tSi any other time. The spring melt rising limb population was not visually differentiated into compact and floc particles but exhibits the lowest population particle diameter mean and its maximum particle size is similar to that of resuspended gravel stored compact particles of the active spawn of August 2000 and the post-spawn of October 2000. Note that the ambient active spawn particles (August 2000) exhibit the smallest floc and compact sizes even though water velocities are similar to those observed in September and October sampling periods (Table 4.1). In fact its maximum floc size is slightly smaller than the maximum aggregate measured in the 1997 spring melt when flows were four times as fast.

To differentiate size and density, each subpopulation was separated into size categories based on a criterion diameter of 500 /m while low density and high density particles were separated at 1.10g cm-3. These values were selected as they characterize the boundaries of the bulk of overlapping data points in Figure 4.2. In Table 4.3 the floc subpopulations are classified as large (>80% of the particles always exceed 500 /m) and low density (100% < 1.1 g cm-3). Compact particle subpopulations tend to be comprised predominantly (>79%) of smaller (<500 /m) particles. The exception is the 1996 die-off when larger compact particles comprised 65% of the population with the other 35% being <500 /m. The compact particles also predominate in the high density classification with 11 to 30% of their population exhibiting densities >1.1 g cm-3, excluding the 1996 post-spawn die-off when only 6% were of higher density. Compact-organic particles were not included in this evaluation of compact particles but comprised a separate subpopulation not presented in Table 4.3.

In the data sets that were also characterized for sphericity (all 2000 settling runs) all floc populations are significantly less circular than the compact particles (Table 4.3). While the floc shapes are not significantly different (p = 0.05) over time or by source (suspended or gravel stored) the compact particles do exhibit differences over time. The compact particles become significantly more rounded in the post-fish ambient and resuspended samples.

Fractal (D) values and their 95% confidence limits for the population of particles measured for settling velocities in 2000 are shown in Figure 4.4. A fractal value for the total population is shown for each sample date as well as the fractal value for the floc, compact and compact-organic particle subpopulations. The fractal values for the total populations indicate that there is no significant difference by source (ambient versus resuspended sediment) but there is by time, in that the suspended (ambient) sediment has significantly smaller fractal values in October than in August for the total population. Fractals for gravel stored (resuspended) sediment do not vary significantly between these dates. An evaluation of the subpopulations indicates that the floc and compact-organic particles exhibit a large amount of variation, while the compact particles have smaller confidence limits, indicating less variability in shape.

A similar fractal analysis of particles collected on filters is shown in Figure 4.5 for the years 1996 through to 2000. The sampling dates are not graphed chronologically by year, but rather grouped by date within the season so that the periods of spring melt, active spawn, fish die-off, and post-spawn can be viewed consecutively. The fractal values are lowest for the ambient suspended sediment of the spring melt period

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