The 2017 Rigopiano Avalanche—Dynamics Inferred from Field Observations

Dieter Issler

doi:10.3390/geosciences10110466

Abstract

Data on the disastrous snow avalanche that occurred on 18 January 2017 at the spa hotel Rigopiano, municipality of Farindola in the Abruzzo region of central Italy, are analyzed in different ways. The main results are the following. (i) The 2017 Rigopiano avalanche went beyond the run-out point predicted by the topographic-statistical α-β model with standard Norwegian calibration, while avalanches in neighboring paths appear to have run no farther than the β-point of their respective paths during the same period. (ii) The curvature and super-elevation of the trimline between 1500 and 1300 m a.s.l. indicate that the velocity of the front was around 40 m s−1. In contrast, the tail velocity of the avalanche can hardly have exceeded 25 m s−1 in the same segment. (iii) The deposits observed along all of the lower track and in the run-out zone suggest that the avalanche eroded essentially the entire snow cover, but fully entrained only a moderate amount of snow (and debris). The entrainment appears to have had a considerable decelerating effect on the flow front. (iv) Estimates of the degree to which different parts of the building were damaged is combined with information about the location of the persons in the building and their fates. This allows to refine a preliminary vulnerability curve for persons in buildings obtained from the 2015 Longyearbyen avalanche, Svalbard.

Highlights

In the evening of 18 January 2017, a large snow avalanche released at about 1900 m a.s.l. on the east flank of Monte Siella in the Abruzzo region of central Italy (Figure 1)
In early June 2017, the author surveyed the release area and track of this avalanche path, with regard to the forest damage, and summarized the findings together with information retrieved from the Internet in a report [1]
The upper values result if we assume φ = 30°; more likely, φ < θ due to full fluidization so that one should neglect the square root in the equation for u1 and obtains the lower bounds

Summary

Introduction

In the evening of 18 January 2017, a large snow avalanche released at about 1900 m a.s.l. on the east flank of Monte Siella in the Abruzzo region of central Italy (Figure 1). In early June 2017, the author surveyed the release area and track of this avalanche path, with regard to the forest damage, and summarized the findings together with information retrieved from the Internet in a report [1]. Aerial photos of the area [2] and a letter to the authorities in Farindola [3], published on the Internet after the disaster, show that an avalanche of similar or even larger size completely destroyed the forest in or around 1936 and a smaller one—benefiting from the absence of mature forest in the path—almost reached the location of the hotel in 1959. The large number of persons involved in this catastrophe and sufficient information on the degree of building damage at their respective locations allows an update of the vulnerability curve derived from the avalanche at Longyearbyen, Svalbard, on 19 December 2015 [10], see Section 6

Comparison with a Topographic-Statistical Run-Out Model

Velocity Estimates

Estimate of the Mass Balance

Limits Inferred From Forest Destruction

Limits from Damage to Hotel Rigopiano

On the Vulnerability of Buildings and Persons Hit by Snow Avalanches

Findings

Conclusions