11:30 AM - 11:45 AM
[HTT13-04] Evaluation of actual sandy coast erosion using the change in coastal dunes based on 3D data as an indicator
★Invited Papers
Keywords:Coastal erosion, Coastal sand dune, RTK-UAV, ALS, Lidar, DEM
The sandy coast is an important ecosystem because it has developed as a unique ecosystem and has multilateral functions. It is the boundary between the sea and land, where water and wind forces move sand back and forth and are dynamically maintained. This system is known as the Beach Dune System. Many plants and animals adapted to dynamic environments live and grow here. In addition, the coastal dunes that develop on sandy coasts have attracted attention as protective barriers and buffer zones that prevent seawater from entering inland during tsunamis and storm surges. Therefore, these have been conserved in countries with large areas of low elevation land, such as the in Netherlands.
Since the late 20th century, increased development and recreational activity near the coast have caused ecological destruction and landscape degradation. Furthermore, there is a concern that rising sea levels due to climate change will accelerate coastal erosion. Progressive coastal erosion worldwide not only means a decrease in the land area but also directly leads to the loss of habitat for a variety of marine and terrestrial ecotone-dependent organisms. Therefore, coastal erosion is an urgent issue for human society and marine and terrestrial ecosystems.
Most studies on the erosion of sandy coasts have used changes in the sandy coast shoreline as an indicator of erosion, while few have targeted changes in the dunes behind the beach. There are also scattered studies that have measured dunes in three dimensions and measured their change, but none have focused on multiple sandy coasts. To realistically clarify coastal erosion, it is necessary to understand and evaluate the topographic changes of multiple sandy coasts in three dimensions. For this purpose, it is necessary to analyze multiple sandy coasts, but until now, the difficulty of obtaining three-dimensional (3D) data from multiple locations at multiple times for analysis has been a limiting factor in advancing this research.
The above issue was overcome in this study through measuring and utilizing high-definition spatial information from Unmanned Aerial Vehicles (UAVs) and Airborne Laser Scanning (ALS). The accuracy of UAV-Structure-from-Motion (SfM) in reconstructing 3D structures of the terrain and vegetation has improved remarkably. With conventional UAV-SfM, multiple ground reference points must be surveyed and established separately owing to the low accuracy (error: several meters) of the aircraft's positioning information. In recent years, Real-Time Kinematic (RTK)-Global Navigation Satellite System, which enables highly accurate position acquisition, and UAVs have been integrated to dramatically improve the positional accuracy (error: several centimeters). As a result, ground control points, which require a great deal of labor to install, are no longer necessary. The use of RTK-UAVs not only improves the accuracy but also enables the acquisition of topographic information at multiple locations. This allowed us to obtain topographic changes of the sandy coasts in three dimensions and across a wide area, and we believe that this will clarify the actual state of coastal erosion.
In this study, the amount of change (erosion and sedimentation) was calculated from the difference analysis between the Digital Elevation Models created by RTK-UAV-SfM and ALS to clarify the actual erosion of coastal dunes on the sandy coasts of Hokkaido, Honshu, and Shikoku, Japan. An analysis was carried out to evaluate the actual erosion of sandy coasts as an indicator of the amount of change, and the results are presented.
Since the late 20th century, increased development and recreational activity near the coast have caused ecological destruction and landscape degradation. Furthermore, there is a concern that rising sea levels due to climate change will accelerate coastal erosion. Progressive coastal erosion worldwide not only means a decrease in the land area but also directly leads to the loss of habitat for a variety of marine and terrestrial ecotone-dependent organisms. Therefore, coastal erosion is an urgent issue for human society and marine and terrestrial ecosystems.
Most studies on the erosion of sandy coasts have used changes in the sandy coast shoreline as an indicator of erosion, while few have targeted changes in the dunes behind the beach. There are also scattered studies that have measured dunes in three dimensions and measured their change, but none have focused on multiple sandy coasts. To realistically clarify coastal erosion, it is necessary to understand and evaluate the topographic changes of multiple sandy coasts in three dimensions. For this purpose, it is necessary to analyze multiple sandy coasts, but until now, the difficulty of obtaining three-dimensional (3D) data from multiple locations at multiple times for analysis has been a limiting factor in advancing this research.
The above issue was overcome in this study through measuring and utilizing high-definition spatial information from Unmanned Aerial Vehicles (UAVs) and Airborne Laser Scanning (ALS). The accuracy of UAV-Structure-from-Motion (SfM) in reconstructing 3D structures of the terrain and vegetation has improved remarkably. With conventional UAV-SfM, multiple ground reference points must be surveyed and established separately owing to the low accuracy (error: several meters) of the aircraft's positioning information. In recent years, Real-Time Kinematic (RTK)-Global Navigation Satellite System, which enables highly accurate position acquisition, and UAVs have been integrated to dramatically improve the positional accuracy (error: several centimeters). As a result, ground control points, which require a great deal of labor to install, are no longer necessary. The use of RTK-UAVs not only improves the accuracy but also enables the acquisition of topographic information at multiple locations. This allowed us to obtain topographic changes of the sandy coasts in three dimensions and across a wide area, and we believe that this will clarify the actual state of coastal erosion.
In this study, the amount of change (erosion and sedimentation) was calculated from the difference analysis between the Digital Elevation Models created by RTK-UAV-SfM and ALS to clarify the actual erosion of coastal dunes on the sandy coasts of Hokkaido, Honshu, and Shikoku, Japan. An analysis was carried out to evaluate the actual erosion of sandy coasts as an indicator of the amount of change, and the results are presented.