High-resolution monitoring of beach topography and its change using unmanned aerial vehicle imagery

Beaches suffer from considerable degradation due to the dual influences from natural and human-induced factors. Higher resolution topographic data are frequently needed for assessment of the rapid changes and for building the models that can predict the evolution of these natural environments. In this paper, a low-altitude quad-rotor unmanned aerial vehicle (UAV), equipped with a non-metric camera, was used to acquire the two periods of UAV images in a complex beach of Wujiao Bay where the significant geomorphic changes occurred mainly due to the strong scouring of the drainage gullies. A detailed practical technique workflow was presented for deploying the low-altitude UAV for high-resolution monitoring the topography and the changes of the beach. The high resolution orthomosaic with geo-reference accuracy less than 1 pixel and the Digital Surface Model data with high vertical accuracy of approximately 10 cm were achieved by applying the UAV photogrammetry process based on Structure from Motion method to numerous overlapped UAV images. These data were further applied to the topographic change monitoring and analysis of the beach. This study greatly enhanced the applicability of the UAV remote sensing and enriched the existing tools for the high resolution topographic survey and geomorphic change detection in the complex beach.