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Department of Geography, Coventry University, Coventry, UK
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- PublicationRestrictedEmpirical hazard mapping of small debris flows in Sarno (Italy) using LAHARZ(2006)
; ; ; ; ; ; ;Oramas Dorta, D.; Cambridge University, Cambridge, England ;Toyos, G.; Cambridge University, Cambridge, England ;Oppenheimer, C.; Cambridge University, Cambridge, England ;Pareschi, M. T.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Sulpizio, R.; Dep. Geomineraologico, Universita di Bari, Italy ;Zanchetta, G.; Dipartimento di Scienze della Terra, Pisa, Italy; ; ;; ; 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.277 40 - PublicationRestrictedGIS-assisted modelling for debris flow hazard assessment based on the events of May 1998 in the area of Sarno, Southern Italy: Part I. Maximum run-out(2007)
; ; ; ; ; ; ;Toyos, G.; Department of Geography, University of Cambridge, Cambridge, UK ;Oramas Dorta, D.; Department of Geography, Coventry University, Coventry, UK ;Oppenheimer, C.; Department of Geography, University of Cambridge, Cambridge, UK ;Pareschi, M. T.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Sulpizio, R.; Dipartimento Geomineralogico, Universita di Bari, Bari, Italy ;Zanchetta, G.; Dipartimento di Scienze della Terra, Universita di Pisa, Pisa, Italy; ; ;; ; Based on the debris flow events that occurred in May 1998 in the area of Sarno, Southern Italy, this paper presents an approach to simulate debris flow maximum run-out. On the basis of the flow source areas and an average thickness of 1•2 m of the scarps, we estimated debris flow volumes of the order of 104 and 105 m3. Flow mobility ratios (ΔΗ/L) derived from the x, y, z coordinates of the lower-most limit of the source areas (i.e. apex of the alluvial fan) and the distal limit of the flows ranged between 0•27 and 0•09. We performed regression analyses that showed a good correlation between the estimated flow volumes and mobility ratios. This paper presents a methodology for predicting maximum run-out of future debris flow events, based on the developed empirical relationship. We implemented the equation that resulted from the calibration as a set of GIS macros written in Visual Basic for Applications (VBA) and running within ArcGIS. We carried out sensitivity analyses and observed that hazard mapping with this methodology should attempt to delineate hazard zones with a minimum horizontal resolution of 0•4 km. The developed procedure enables the rapid delineation of debris flow maximum extent within reasonable levels of uncertainty, it incorporates sensitivities and it facilitates hazard assessments via graphic user interfaces and with modest computing resources.186 21