The Romans had a major ditch running through Rome called the Grand Cloaca... a cloaca is the common pipe into which everything washes in birds, amphibians, reptiles, earthworms, and some fish.. the common outflow pipe.

This is one of several Grand Cloacas for Hoover Dam... the thing is about 50 feet across, and can carry an unbeleivable volume of, let's say, water every second... an exit on the grand scale, to be sure.