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Corresponding Author

Hyunchul Shin

Abstract

This study was designed to determine the slope changes on Dokdo Island, focusing on Seodo islet (slopes consisting of colluvial debris) and Dongdo islet (slopes consisting of large-scale tafoni). To do so, we obtained high-resolution 3D LiDAR data in May and November 2020 and calculated the changes in slope shape and volume over this period. Our results showed that during this time, approximately 136m3 of colluvial debris was removed from the slopes of Seodo islet and a boulder that had separated from the massive tuff breccia migrated approximately 5 cm downslope. The major causes of such rapid changes on the slopes of Seodo were sediment movement caused by heavy precipitation and load variation by slope-toe erosion due to high waves during typhoon events in September. On the contrary, no significant changes were observed on the slopes on Dongdo islet. While we predicted that weathering would cause major changes on the slopes, the measurement interval of this study was too short to observe such changes on the slopes consisting of tafoni. The 3D LiDAR data measures reflection intensity as well as 3D information on the surface of the earth. We measured the reflection intensity ranges of breccia, tuff, and vegetation, and subsequently ordered the intensity to increase from vegetation, breccia, and tuff. The reflection intensity ranges of the three different materials could be used to analyze the weathering rates according to the material types in future studies. In addition, the 3D scanning data on the Dokdo slopes could be used to monitor long-term slope changes and weathering rates.

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