Abstract
Abstract. A critical pluviometric event occurred in the central-eastern Ligurian Riviera, 15 km from Genoa, on 1 June 2007. This event caused landslides and hydraulic problems between Sori and Camogli and in the inland area of the Recco Valley. An analysis of the heavy rainfall was conducted. Hourly precipitation data revealed a critical event between 04:00 a.m. and 07:00 a.m. local time, with more than 220 mm of precipitation over three hours. Slope movements were mainly debris flows that detached from the lateral valleys of the Recco Stream catchment and from well-maintained, wooded slopes that were also characterised by cultivated terraces. Numerous slide planes corresponded to the interface between the surface cover and the underlying bedrock, which presents an unfavourable geologic structure in terms of stability assessment. In most cases, the displaced material had a limited thickness. Debris cover was rapidly channelled along small valleys, which controlled the critical hydraulic conditions in the secondary drainage network. Man-made drainage systems were partially or totally blocked in a very short time and, like the natural watercourses, accumulated thick and extensive alluvial fans. Most of the instability phenomena occurred in areas that had been designated medium or low-risk areas during land planning, and in sectors that were defined as stable, because they lacked geomorphic indicators connected to landslide risks. The above considerations highlight some gaps of the Recco Stream Master Plan. Therefore, to update this land planning tool, it is necessary to extensively investigate local geomorphological characteristics and to adopt a different method for assigning weights to the geohazard maps.
Highlights
It is widely acknowledged that current climate changes have rainfall tropicalisation effects at temperate latitudes (IPCC, 2007)
The present paper investigates a rainfall event that occurred on 1 June 2007 in the eastern sector of the Paradiso Gulf, central-eastern Ligurian Riviera (Fig. 1)
In this area, which is typical of the Mediterranean coast, a heavy and short rainfall event triggered a number of shallow landslides and several hydrographic network instabilities
Summary
It is widely acknowledged that current climate changes have rainfall tropicalisation effects at temperate latitudes (IPCC, 2007). Heavy precipitation events frequently interrupt long dry periods; extreme events, which can deliver more than 100 mm h−1 in Liguria, cause geomorphological hazards, both on slopes and within the hydrographic network (Crosta and Frattini, 2000; Luino, 2005; Jakob and Lambert, 2009). The present paper investigates a rainfall event that occurred on 1 June 2007 in the eastern sector of the Paradiso Gulf, central-eastern Ligurian Riviera (Fig. 1). In this area, which is typical of the Mediterranean coast, a heavy and short rainfall event triggered a number of shallow landslides and several hydrographic network instabilities. A number of similar events occurred at this location over the last several decades (Faccini et al, 2005, 2009) and the well-known flash floods of 2010 and 2011 events in the Genoa municipality and surrounding areas caused human losses (Sacchini et al, 2011; Faccini et al, 2012)
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