Landslide susceptibility mapping is essential for a suitable land use managing and risk assessment. In this work a GIS-based approach has been proposed to map landslide susceptibility in the Portofino promontory, a Mediterranean area that is periodically hit by intense rain events that induce often shallow landslides. Based on over 110 years landslides inventory and experts’ judgements, a semi-quantitative analytical hierarchy process (AHP) method has been applied to assess the role of nine landslide conditioning factors, which include both natural and anthropogenic elements. A separated subset of landslide data has been used to validate the map. Our findings reveal that areas where possible future landslides may occur are larger than those identified in the actual official map adopted in land use and risk management. The way the new map has been compiled seems more oriented towards the possible future landslide scenario, rather than weighting with higher importance the existing landslides as in the current model. The paper provides a useful decision support tool to implement risk mitigation strategies and to better apply land use planning. Allowing to modify factors in order to local features, the proposed methodology may be adopted in different conditions or geographical context featured by rainfall induced landslide risk.

The metropolitan area and the city of Genoa has become a national and international case study for geohydrological risk, mainly due to the frequency of floods. In 2014, there were landslides again, as well as flash floods that have particularly caused casualties and economic damage. The weather features of the Gulf of Genoa and the geomorphological–environmental setting of the Ligurian coastal land are the predisposing factors that determine heavy rains and their resulting effects on the ground. This study analysed the characteristics of the main meteorological disasters that have hit Genoa since the start of the 20th century; changes in the rainfall regime are evaluated and the main stages of urbanization of the area are detailed, with the resulting changes to the drainage network, in order to identify the main causes of this high geohydrological risk. To this end, scientists have used climate data recorded at the station of Genoa University, in operation since 1833, and at Ponte Carrega station, located in the middle reach of the Bisagno stream, a well-known watercourse because of its frequent floods. Urban sprawl was evaluated through a multi-temporal mapping comparison, using maps available from the beginning of the 19th century up to the current regional technical maps. The average air temperature in Genoa shows a statistically significant increase, while the number of rainy days displays an equally clear decrease over time. The total annual rain value does not seem to indicate rather noticeable changes. The intensity of rain in Genoa expressed as rainfall rate, i.e.~the ratio of annual rainfall and number of rainy days, shows statistically significant growth. The geohydrological vulnerability in Genoa has increased over time due to urban development which has established modifications in land use, from agricultural to urban, especially in the valley floor. Waterways have been confined and reduced to artificial channels, often covered in their final stretch; in some cases they have even been totally removed. These actions should be at least partially reversed in order to reduce the presently high hydrological risk.

In the framework of geosite management, specific targeted symbols for geomorphological legends are still lacking. Concerning geosites of geomorphological interest, geomorphological mapping requires targeted symbols in relation to goals and applications, either concerning geomorphic hazards and risk detection or the enhancement of resources, in particular those related to cultural heritage and, hence, geoheritage. A new methodology for mapping geo(morpho)heritage on geomorphological maps is presented in this paper. Nine iconic examples from the Italian landscape, selected in different morphogenetic and morphoclimatic contexts, are proposed to test the methodology in relation to point, polyline and polygon features. Moreover, guidelines for mapping are suggested according to the importance of the site and to the complexity of processes characterizing each case study.

Flash floods represent one of the natural hazards that causes the greatest number of victims in the Mediterranean area. These processes occur by short and intense rainfall affecting limited areas of a few square kilometers, with rapid hydrological responses. Among the causes of the flood frequency increase in the last decades are the effects of the urban expansion in areas of fluvial pertinence and climatic change, namely the interaction between anthropogenic landforms and hydro-geomorphological dynamics. In this paper the authors show a comparison between flood events with very similar weather-hydrological characteristics and the ground effects occurred in coastal areas of three regions located at the top of a triangle in the Ligurian Sea, namely Liguria, Tuscany and Sardinia. With respect to the meteorological-hydrological hazard, it should be noted that the events analyzed occurred during autumn, in the conditions of a storm system triggered by cyclogenesis on the Genoa Gulf or by the extra-tropical cyclone Cleopatra. The “flash floods” damage recorded in the inhabited areas is due to the vulnerability of the elements at risk in the fluvio-coastal plains examined. There are numerous anthropogenic forcings that have influenced the hydro-geomorphological dynamics and that have led to an increase in risk conditions.

The effects of climate change on landslide activity may have important environmental, socio-economic, and political consequences. In the last decades, several short-term extreme rainfall events affected Mediterranean regions, resulted in damaging geo-hydrological processes and casualties. It is unequivocal that the impact of landslides in several Mediterranean countries is increasing with time, but until now, there has been little or no quantitative data to support these increases. In this paper, both rainfall conditions for the occurrence of shallow landslides and rainfall trends were investigated in the Portofino promontory, which extends in the Ligurian Sea, where heavy rainfall and related ground effects often occur. Adopting a frequentist approach, the empirical intensity-duration threshold was estimated. Our findings highlight that the rainfall intensity required to trigger landslides is lower for the same duration than those expected in other similar environments, suggesting a high susceptibility to rainfall-induced landslides in the Portofino territory. Further, the Mann-Kendall test and Hurst exponent were used for detecting potential trends. Analysis of long-term rainfall time series showed statistically significant increasing trends in short duration precipitation occurrence and rainfall rates, suggesting a possible future scenario with a more frequent exceedance of the threshold triggering value and an increase of landslide risk.