The Island of Ischia is located in the Tyrrhenian Sea, approximately 30 km WSW from the city of Naples in Southern Italy. The Island is a debris-flow prone area due to its steep slopes covered by loose volcanic lithologies. On April 30th 2006, following several hours of rainfall, four soil slips were triggered on the slopes of Mt. Vezzi (about 400 m a.s.l.) in the SE portion of the island. The soil slips changed quickly into debris flows that reached the inhabited at the foot of the hill, causing four victims, destroying several buildings and forcing the evacuation of 250 inhabitants. This work presents the analysis of the triggering and propagation phase of the phenomena. In particular, to model the triggering conditions, a finite element analysis was used to reconstruct the variations in pore water pressure during the event in transient conditions. The limit equilibrium slope-stability method was then applied using the temporal pore water pressure distributions derived from the seepage analysis. The dynamic modeling of the propagation phase was carried out by means of two dynamic codes DAN-W and FLO2D, with the aim of evaluating the residual hazard linked to other potential debris flows recognized in the same area. Once the DAN-W and FLO2D models satisfactorily reproduced the 30th April events, the simulations were extended to a larger area, whose susceptibility to future landslide events has been determined through a detailed geomorphological survey and a following GIS analysis.
TXT-tool 4.039-3.3: Debris flows modeling for hazard mapping / Nocentini M.; Tofani V.; Gigli G.; Fidolini F.; Casagli N.. - STAMPA. - (2018), pp. 761-770. [10.1007/978-3-319-57777-7_49]
TXT-tool 4.039-3.3: Debris flows modeling for hazard mapping
Nocentini M.;Tofani V.;Gigli G.;Fidolini F.;Casagli N.
2018
Abstract
The Island of Ischia is located in the Tyrrhenian Sea, approximately 30 km WSW from the city of Naples in Southern Italy. The Island is a debris-flow prone area due to its steep slopes covered by loose volcanic lithologies. On April 30th 2006, following several hours of rainfall, four soil slips were triggered on the slopes of Mt. Vezzi (about 400 m a.s.l.) in the SE portion of the island. The soil slips changed quickly into debris flows that reached the inhabited at the foot of the hill, causing four victims, destroying several buildings and forcing the evacuation of 250 inhabitants. This work presents the analysis of the triggering and propagation phase of the phenomena. In particular, to model the triggering conditions, a finite element analysis was used to reconstruct the variations in pore water pressure during the event in transient conditions. The limit equilibrium slope-stability method was then applied using the temporal pore water pressure distributions derived from the seepage analysis. The dynamic modeling of the propagation phase was carried out by means of two dynamic codes DAN-W and FLO2D, with the aim of evaluating the residual hazard linked to other potential debris flows recognized in the same area. Once the DAN-W and FLO2D models satisfactorily reproduced the 30th April events, the simulations were extended to a larger area, whose susceptibility to future landslide events has been determined through a detailed geomorphological survey and a following GIS analysis.
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