AREA CHANGE DETECTION IN RIVER MOUTHBARS AT THE MEKONG RIVER DELTA USING SYNTHETIC APERTURE RADAR (SAR) DATA

摘要

We propose the use of SAR (Synthetic Aperture Radar) backscatter intensity data as a tool for monitoring coast. ALOS (Advanced Land Observing Satellite) PALSAR (Phased Array type L-band SAR) data are analyzed to investigate the temporal changes in shape and area of mouthbars in the Mekong River distributaries. River mouthbars with strong backscatter, which is surrounded by the water, are successfully extracted using a histogram thresholding algorithm. Estimated areas of river mouthbars gradually increase on an annual time scale. Seasonal variations of areas were also recognized, and they appear to be related to the mean monthly sea level, discharge, and rainfall. Moreover, it is highly likely that tidal height at the time of SAR data acquisition clearly reflect the area of river mouthbar by examining over half-day intervals for ascending and descending images. This study shows that if appropriately calibrated, the SAR data is useful to quantifying long-term changes in river mouthbar.