630 / HARLEN BRETZ 



Gradients : 



Spangle to Hooper, 21.9 feet per mile 

 Cheney to Hooper, 22.6 feet per mile 

 Medical Lake to Sprague, 24 feet per mile 

 Medical Lake to Hooper, 22.5 feet per mile 



3. Reardan channel. Altitude of head, 2,500+ 

 Gradient, Reardan to Odessa, 20 feet per mile 



4. Davenport-Harrington channel. Altitude of head, 2,450 ± 

 Gradient : 



Davenport to Harrington, 27 feet per mile 

 Harrington to Odessa, 26 feet per mile 



5. Telford tract 



a) Eastern head. Altitude, 2,5oo± 

 Gradient : 

 Rocklyn to Odessa, 30 feet per mile 

 Rocklyn to Krupp (Marlin), 26 feet per mile 

 h) Western head. Altitude, 2,5oo± 

 Gradient : 

 Near Creston to Krupp (Marlin), 32 feet per mile 

 Near Creston to Wilson Creek, 30 feet per mile 

 Total width of heads is 1 7 miles 

 c) Wilbur branch 

 Gradient : 

 Creston to Wilson Creek, 32 feet per mile 

 Wilbur to Wilson Creek, 25 feet per mile 

 Almira to Wilson Creek, 26 feet per mile 



The only scabland tracts which do not open on the basalt plain 

 are Grand Coulee and Moses Coulee. For the head of Moses 

 Coulee there are no altitude measurements. Grand Coulee has had 

 a peculiar history, not yet fully deciphered, but the significant 

 altitude at its head for present purposes is not the coulee floor (1,530 

 feet A.T.) but the scabland margining the brink of the canyon, 

 about 2,500 feet A.T. The canyon has been cut subsequent to the 

 first spilling over of glacial waters. The floor near Coulee City is 

 1,510 feet A.T. Most of this descent occurred within a few miles 

 of Coulee City, the original slope being as steep as 20° in part and 

 averaging perhaps 10° for 1,000 feet of descent. This is the chief 

 reason for the great canyon across the divide. No other scabland 

 head has been notably canyoned. None other had a gradient to 

 exceed about 30 feet to the mile. All the canyons of the channeled 



