Wetland monitoring using ALOS dual-pol SAR interferometry

Wetland Interferometric Synthetic Aperture Radar (InSAR) is a relatively new application of the InSAR technique, which enable us to detect water level changes in aquatic environments with emergent vegetation [1, 2]. It provides unique hydrological observations of wetland and floodplains with high spatial resolution that cannot be obtained by any terrestrial-based method [3-5]. The previous studies indicate that longer wavelength SAR systems (L-band), horizontal (HH) polarization of the radar pulse, and short repeat orbits provide best results. We investigate new ALOS PALSAR dual-pol (HH/HV) data in terms of detecting water level changes in various wetland environments using InSAR technique, and detecting flow patterns and flow discontinuities, which can be useful for wetlands restoration. The results of InSAR study of two study sites (Everglades, Tonle Sap) show that HH co-pol interferograms clearly reveal the fringe patterns due to water level change during two SAR acquisitions while HV cross-pol interferograms do not always reveal (Fig. 1). This effect is probably associated with scattering mechanism depending on vegetation types because we believe only double-bounce from the water surface and vegetation is responsible for providing information about water level change beneath emergent plant. The detail analysis to account for the difference in HV cross-pol observations will be carried out. In addition, we will measure and analyze backscattering and coherence variations of ALOS L-band dual-pol data in wetlands according to various wetland vegetations.