Mapping relative sea-level rise with satellite geodesy along subsiding coast near Galveston, Texas

The combined effect of absolute sea-level rise (ASLR) and coastal subsidence has been long monitored via tide gauges (TGs), which measure sea-level rise relative to land-fixed benchmarks, referred to as relative sea- level rise (RSLR). The importance of TG observations lies in dynamically reflecting land-water interaction which also is shaping the coastal living environment. However, TGs are usually sparsely distributed along coastline, providing limited information about the spatial patterns and variability of RSLR. Thanks to emerging satellite geodesy technologies such as satellite radar altimetry (SRA) and interferometric synthetic aperture radar (InSAR), changes of sea surface height can be measured in the ocean and largescale high- accuracy land deformation can be estimated. This study combines ASLR data derivied from SRA with coastal land deformation derived from InSAR to estimate and map RLSR along coastline near Galveston, Texas, one of leading subsidence hotspots in the United States. Specifically, the radar altimetry product “MEaSUREs” from NASA’s Jet Propulsion Laboratory (JPL) was used to extract the time series of sea surface height anomalies for estimating ASLR rate. Meanwhile, the persistent scatter (PS) InSAR technique was utilized to generate land subsidence from Sentinel-1 data between 2017 and 2021. The RSLR map is generated by combining ASLR and InSAR data via designed grid pattern defined by geographic information system (GIS) analysis near the coastline. The performance of the RSLR grid map is validated through comparing against results obtained by TG measurements. This study hopes to provide improved capability for monitoring RSLR along coastline in response to increased demands for coastal resilience and sustainable development.