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A space-based hydrological monitoring of wetlands using ALOS dual-pol SAR interferometry

Sang-Wan Kim(1), Joong-Sun Won(2), Sang-Hoon Hong(3) and Shimon Wdowinski(3)

(1) Sejong University, Department of Geoinformation Engineering, Seoul 143-747, Korea
(2) Yonsei University, 134 Shinchon-Dong, Seodaemun-Gu, Seoul 120-749, Korea
(3) University of Miami, 4600 Rickenbacker Causeway, Miami, Florida 33149-1098, United States


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. It provides unique hydrological observations of wetland and floodplains with high spatial resolution that cannot be obtained by any terrestrial-based method. 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. Preliminary results of InSAR study of several study sites (Everglades, Tonle Sap, Brazil) show that HH co-pol interferogram reveals well fringe patterns due to water level change during two SAR acquisitions while HV cross-pol interferogram sometimes still reveals and sometimes does not reveal phase changes related with water level changes. 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.



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