GIS‐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

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 (ΔH/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. Copyright © 2007 John Wiley & Sons, Ltd.

[1]  Richard M. Iverson,et al.  Flow of variably fluidized granular masses across three‐dimensional terrain: 2. Numerical predictions and experimental tests , 2001 .

[2]  Vern Manville,et al.  The sensitivity of a volcanic flow model to digital elevation model accuracy: experiments with digitised map contours and interferometric SAR at Ruapehu and Taranaki volcanoes, New Zealand , 2003 .

[3]  S. Self,et al.  A comparison of pyroclastic flow and debris avalanche mobility , 1992 .

[4]  Richard M. Iverson,et al.  Flow of variably fluidized granular masses across three‐dimensional terrain: 1. Coulomb mixture theory , 2001 .

[5]  M. Pareschi,et al.  Volcaniclastic debris flows in the Clanio Valley (Campania, Italy): insights for the assessment of hazard potential , 2002 .

[6]  Kenneth J. Hsü,et al.  Catastrophic Debris Streams (Sturzstroms) Generated by Rockfalls , 1975 .

[7]  L. Siebert.  Large volcanic debris avalanches: Characteristics of source areas, deposits, and associated eruptions , 1984 .

[8]  Dieter Rickenmann,et al.  Empirical Relationships for Debris Flows , 1999 .

[9]  M. Pareschi,et al.  Numerical simulation of some lahars from Mount St. Helens , 1992 .

[10]  Giovanni B. Crosta,et al.  Observations and modelling of soil slip-debris flow initiation processes in pyroclastic deposits: the Sarno 1998 event , 2003 .

[11]  Jordi Corominas,et al.  The angle of reach as a mobility index for small and large landslides , 1996 .

[12]  Roberto Santacroce,et al.  Characteristics of May 5–6, 1998 volcaniclastic debris flows in the Sarno area (Campania, southern Italy): relationships to structural damage and hazard zonation , 2004 .

[13]  J. Vallance,et al.  OBJECTIVE DELINEATION OF LAHAR-INUNDATION HAZARD ZONES , 1998 .

[14]  R. Iverson,et al.  U. S. Geological Survey , 1967, Radiocarbon.

[15]  M C Malin,et al.  Computer-Assisted Mapping of Pyroclastic Surges , 1982, Science.

[16]  Clive Oppenheimer,et al.  Empirical modelling of the May 1998 small debris flows in Sarno (Italy) using LAHARZ , 2007 .

[17]  Clive Oppenheimer,et al.  GIS‐assisted modelling for debris flow hazard assessment based on the events of May 1998 in the area of Sarno, Southern Italy: II. Velocity and dynamic pressure , 2008 .

[18]  T. Pierson,et al.  Flow characteristics of large eruption-triggered debris flows at snow-clad volcanoes: constraints for debris-flow models , 1995 .

[19]  Richard M. Iverson,et al.  The debris-flow rheology myth , 2003 .

[20]  Michael C. Malin,et al.  Application of computer-assisted mapping to volcanic hazard evaluation of surge eruptions: Vulcano, lipari, and vesuvius , 1983 .