Detecting water surface dynamics of a narrower man-made canal using SWOT

The monitoring of global surface water is of critical scientific and societal importance, as these resources are essential for human activities and pose significant risks during extreme flood events. Accurately measuring river hydrodynamics, particularly water surface elevation (WSE), is fundamental for improving flood forecasting, validating hydraulic models, and understanding the global water cycle.

The launch of the Surface Water and Ocean Topography (SWOT) satellite in December 2022 represents a paradigm shift in remote sensing of hydrology. Equipped with the novel Ka-band Radar Interferometer (KaRIn), SWOT provides wide-swath, high-resolution measurements of water elevation and extent across two 50-km-wide swaths. Unlike traditional nadir altimeters, SWOT's 2D imaging capabilities allow for the characterization of complex hydrological processes at unprecedented scales. Despite these advancements, a major challenge remains in accurately observing "narrow" rivers—those below the mission's formal science requirement of 100 meters (with a goal of 50 meters). At the spatial resolution of current SAR sensors, extracting these narrow features is extremely difficult due to strong multiplicative speckle noise, low water-land contrast, and interference from surrounding land structures like roads or terrain artifacts. Furthermore, standard operational algorithms often rely on fixed prior databases (e.g., SWORD or GRWL) that may not account for real-time changes in river morphology, such as meandering or seasonal variations, or may suffer from positional shifts in radar geometry.

In this work, we assess SWOT’s capability to detect water surface elevation and slope of a narrower (~40 m wide) man-made canal. Instead of RiverSP and Raster products, PIXC offers the opportunity to detect such a narrower channel. Preliminary results show that SWOT can detect the canal although the data quality is not very high. In general, the longitudinal profile obtained from SWOT generally agrees with existing documentation, showcasing the potential to monitor narrower canals by analyzing PIXC product.