more fine sediment deposition. 



Reach 3: Nevada Creek to Monture Creek 



(RM 67.8 to 45.9) 



In the Wales Creek area, about 4 miles below Nevada Creek, 

 the Blackfoot River takes a sharp drop in grade increasing to 

 20.2 ft/mi to the North Fork of the Blackfoot. Boulders (> 12.0 

 in. dia.) and rubble reappear in the bottom substrate. Woody 

 debris jams are less common, strong meandering disappears, and 

 the riffle-pool sequence becomes noticeable. This section had 

 dense growths of filamentous green algae and rooted aquatic 

 plants covering much of the bottom in 1988. Local residents 

 indicated that 1987 was the first time these dense growths were 

 observed in the river. Fine sediments are abundant in eddies, 

 behind boulders, along the banks and in the interstitial spaces 

 in the riffle substrate. Aquatic plant masses throughout the 

 channel appear to encourage sediment deposition in and downstream 

 from the mass. Stream bank cover is dominated by grasses with 

 some brush in this section. Below the North Fork gradient 

 moderates to 14.8 ft/mi for most of the remaining 52 miles to the 

 Milltown pool. 



Reach 4 and 5: Monture Creek to Mouth of Blackfoot River 



(RM 45.9 to 0) 



These two reach possess similar habitat characteristics 

 except that the river increases in size in Reach 5 due to 

 significant tributary inflows. In this river segment, gradient 

 remains moderate at 14.8 ft/mi except for some short reaches of 

 higher gradient near the Roundup Bar and below Whittaker Bridge. 

 The bottom substrate in this reach are dominated by boulder and 

 rubble sized particles. Fine sediment is easily observed in the 

 interstitial spaces in the wide riffle areas, and is relatively 

 absent in the narrow riffles with high current velocities. This 

 reach of the Blackfoot has deep boulder runs and deep pools 

 tailing into broad riffles. Several major tributaries feed the 

 Blackfoot River in Reach 4 and 5 including: Monture, Cottonwood, 

 Clearwater, Belmont, Gold, E. and W. Twin Creeks, Johnson Gulch, 

 and a few more smaller creeks. 



STREAMFLOW 



Stream discharge in Blackfoot river has been recorded at the 

 USGS gaging station near Bonner (RM 7.9) since 1939. The maximum 

 recorded flow of 19,200 cfs occurred on June 10, 1964. The 

 lowest recorded flow of 200 cfs occurred on Jan. 4,5, 1950. 



Both the seasonal high and low flows over the last 5 years 

 (1983 - 1988) have been below the historic 50% exceedance level 

 (ie. the level you would expect to exceed 50% of the time based 



8 



