GIS and volcanic risk management

Volcanic catastrophes constitute a major problem in many developing and dev eloped countries. In recent years population growth and the expansion of se ttlements and basic supply lines (e.g., water, gas, etc.) have greatly incr eased the impact of volcanic disasters. Correct land-use planning is fundam ental in minimising both loss of life and damage to property. In this contr ibution Geographical Information Systems (GIS), linked with remote sensing technology and telecommunications/warning systems, have emerged as one of t he most promising tools to support the decision-making process. Some GIS ar e presented for two volcanic areas in Italy, Mt. Etna and Vesuvius. GIS rol e in risk management is then discussed, keeping in mind the different volca nic scenarios of effusive and explosive phenomena. Mt. Etna system covers a large area (more than 1,000 km(2)) potentially affected by effusive phenom ena (lava flows) which cause damage to both houses and properties in genera l. No risk to life is expected. The time-scales of lava flows allow, at lea st in principle, modification of the lava path by the building of artificia l barriers. Vesuvius shows typically an explosive behaviour. In the case of a medium size explosive eruption, 600,000 people would potentially have to be evacuated from an area of about 200 km(2) around the Volcano, since the y are exposed to ruinous, very fast phenomena like pyroclastic surges and f lows, lahars, ash fallout, etc. Ash fallout and floods/lahars are also expe cted in distal areas, between Vesuvius and Avellino, downwind of the volcan o. GIS include digital elevation models, satellite images, volcanic hazard maps and vector data on natural and artificial features (energy supply line s, strategic buildings, roads, railways, etc.). The nature and the level of detail in the two data bases are different, on the basis of the different expected volcanic phenomena. The GIS have been planned: (a) for volcanic ri sk mitigation (hazard, value, vulnerability and risk map assessing), (b) to provide suitable tools during an impending crisis, (c) to provide a basis for emergency plans.