Territorial evolution and volcanic hazard at Ischia island (Southern Italy).

The Ischia Island, located in the north-western zone of Napoli bay (Southern Italy), is exposed to many natural events that represent sources of risk for both the tourists visiting the island all over the year and the local inhabitants. In this paper, we take advantage of spatial and temporal analysis available in a Geographic Information System framework in order to compare the spatial distribution of volcanic hazard zones to the temporal evolution of population and urban development over the last 80 years. The volcanic hazard map refers to pyroclastic flows from low to intermediate size explosive events, that could affect the Ischia Island in the next future. The main result of the study centered on the finding that the territorial system development was not sensitive to volcanic hazard as testified by the expansion of urbanized areas within the medium-high hazard zones. The seriousness of the present territorial system status indicates an urgent need for planning aimed at a proper cohabitation of the inhabitants with the hazardous events and at the achievement of acceptable safeness levels. The map presented here gives a synoptic view of the territorial system evolution related to volcanic hazard and it can therefore be considered a valuable tool to support a sustainable territorial planning. The urban development data can be suitably used to assess their relationship with other natural events which could affect the island.