Table 2.3. Characteristics of Water Surface Profiles.

Class

Bed Slope

Depth

Type

Classification

Mild

So>0

y>yo>yc

1

M1

Mild

So>0

yo>y>yc

2

M2

Mild

So>0

yo>Yc>y

3

M3

Critical

So>0

y>yo=yc

1

C1

Critical

So>0

y<yo=yc

3

C2

Steep

So>0

y>yc>yo

1

S1

Steep

So>0

yc>y>yo

2

S2

Steep

So>0

yc>yo>y

3

S3

Horizontal

So = 0

y>yc

2

H2

Horizontal

So = 0

yc>y

3

H3

Adverse

So<0

y>yc

2

A2

Adverse

So<0

yc>y

3

A3

Note:

(1)

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

downstream.

With a type 2 curve (M2, S2, A2, H2), the actual depth y is between the normal depth yo and

(2)

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.

(3)

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.

(4)

For a steep slope, So is larger than Sc and yo < yc.

(5)

For a critical slope, So equals Sc and yo = yc.

(6)

For an adverse slope, So is negative.

(7)

(8)

For a horizontal slope, So equals zero.

The case where y → yc is of special interest. See paragraph preceding Figure 2.28.

(9)

2.53

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