Comparison of Remote Sensing Techniques for Geostructural Analysis and Cliff Monitoring in Coastal Areas of High Tourist Attraction: The Case Study of Polignano a Mare (Southern Italy)

Lidia Loiotine,Marc-Henri Derron,Gioacchino Francesco Andriani,Michel Jaboyedoff,Mario Parise

doi:10.3390/rs13245045

Lidia Loiotine, Marc-Henri Derron + Show 3 more

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https://doi.org/10.3390/rs13245045

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Abstract

Rock slope failures in urban areas may represent a serious hazard for human life, as well as private and public property, even on the occasion of sporadic episodes. Prevention and mitigation measures indispensably require a proper rock mass characterization, which is often achieved by means of time-consuming, costly and dangerous field surveys. In the last decades, remote sensing devices such as high-resolution digital cameras, laser scanners and drones have been widely used as supplementary techniques for rock slope analysis and monitoring, especially in poorly accessible areas, or in sites of large extension. Although several methods for rock mass characterization by means of remote sensing techniques have been reported in specific studies, there are very few contributions that focused on comparing the different methods in an attempt to establish their advantages and limitations. With this study, we performed digital photogrammetry, Terrestrial Laser Scanning and Unmanned Aerial Vehicle surveys on a cliff located in a popular tourist attraction site, characterized by complex geological and geomorphological settings, as well as by disturbance elements such as vegetation and human activities. For each point cloud, we applied geostructural analysis by means of semi-automatic methods, and then compared multi-temporal acquisitions for cliff monitoring. By quantitative comparison of the results and validation by means of conventional geostructural field surveys, the pros and cons of each method were outlined in attempt to depict the conditions and goals the different techniques seem to be more suitable for.

Highlights

Local to global failures in urbanized steep rock coasts represent a serious threat to the natural landscape, infrastructure and human activities
As regards the comparison between the Terrestrial Laser Scanning (TLS) and the Terrestrial Photogrammetry point clouds by means of Cloud-to-Cloud distance computation, high values of the scalar field were detected in the southern part of the model (Figure 5)
Remote sensing techniques are of paramount importance to overcome the limitations Remote sensing techniques are of paramount importance to overcome the limitations of conventional field methods for rock slope investigations, especially when dealing with of conventional field methods for rock slope investigations, especially when dealing with poorly accessible areas of large size and with unsafe conditions

Summary

Introduction

Local to global failures in urbanized steep rock coasts represent a serious threat to the natural landscape, infrastructure and human activities. Given the interaction between geo-environmental processes and material properties, hazard assessment and planning of prevention or mitigation measures in coastal areas require a full understanding of the specific site conditions, with particular emphasis on the mechanical behavior of the rock mass, as well as the failure volumes, time frequency and modes. Numerical simulations are carried out on the geotechnical models to predict the location and kinematics of potential instabilities by adopting the appropriate technique [23,24,25,26] Based on these considerations, the success in numerical modelling and in susceptibility assessment depends on the quality of the geotechnical model, which necessarily requires a proper rock mass characterization

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