Casagli, Nicola

Mucci, A.

Segoni, Samuele

English

Florence Research

Geophysical Research AbstractsVol. 12, EGU2010-8528, 2010EGU General Assembly 2010© Author(s) 2010The influence of lithology, land cover, road network and slope gradient inthe landslides triggered during the period November 2008 – February2009 in northern Tuscany (Italy)Samuele Segoni, Alessandra Mucci, and Nicola CasagliUniversity of Firenze, Department of Earth Sciences, Florence, Italy (samuele.segoni@gmail.com)In the provinces of Lucca and Pistoia (Tuscany, Central Italy) 650 landslides (mainly shallow rapid slides anddebris flows) were registered by Civil Protection during the period spanning from November 2008 to February2009.During that period both provinces were struck by widespread precipitations: in November three distinct brief butvery intense events brought the monthly precipitation well above the mean value, while the month of Decemberwas conversely characterized by heavy and prolonged precipitations whose cumulative amount doubled themonthly mean value. During January and February brief and intense precipitations struck again diffusively thewhole studied area.As a consequence of such a prolonged period of abundant rainfall, hundreds of landslides occurred in the provincesof Lucca and Pistoia damaging private and public buildings, assets and infrastructures. The state of emergencywas declared by the National Civil Protection from December to February.Rainfall has been without doubt the triggering factor of the landslides, but can some predisposing feature beidentified? The answer is decisive for improving risk assessments and for developing effective emergency plansfor civil protection purposes.For example, rainfall thresholds can be easily used to set up warning systems that can forecast the time ofoccurrence of landslides but such methods have a very coarse spatial resolution: the identification of predisposingelements could be helpful to identify the most risky locations in order to reduce the spatial uncertainty.From the Provincial and Regional Civil Protection archives many information about the occurred landslides weregathered and organized into a geographic database making use of a GIS system. Data include the exact locationand day of occurrence of the landslides and their type.By means of a GIS analysis, the landslides database was superimposed to various thematic maps (geology, landcover, road network, slope gradient) in order to estimate which value or class had been more often associated tolandsliding during the studied event.Results highlights that road cuts seem to be one of the most predisposing features, together with the presenceof layered or schistous geologic formations. Many landslides concentrated in agricultural areas or in artificiallymodified slopes and, quite surprisingly, slope gradient seems to have played a secondary role.Landslides are very recurrent phenomena in the studied area and on behalf of the local civil protection agenciesthe Earth Science Department of the Florence University is at present defining an alert system based on spatiallyvariable rainfall thresholds. The alert system is still in a test phase and it is not yet operative, but some ofthe thresholds it is based upon have been validated making use of the data concerning the reported event. Acomparison with other classic literature thresholds has been performed as well. The errors committed by eachmodel have been then characterized in light of the afore discussed predisposing factors.

The influence of lithology, land cover, road network and slope gradient in the landslides triggered during the period November 2008 &#8211; February 2009 in northern Tuscany (Italy)

https://flore.unifi.it/bitstream/2158/384873/1/Segoni%20et%20al%20GRA%20vol%2012%20EGU%202010.pdf

The influence of lithology, land cover, road network and slope gradient in the landslides triggered during the period November 2008 – February 2009 in northern Tuscany (Italy)

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Florence Research

The influence of lithology, land cover, road network and slope gradient in the landslides triggered during the period November 2008 &#8211; February 2009 in northern Tuscany (Italy)

Abstract

Similar works

Full text

Available Versions

Florence Research

The influence of lithology, land cover, road network and slope gradient in the landslides triggered during the period November 2008 – February 2009 in northern Tuscany (Italy)