Table 2.3. Characteristics of Water Surface Profiles.
So = 0
So = 0
With a type 1 curve (M1, S1, C1), the actual depth of flow y is greater than both the normal
depth yo and the critical depth yc. Because flow is tranquil, control of the flow is
With a type 2 curve (M2, S2, A2, H2), the actual depth y is between the normal depth yo and
the critical depth yc. The flow is tranquil for M2, A2 and H2 and thus the control is
downstream. Flow is rapid for S2 and the control is upstream.
With a type 3 curve (M3, S3, C3, A3, H3), the actual depth y is smaller than both the normal
depth yo and the critical depth yc. The flow is rapid and control is upstream.
For a mild slope, So is smaller than Sc and yo > yc.
For a steep slope, So is larger than Sc and yo < yc.
For a critical slope, So equals Sc and yo = yc.
For an adverse slope, So is negative.
For a horizontal slope, So equals zero.
The case where y → yc is of special interest. See paragraph preceding Figure 2.28.