Fish Ladder for Charles River Dam, Charles River, Massachusetts
alewife, Army Corps of Engineers, Charles River, Charles River Dam, design, fish ladder, hydraulic design, hydraulic models, model studies, models, pool, screens, shad, slot and weir, upstream, vertical slot, weir
Technical Report No. 157-1
U.S. Army Engineer Division, North Pacific
The design of a fish ladder that would operate with downstream tide fluctuations of 14 ft and upstream river fluctuations of 1 ft were developed in two hydraulic models. The hydraulic design of the ladder was developed in a 1:8-scale model. Hydraulic characteristics of a false weir at the upstream end of the ladder were studied in a 1:4-scale model. The ladder was intended to pass primarily shad and alewives. The initial fish ladder was of the vertical-slot type with 29 pools and a false weir above high tide level to lead fish into a steep chute to the river 6.5 ft below. The design was hydraulically satisfactory. The design was modified to include a direct swim-through exit to the river for use during low and intermediate tides. The low tide ladder section consisted of five pools with notched weirs and a weir gate exit. The false weir exit was designed to operate with all tide levels, but fish were to be blocked from that section by a barrier rack during the use of the low tide exit. In a further modification, the notched weirs of the low tide section were replaced with a submerged screen barrier that would force fish toward the surface for better public viewing. With that plan, the false weir exit operated only when the low tide exit was closed. All the plans were satisfactory. The plan with a false weir exit and a low tide exit with submerged barrier screen was selected for construction.