[This dataset is embargoed until January 4, 2027]. This dataset contains ADCP, riverbed bathymetry, water quality and bed grainsize data for two study reaches of the Red River (Song Hong) Delta, Northern Vietnam, including Son Tay (the uppermost region of the Red River Delta) and the Hong- (Red) Luoc junction (in the mid-point of the delta) collected in February 2023. Bathymetry data are only available for the Hồng-Luộc junction. Riverbed bathymetry data are available for the Hồng-Luộc junction at 1 m² resolution. To assess the validity of our bathymetry surveys, we overlaid this data with the ADCP transects collected at four locations during the same period at the Hồng-Luộc junction. Comparisons between ADCP transects and bathymetry data reveal broadly similar transect profiles, but a consistent 2 m offset in elevation after water level and GPS corrections. This discrepancy would have implications for the comparison of our bathymetry data with other ADCP transect data. No alterations have been made to our bathymetry survey elevations for this comparison. ADCP data are available for the relative upstream and downstream portions of the Son Tay study reach, and across the main channel (Red River), secondary channel (Red River) and tributary channel (Luoc River) at the Hong-Luoc junction across multiple dates. Water level data are also available at Son Tay, Trieu Duong (on the Luoc river, a tributary of the Hong-Luoc junction) and Tien Duc (the downstream-most portion of the Hong-Luoc junction) during the study period. These data were provided by the Vietnam Meteorological and Hydrological Organisation. Riverbed grainsize data are available at Son Tay - including the surface of an exposed island sand bar (its top and tail) and the relative upstream (collected in the centre of the channel cross-section) and downstream (collected in both the centre, left-bank and right-bank of the channel cross-section) - and the Hong-Luoc junction at three locations across the reach. Each bedload sample was sub-sampled into two - each sample contains five repeated measurements and an average for grainsize. Available data include D10, D50, D84, D90, kurtosis and the proportion of the sample across different grain sizes. Water quality parameters include RDO concentration (mg/L), RDO saturation (%), oxygen partial pressure (Torr), pH (pH and mV), ORP (mV), specific conductivity (uS/cm), actual conductivity (uS/cm), salinity (PSU), resistivity (ohm/cm), water density (g/cm3), temperature (oC), barometric pressure (mm Hg), pressure (psi), depth (m), external voltage (V), barometric pressure (mbar), latitude and longitude. Full details about this dataset can be found at https://doi.org/10.5285/47d7811a-1ee4-4934-a67e-f1c064d05a32
