The purpose of this work is to present a study of the geologic and geotechnical susceptibility of units located in the Figueira da Foz municipality (Central-Western Portugal). A geological and geotechnical susceptibility classification was established to evaluate rock masses which are constituted by Jurassic and Cretaceous rocks (limestones, marls and sandstones). The classification, divided into qualitative and quantitative parameters and sub-parameters, was applied in 43 outcrops located in the study area. The main parameters are the historical record, lithology, geological structures, geomorphology, floods and in situ stress relief. The sum of the several parameters varies from 0 to 100. The results can be grouped in classes, from very low to very high degree of susceptibility. Two outcrops showed low susceptibility. The majority of the sites scored between 40 and 60 and belong to the medium susceptibility class. The high susceptibility degree is located on costal and quarry areas.
The concepts of ‘hazard’, ‘susceptibility’, ‘vulnerability’ and ‘risk’ have all been used in studies on natural phenomena, corresponding to catastrophic events. Several recent publications have been based on natural hazards and their impact on human activity.
UNDRO(United Nations Disaster Relief Organization), in collaboration with UNESCO (United Nations Educational, Scientific and Cultural Organization), carried out a study aimed at clarifying the concepts of ‘hazard’, ‘susceptibility’ and ‘risk’ (Varnes 1984). ‘Hazard’ refers to situations or events which pose a threat to man, society or the environment (Bell 2002). According to Cantos & Ayala-Carcedo (2002), ‘susceptibility’is the propensity of an area to be affected by a hazard, compared to other areaswhich have been previously affected. ‘Susceptibility’ can also be defined as the probability of a given area to be affected by a process, which can be classified using qualitative methods (Vallejo & Ferrer 2011).
‘Hazards’ can be defined as natural, technological or a mixture of both (Schmidt-Thomé & Kallio 2006). ‘Risk’refers to exposure to a hazard and can be defined as the product of probability and loss (Smith 2001).
