This paper examines the archaeological evidence for steep chutes, cascades, and dropshafts in Roman aqueducts. It also presents comparative data on steep-descent water flow in aqueducts based on physical model tests. It is suggested that the Romans were aware of the hydraulic problems posed by supercritical water flows and that the technological solutions they imposed were rudimentary but sound: for example, they understood the need for energy dissipation devices such as the stilling basin and the dropshaft