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Caption: This chart shows the cumulative particle size distribution of spawning gravels in the Trinity River 2000' upstream from the Poker Bar Bridge. Data were collected and analyzed by Graham Matthews and Associates in 2000. Both surface (the depth of the largest particle) and sub-surface (down to 1 ft depth) samples are represented. The median particle size (D50) of all surface samples was approximately 25 mm to 45 mm; the sub-surface median particle size was approximately 3 mm to 4 mm. Percent fines less than 1 mm ranged from 2.3-21%. GMA (2003) noted that that the fines at Poker Bar are large grain decomposed granite and are likely from Grass Valley Creek. See Info Links for more information.
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