Detection of Annual Coastal Boulder Mobility From 2017–2021 Remote Sensing Imagery (Gulf of Taranto, Mediterranean Sea) and Relation With Marine Weather Conditions

Landward displacement of coastal boulders is a morphodynamic signature of inundation and erosion processes. The study of these movements can provide useful elements for coastal hazards assessment. In this note, using open-access remote sensing resources, the 2017 to 2021 annual mobility of medium, coarse, and very coarse boulders spread over about 100 km of the eastern coast of the Gulf of Taranto (Italy) is detected. A large interannual variability was found. As established by multi-temporal object-based image analysis, one hundred and ten boulders changed position between July 2019 and June 2020, no boulder was displaced between July 2017 and July 2018, and few boulders were displaced between July 2018 and July 2019, and June 2020 and September 2021. A hydrodynamic analysis of the investigated boulder displacement led to the estimation of the energy of nearshore waves that hit the coast. The storm Detlef, that crossed over the Mediterranean Sea during 11-13 November 2019, is presumed to be the main cause of the massive displacement phenomenon.