Leveraging SWOT data to analyze river hydrodynamic and coastal interactions during extreme events: A case study of the Po river

The interaction between rivers and coastal water bodies is critical to hydrological and ecological systems, particularly under the accelerating impacts of climate change. This study investigates the hydrodynamics of the Po river and its interactions with the Adriatic Sea during extreme events such as backwater effects during floods and saline intrusion during droughts. Using high-resolution data from Surface Water and Ocean Topography (SWOT) mission, integrated with in situ measurements, detailed LiDAR datasets, and a hybrid 1D-2D modeling approach in HEC-RAS, the research advances understanding of river-coast dynamics and their responses to climate-induced pressures.

The SWOT satellite, launched in December 2022, employs cutting-edge Ka-band Radar Interferometry (KaRIn) technology. The mission provides a variety of hydrological products for the surface water dynamics, with a revisit cycle of 21 days. For the inland rivers, the products include high-accuracy observations of water surface elevation, width, and slope, over a 120 km swath, allowing for improved rating curves and flow duration analysis. Stretching over 650 kilometers and flowing through eight Italian regions, the Po river is a lifeline for the northern region.

HEC-RAS is used to simulate riverine and floodplain dynamics, combining the computational efficiency of 1D modeling for long river reaches with the spatial detail of 2D modeling in areas with complex flow patterns, such as floodplains and river-coast interfaces. LiDAR-derived digital elevation models (DEMs) provide the foundation for defining cross-sectional profiles and updating hydraulic geometry, enabling precise representation of terrain and channel morphology.

The research follows a multi-phase methodology: SWOT data are processed to derive water surface elevations and extents, validated using in situ measurements and compared with HEC-RAS simulations. The study emphasizes extreme conditions, quantifying backwater effects during high flows and the severity of saline intrusion under low-flow scenarios. The integration of SWOT data with the HEC-RAS model allows for a detailed analysis of hydrodynamic processes, supporting the development of risk prediction models and improving water resource management strategies.