Significant changes in slope most often reflect changes in channel 

 length. If a channel is shortened by mining then the slope is increased; if 

 the channel is lengthened, the slope is decreased. At all study sites the 

 slope was either unchanged or it increased. The likelihood of decreasing 

 channel slope by lengthening the channel is slight because water tends to 

 flow downvalley over the shortest distance. However, if channel lengthening 

 should occur by diversion through a site, then the effects would reflect 

 reduced velocities. 



Stream Origin. The origin of the stream was found to have little or no 

 relationship to the effects of gravel removal activities. Origin can in- 

 fluence, at least in part, other characteristics of a river system, e.g., 

 channel configuration and shape. Therefore, the preceding discussions are 

 indirectly related to this characteristic. The origin of a stream determines 

 greatly the quality and quantity of gravel materials available in downstream 

 areas. 



The original purpose for including stream origin in the study was 

 to maximize diversification of the types of sites to be studied. The origins 

 of streams included were mountain, foothill, coastal plain, and glacial. 

 Twelve of the sites studied were of mountain origin, 9 were of foothill 

 origin, and only 4 were of glacial or coastal plain origin. 



The availability of gravels in streams of coastal plain origin is 

 general ly low and the materials are finer in texture than those found in 

 other systems. Within the geographical limits of our study, only the Seward 

 Peninsula and North Slope have coastal plains. The coastal plain of the 

 Seward Peninsula is so narrow it precludes the existence of such river 

 systems. On the North Slope material sites were located on the Sakonowyak, 

 Putuligayuk, and Ugnuravik Rivers, but only the latter was studied. Gener- 

 al ly, these sites are not favored and are only used if alternative sites are 

 not aval lable. The lack of rock in the headwaters and the low mean annual 

 discharges are the reasons that gravel materials are only minimally avail- 

 able in coastal plain streams. If these sites are utilized, the potential 

 for replacement of gravel sources is very low even over extended time 



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