Empirical hazard mapping of small debris flows in Sarno (Italy) using LAHARZ

Abstract

The catastrophic events that occurred in May 1998 in the area of Sarno (Southern Italy) highlight the destructive potential of debris flows, even when they are of relatively low magnitude. More than 130 people were killed and severe property damage took place when volcaniclastic debris flows triggered by heavy rainfall inundated various towns located in piedmont areas. This work investigates the suitability of LAHARZ, a GIS-assisted method for the automatic delineation of lahar inundation areas, for reproducing the May 1998 flows at Sarno. It was found that recalibration of the empirical relationship employed by LAHARZ is required in order to realistically hind-cast the inundation areas of considered events. The potential for further improvements in prediction outputs for this type of geomorphic setting is discussed, taking into account the observed lower mobility of these small volcaniclastic debris flows as compared to lahars of similar size.