Water surface elevation across the river-ocean interface from the SWOT mission

Low-lying deltas are highly vulnerable to fluvial-coastal compound-flooding from interactions between coastal forcings and river discharge, yet observations spanning the river-estuary-ocean continuum remain sparse. We use the SWOT L2 HR Raster product to build continuous river-ocean water surface elevation (WSE) profiles for the Meghna River (Bengal Delta) and the Mekong Delta. Assuming 1D hydraulic continuity, we apply outlier filtering and interpolation to obtain spatially consistent profiles. Validation against in-situ gauges yields an RMSE of 0.32 m in the Mekong and 0.34 m in the Meghna after correcting for the datum offset. Classifying the profiles according to tidal amplitude and discharge regime reveals coherent WSE profile groups, where river-ocean interactions strongly modulate WSE profiles over the Meghna, and reveal the extent of tidal influence in both deltas. SWOT provides WSE along the river-ocean interface supporting analyses of tidal propagation and backwater effects to inform compound-flood modelling in climate vulnerable deltas.