Bed elevation and bed surface grain size (D50) Bovenrijn and Waal, 1926-2020

Bed elevation has been measured annually by Rijkswaterstaat since 1926, with single beam echo sounders until 1999, and multibeam echo sounders since 1999. Single beam measurements were taken at cross sections spaced 25 m, and were averaged over 1 km. Multibeam measurements covered the entire length of the river, and were averaged over 100 m. All bed elevation data are cross-section averaged. 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) Grain size data has been measured by Rijkswaterstaat, using a digging bucket until 1984, and grab samplers since 1984. The data set includes measurements from 1966, 1976, 1984, 2008, 2016, 2017, and 2020. Samples have been taken at cross-sections spaced 500 m to 1 km. Three samples (spaced 65 m) have been taken 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.

荷兰公共工程与水管理总局（Rijkswaterstaat）自1926年起每年开展河床高程测量工作：1999年之前采用单波束测深仪（single beam echo sounders），1999年起改用多波束测深仪（multibeam echo sounders）。其中，单波束测量的断面布设间距为25米，测量数据按1千米范围取平均；多波束测量覆盖整条河道，测量数据按100米范围取平均。所有河床高程数据均为断面平均值。
河床高程数据的误差（定义为两倍标准差）估算结果如下：1990年之前最高可达0.2~0.5米；1990年至1999年为0.2~0.3米；1999年起为0.05~0.1米（Wiegmann, 2002）。
荷兰公共工程与水管理总局（Rijkswaterstaat）同时开展了沉积物粒度数据的测量工作：1984年之前采用挖掘铲取样，1984年起改用抓斗采样器（grab samplers）。本数据集涵盖1966、1976、1984、2008、2016、2017及2020年的测量数据。采样断面布设间距为500米至1千米，每个断面上间隔65米采集3个样品。受自然时空变异性较强、时空采样密度有限的影响，沉积物粒度数据的不确定性较高。