Title

Quantifying decadal volumetric changes along sandy beaches using improved historical aerial photographic models and contemporary data

Publication Name

Earth Surface Processes and Landforms

Abstract

Technological advances have reinvigorated the aerial photogrammetric technique using both historical and contemporary imagery, and fostered new perspectives in geomorphology studies. On sandy beaches, however, the dynamic processes, the lack of tonal contrast and reduced texture, make the application of photogrammetry extremely more difficult than in most other landscapes. This study quantifies decadal volumetric changes along the beaches of the Great Ocean Road, Australia, using improved digital surface models (DSMs) derived from structure-from-motion (SfM) photogrammetry applied to historical archives and a contemporary unmanned aerial vehicle survey. Alongside surficial sediment analysis, this approach demonstrates the potential to relate present-day to historical morphological changes at sandy beaches worldwide. The discussion highlights the influence of photographic scale, lens distortions, ground control points in segmented blocks, and the use of shoreline as a proxy of volumetric change. DSMs were derived using datasets obtained in 1946, 1966, 1971, 1977, 1986 and 2019, and compared to a 2007 light detection and ranging (LiDAR)-derived DSM. The emerging approach produced suitable DSMs for volumetric analysis, except for the 1946 dataset, which had the smallest scale and was significantly vertically offset. Volumetric losses of up to 60 m /m of beach length were calculated for parts of Mounts Bay between 1977 and 2007, and up to 21 m /m in recent years. At Apollo Bay, the construction of the port in the early 1950s significantly impacted the natural longshore drift to the beach. The adjacent stretch of coastline accreted at a rate of ~35 m /m between 1966 and 2007, as a function of dredge disposal and changes in sediment transport, whereas a maximum volumetric loss of ~47 m /m was detected further north between 1977 and 2007. A volume of ~71,330 ± 15,200 m was lost from the system from 2007 to 2019, despite the continued deposition along the northern section of the beach. 3 3 3 3 3

Open Access Status

This publication is not available as open access

Funding Sponsor

Deakin University

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Link to publisher version (DOI)

http://dx.doi.org/10.1002/esp.5130