UNIVERSITÀ DI PISA
Corso di Laurea in
. SCIENZE E TECNOLOGIE GEOLOGICHE Anno Accademico 2011/2012
Candidata: Stefania Faiello (Matr: 459209)
Titolo della tesi
Condizioni di innesco dei soil slip - debris flow avvenuti in Val di Vara (SP) il 25/10/2011
Relatore: Giacomo D’Amato Avanzi
Correlatori: Roberto Giannecchini, Yuri Galanti, Daria Marchetti
Abstract
On 25th october 2011 an a disastrous flood occurred on Levante ligure; it was originated by an extremely heavy storm which hit the area between the Tigullio, the Cinque Terre and the Magra basin, where rains exceeded 400 mm in 6 hours, with 522mm/24h in Brugnato and 382mm/24h in Monterosso.
In the most affected areas, rainfalls caused the overflowing of the Magra and Vara rivers and some tributaries. A great number of soil slips – debris flow occurred on the slopes; this material invaded the fluvio- torrential riverbeds, increasing a lot the solid load of the stream. Flood waves and landslides caused the death of many people and very serious damages to buildings and facilities (bridges’ collapse, holdup on provincial and municipal roads, interruption of essential services, such as water, gas and telephony supplies).
This degree thesis esamined the basin of Pogliaschina torrent.
The thesis’ takes aim at study landslides triggering factors, through various steps 1) Reconstruction of the rainy event on 25th october 2011;
2) Analysis of the geological, geomorphologic and lithotechnical context;
3) Soil slope stability analysis and sensitivity analysis on landslide sampling.
In the analized area, the 25 october 2011 event caused about 300 landslide. The stability analysis has confirmed the necessity of heavy rainfall to trigger landslide movements and, the critical role of coesion and water- level change.
The gathered up data and the obtained results can be the cognitive basis to build the chart of soil
slips’ susceptibility and event’s backgrounds to determine prevention and protection measures.
Riassunto
Il 25 ottobre 2011 si è verificato sul Levante ligure un evento meteo - alluvionale di straordinaria entità, originatosi da un violento sistema temporalesco che ha investito l’area compresa tra il Tigullio, le Cinque Terre ed il bacino del Magra (fig 1); le piogge hanno superato i 400 mm in 6 ore, con cumulate di 522 mm/24 h a Brugnato (fig 2 A) e di 382 mm/24h a Monterosso (fig 2 B).
Fig 1 Inquadramento dell’area colpita dalle precipitazioni piovose del 25 ottobre 2011 bacino (Autorità di Bacino del Fiume Magra)
Fig 2grafici delle piogge registrate il 25 ottobre 2011 dal pluviometro di Brugnato (A) e di Monterosso(B)