In situ determination of particle friction angles of fluvial gravels

Water Resources Research
By: , and 



Particle friction angles Φ represent the physical resistance to initial movement of a sediment particle and are therefore useful for relating initiation of motion to particular flows. We determined over 8000 friction angle values at five natural rivers by applying a new method that uses a digital load cell to directly measure the force Fd required to pivot or slide a particle out of its natural resting place. Within each site, median Φ values were very similar to previously reported relations, yet different enough between sites that a location-general predictive empirical relation would produce errors in Φ of ±10 degrees for Di/Ks > 1. Furthermore, within a Di/Ks class at a given site the range in Φ was as large as 80°, much greater than the range of median values between classes for natural sediment mixtures. Using estimates of τc* from extensive bed load measurements made by Andrews and Erman [1986] at Sagehen Creek and the in situ Φ measurements made in this study together with a theoretical model developed by Wiberg and Smith [1987], we show that Φ measurements made with this new method can be used to accurately predict τc* for natural, water-worked sediments. Additionally, these results confirm that a Φ value ≪Φ50 is more appropriate for predicting τc* of a given size class.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title In situ determination of particle friction angles of fluvial gravels
Series title Water Resources Research
DOI 10.1029/98WR00312
Volume 34
Issue 8
Year Published 1998
Language English
Publisher American Geophysical Union
Description 14 p.
First page 2017
Last page 2030
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