Shifting sands: tracking erosion trends in middens using RPA and 3D models

Shell midden sites are a common archaeological record of human coastal resource use and important palaeontological records of species abundance and ecological changes over time, but coastal middens are vulnerable to damage by natural and anthropogenic processes. In Sydney, shell midden sites provide a unique historical record of human impact on local ecology, offering insights into the effects of urban development on species since European settlement. As protected heritage features, excavation of midden sites is limited, and remedial preservation impedes study. Here I show that images taken by remotely piloted aircraft (RPAs) can be used to create 3D models of middens for monitoring erosion and utilised to successfully calculate site-scale volumetric and morphological changes over time. Orthophotographic images are used to analyse the eroding margin of middens to quantify shell diversity and abundance, and build a digital map of the midden contents, preserving its record without excavation. This project demonstrates an inexpensive means of quantifying midden erosion for monitoring, protection, and archiving, and investigates what midden characteristics are linked to higher erosion rates using entirely non-contact data. New sensitivities to cultural heritage limit destructive analyses. As a result, non-destructive technologies should be key tools for future studies of middens internationally.