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We investigate the interfacial topology of liquid-film flows falling under an inverted planar substrate by conducting space-and time-resolved film-height measurements. A planar laser-induced fluorescence (PLIF) technique is employed for this purpose, with a two-camera arrangement that allows us to image a region of the flow extending≈ 40 mm on either side of the center of the film span, at a distance 330 mm downstream of the flow inlet. The substrate inclination angle is set to β=− 30, the working fluid comprises 82% glycerol and 18% water (by weight), and the flow Reynolds number, Re, is varied in the range Re= 0.6− 8.2. The uncertainty associated with the instantaneous film-height measurement is estimated at less than 3%. Depending on the flow Re, we observe a range of interesting flow regimes typically characterized by pronounced rivulet formation and spatiotemporal coherence, which deviate from …