The graph shows results of sampling for downstream variation in particle size, Poudre River valley gravel:

1-Graph shows the range in particle size, by wt pct > given size, along a 30-mile stretch of the Poudre valley. Straight lines are least-squares best fit. Colored symbols are average values at each sampling site.

2-The weight pct of coarse gravel sizes declines abruptly. Note the decline in weight pct > 3-inch gravel. The variance due to downstream decline is large relative to error variance.

3-The weight pct of fine gravel does not decline noticeably. Note the flat line for weight pct > 3/16 inch gravel. Any possibility of measuring downstream decline is overwhelmed by error variance, which is much larger than the variance attributed to downstream decline.

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Last updated 07 Dec 2016