ones formed in eddies below protruding rocks, 

 were less evident. Fortunately, these smaller 

 pools comprised only a small part of the total 

 pool area. 



Five pool-quality classes were designed 

 on the basis of pool size, water depth, and 

 fish shelter, see guide, page 7. The deeper and 

 larger pools with abundant shelter were con- 

 sidered better fish habitat than the smaller, 

 •shallower, and more exposed pools. 



The width of each pool along the transect 

 was measured to the nearest foot and was 

 recorded according to quality classes (fig. 5). 



Riffles, in effect, were defined as all water 

 surface areas not designated as pools. There- 

 fore, the sum of all pool widths was sub- 

 tracted from the width of the channel to 

 determine riffle width for that channel. 



BOnOM COMPOSITION 



Five types of bottom material were defined 

 as follows: 



Boulder — Rocks over 12 inches in 

 diameter 



Rubble — Rocks :> to 11.9 inches in 

 diameter 



Gravel — Rocks 0.1 to 2.9 inches in 

 diameter 



Sand-silt — Particles less than 0.1 inch 



in diameter 

 Other — Other matter (sunken logs or 



other debris) 



Bottom material was not always visible 

 because of suspended silt, shadows, or water 

 depth. Classification in such cases was based 

 largely on the "feel" of the bottom as a field- 



Figure 5. — This hypothetical trarusect shows the type pool and riffle data that 

 were recorded. One pool, of number three quality, is 6 feet wide along the transect. 

 The second pool, of number five quality, is 2 feet wide along the transect. The 

 remainder of the total transect length — 14 feet — is recorded as riffle area. 



6 



