The Pogliaschina valley extends for about 11 km2 in the Municipality of Borghetto Vara in the Liguria Region. The Pogliaschina torrent and the Cassana torrent flow into the Vara River close to the Borghetto Vara village. In the Pogliaschina valley crop out sedimentary rocks mainly belonging to the M. Gottero sandstones formation (Upper Cretaceous and Paleocene) with minor outcrops of the Macigno and Scaglia Toscana formations.
On 25 e 26 October 2011, a high intensity storm hit the Eastern part of the Liguria Region causing 13 fatalities and severe damages to villages. The main intense rainfall has been recorded during the 25 October when more than 400 mm of rain has been recorded in 6 hours. In the study area main damages have been recorded in the area between the L'ago Village and the Cassana Torrent. The high intensity rainfall triggered abundant slope failures, predominately shallow flows and soil slides, debris flows, and rock falls. The intense rainfall event also resulted in widespread erosion along the slopes and the main bottom valley with deposition of debris along drainage channels, extensive inundation, and deposition of debris and trees along the main state road (Statale Aurelia). The torrent flooding has affected the valley bottom for an area expected to be inundated by the 500-year flood.
Tested LAMPRE products
Physiographic settings
The landscape is rather rugged, with steep slopes and narrow alluvial plains. The area is characterized by a high geological variability.
Relevant phenomena
Flash floods, shallow flows and soil slides, debris flows, and rock falls.
Activities
Production and quality assessment of an event-induced landslide inventory map (based on a November 2011 event) was carried out through conventional and new metrics. These metrics might be proposed as standards.
LAMPRE products testing
LAMPRE has prepared ELIMs for different test sites ranging in areas from 25 to 80 square kilometres, including two ELIMs for the Kaopin area (Taiwan), two ELIMs for the Pogliaschina area (Liguria, Italy) and an ELIM for the Giampilieri area (Sicily, Italy).
For the Pogliaschina catchment (Italy), LAMPRE has exploited a pair of VHR stereoscopic images taken by the WorldView-2 satellite shortly after a rainfall event that triggered hundreds of landslides. In the non-shadowed areas, the ELIM was prepared semi-automatically through a standard classification of the VHR images. In the shadowed areas, landslides were not visible in the images (Figure A). By stretching the Normalized Differential Vegetation Index (NDVI) the traces left by the landslides became apparent (Figure B). Exploiting stereoscopy, a 3D model was prepared to facilitate the recognition of the event landslides, allowing for their accurate mapping (Figure C).
