Associated with the trend towards larger top widths in the gravel 

 removal areas, the hydraulic depth in seven of these areas decreased. Sites 

 with smaller hydraulic depths, in the mined area, for all discharges in- 

 cluded Washington Creek, Nome River, Aufeis Creek, Skeetercake Creek, 

 Sagavan irktok River, and both sites on the Middle Fork Koyukuk River. 



The mean velocity was consistently less at the disturbed cross section 

 than at the undisturbed cross section at nine of the sites for the range of 

 discharges included in the backwater analysis. These sites included Gold Run 

 Creek, Washington Creek, Ugnuravik River, Aufeis Creek, Skeetercake Creek, 

 Sagavan irktok River, Dietrich River-Downstream, and both of the Middle Fork 

 Koyukuk River sites. At two sites, the rate of increase of velocity with 

 discharge was different in the disturbed area than in the undisturbed area. 

 At Sinuk River, the velocity increased at a lesser rate at the disturbed 

 cross section than at the undisturbed cross section. At Middle Fork Koyukuk 

 River-Downstream, the reverse was found. 



The conveyance, or carrying capacity of the channel, was consistently 

 greater in the gravel removal area of eight sites compared with conveyances 

 at undisturbed cross sections. These sites were Gold Run Creek, Sinuk River, 

 Washington Creek, Aufeis Creek, Sagavan i rktok River, Kavik River, Dietrich 

 River-Downstream, and Middle Fork Koyukuk R i ver-Upstream. The Sinuk River 

 had a larger exponent or, equ i va I ent I y , a more rapid increase in conveyance 

 with discharge than cross sections which were not disturbed by the gravel 

 removal operation. Conversely, the conveyance at the downstream site on 

 the Middle Fork Koyukuk River increased with discharge at a slower rate 

 than did the conveyance of the undisturbed cross sections. 



Significant changes in hydraulic geometry were observed primarily 

 at sites which were scraped, although not all scraped sites showed a signif- 

 icant increase. Most of the significant changes were observed at meandering, 

 sinuous, and straight rivers. Although no single gravel removal location 

 caused a significantly greater change in hydraulic geometry than others, 

 most of the sites that had significant change were those sites that were 

 excavated by scraping in-channel and immediately adjacent-to-channe I loca- 

 t ions. 



I N 



