Abstract
This paper deals with the problem of cliff stability and proposes a geomorphological zonation of a cliff using a sector of the Posillipo promontory (named the Coroglio-Trentaremi sea cliff, Italy), in the Campi Flegrei coastal area, as a case study. A detailed geological and geomorphological analysis was carried out, by combining field work with analysis of detailed scale topographic maps, orthophoto, and stratigraphical data from deep boreholes. Field and borehole data, together with structural data collected in seven different stations along the cliff, allowed us to derive six geological cross-sections and to reconstruct the complex stratigraphical and structural setting of the cliff. Geomorphological analysis focused on the detection of the main geomorphological factors predisposing to cliff instability. We selected the most significant factors and divided them into two groups: factors influencing landslide intensity and factors influencing cliff instability. Then, by means of a heuristic approach, we constructed a matrix that was used to derive a map showing the geomorphological zonation of the sea cliff. This map may enable to development of a reliable scenario of cliff instability and consequent retreat, which may be useful either to plan intervention works in the most critical areas or to organize prevention plans aimed at risk mitigation.
Highlights
Studying the evolution of coastal areas is a crucial issue because coastal areas have experienced human frequentation since historical and even pre-historical times [1,2] and host many socio-economic activities [3]
This paper deals with the problem of cliff stability and proposes a geomorphological zonation of a cliff using a sector of the Posillipo promontory, in the Campi Flegrei coastal area, as a case study
The geological setting of the Coroglio-Trentaremi sea cliff is reported in Figure 3, whereas the stratigraphical relationships between the outcropping rock-types are reported in the stratigraphical columns of Figure 4 and in the geological cross-sections of Figure 5
Summary
Studying the evolution of coastal areas is a crucial issue because coastal areas have experienced human frequentation since historical and even pre-historical times [1,2] and host many socio-economic activities [3]. Coastal areas are very dynamic environments that are subject to modifications even at short timescales Such modifications depend on several factors, such as climate change, wave action, isostasy, geology, tectonics, and anthropic actions [4]. This is true both for sandy and rocky coasts. Brooks and Spencer [6] estimated a retreat rate of 0.9–3.5 m/y since 1883 for a sector of the East Anglia sea cliff carved in soft sediments, e.g., mainly unconsolidated sands and clays. Epifano et al [8] estimated an average retreat rate of 0.044 m/y in a 60-year-long period for a rocky coast carved in Jurassic marls and sandstones in Portugal. Naylor and Stephenson [9] analyzed discontinuities within shore platform in Wales and Australia and derived that the higher the density of discontinuities the more rapidly the shore platform will erode, with consequences for sea cliffs behind shore platforms
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