The Use of Interferometric Coherence of Sentinel-1a Images to Study Silting in South-East Morocco

South-East of Morocco is threatened by active dunes; this is due to the scarcity of soil cover due to the combined effects of drought and anthropogenic actions. Terrain Observation by Progressive Scans (TOPS) mode from the Sentinel-1 satellite provides us with up-to-date high-quality Synthetic Aperture Radar (SAR) images over a wide ground coverage (250 × 250 km), enabling full exploitation of various In SAR applications. The SAR (Synthetic Aperture Radar) Interferometric Coherence Information provides an original measure of the dynamics and surface changes that occur between two SAR acquisitions. In this study, Sentinel-1 TOPS data were employed to investigate dunes activities and silting. The Sentinel-1A mission allows the acquisition of radar images at 12 days apart. Thanks to this temporal base, the images of interferometric coherence combined with the amplitude images made it possible to detect the active sand zones as well as the areas of Ossian vegetation. In this paper we used four images SAR sentinel-1A in SLC mode (Single Look Complex) were acquired with 12 days interval on the study area: two in May 2015 and the other two in November 2017. The temporal analysis of the images of coherence was able to highlight the extension of the active sandy areas over time and the migration of the dunes. Interferometric coherence therefore seems to be a very good tool for mapping dune activity, as well as for tracking dune movements and silting. The results illustrate the potential of interferometric coherence images as a useful source of information for the detection of sand dune movements in semi-arid zones.

Keywords: Radar interferometer, Sentinel-1A images, coherence, dune migration, silting.