See https://what-if.xkcd.com/147/ https://what-if.xkcd.com/147/. Niagra Falls is usually flowing at 100,000 ft^3/sec, the same as the spilway. Granted your 3f

See https://what-if.xkcd.com/147/ https://what-if.xkcd.com/147/. Niagra Falls is usually flowing at 100,000 ft^3/sec, the same as the spilway. Granted your 3ft pipe is a bit bigger than a drinking straw, but closer to the straw's scale than the spillway's!