Study of Hydrologic Connectivity and Tidal Influence on Water Flow Within Louisiana Coastal Wetlands Using Rapid-Repeat Interferometric Synthetic Aperture Radar

The exchange of water, sediment, and nutrients in wetlands occurs through a complex network of channels and overbank flow. Although optical sensors can map channels at high resolution, they fail to identify narrow intermittent channels colonized by vegetation. We applied interferometry techniques to rapid-repeat (~30 min) Synthetic Aperture Radar (SAR) imagery of the southern Atchafalaya basin in Louisiana acquired during rising-to-high and ebbing-to-low tides to identify and differentiate permanent open water channels from intermittent channels in which flow varies with tidal conditions and to identify locations where overbank flow occurs. Open water surfaces appear as low interferometric coherence pixels, and the coherence in 60-minute and 90-minute in-terferograms can efficiently identify channels, some less than 10m wide. The channel networks at rising and ebbing tide show significant differences in the extent of flow, with vegetation-filled small channels more clearly identified at rising-to-high tide. InSAR phase change is used to iden-tify locations on channel banks where overbank flow occurs at rising and ebbing tides, which is a critical component for modelling wetland hydrodynamics. SAR maps the channel network in our study area better than the optical instruments tested, particularly the small channels that are pri-marily active at higher tides and extend deep into the island interiors. The study shows the capa-bility of rapid repeat InSAR to track how water moves through wetlands during a tidal cycle