Deltas and estuaries are critical ecological and socio-economic nexuses, hosting approximately 500 million people within some of the most dynamic environments on Earth. The complex feedback between physical, biological, geochemical, and anthropogenic processes continuously reshapes their hydrology and morphology, driven by a multi-scale interplay of short-term forcings, such as extreme events and human impacts, and long-term controls including tectonics and climate change. As sea-level rise accelerates, sediment supplies decline, and subsidence continues, a deeper understanding of these formative processes is urgent to ensure coastal resilience and to support decision-making under the current climate emergency.

It is essential to understand how evolving processes interact at a system-wide level and how adaptation measures, both nature-based and conventional, can inform management strategies. This session bridges the gap between past records and future evolution by integrating insights from Quaternary geological archives, essential for reconstructing responses to relative sea-level change, with present-day process studies and predictive modelling. By connecting longer-term records with contemporary observations, we aim to place ongoing changes in context and inform sustainable adaptation strategies.

The research presented encompasses inter- and transdisciplinary work focused on the fluvial-to-marine transition zone including the hydrology and geomorphology of changing coastal, deltaic, and estuarine environments across timescales. It includes studies focused on adaptation, restoration, and management strategies, along with the reconstruction of Quaternary sea-level through geological and geomorphological proxies. The session provides a comprehensive overview of the processes and timescales that have shaped, and will continue to shape deltaic, estuarine, and coastal systems.