Assessing complex aeolian dune field morphology and evolution with Sentinel-1 SAR imagery – Possibilities and limitations

Aeolian dune movement poses a threat to critical infrastructure, urban areas, water resources as well as agriculture. This threat is expected to increase in the coming years due to land degradation, desertification and climate change. Several approaches have been used to investigate the evolution of dune fields. Satellite remote sensing can be considered one of the most accurate tools for the continuous monitoring of global sand covered surfaces. Although early studies found a great potential in synthetic aperture radar (SAR) for dune assessment, the full potential has not been explored as of yet. Therefore, in this study, we present a novel method for assessing complex dune field morphology based on the easily accessible and globally available Sentinel-1 ground range detected (GRD) SAR dataset. In this application, dune features are extracted based on backscatter properties related to the local incidence angle. This provides a clear identification of (1) active dune sand, (2) dune ridges and (3) inter-dune ripples. By extracting these features through profiles, the multi-timescale evolution of the Western Mongolian dune field Bor Khyar was analysed through three areas of interest (AOIs) based on the spectral technique of continuous wavelets. The result of this investigation gives new insights into the temporal and spatial dynamics of dunes scale and their response to aeolian activity, revealing differences in aeolian activity as well as inter- and intra-annual variations in the dune morphology. These results are promising and highlight the potential in using satellite SAR imagery for dune monitoring.