The Debris Flow Occurred at Ru Secco Creek, Venetian Dolomites, on 4 August 2015: Analysis of the Phenomenon, Its Characteristics and Reproduction by Models

Abstract

On 4 August 2015, a very high intensity storm, 31.5 mm in 20 min (94.5 mm/h), hit the massif of Mount Antelao on the Venetian Dolomites triggering three stony debris flows characterized by high magnitude. Two of them occurred in the historical sites of Rovina di Cancia and Rudan Creek and were stopped by the retaining works upstream the inhabited areas, while the third routed along the Ru Secco Creek and progressively reached the resort area and the village of San Vito di Cadore, causing fatalities and damages. The main triggering factor of the Ru Secco debris flow was a large rock collapse on the northern cliffs of Mount Antelao occurred the previous autumn. The fallen debris material deposited on the Vallon d'Antrimoia inclined plateau at the base of the collapsed cliffs and, below it, on the Ru Salvela Creek, covering it from the head to the confluence with the Ru Secco Creek. The abundant runoff, caused by the high intensity rainfall on 4 August 2015, entrained about 52,500 m 3 of the debris material laying on the Vallon d'Antrimoia forming a debris flow surge that hit and eroded the debris deposit covering the downstream Ru Salvela Creek, increasing its volume, about 110,000 m 3 of mobilized sediments. This debris flow routed downstream the confluence, flooding the parking of a resort area where three people died, and reached the village downstream damaging some buildings. A geomorphological analysis was initially carried out after surveying the whole basin. All liquid and solid-liquid contributions to the phenomenon were recognized together with the areas subjected to erosion and deposition. The elaboration of pre and post-event topographical surveys provided the map of deposition-erosion depths. Using the rainfall estimated by weather radar and corrected by the nearest rain gauge, about 0.8 km far, we estimated runoff by using a rainfall-runoff model designed for the headwater rocky basins of Dolomites. A triggering model provided the debris flow hydrographs in the initiation areas, after using the simulated runoff. The initial solid-liquid surge hydrographs were, then, routed downstream by means of a cell model. The comparison between the simulated and estimated deposition-erosion pattern resulted satisfactory. The results of the simulation captured, in fact, the main features of the occurred phenomenon.

Temporal evolution of flow-like landslide hazard for a road infrastructure in the municipality of Nocera Inferiore (southern Italy) under the effect of climate change

“…An example of the application of the proposed method was conducted for a short section of a motorway. The quantitative approach to hazard estimation was pursued through the implementation of models that are capable of simulating both deposition and entrainment, similar to other notable literature contributions (e.g., Deangeli, 2008;Rosatti and Begnudelli, 2013;Frank et al, 2015;Stancanelli et al, 2015;Cuomo et al, 2016;Gregoretti et al, 2018). Despite the limited extension of the study area, the results displayed a marked temporal and spatial variability of hazard.…”

“…In the present study, climate simulations included in EURO-CORDEX multi-model ensemble at 0.11' (approximately 12 km) are considered under the RCP4.5 and RCP8.5 scenarios, as described in Table 3 (Giorgi and Gutowski, 2016). Climate simulations are adjusted for bias through an empirical quantile mapping approach (Gudmundsson et al, 2012) using data from Nocera Inferiore weather stations from the period 1981-2010.…”

Contribution of Excessive Supply of Solid Material to a Runoff-Generated Debris Flow during Its Routing Along a Gully and Its Impact on the Downstream Village with Blockage Effects

“…Such a triggering mechanism, initially revealed by laboratory experiments on flumes [9] and slopes [10][11][12], has also been shown by field investigations in all different environments around the world [13][14][15][16][17][18][19][20], including China [20,21]. These debris flows, once being triggered, can dramatically grow in volume [22][23][24][25][26][27][28][29] due to the entrainment of debris deposits on the propagation direction. The runout area and deposition depth depend on the debris flow volume [30][31][32][33][34].…”

Laboratory investigations of the role of biofilms on stream‐bed surfaces in debris‐flow runout

“…Debris flows are gravity‐driven flows of mixtures of water and particulate solids ranging from clay to boulder and can move down channels and deposit on fans after long runout distances (Iverson, ; Rickenmann, ; Iverson, ; Zhou and Ng, ; Tian et al ., ; Kaitna et al ., ; Zhou et al ., ). They can transport and deposit large quantities of debris over short time intervals, which is hazardous to residents and structures in their paths (Naef et al ., ; Sepúlveda et al ., ; Fuchs et al ., ; D'Agostino et al ., ; Remaître et al ., ; Ng et al ., ; Gregoretti et al ., ). The harmfulness of debris flows depends on their runout and dynamic characteristics, which could be controlled to some degree by flow resistance.…”