METHODS OF DATA ANALYSIS 



The data from each of the 25 sites were first analyzed on a site- 

 by-site basis to determine the effect of gravel removal operations on the 

 aquatic environment at each study site. These individual site evaluations 

 provided the basis for further analysis to identify trends and correlations 

 relating to major site variables (Table I, Major Variable Matrix). These 

 individual site evaluations are not included because of space limitations 

 but are part of the permanent data base maintained by the U. S. Fish and 

 Wi I d I i f e Service. 



The various physical and biological parameters measured at the dif- 

 ferent sites varied greatly in magnitude and the variation made the direct 

 comparison of data among sites impractical. The various parameters recorded 

 at the study sites were standardized on a scale of to 10 to obtain a 

 relative measure of the degree of change. A rating of 5 indicates that a 

 parameter measured in the mined area had not changed from the same parameter 

 in the upstream area; ratings of 0-4 and 6-10 indicate decreased and in- 

 creased parameter values in the mined area relative to the upstream area. 

 The rating was determined by calculating the percentage change in the mined 

 area relative to the upstream area for each site and subjectively assigning 

 rating values to various percentage intervals such that all or most of the 

 0-10 scale was utilized for those sites at which the parameter was evalu- 

 ated. Data from study sites with similar ratings were examined for similar 

 alterations that might lead to a similar parameter response. 



The analysis of habitat alteration was based on field notes from the 

 site surveys, ground and aerial photographs, direct measurement of habitat 

 parameters, results of hydraulic analysis, and visual observations. Habitat 

 parameters considered in the analysis included changes in substrate type. 



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