<?xml version='1.0' encoding='utf-8'?>
<oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd">
  <dc:contributor>E.D. Andrews</dc:contributor>
  <dc:contributor>John Pitlick</dc:contributor>
  <dc:creator>Christopher E. Johnston</dc:creator>
  <dc:date>1998</dc:date>
  <dc:description>&lt;p&gt;&lt;span&gt;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&amp;nbsp;&lt;/span&gt;&lt;i&gt;F&lt;/i&gt;&lt;sub&gt;&lt;i&gt;d&lt;/i&gt;&lt;/sub&gt;&lt;span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;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&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;/span&gt;&lt;i&gt;D&lt;/i&gt;&lt;sub&gt;&lt;i&gt;i&lt;/i&gt;&lt;/sub&gt;&lt;span&gt;/&lt;/span&gt;&lt;i&gt;K&lt;/i&gt;&lt;sub&gt;&lt;i&gt;s&lt;/i&gt;&lt;/sub&gt;&lt;span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;&amp;gt; 1. Furthermore, within a&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;/span&gt;&lt;i&gt;D&lt;/i&gt;&lt;sub&gt;&lt;i&gt;i&lt;/i&gt;&lt;/sub&gt;&lt;span&gt;/&lt;/span&gt;&lt;i&gt;K&lt;/i&gt;&lt;sub&gt;&lt;i&gt;s&lt;/i&gt;&lt;/sub&gt;&lt;span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;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 τ&lt;/span&gt;&lt;sub&gt;&lt;i&gt;c&lt;/i&gt;&lt;/sub&gt;&lt;sup&gt;*&lt;/sup&gt;&lt;span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;from extensive bed load measurements made by&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;/span&gt;&lt;i&gt;Andrews and Erman&lt;/i&gt;&lt;span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;[1986] at Sagehen Creek and the in situ Φ measurements made in this study together with a theoretical model developed by&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;/span&gt;&lt;i&gt;Wiberg and Smith&lt;/i&gt;&lt;span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;[1987], we show that Φ measurements made with this new method can be used to accurately predict τ&lt;/span&gt;&lt;sub&gt;&lt;i&gt;c&lt;/i&gt;&lt;/sub&gt;&lt;sup&gt;*&lt;/sup&gt;&lt;span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;for natural, water-worked sediments. Additionally, these results confirm that a Φ value ≪Φ&lt;/span&gt;&lt;sub&gt;50&lt;/sub&gt;&lt;span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;is more appropriate for predicting τ&lt;/span&gt;&lt;sub&gt;&lt;i&gt;c&lt;/i&gt;&lt;/sub&gt;&lt;sup&gt;*&lt;/sup&gt;&lt;span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;of a given size class.&lt;/span&gt;&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.1029/98WR00312</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>American Geophysical Union</dc:publisher>
  <dc:title>In situ determination of particle friction angles of fluvial gravels</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>