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ABSTRACT

The present research focuses on the mass wasting processes such as landslides and rockfalls

observed at Puerto Saveedra. To better understand how these processes occurred, a field

survey was carried out to generate topographic maps and collect representative samples for

mineral analyses. More specifically, this study aims to determine the mechanisms of mass

wasting, to link the triggering conditions and to mitigate risks of such events.

To this end, three surveys were carried out to observe susceptible mass wasting zones, collect

samples and establish its mineralogy through X-raydiffraction. A detailed topographic map

was created to to create a Digital Elevation Model (DEM) and to analyse slope stability

zones. Slope, landcover, geomorphology and lithology were identified as the main triggering

factors of the landslides and rockfalls of Puerto Saveedra. This allowed to assess the risks of

this área using heuristic models and multiparameter analyses.

The mineralogical results show that clay minerals such as halloysite, palygorskite, sepiolite,

kaolinite, illite and montmorillonite are common and are known to generate impermeable

layers. However, some minerals appear to have variations in their internal structure under

hydrous conditions: indeed, montmorillonite and illite can deform in contact with water,

which consequently generates potential instability scenarios. Thus, the effects of rainfall

would favor change in the geomechanical behaviour of the deposits.

Susceptibility map highlight the increased risks near the coastal escarpment, resulting from

the steep slope and due to residual soil which are likely to collapse following rainy events.

Further, susceptibility values are elevated north west of the fluviomarine plains and near Bud

lake, where deforestation and agricultural activities increase erosion, decrease the water

holding capacity and thus increase flooding risks during rainfall. This implication, combined

with the slope factor and the clay minerals presence, generate a potential scenario of slopes

instability.

Therefore, this thesis project presents the first susceptibility mass wasting map of Puerto

Saavedra, which provides important contribution as it allows a deeper understanding of these

processes for the study area.

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