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Looking Glass River Watershed Management Plan - Greater ...

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which is used in hydrology computations. Some flow conveyance<br />

information is available from the respective County Drain Commissioner’s<br />

offices, the MDEQ and as well as from some municipalities.<br />

Information on indicators is available in the form of organism biodiversity<br />

and population data, and physical characteristics as observed from the<br />

various inventory and screening efforts are all discussed in Section 3.<br />

Load Estimates<br />

Load estimates for altered hydrology are not specifically available rather<br />

surrogate estimates are used, namely the stream flow variations, flashiness<br />

indices and the amount of imperviousness within the watershed.<br />

Average annual stream flow statistics (annual minimums, maximums and<br />

average annual flows) are provided in Figure 5-1. This data shows that the<br />

<strong>Looking</strong> <strong>Glass</strong> <strong>River</strong> experienced much higher peak flows during the period<br />

of record than it has in the last 10 years. What is not evident in this<br />

information is the cause of the maximum flows, i.e. the combination of land<br />

use, conveyance pathways and precipitation. A detailed historical flow<br />

characterization of the <strong>Looking</strong> <strong>Glass</strong> <strong>River</strong> is beyond the scope of this<br />

watershed management plan.<br />

Figure 5-1 Stream Flow at Eagle (USGS 04114498)<br />

1200<br />

1000<br />

Streamflow (cfs)<br />

800<br />

600<br />

400<br />

200<br />

0<br />

1944<br />

1949<br />

1954<br />

1959<br />

1964<br />

1969<br />

1974<br />

1979<br />

1984<br />

1989<br />

1994<br />

1999<br />

2004<br />

The term “flashy” as applied to stream flow has no set definition and in<br />

general flashy streams have rapid rates of change and stable streams have<br />

slow rates of change. The Richards-Baker Flashiness Index (abbreviated R-B<br />

Index) was calculated for the available stream flow data (Baker 2004). The R-<br />

B Index measures oscillations in flow relative to the total flow.<br />

The calculated R-B Index has varied over time with an average value of 0.10<br />

based on the USGS gauging station data, refer to Figure 5-2. According to<br />

the paper on the R-B index (Baker, 2004) an index value of 0.10 for these size<br />

watersheds is in the lowest quartile of flashiness when compared to the data<br />

from other sites. It should be noted that in the Baker study the flashier<br />

streams were outside of Michigan. For comparison purposes one of the most<br />

stable streams in Michigan is the Au Sable <strong>River</strong> which has an R-B Index of<br />

0.043 computed on the South Branch near Luzern.<br />

Another way to look at the R-B Index is to consider the trend over time.<br />

Based on the graph the <strong>Looking</strong> <strong>Glass</strong> <strong>River</strong> appears relatively stable over<br />

the last 50 years.<br />

Section 5: Stressor Summary 5-11

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