Engineering in the viewer
For a rectangular, open-flow channel: A = b × y (m²); wetted perimeter P = b + 2y (m); hydraulic radius R = A/P (m). In SI units, Manning's uniform-flow approximation is Q = (1/n) × A × R2/3 × √S (m³/s), where S is the energy grade expressed as a decimal slope. The model also calculates v = Q/A (m/s) and t = 270/v (seconds). The independent check recomputes v from discharge and area in a separate function.
Simplifications: fixed rectangular cross-section, constant depth and slope, steady uniform water, no entrances, deposits, leakage, weather, backwater or sediment transport. A numerical result is a scenario, not a claim about ancient actual performance. The 270 m distance is a modelled central study reach, not the full aqueduct route.