Recent damaging events on alluvial fans along a stretch of the Tyrrhenian coast of Calabria (southern Italy)

Debris flow and flood phenomena constitute the main natural hazards on alluvial fans. These processes, often occurring during intense rainfall events, may put many communities living on fan surfaces at high risk. This article focuses on an area along the Tyrrhenian coast of Calabria (southern Italy) where a set of mountain front alluvial fans has developed on the narrow coastal plain. This area has been heavily exploited, and tourism constitutes an important source of income. Rainfall events occurring in 2009, 2010 and 2011, albeit not significantly intense, induced debris flows endangering the population and damaging private property and infrastructures. The analysis highlighted that in the study area the risk due to debris flow and the vulnerability of the area have increased as a consequence of both the reactivation of construction processes in the alluvial fan feeder basin and the intense development of human activities in the same areas. The construction of protection facilities and the loss of the historical accounts of past catastrophic events have encouraged this development. Given the characteristics of the study area, the choice and design of the most appropriate measures need particular attention.