Numerical modelling of volcanic hazards
A challenge for the characterization and assessment of volcanic risk is the variety of hazards posed by volcanic eruptions. Thus, assessing volcanic risk requires the analysis of a multi-hazard process. Volcanic hazards include flow processes as lava flows, mud flows, ash flows and pyroclastic flows which are usually confined to valleys in the surrounding of the volcano. In contrast, deposits from fall processes like volcanic bombs, lapilli, and fine ash transported through the air can be lifted over the crater rim and accumulate in all directions from the crater. Those deposits can even be found in distal areas and pose risk to regions at large distance from the volcano. Similarly, hazard due to volcanic degassing is relevant at proximal distances as well as on a global scale. Further hazards are posed by mass movements like landslides due to flank instabilities. Those can, as well as submarine volcanic eruptions, generate volcanic tsunamis. Physical models can help to better understand the physics of the eruption process and the process of transport and deposition, and thus to quantify both, the individual hazard posed by a volcano, and the risk connected to it.
Research recently carried out in the group Natural Hazards and Risk at GPI deals with numerical modelling volcanic hazards and their impacts on critical infrastructure and population. For a re-eruption of Laacher See volcano with comparable eruption intensity as the 10900 BC eruption, Leder (2015) simulated different fallout scenarios using a present-day wind-field derived from 44 years of radiosonde observations. The fallout fans of fine ash particles spread mainly westwards with some variation to the North and to the South, and affect the cities of Cologne, Bonn, Koblenz, and Frankfurt. Schuh (2016) computed that - depending on the wind speed – an area between 770 km² and 850 km² would be covered with at least 1 m of ash, and an area between 4800 km² and 5800 km² would be covered with at least 0,1 m of ash. Subject to the prevailing wind direction and thus to the season, Schuh (2016) showed that this corresponds to a coverage of the German autobahn at a total length of 280 km – 340 km. Dietzmann (2016) worked on the influence of volcanic ash of on respiratory disorders and quantified the additional number of doctors, hospitals and medical equipment needed in a re-eruption of Laacher See volcano. A comparison of different modeling tools for ash deposits was performed by Steinau (2017).