Partial entrainment of gravel bars during floods

Water Resources Research
By: , and 



Spatial patterns of bed material entrainment by floods were documented at seven gravel bars using arrays of metal washers (bed tags) placed in the streambed. The observed patterns were used to test a general stochastic model that bed material entrainment is a spatially independent, random process where the probability of entrainment is uniform over a gravel bar and a function of the peak dimensionless shear stress τ0* of the flood. The fraction of tags missing from a gravel bar during a flood, or partial entrainment, had an approximately normal distribution with respect to τ0* with a mean value (50% of the tags entrained) of 0.085 and standard deviation of 0.022 (root‐mean‐square error of 0.09). Variation in partial entrainment for a given τ0* demonstrated the effects of flow conditioning on bed strength, with lower values of partial entrainment after intermediate magnitude floods (0.065 < τ0*< 0.08) than after higher magnitude floods. Although the probability of bed material entrainment was approximately uniform over a gravel bar during individual floods and independent from flood to flood, regions of preferential stability and instability emerged at some bars over the course of a wet season. Deviations from spatially uniform and independent bed material entrainment were most pronounced for reaches with varied flow and in consecutive floods with small to intermediate magnitudes.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Partial entrainment of gravel bars during floods
Series title Water Resources Research
DOI 10.1029/2001WR000828
Volume 38
Issue 7
Year Published 2002
Language English
Publisher American Geophysical Union
Contributing office(s) Washington Water Science Center
Description Article 1104; 16 p.
First page 9-1
Last page 9-16
Online Only (Y/N) N
Additional Online Files (Y/N) N