Articles | Volume 16, issue 2
Research article
04 Feb 2016
Research article |  | 04 Feb 2016

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

C. Violante, G. Braca, E. Esposito, and G. Tranfaglia

Abstract. In this paper we use a multi-hazard approach to analyse the 9 September 2010 flash flood in the Dragone basin, a 9 km2 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 m3 of materials with a total (water and sediment) peak flow of 80 m3 s−1. The estimated peak discharge of only clear water was about 65 m3 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.

Short summary
The paper integrates land and marine geological data with meteorological, hydraulic, and hydrological analyses, as well as historical documentation of past events, to model the 9 September 2010 flash flood which occurred at Atrani, Amalfi Coast, southern Italy. The approach used is representative of small ungauged watersheds with local communities living at stream mouths, aiding proper land use planning, damage mitigation, and reduction of human fatalities.
Final-revised paper