Wetland monitoring in Mali using SAR interferometry

Wetland environments are found worldwide, from the Sudd Marshes in Africa to the Amazon river basin. Wetlands are important elements of continental hydrological networks, attenuating flood surges, forming sinks or stores for runoff and providing an important link in the hydrological cycle between river channels and the atmosphere. The study area in this project is a region of wetlands in Mali on the River Niger ∼(15degN, 5degW). These wetlands were chosen for environmental and pragmatic reasons. The wetlands lie in the Sahelian semi-arid zone and are therefore a major regional source of water to the atmosphere through evapotranspiration. The wetlands also lie in both Libreville and Maspalomas receiving station masks, increasing the available coverage by ERS SAR. In this paper we examine the use of ERS phase coherence data in delineation of the flooded extents, comparing a pair of scenes from the dry season (January/February 1993) with scenes from the wet season (September/October 1993). Phase coherence is shown to provide greatly increased contrast between flooded and non-flooded regions. For the dry season pair, we demonstrate that usual image classification methods produce apparently acceptable land cover interpretations, although we currently have no land cover map to verify this.