314 



Illinois Natural History Survey Bulletin 



Vol. 28, Art. 2 



Table 4. — Champai)5n County stream habitats, the extent of their occurrence, and their 

 physical characteristics. 



Habitat 



Rivulet and small creek 



Large creek 



Riffle 



Sand and fine gravel 



Gravel and boulder 



Pool 



Sh a I low - 



Deep 



Small river 



Riffle 



Sand and gravel 



Boulder and rubble 



Pool 



Shallow 



Deep .- — - 



Miles in 



COUNTV 



189 

 176 



Drainage 



Area 

 (Square 



Miles) 



10 

 10-200 



200-400 



Average 



CJradient 



(Feet per 



Mile) 



7 

 3 



Maximum 



Depth 

 (Range in 

 Inches) 



1-10 



1-12 

 1-12 



•V-24 



3-18 

 3-18 



18-36 

 36-96 



Current 



Variable 



Swift 

 Swift 



Moderate 

 Sluggish 



Swift 

 Swift 



Moderate 

 Sluggish 



and riffles ; moderately deep, smoothly 

 flowinji stretches ; and long, deep pools. 

 They described each habitat and listed 

 characteristic species of fishes. 



We prefer a classification based on the 

 same ecolojjical characteristics but having 

 divisions with more easily definable limits, 

 table 4. 



Rivulets and Small Greeks. — Our 

 rivulets and small creeks include the ver- 

 nal rivulets of Thompson & Hunt and 

 also intermittent streams of slightly 

 greater size. They arise as small open 



gullies coming ofi the face of moraine 

 slopes, as seeps in grass waterways, or as 

 discharges at field tiles, fig. 7, draining 

 flat marshy areas. The type that originates 

 at a field tile may have an unusual be- 

 ginning because of the large, and some- 

 times surprisingly deep, hole that is 

 scoured out at the base of the tile. In 

 many cases, the pool contains a large con- 

 centration of fish. 



Most rivulets and small creeks in 

 Champaign Count\' have been modified 

 by dredging and straightening of the chan- 



Fig. 7. — Drain tile mouth and pool on the East Branch of the Salt Fork of the Vermilion 

 River. A tile mouth is Champaign County's analogue of a spring. 



