Water flows in a trapezoidal channel in which the bottom width is 6 m and the side slopes are 2:1 (H:V). The channel lining has an estimated Manning n of 0.045, and the longitudinal slope of the channel is 1.5 %. When the flow rate is 80 m ³ /s, the depth of flow at a gaging station is 5 m. Classify the water-surface profile, state whether the depth increases or decreases in the downstream direction.