Intertidal Area Dynamics in an Unstable Delta

Intertidal areas are considered critical ecosystems as they serve as dynamic zones of interaction between land, ocean, and atmosphere; influencing sediment transport, coastal erosion, and habitat formation. Intertidal areas can also influence larger-scale hydro-morphodynamics and perhaps explain delta instability. However, intertidal areas are notoriously difficult to monitor. Here we present on work on multispectral remote sensing in combination of non-stationary harmonic analysis (NHSA) to explore time changes in the size and elevation of intertidal areas in the Ganges-Brahmaputra delta. Using Unified Tidal Analysis and Prediction (UTide) and earth engine platform in python programming, we analyzed tidal variations, reconstructed water levels, and quantified changes in intertidal geometry over multiple decades .  We find a long-term decline in intertidal area across the delta, and we also find that only a small fraction of intertidal areas remains stable, with an average lifespan of only 2–3 years. This short time is likely the combined effect of cyclones, tidal range amplification downstream, and channel migration, which collectively drive sediment reworking and result in significant spatiotemporal variability in intertidal extents and elevations. The processes thus highlight the dynamic and transient nature of intertidal zones in abruptly changing planform. This research provides critical insights into potential geophysical processes and their impacts on intertidal habitats, emphasizing the need for further studies and monitoring that can help in adaptive management strategies in response to the rapid geomorphological changes occurring in unstable deltaic systems.