Mapping salt marsh hydroperiod using Synthetic Aperture Radar time series

Coastal wetlands are highly vulnerable to climate change and sea level rise. Hydroperiod, defined as the duration of flooding, is a key indicator of salt marsh resilience, influencing vegetation zonation and health, sediment deposition, and overall ecosystem stability. This study uses Synthetic Aperture Radar (SAR) time series analysis to map hydroperiod in the salt marshes of Plum Island Sound, Massachusetts, USA. We integrate in situ water level measurements to overcome the limited temporal sampling of SAR observations. SAR-derived hydroperiod was evaluated against a ’bathtub’ model that simulates flooding by filling a LiDAR-derived digital terrain model (DTM) including bathymetry and topography. The method shows strong agreement in hydroperiod estimates ( R 2 = 0 . 92 , R M S E ≈ 12 . 3 % ). These findings demonstrate the capability of SAR time series to provide high-resolution, spatially extensive estimates of hydroperiod. We anticipate that this method will enable large-scale monitoring of seasonal and interannual variations in saltmarsh hydrology, supporting assessments of wetland vulnerability and resilience in the face of accelerating sea-level rise.