The channel configuration is a function of river stage (water level); 

 the optimum stage for defining the channel configuration is at low flow. 

 The channel configuration is also a function of location along the river; 

 a river could conceivably exhibit all channel configurations between its 

 headwaters and its mouth. The channel configurations describing the 25 

 study sites are those only through the reach studied. Configuration combi- 

 nations, local spatial variations, and variations over time complicate 

 channel configuration selection. 



Undisturbed Condition 



Braided Configuration . A braided river typically contains two or more 

 interconnecting channels separated by unvegetated or sparsely vegetated 

 gravel bars (Figure 16). Its active floodplain is typically wide and 

 sparsely vegetated, and contains numerous high-water channels and occasional 

 vegetated islands. Active channels are typically wide and shallow and carry 

 large quantities of sediment at high flows. Bars separating the channels are 

 usually low, gravel surfaced, and easily erodible. The lateral stability of 

 the channels is quite low; channels shift by bank erosion and/or by channel 

 diversion into what was previously a high-water channel. The lateral activ- 

 ity of channels within the active floodplain of a braided river that carries 

 large quantities of bed load, is expected to be high because gravel deposits 

 may partially or fully block channels, thereby forcing flow out of the 

 channel. Maximum depths and corresponding top widths of undisturbed major, 

 side, and high-water channels, at four braided study sites, are plotted in 

 F i gure I 7. 



Split Configuration. A split channel river has numerous stable islands 

 which divide the flow into two channels (Figure 18). The banks of the chan- 

 nels are typically vegetated and stable. The split river floodplain is 

 typical ly narrow relative to the channel width. There are usual ly no more 

 than two channels in a given reach and other reaches are single channel. One 

 of the two channels in a split reach may be dry during periods of low flow. 

 The channel cross section is narrower and deeper than a braided river with 

 similar flow characteristics. Maximum depths and corresponding top widths of 



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