Abstract
Unmanned Aerial Vehicles (UAVs) are being increasingly used to monitor topographic changes in coastal areas. Compared to Light Detection And Ranging (LiDAR) data or Terrestrial Laser Scanning data, this solution is low-cost and easy to use, while allowing the production of a Digital Surface Model (DSM) with a similar accuracy. Three campaigns were carried out within a three-month period at a lagoon-inlet system (Bonne-Anse Bay, La Palmyre, France), with a flying wing (eBee) combined with a digital camera. Ground Control Points (GCPs), surveyed by the Global Navigation Satellite System (GNSS) and post-processed by differential correction, allowed georeferencing DSMs. Using a photogrammetry process (Structure From Motion algorithm), DSMs and orthomosaics were produced. The DSM accuracy was assessed against the ellipsoidal height of a GNSS profile and Independent Control Points (ICPs) and the root mean square discrepancies were about 10 and 17 cm, respectively. Compared to traditional topographic surveys, this solution allows the accurate representation of bedforms with a wavelength of the order of 1 m and a height of 0.1 m. Finally, changes identified between both main campaigns revealed erosion/accretion areas and the progradation of a sandspit. These results open new perspectives to validate detailed morphological predictions or to parameterize bottom friction in coastal numerical models.
Highlights
Due to their exposure to both marine and terrestrial natural processes as well as anthropogenic activities, coastal environments can exhibit fast morphological changes
This study aims at assessing the applicability of photogrammetry photogrammetry from from Unmanned Aerial Vehicles (UAVs) to a lagoon-inlet system, to generate high resolution Digital Surface Models (DSM) and provide a detailed description of the morphological changes that the inlet experienced over a three-month summer summer period
Compared to similar studies realized in a coastal environment [17,19], our UAV solution was deployed over a larger surface area
Summary
Due to their exposure to both marine and terrestrial natural processes as well as anthropogenic activities, coastal environments can exhibit fast morphological changes. To improve the knowledge about these processes, a first step is often to perform repetitive topographic surveys. The morphology of small estuaries and inlets evolves very quickly and can change drastically within several weeks only. Accurate data with a high temporal frequency are often required [1,2,3,4]. Several solutions have emerged over the last decade. Satellite images were used to delineate coastal landforms and to demonstrate their temporal changes [5,6,7,8].
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