The 9 September 2010 torrential rain and flash flood in the Dragone catchment, Atrani, Amalfi Coast (southern Italy)

Abstract

Abstract. In this paper we use a multi-hazard approach to analyse the 9 September 2010 flash flood in the Dragone basin, a 9 km 2 catchment located along the Amalfi rocky coastal range, southern Italy. In this area, alluvial fan flooding has been the most frequent and destructive geologic hazard since Roman times. Sudden torrents of water (flash floods) are caused by high-intensity and very localized cloudbursts of short duration, inducing slope erosion and sediment delivery from slope to stream. The elevated bed load transport produces fast-moving hyperconcentrated flows with significant catastrophic implications for communities living at the stream mouth.The 9 September 2010 rainstorm event lasted 1 h with an intensity rainfall peak of nearly 120 mm h −1 . High topographic relief of the Amalfi coastal range and positive anomalies of the coastal waters conditioned the character of the convective system. Based on geological data and post-event field evidence and surveys, as well as homemade videos and eyewitness accounts, it is reported that the flash flood mobilized some 25 000 m 3 of materials with a total (water and sediment) peak flow of 80 m 3 s −1 . The estimated peak discharge of only clear water was about 65 m 3 s −1 . This leads to a sediment bulking factor of 1.2 that corresponds to a flow with velocities similar to those of water during a flood.

Multiple Effects of Intense Meteorological Events in the Benevento Province, Southern Italy

“…The maps in Figure 2 show the rainfall distribution during the first ( Figure 2A) and second ( Figure 2B) storm event. The first storm on [14][15] October developed in the NE-SW direction. It principally affected the area surrounding the Taburno-Camposauro massif and the middle Calore river valley, and it elongated toward the upper Tammaro river basin, which was involved in the full extent of the storm.…”

“…In Italy, the Campania Region has suffered tragic consequences of hydrogeological events e.g., [10][11][12][13][14][15]: It has experienced the largest number of landslide-and flood-related casualties (2164 casualties from 321 events between 1850 and 2008) in the country [16]. Within the Campania Region, the Benevento province has been historically affected by hazardous phenomena triggered by intense rainfall e.g., [17][18][19].…”

Possible impacts of a changing climate on intense Ligurian Sea rainfall events

“…The most common period for such events is during the autumn when the warm water and favourable large‐scale atmospheric conditions (e.g. Reale et al, ; Pinto et al, ) can result in strong mesoscale convective systems (MCSs) that remain quasi‐stationary as they experience back‐building (Schumacher and Johnson, ; Duffourg et al, ; Violante et al, ; Fiori et al, ; Lagasio et al, ). The back‐building may be especially favoured in parts of this region by the local topography as it encourages convergence of the warm, moist south‐easterly flow over the Mediterranean with cooler air from the north that funnels through the relatively low passes of the Apennine mountains in northwestern Italy and to the south into the northern parts of the Ligurian Sea.…”

Replies to reviewer 1 - integration (figures 2 and 3)

“…Among the flash-flood-producing storms in the Mediterranean area, a prominent feature is the highly localized and persistent back-building of mesoscale convective systems (MCSs; Schumacher and Johnson, 2005;Duffourg et al, 2015;Violante et al, 2016). Such a scenario has often been observed in the last decade, when Liguria (NW Italy) and southern France have been repeatedly hit by severe floods: 2010 Varazze and Sestri Ponente, 2011Cinque Terre and Genoa, 2012Marseille and Isle du Levant, 2014Genoa and Chiavari, 2015 Nice.…”