ETD system

Electronic theses and dissertations repository

 

Tesi etd-05172018-002632


Thesis type
Tesi di dottorato di ricerca
Author
ESPOSITO, GIUSEPPE
URN
etd-05172018-002632
Title
The use of Geomatics for the analysis of mass wasting processes in volcaniclastic coastal cliffs of the Flegrean area (Italy)
Settore scientifico disciplinare
GEO/04
Corso di studi
SCIENZE DELLA TERRA
Commissione
tutor Prof. Salvini, Riccardo
correlatore Dott. Sacchi, Marco
Parole chiave
  • coastal cliff
  • retreat
  • weathering
  • erosion
  • landslide
  • lidar
  • digital photogrammetry
  • geomorphic monitoring
  • geotechnical characterization
  • Campi Flegrei
Data inizio appello
25/05/2018;
Consultabilità
parziale
Data di rilascio
25/05/2021
Riassunto analitico
Many coastal cliffs forming part of the Italian coastlines are affected by retreat processes, mainly<br>occurring through landslides and surface weathering. Coastal landslides represent a serious risk for<br>population living in littoral settlements, where a massive urbanization occurred in the last decades.<br>New tourist settlements, railway networks and roads were built in these areas, altering in several cases<br>the natural evolution of coastal dynamics. Actually, 28.4% of Italians live here with an average<br>density of 400 inhabitants per square kilometer.<br>The coastal sector of the Campi Flegrei volcanic area (southern Italy) is partially formed by sea cliffs.<br>These are made by volcaniclastic deposits and are affected by rapid recession since their origin.<br>Several cliffs consist in remnants of ancient volcanic edifices formed in the last 15 ka, during<br>explosive eruptions of the Campi Flegrei volcanic activity. The lacking of entire flanks of edifices<br>located in the actual coastal area highlights the rapid action characterizing dismantling processes. In<br>order to achieve a quantitative knowledge about mass movements that are contributing to the<br>geomorphic evolution of the volcaniclastic coastal cliffs, a multidisciplinary approach mainly based<br>on the use of geomatic techniques and secondarily on geotechnical laboratory tests is applied in this<br>thesis. The study is articulated in a large-scale analysis, aimed at characterizing slope failures<br>occurring in the whole Flegrean area and along the coastline, as well as in site-specific analyses<br>focused on two representative coastal cliffs: the “Baia dei Porci” and “Torrefumo” cliffs. Both sites<br>are located in the municipality of Monte di Procida, in the western sector of Campi Flegrei. The longterm<br>geomorphic evolution of the Torrefumo cliff (1956 - 2008) was investigated by comparing<br>digital elevation models (DEM) derived from aerial images and airborne lidar data. This activity<br>allowed quantifying volumetric changes, retreat rates and maximum retreat of the cliff top. Shortterm<br>geomorphic changes (2013 - 2016) that affected this cliff were detected by comparing 3D point<br>clouds acquired with terrestrial laser scanning technique (TLS). In this way, a cliff failures inventory<br>map was developed and the magnitude-frequency distribution of events was calculated. Further<br>statistical analyses of the inventory data, together with field and topographic observations, showed<br>that different geomorphic processes are contributing to the cliff retreat, and vary according to the<br>outcropping lithotypes. The TLS-based analysis was also used to develop a cliff failure susceptibility<br>map through the application of a bivariate statistical method. In this site, laboratory tests were also<br>performed on representative rock samples of the outcropping lithologies, collected at the base of the<br>cliff. These tests allowed verifying mechanical strength of rocks, resistance to weathering and<br>mineralogical composition of the altered rock surfaces.<br>At the Baia dei Porci cliff site, a large landslide displacing about 40,000 m3 of volcaniclastic deposits<br>occurred in October 2013. The landslide was monitored until January 2016 to assess its geomorphic<br>evolution. In this case, the “Structure-from-Motion” (SfM) photogrammetry technique was used by<br>performing four surveys with a boat and a remotely piloted aircraft system (RPAS), as well as a<br>topographic survey of the ground control points. Comparison of the 3D point clouds derived from<br>processing of photogrammetric data, allowed accurate identification of areas where geomorphic<br>changes occurred, and to quantify volumes of material mobilized after the 2013 failure. This case<br>study highlighted the high potential of the used techniques for accurate monitoring of inaccessible<br>coastal cliffs.<br>This research provides a valuable contribution to fill the research gap concerning a quantitative<br>understanding of erosion affecting volcaniclastic coastal cliffs, and it can be considered among the<br>first comprehensive studies dealing with monitoring of cliff retreat processes in the Campi Flegrei<br>area. Insights emerged from monitoring activities and laboratory analyses demonstrate that behavior<br>of these cliffs is controlled by a complex set of factors that need further in-depth analyses. In addition,<br>more efforts should be carried out to assess risk conditions affecting urban settlements built close to<br>the retreating cliff tops.
File