UNIVERSITE DE BORDEAUX (FR)
In the context of the ESA BIOMASS Earth Explorer mission, the Namib Desert was selected as a test site to assess the performance of P-band SAR for subsurface imaging in arid environments.
In cooperation with the Gobabeb Research and Training Centre, a study of the paleo-hydrology of the Kuiseb River was started, combining field work measurements (soil properties, ground penetrating radar, scatterometry, drone imaging, GNSS reflectometry) and airborne radar sensors (L- and P-band polarimetric and interferometric SAR). The Kuiseb River is one of the major ephemeral rivers of western Namibia, marking the northern limit of the Namib Sand Sea and outflowing in the Atlantic Ocean.
This research project aims to develop novel methods for the monitoring of ephemeral rivers in arid environments, based of the combined use of Sentinel 1, 2 and 3 sensors. We shall process and analyse time series acquired by the Sentinel missions from 2016 to 2020, in order to study the dynamics of the Kuiseb River over years. SAR data provided by Sentinel 1 will be used to produce interferograms, to track changes in soil moisture due to the aquifer level dynamics. Multispectral data provided by Sentinel 2 will allow to map the river floods and the vegetation change related to the aquifer changes. Finally, we shall monitor the variations of the river bed surface and subsurface properties thanks to the altimeter data provided by Sentinel 3. We expect to demonstrate that the combined use of datasets provided by the Sentinel missions allows to monitor the dynamics of ephemeral rivers in arid regions. Sentinel data, combined to the subsurface imaging capabilities of L- band (ALOS-2) and P-band (BIOMASS) SAR and to field work investigations, will then allow to better understand the ephemeral rivers related processes at the surface – subsurface interface. Such studies are of highest importance for countries in arid regions, since they are both relevant to recent past climatic conditions and to potential fossil water resources.