Determination of Gaffed Coastline Sensitivity and Associated Risk for Human Structures: A Methodological Approach

Human developments along the coastal zone have been increasing greatly during the past decades, and many of those developments are now threatened by coastal erosion. Sea cliff sensitivity to such process can be assessed in different ways, e.g. by coastal morphology, elevation, lithologies, etc. Important parameters controlling rock quality, and hence cliff stability, are its lithology and the presence and characteristics of discontinuities. In this article, a methodological approach is proposed for determining cliff characteristics and the probability of collapse, according to the Bieniawski Method, widely used in geotechnical and applied geologic studies, and for assessing the role of cliff verticality and the presence/absence of protective structures. The vulnerability of human structures depends on their distance from the cliff top, which can be expressed according to their location within the Imminent Collapse Zone and the 10-, 20-, and 30-year, predicted coastline positions obtained from aerial photographs.