Towards operational monitoring of wetland water levels using InSAR: Applications for the Everglades Restoration Project.

In a recent study [Wdowinski et al., 2004], we demonstrated that L-band InSAR can measure water levels in the Everglades with a vertical precision of 5-10 cm and horizontal resolution of a few hundred meters. The observations reveal spatially detailed, quantitative images of water levels in the Everglades, capturing dynamic water level topography and providing the first detailed picture of wetland sheet flow. We observed localized radial sheet flow in addition to well-known southward unidirectional sheet flow. The observation were used to constrain a linear diffusive flow model, which allowed us to obtain quantitative estimates of flow diffusivity (23-91 m2/s), the first space-based estimates of such hydrologic parameter for the Everglades. Although conventional wisdom suggests that C-band interferometry does not work in vegetated areas, we recently found, to our great surprise, that C-band interferograms with short acquisition intervals (1-105 days) can maintain excellent coherence over the Everglades wetlands. Our experimental study was part of an ESA CAT-1 proposal, where we used archived ERS-1/2 acquired over south Florida during the years1995-1998. Initial data processing shows superb interferometric coherence with the tandem mission (1-day interval between acquisitions) and variable coherence levels with the 1-3 repeated orbit cycles (35 days), depending on the acquisition time interval, baseline, and atmospheric conditions. The immediate advantage in using C-band SAR data for detecting wetland water level changes is the availability of current data, due to two active C-band satellites - RADARSAT-1 and ENVISAT. We are currently ordering SAR data from both satellites in order to evaluate optimal acquisition parameters (view angel, polarization, and resolution) and access near-real time operation of InSAR based monitoring of water level changes. * Wdowinski, S., F. Amelung, F. Miralles-Wilhelm, T. Dixon, and R. Carande, Space-based measurements of sheet-flow characteristics in the Everglades wetland, Florida, Geophys. Res. Lett., 31, L15503, 10.1029/2004GL020383, 2004.