio of absolute loss to Capital Stock in the affected area) of about 4%. This is very close to the MDR of the 1991 VEI 6 Pinatubo eruption in the Philippines.