Using Helley-Smith sampler, 288 bed load samples were collected from 16 cross sections along 18 km reach length of Tigris River within Baghdad. The spatial distribution of sampling along the reach took into consideration the variance of river topography where 7 meanders, 2 islands and several bank depositions characterize the geometry of the river. The implemented regulation schemes on Tigris River have reduced 44% of water discharges compared to previous period. The spatial variance in topography was effectively scattering the results of the applied twenty bed load formulas. The study results indicated that the complicated geometry of the river reach makes finding a unique representative bed load formula along the study reach rather difficult, and there is no grantee to have good agreement with measurements in the irregular cross sections (meanders, sand bars, etc.). The closest bed load prediction formulas were van Rijn1984. The annual transported quantities of bed load were estimated to be 30 thousand tons (minimum) in 2009 and 50 thousand tons (maximum) in 2013.
Keywords: Bed load sampling, spatial bed load, Helley-Smith sampler, meandering river, sand bed, prediction formula, Tigris River.
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