Volcanic eruption induced floods. A rainfall-runoff model applied to the Vesuvian Region (Italy)

Abstract

Explosive events are commonly accompanied or followed by heavy rains. These eruption- induced storms together with the deposition of large amounts of ash contribute to destabilise the hydrological cycle in the areas affected by volcanic eruptions. Flooding of the region surround- ing the active volcano can easily follow, increasing the complexity of the volcanic crisis and its management. This is particularly true in the case of Vesuvius, that is not only characterized by a dramatic volcanic hazard, but it is also located within an area that is normally prone to flood hazard. A complete assessment of the impact associated with explosive volcanic eruptions should involve a flood hazard assessment for the region. This work represents a first attempt to address the problem: a topographically based rainfall-runoff model was here applied to the Vesuvian area where two main sub-basins were analysed. The model was applied to evaluate the role of selected parameters on the total discharge at the basins’ outlet. These parameters were chosen among those likely to be affected by an explosive event and were varied through a reasonable range. Results confirm that the deposition of large amounts of ash can affect the temporal evolution of the discharge and its maximum value, for a given precipitation event. The simulations presented outline the need for a detailed flood forecasting study for the Vesuvian area, that should be included within the hazard mitigation strategies.