Bed elevation, bed surface grain size (D50 and D90), and water discharge- Waal, Pannerden Channel, Nederrijn, and IJssel, 1928-2020

Rijkswaterstaat has measured bed level along the Rhine branches since 1926 (Bovenrijn-Waal), 1928 (Pannerden Canal- Nederrijn), and 1941 (IJssel). The measurements were done using single beam echo sounders until 1999 and multibeam echo sounders since 1999-2002. Single beam measurements were taken at cross-sections spaced roughly 25 m apart and were averaged over 1 km. Multibeam measurements cover the river's entire length, and 100 m averaged data is provided here. Only cross-section averaged data is provided here. The error in bed elevation data (defined as two times the standard deviation) has been estimated to be up to 0.2-0.5 m until 1990; 0.2-0.3 m between 1990-1999, and 0.05-0.1 m since 1999 (Wiegmann, 2002). Water discharge data at Lobith, Waal, and IJssel have been measured by Rijkswaterstaat using Ott current meters until 1999 and acoustic Doppler current profiler (ADCP) since 2000. Uncertainty related to Ott current meter measurement is smaller than 20% and smaller than 10% for ADCP. Rijkswaterstaat has measured grain size data using digging buckets (until 1984) and grab-samplers (since 1984). We have included data from 1966, 1976, 1984, 2008, 2016, 2017, and 2020 measurement campaigns in this dataset. The samples were taken at cross-sections spaced 500 m to 1 km, with three samples (spaced 65 m) at each cross-section. The uncertainty of grain size data is high due to the high natural Spatio-temporal variability and limited spatial and temporal sampling density.