DECADAL VOLUMETRIC CHANGES OF COASTAL DUNES BASED ON AERIAL PHOTOGRAMMETRY

Coastal dunes are deformed under hydrodynamic and aeolian processes as well as human activity. Understanding the mechanism behind these changes is crucial for erosion control and effective coastal management. In locations where observational data is scarce, aerial photogrammetry serves as a valuable tool for coastal dune monitoring and sediment budgeting. This research aims to evaluate the accuracy of decadal-scale volumetric changes in coastal dunes using aerial photogrammetry in a data-rich area, such as Hasaki Beach, Japan. Historical aerial photographs covering multiple time periods between 1983 and 2012 were obtained from the Geospatial Information Authority of Japan (GSI) to capture long-term beach evolution. Validation was conducted against the Hasaki Oceanographical Research Station (HORS) beach profile observation transect to evaluate the results. The volumetric changes were calculated by performing a Digital Elevation Model (DEM) of Difference (DoD) analysis on the historical Digital Surface Model (DSM). The DSMs were generated with a pixel size of 0.6 to 1.3 meters. The accuracy of the result depends on factors such as the photograph scale and overlapping image, which vary each year. Over the years, the coastal dunes actively shifted with observable dune height growth and erosion. Overall, aerial photogrammetry has shown good performance in explaining the trends in volumetric changes in coastal dunes. Despite the limitation, photogrammetry remains valuable for understanding coastal dynamics and trends.