DERIVING WATER CHANNEL MASKS AND OVERBANK FLOW IN COASTAL WETLANDS USING RAPID-REPEAT SAR

Hydrodynamic models of the exchange of water between the ocean, rivers, and wetlands require high resolution maps of the water channel network and information on areas with overland flow. Furthermore, understanding the processes benefits from maps showing how the exchange changes during a tidal cycle, i.e., on an hourly-to-daily timescale, and with river discharge, which varies seasonally. Conventional water masks are not updated regularly and they do not always include seasonally active narrow channels in the inland areas which are required for the modelling. In this study, we use high resolution(~6m) airborne Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) images to map water channels and areas with discernible water level increase using data acquired for the Delta-X mission. The SAR intensity difference in multiple polarization channels and interferometric coherence are used to differentiate water channels from land areas, and the water channel masks produced are able to identify most channels with width >20m. We also developed a method combining interferometric amplitude and phase to identify areas with significant water depth change along the edges of small channels. Geocoded channel masks were produced for UAVSAR tracks covering two deltas (Wax Lake and Terrebonne) in coastal Louisiana for both low tide and high tide acquisitions. The methods developed can be extended to other deltas worldwide.