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The debris flow occurred at ru secco creek, venetian dolomites, on 4 august 2015: Analysis of the phenomenon, its characteristics and reproduction by models
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
\ufb02ows 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 \ufb02ow 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\u2019Antrimoia inclined plateau at the base
of the collapsed cliffs and, below it, on the Ru Salvela Creek, covering it from the
head to the con\ufb02uence with the Ru Secco Creek. The abundant runoff, caused by
the high intensity rainfall on 4 August 2015, entrained about 52,500 m3 of the debris
material laying on the Vallon d\u2019Antrimoia forming a debris \ufb02ow surge that hit and eroded
the debris deposit covering the downstream Ru Salvela Creek, increasing its volume,
about 110,000 m3 of mobilized sediments. This debris \ufb02ow routed downstream the
con\ufb02uence, \ufb02ooding 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 \ufb02ow 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
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