Clogging of Fine Sediment within Gravel Substrates: Dimensional Analysis and Macroanalysis of Experiments in Hydraulic Flumes

Abstract

An understanding of the clogging of fine sediments within gravel substrates is advanced through use of dimensional analysis and macroanalysis of previously conducted clogging experiments in hydraulic flumes. Dimensional analysis via the Buckingham pi theorem is used to suggest that the dimensionless clogging depth can be potentially collapsed using the original and adjusted bed-to-grain ratios, i.e., ratio of substrate diameter to fine sediment diameter, substrate porosity, roughness Reynolds number, and Peclet number. Macroanalysis and statistical analysis is performed using 10 previously published studies that include a total of 146 different test conditions reporting noncohesive, fine sediment clogging, or deposition in porous gravel-beds with hydraulically rough turbulent open channel flow. Results suggest that the adjusted bed-to-grain ratio is a reliable predictor of the initiation of clogging with clogging occurring below 27 for the fine fluvial sediment clogging in a gravel bed substrate for hydraulically rough turbulent flow flumes considered. The original and adjusted bed-to-grain ratios show little influence on the depth of clogging once the lower threshold for bed filling is reached. Contrary to conventional wisdom, the bed-to-grain ratio is not used to predict the maximum depth of clogging. Rather, results suggest that the dimensionless clogging depth can be collapsed using the substrate porosity and roughness Reynolds number reflecting the impact of the pore water velocity distribution on the dispersion of fine sediment into the gravel substrate. The clogging depth results are used to estimate the clogging profile for fine sands in gravel substrate for the datasets.