Major habitat components of the lower Yellowstone River are 

 main channel pools, runs and riffles, side channels or chutes, and 

 backwaters. Pools are generally 1.5 m to 3.0 m deep, although some 

 are at least 5.5 m deep during summer flows. Backwaters, an 

 integral part of the river ecosystem, are much more common in 

 island or braided sections of the Yellowstone River. 



The lower Yellowstone River contains many islands and braided 

 areas with the exception of the reaches from Miles City (river km 

 306) to Cedar Creek (river km 172) and Sidney (river km 40) to the 

 mouth. The Miles City to Cedar Creek sections runs through several 

 bedrock outcrops. Downstream from Sidney (river km 56) , the 

 Yellowstone widens and has a shifting sand and silt bottom. 



Substrate in the main channel of the Yellowstone upstream from 

 Sidney, Montana (river km 56) is dominated by clean, rounded 

 cobble. Side channels are also dominated by a cobble or pebble 

 substrate. When flows decline in late summer, many of the side 

 channels become backwaters at which time large amounts of silt are 

 deposited at the mouths of these channels. 



The Yellowstone River is undammed. There are two periods of 

 peak flows (Figure 2) . The first and smaller peak occurs during 

 mid March to early April and is a result of lowland or prairie 

 runoff. This runoff period usually accompanies ice breakup. 

 Because ice out begins in upstream areas, ice jams often fonn which 

 can cause severe flooding. Ice out can be as much as 3 weeks 



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