Dimensionless erosion laws for cohesive sediment

Journal of Hydraulic Engineering



A method of achieving a dimensionless collapse of erosion-rate data for cohesive sediments is proposed and shown to work well for data collected in flume-erosion tests on mixtures of sand and mud (silt plus clay sized particles) for a wide range of mud fraction. The data collapse corresponds to a dimensional erosion law of the form E(ττc)mE∼(τ−τc)m, where EE is erosion rate, ττ is shear stress, τcτc is the threshold shear stress for erosion to occur, and m7/4m≈7/4. This result contrasts with the commonly assumed linear erosion law E=kd(ττc)E=kd(τ−τc), where kdkd is a measure of how easily sediment is eroded. The data collapse prompts a re-examination of the way that results of the hole-erosion test (HET) and jet-erosion test (JET) are customarily analyzed, and also calls into question the meaningfulness not only of proposed empirical relationships between kdkd and τcτc, but also of the erodibility parameter kdkd itself. Fuller comparison of flume-erosion data with hole-erosion and jet-erosion data will require revised analyses of the HET and JET that drop the assumption m=1m=1 and, in the case of the JET, certain simplifying assumptions about the mechanics of jet scour.

Publication type Article
Publication Subtype Journal Article
Title Dimensionless erosion laws for cohesive sediment
Series title Journal of Hydraulic Engineering
DOI 10.1061/(ASCE)HY.1943-7900.0001068
Volume 142
Issue 2
Year Published 2016
Language English
Publisher American Society of Civil Engineers
Contributing office(s) Volcano Science Center
Description 13 p.
First page 1
Last page 13
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