Figure 2. — Little Falls Dam on the Potomac River in the spring of 1963. 



with a 3/4-foot drop between pools. This type 

 of fishway was first developed by the Inter- 

 national Pacific Salmon Fisheries Commis- 

 sion for use at Hells Gate on the Frazer 

 River in British Columbia, Canada. Since 

 its development many facilities of this de- 

 sign installed on west coast rivers have proved 

 effective in passing fish over barriers (U.S. 

 Army Corps of Engineers, 1964). A major 

 advantage is that they can operate over a wide 

 range of water flows and, therefore, are more 

 adaptable and require less attention than cer- 



tain other types of fishways. The Snake Island 

 fishway is designed to be effective at river 

 flows of 3,000 to 32,000 c.f.s. (cubic feet per 

 second). The fishway and attraction chamber 

 are about 360 feet long; the fishway itself is 

 120 feet long. The attraction chamber is 45 

 feet wide and 120 feet long; additional water 

 is introduced through gratings in the floor 

 of the channel to maintain velocities of 2 to 3 

 f.p.s. (feet per second). Little Falls Dam is 

 1,200 feet long; water spills over the full 

 length of the dam at all times. 



