Application of ERS-1 SAR for coastal inundation

ERS-1 Synthetic Aperture Radar (SAR) C-band (5.3 GHz) remote sensing data, together with ground sampled data, have been used to assess hydrologic conditions in the Gulf of Mexico coastal tidal marsh system. Using automatic recorders, water level measurements were continuously collected in creek sites in the marsh which sampled the duration and frequency of tidal floodings. The goal of the present study was to demonstrate the ERS-1 C-band utility for monitoring tidal inundation for coastal wetlands. Satellite delineation of inundation extent under varying vegetation conditions is highly dependent on the SAR wavelength. C-band energy is scattered and absorbed within forest canopies, enhanced by inundated bushy herbaceous and tall marsh vegetation, and reflected away in flooded areas with shorter vegetation. The ERS-1 SAR imagery shows that a significant amount of energy penetrates the Spartina and Juncus canopies which is largely reflected away. There is a low to high tide difference in backscatter which is smallest at the margin with the palmetto and maximum near the gulf/marsh margin. At high tide the backscatter values show distinct margins within the salt marsh which appear to correspond to inundation extent and also correspond to observed changes in tidal flood stages. The magnitude of these inundation related backscatter changes are consistent with model relationships established with Juncus parameterization