Satellite Synthetic Aperture Radar (SAR) was evaluated as a method to operationally monitor the occurrence and distribution of storm and tidal-related flooding of extensive coastal marshes around the north-central Gulf of Mexico. Maps representing the occurrence of marsh subcanopy surface flooding were created from Advanced Land Observing Satellite (ALOS) Phased Array L-band SAR (PALSAR) data and ENVISAT Advanced SAR (ASAR) data during 2006–2009. The ALOS PALSAR data included 21 scenes with HH polarizations in Wide Beam (100 m). The ENVISAT ASAR C-band data included 24 scenes with VV and HH polarizations in Wide Swath (150 m). The data covered 500 km of the Louisiana coastal zone. Mapping success was assessed by the degree of correspondence between inundation mapping and inland water levels. Overall, PALSAR-based subcanopy mapping inundation accuracies averaged 84% (n=160), while ASAR-based mapping accuracies averaged 62% (n=245). PALSAR-based mapping performance remained relatively high to ±5 cm above the ground surface while ASAR-based mapping performance decreased below +20 cm above the ground surface.