Surface deformation from persistent scatterers SAR interferometry and fusion with leveling data: A case study over the Choushui River Alluvial Fan, Taiwan

The Choushui River Alluvial Fan (CRAF), one of the most important agricultural areas in Taiwan, suffers severe subsidence caused by groundwater withdrawal. We use 20 ENVISAT images from 2006 to 2008 to derive vertical deformation over CRAF by persistent scatterer interferometry (PSI), which effectively reduces errors affecting conventional DInSAR techniques. The pixel density over CRAF is 107.6 pixels/km2, compared to 0.19 points/km2 of the leveling benchmarks. PSI yields vertical displacements matching the leveling result to 0.6 cm/year (RMS), and provides a higher spatial resolution of subsidence than the latter. We also develop a data fusion method that considers the high-precision, low point-density leveling result as a smoothed correction to the PSI result. The combined field is more representative of overall deformation characteristics than the PSI-only or leveling-only field, and it is better suited for the assessment of the impact of subsidence over CRAF.

Research Highlights
► Persistent scatterer interferometry (PSI) detects subsidence over central Taiwan.
► Twenty EVISAT images over 2006–2008 are used in the PSI subsidence determination.
► More PS pixels are found by StaMPS/MTI than other PS methods.
► PSI-derived and leveling-derived rates of subsidence match to 0.6 cm/year.
► Data fusion combines PSI and leveling-derived result to better show the subsidence.