ALOS-4 PALSAR-3 Stripmap/ScanSAR Dataset for Wide-Area Wetland Water-Level Change Monitoring

Abstract

Coastal wetlands provide critical ecosystem services but remain highly vulnerable to hydrological alteration. The Ciénaga Grande de Santa Marta (CGSM), a coastal lagoon- delta complex on Colombia’s Caribbean coast, has experienced substantial degradation due to land-use change, disrupted hydrological connectivity, and climate variability. As an ungauged wetland with no in-situ water-level observations, the CGSM requires remote sensing techniques for continuous, large-scale monitoring. We evaluate the feasibility of the ALOS-4 PALSAR-3 Interferometric Synthetic Aperture Radar dataset for monitoring wetland water-level changes using Stripmap-Stripmap and Stripmap-ScanSAR interferometry. Nine adjacent Stripmap scenes acquired on 17 June and 26 August 2025 were mosaicked to provide continuous coverage of CGSM, while a ScanSAR scene acquired on 2 December 2025 was used to evaluate cross-mode interferometry. The Stripmap-Stripmap interferogram achieved a mean coherence of 0.76 and revealed continuous phase patterns associated with water-level change across the entire CGSM. The Stripmap-ScanSAR interferogram exhibited a lower mean coherence of approximately 0.40 because of differences in acquisition mode and the longer temporal baseline. Nevertheless, phase patterns related to water-level change were observed across most of the CGSM except in blind areas caused by fixed pulse repetition frequency operation. The locations of these blind areas varied with acquisition mode and observation date, suggesting that combining Stripmap and ScanSAR observations could improve both spatial coverage and observation frequency. Overall, ALOS-4 PALSAR-3 Stripmap-Stripmap and Stripmap-Scan- SAR interferometric datasets provide a practical approach for large-scale water-level monitoring in ungauged wetlands and offer a basis for future time-series analysis and wetland management.