Università di Napoli “Federico II”, Dipartimento di Ingegneria Civile, Edile ed Ambientale

The aim of this paper is to recognize and map the Somma-Vesuvius volcano landslide-prone areas by means of multi-disciplinary terrain analysis and classification; in detail, high-resolution DTM of landslides areas occurred over long time periods, remote sensing, and geophysical and geomorphological data are presented for assessing hydrogeological hazard parameters of this volcanic district. The Somma-Vesuvius volcano, due to its explosive volcanism and the dense urbanization of the surrounding area with a population exceeding 650,000, is one of the most dangerous active volcanoes of the world. The main hazard of the perivolcanic area is associated to effusive eruptions and explosive Plinian and sub-Plinian eruptions, alternated to long-lasting quiescence periods. Moreover, additional hazard is related to lahars: flows of unconsolidated debris and water that typically include fragments of volcanic origin, colluvium, and soil. The features of lahars can range from debris flow to hyperconcentrated flow. The most important lahars phenomena of the Somma-Vesuvius occurred with the main historical eruptions of 79 A.D., 472 A.D., and 1631 (Mastrolorenzo et al. 2002; Rosi et al. 1993; Rosi et al. 1996). Recently, remobilization of the pyroclastic cover has produced several debris flows and alluvial phenomena that invaded the surrounding plains affecting towns and roads. Our methodological approach is based on landslides data recognizing and mapping both from geological maps, papers, historical chronicles, and from aerial photos, orthophoto, and available DTM image analysis of the Somma-Vesuvius complex. Through detailed study of this material the main landslides depositional areas have been surveyed; moreover, other geophysical and geomorphological parameters have been considered jointly with the landslides occurrence in order to correlate and interpret the soil movements phenomena. The analysis of several space-time series of data, together with the updated territorial information has been carried out through the Geographic Information System (GIS) (software ArcGIs 9.3), in order to store, manage and process large amount of spatial data. Finally, the achievement of landslide hazard high-resolution mapping of the Somma-Vesuvius volcano is performed in this paper through investigation of the flowslides deposits (lahar) of this area (Di Crescenzo et al. 2008). Actually, the recent heavy urbanization of landslide-prone areas has increased their vulnerability, consequently buildings and infrastructure could be seriously damaged and safety of the people endangered (Davoli et al., 2001). Therefore the obtained maps are necessary for identifying the future inundation areas and for evaluating the possible hydrogeological risk scenarios.

This paper presents a preliminary susceptibility map of the flood hazard for the Somma-Vesuvius volcanic district, worked out by means of multidisciplinary historical, geological, geomorphological and rainfall data processing. It is well known that the Somma-Vesuvius volcano, due to its explosive volcanism and the dense urbanization of the surrounding area, with a population exceeding 650,000 is one of the most dangerous active volcanoes of the world. Although this area has been extensively studied from the volcanological point of view with regards to its volcanic hazard, there are currently not many detailed studies about its flood hazard factors, despite the fact that, in the last century, many intense rainfall events in this area have produced several floods that invaded the surrounding plains affecting towns and roads, and causing much damages and loss of lives. Accordingly, in this paper high-resolution DEM (5×5 m pixel) and detailed geomorphological maps of the whole area have been analyzed and processed in GIS environment, carrying out a comparative study of the present-day morphology and the morphology of the 1900’s volcanic edifice, including changes of infrastructures and buildings throughout the last century. These results, together with historical chronicles data and the rainfall accurate data for all flood events, have been processed in this paper for highlighting the drainage basins areas of Somma-Vesuvius where the flood phenomena could be more probable in the future, working out a preliminary zoning map, also suggesting in which sectors interventions useful for mitigation of flood risk should be implemented.

The aim of this paper is to recognize and map the Somma-Vesuvius volcano landslide-prone areas by means of multi-disciplinary terrain analysis and classification; in detail, high-resolution DTM of landslides areas occurred over long time periods, remote sensing, and geophysical and geomorphological data are presented for assessing hydrogeological hazard parameters of this volcanic district.