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THE USE OF SAR INTERFEROMETRIC COHERENCE IMAGES TO STUDY SANDY DESERTIFICATION IN SOUTHEAST NIGER : PRELIMINARY RESULTS

Sand encroachment is the dominant form of desertification in southeast Niger. In this Sahel region, the reactivation of the fossil dunes results from the reduction of the natural vegetation cover which is mainly controlled by the interaction of human activity and climatic variability. In this paper, we discuss some results of AO824 project FADA (Fight Against Desertification in West Africa). One of the goals of this project is to evaluate the potential of Envisat ASAR and ERS 1⁄2 data for their application to desertification study. As preliminary research, the value of ERS 1⁄2 interferometric coherence images was assessed using seven tandem pairs in southeast Niger. The interpretation of the coherence was validated using aerial photos, very high resolution satellite data and field observations. The results illustrate the potential of interferometric coherence images as a useful source of information for the detection of light sand dune movements in semi-arid zones.