Flood hazard mitigation in volcanic areas

M. Todesco¹, E. Todini²
DSTGA, v. Zamboni, 67, 40127 Bologna, Italy.
Tel. : +39-51-354537; Fax: +39-51-354522;
E-mail: ¹todesco@geomin.unibo.de, ²todini@geomin.unibo.it

Abstract:
Major volcanic eruptions are often accompanied by serious flooding. The condensation of water vapour being erupted is responsible for prolonged and intense precipitations that occur in a region where the soil infiltration is drastically reduced by ash deposition. As a consequence, a flood wave may form and propagate with very short warning time in the areas surrounding the volcanic edifice.

A complete hazard assessment and risk mitigation in volcanic areas should therefore carefully consider the possible occurrence of eruption-induced floods. This work belongs to a research project aimed at developing an understanding of these flood episodes, and at the assessment of the associated hazard. Hydrological models will be applied to the Vesuvian area to evaluate the flood wave that may develop, the maximum expected water level, the extent of the flooded area, and the time required for the restoration of an effective draining system. As a first step, a rainfall-runoff model will be applied, based on an estimate of the maximum expected precipitation induced by the eruption. Based on the calculated hydrograph, the flood propagation in the area of interest will be evaluated by applying a mixed 1-2D model, based on a control volume finite element formulation.