Abstract
Unmanned Aerial Vehicle (UAV)-based remote sensing techniques have demonstrated great potential for monitoring rapid shoreline changes. With image-based approaches utilizing Structure from Motion (SfM), high-resolution Digital Surface Models (DSM), and orthophotos can be generated efficiently using UAV imagery. However, image-based mapping yields relatively poor results in low textured areas as compared to those from LiDAR. This study demonstrates the applicability of UAV LiDAR for mapping coastal environments. A custom-built UAV-based mobile mapping system is used to simultaneously collect LiDAR and imagery data. The quality of LiDAR, as well as image-based point clouds, are investigated and compared over different geomorphic environments in terms of their point density, relative and absolute accuracy, and area coverage. The results suggest that both UAV LiDAR and image-based techniques provide high-resolution and high-quality topographic data, and the point clouds generated by both techniques are compatible within a 5 to 10 cm range. UAV LiDAR has a clear advantage in terms of large and uniform ground coverage over different geomorphic environments, higher point density, and ability to penetrate through vegetation to capture points below the canopy. Furthermore, UAV LiDAR-based data acquisitions are assessed for their applicability in monitoring shoreline changes over two actively eroding sandy beaches along southern Lake Michigan, Dune Acres, and Beverly Shores, through repeated field surveys. The results indicate a considerable volume loss and ridge point retreat over an extended period of one year (May 2018 to May 2019) as well as a short storm-induced period of one month (November 2018 to December 2018). The foredune ridge recession ranges from 0 m to 9 m. The average volume loss at Dune Acres is 18.2 cubic meters per meter and 12.2 cubic meters per meter within the one-year period and storm-induced period, respectively, highlighting the importance of episodic events in coastline changes. The average volume loss at Beverly Shores is 2.8 cubic meters per meter and 2.6 cubic meters per meter within the survey period and storm-induced period, respectively.
Highlights
Coastal erosion can cause significant damages to buildings, infrastructure, utilities, and ecosystems, and mitigating its effect has become increasingly important, especially considering recent climate change manifestations
Based on our analyses, Unmanned Aerial Vehicles (UAV) LiDAR has a clear advantage in terms of large and uniform ground coverage over different surface types, higher point density, and the ability to penetrate through vegetation to capture points over the ground surface
This paper presents the evaluation and application of UAV LiDAR for coastal change monitoring
Summary
Coastal erosion can cause significant damages to buildings, infrastructure, utilities, and ecosystems, and mitigating its effect has become increasingly important, especially considering recent climate change manifestations. A well-developed understanding of complex shoreline movement, i.e., their spatial distribution at local, regional, and national scale, as well as their temporal distribution at event-, seasonal-, and decadal-scale, serves as the foundation for effective coastal management. To meet the increasing demand for accurate and recurrent monitoring of coastal change, remote sensing techniques are showing superior performance compared to the conventional time and labor-intensive field survey. A wide range of remote sensing techniques have been used to monitor coastal changes, including satellite imagery, aerial photography, Synthetic Aperture Radar (SAR), ground-penetrating radar, airborne and terrestrial LiDAR, and most recently, Unmanned Aerial Vehicles (UAV) imagery. While UAV surveys have a clear advantage in terms of low-cost equipment, rapid survey time, and ease of deployment, terrestrial LiDAR has been proven to produce more reliable surface representation in complex geomorphic environments [2,4]
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