In situ determination of particle friction angles of fluvial gravels
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Abstract
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.
| 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 |
| Google Analytic Metrics | Metrics page |