Integrated Field Surveying and Land Surface Quantitative Analysis to Assess Landslide Proneness in the Conero Promontory Rocky Coast (Italy)

Abstract

Rock slopes involved in extensive landslide processes are often characterized by complex morphodynamics acting at different scales of space and time, responsible for different evolutionary scenarios. Mass Rock Creep (MRC) is a critical process for long-term geomorphological evolution of slopes and can likewise characterize actively retreating coastal cliffs where, in addition, landslides of different typologies and size superimpose in space and time to marine processes. The rocky coast at the Conero promontory (central Adriatic Sea, Italy) offers a rare opportunity for better understanding the predisposing role of the morphostructural setting on coastal slope instability on a long-time scale. In fact, the area presents several landslides of different typologies and size and state of activity, together with a wide set of landforms and structural features effective for better comprehending the evolution mechanisms of slope instability processes. Different investigation methods were implemented; in particular, traditional geomorphological and structural field surveys were combined with land surface quantitative analysis based on a Digital Elevation Model (DEM) with ground-resolution of 2 m. The results obtained demonstrate that MRC involves the entire coastal slope, which can be zoned in two distinct sectors as a function of a different morphostructural setting responsible for highly differentiated landslide processes. Therefore, at the long-time scale, two different morphodynamic styles can be depicted along the coastal slopes that correspond to specific evolutionary scenarios. The first scenario is characterized by MRC-driven, time-dependent slope processes involving the entire slope, whereas the second one includes force-driven slope processes acting at smaller space–time scales. The Conero promontory case study highlights that the relationships between slope shape and structural setting of the deforming areas are crucial for reaching critical volumes to induce generalized slope collapse as the final stage of the MRC process. The results from this study stress the importance of understanding the role of morphostructures as predisposing conditions for generalized slope failures along rocky coasts involved in MRC. The findings discussed here suggest the importance of the assessment of the slope instability at the long time scale for a better comprehension of the present-day slope dynamics and its major implications for landslide monitoring strategies and the hazard mitigation strategies.

BEGEOSCIENTIST a young network - I Congresso Nazionale dei Giovani Geoscienziati

“…Both hard and soft rocky cliffs characterize the central Adriatic coastal sector in the Marche region (Italy). Here, either active or relict landforms occur and, a strong litho-structural control on the gravitational morphodynamics has been recognized (Troiani et al, 2020). In such landscape contexts, the assessing of rock slope instabilities is possible using different traditional and advanced structural and geomorphological investigation techniques; furthermore, these techniques can take advantage of the use of DEM-based land surface quantitative analysis and, of remote sensing.…”

“…Rocky coasts in the central Adriatic Sea offer a rare opportunity for better understanding the predisposing role of the morphological and structural setting on coastal slope instability (Torre, 2019;Troiani et al, 2020) and quantify the wave energy impact on the rocky cliffs.…”

“Novel Approaches in Landslide Monitoring and Data Analysis” Special Issue: Trends and Challenges

“…Troiani et al [7] applied different surface analysis and monitoring methods to decipher the structural controls of rock slope stability in coastal areas. They worked on the Adriatic coast of the Conero promontory in Central Italy, and their results stress the need to analyze slope stability over a long timescale, to understand the current processes.…”

Land-Surface Quantitative Analysis to Investigate the Spatial Distribution of Gravitational Landforms along Rocky Coasts

“…Rocky coasts represent zones with high economic, social, cultural, and touristic value; consequently, many geomorphological studies have been completed along both hard and soft rocky coasts, which generally focused on the factors controlling erosional processes [3]. Moreover, other studies focused on the active morphodynamics along coastal reliefs, emphasizing the role of mass movements along sea cliffs on the present morphoevolution of the coastlines, also considering the associated geomorphologic hazards [4][5][6][7].…”

“…On the other hand, the use of remotely sensed datasets from satellite and/or from aerial platforms, such as from ad hoc flights of unmanned aerial vehicles (UAVs), are suitable for the acquisition of detailed data in inaccessible coastal areas [10,11]. Along the central Adriatic coastline of Italy, a combination of geological-geomorphological field surveys and the spatial interpretation of morphometric variables, derived from digital elevation model (DEM) data, has been successfully proposed by [6] for the study of the slope instabilities in relation with the long-term morphoevolution of a 5 km-long rocky sea cliff.…”