a) Dietrich River-Downstream - inundated mined study area. 



b) Middle Fork Koyukuk R i ver-Upstream - backwater in lower 

 m i ned area . 



Figure 47. Low velocity backwaters formed by gravel removal 

 at Dietricti River-Downstream (13 July 1978) and Middle Fork 

 Koyukuk R i ver-Upstream (18 July 1978), note extensive silt 

 deposition in both cases. 



159 



