Abstract
The objective of the present study is to achieve a better understanding of the possible rotation of embayed beaches using shoreline position data from two beaches on the central Tyrrhenian Sea (Italy) during a 64-year period. With this aim, this study tests the utility of Differential Global Positioning System (DGPS) and GPS RTK (Real Time Kinematic) dual-frequency navigation system for the in situ surveys, low-altitude aerial imagery collected by Unmanned Aerial Vehicle (UAV), and satellite polarimetric Synthetic Aperture Radar (SAR) measurements. The dataset consists of aerial photographs and orthophotos, DGPS, and remote surveys performed by UAV and SAR platform in 2018 along with wave data coming from the Ponza buoy. The results of the field data analysis explained a part of the beach variations in terms of coastline rotation around a virtual pivotal point. This rotation has been correlated with the wave directional shift in the recent period. The results of the comparison between the different techniques gave the possibility to investigate the limitations of remote survey methods for the identification of shoreline rotation.
Highlights
Coastal areas are highly dynamic natural environments providing outstanding ecological benefits
Shoreline survey can be generally performed, by remote sensing [3,4,5], Unmanned Aerial Vehicle (UAV) [6] and video monitoring [7,8], which was already introduced by Aarninkhof [9], Turner et al [10] and Holman and Stanley [11]; the final aim is the assessment of coastal vulnerability and risk which has been performed in different contexts [12,13,14,15]
The results show that changes in the wave directional distribution during summer can be responsible for the observed beach rotation around a pivotal zone
Summary
Coastal areas are highly dynamic natural environments providing outstanding ecological benefits Those environments are subject to diverse and different natural hazards such as erosion, tsunamis and floods [1]. Embayed beaches are more common than generally thought and represent about 50% of the world’s coastline [16]. These beaches are typically protected by structures or headlands at their extremities which trap alongshore moving sediments, resulting in net erosion\accretion at the updrift\downdrift ends of the beach, and beach rotation, i.e., lateral movement of sand along the beach in response to a modification in the incident wave direction [16]. The process of beach rotation, as alteration in the shoreline orientation, is due to a temporal change in the shoreline which implies an advance (retreat) of the shoreline which is maxima near the extremities of the beach and minima or zero in the central section represented by the pivotal point
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