Abstract
Mountain landscapes are characterised by a very variable environment under different points of view (topography, geology, meteorological conditions), and they are frequently affected by mass wasting processes. A debris flow that occurred along the Croso stream, located in the Italian Lepontine Alps in the Northern Ossola Valley, during summer 2019, was analysed from a geological/geomorphological and meteorological point of view. The debris flow was triggered by an intense precipitation event that heavily impacted a very restricted area over the course of three hours. A previous debris flow along the same stream occurred in Autumn 2000, but it was related to an intense and prolonged rainfall event. The slope was characterised in terms of sediment connectivity, and data were retrieved and elaborated from the Web-GIS (Web-Geographic Information System) database of the IFFI-Italian Landslide Inventory and historical archives of landslides. Both the events were analysed through the weather research and forecasting (WRF) model applying a very high horizontal grid spacing with the aim of catching the precipitation patterns and timings. The obtained results are compared with the observed precipitation at a selection of weather stations in the area. The simulation of WRF that measured the timing in total precipitation and in its minor steps could be considered reliable. Moreover, it reveals to be appropriate for detecting in advance the meteorological conditions potentially triggering mass-wasting processes affecting slopes featuring high connectivity conditions and lithotypes characterised by a high Landslide Susceptibility Index.
Highlights
Mountain environments are being affected by climate change, especially in terms of water resources and streamflow regimes [1]
The structure of the Croso stream hydrographic basin is clear in terms of sediment connectivity in Figure 5a, where the Index of Connectivity map is reported
The meteorological conditions were computed using weather research and forecasting (WRF) model at high horizontal and vertical resolution, in order to capture local phenomena occurring in very complex terrains
Summary
Mountain environments are being affected by climate change, especially in terms of water resources and streamflow regimes [1]. The study area (i.e., the investigated slope in Figure 1a,b) is located in the Central-Western Alps, and more in particular in the Lepontine gneiss dome area, where basement nappes alternate with (meta)sedimentary cover series constituting a NW-verging stack of basement and post-Carboniferous cover nappes [29]. The Lower Penninic nappes characterise in particular the investigated slope They are highly metamorphic crustal nappes representing the former rift shoulder and syn-rift European margin [31]. The Antigorio Unit is constituted by monzogranitic to granodioritic orthogneiss representing the basement of the series [29,31] It is overlain by the Teggiolo Unit, comprised of several sedimentary cycles, separated by erosive surfaces and large stratigraphic gaps, whose age ranges from Triassic to Eocene [30]. North from to Ireland to Norway related with troposphere a high surface hPa)(995 moving Ireland
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