It's a blocking/capacity thing. The blocking on a flume ride is a bit strange. By now everyone knows how roller coaster block systems work, right? Well, on flumes, it's a little different in that the whole ride is not divided up into exclusive block zones. Instead, in the slow, free-floating areas, there isn't any block safety system because collisions in those areas would be trivial. As a result it isn't uncommon to have boats stacked up on the brake just ahead of the downchute diverter gate.
Anyway, the ride does have a block safety system for the downchute and the Hydro-Jump. The blocking is simple: Only one boat may occupy the segment from the brake at the top of the downchute to the end of the Hydro-Jump. Then, beyond the Hydro-Jump, where the boat speed returns to a mere crawl, the safety system ends and the boats return to the loading turntable. With the dual down-chute, one boat may be dispatched down one chute while the boat ahead is still in the Hydro-Jump, rather than waiting until it completely clears the high-speed section. The result is that the boats will arrive at the rejoin-point at a faster interval, allowing more boats to run on the circuit.
As for the guy on the catwalk...I don't know for certain, but at one time I thought that person was dispatching the boats down the drop. Anybody here know for sure?
--Dave Althoff, Jr.