Handbook of Civil Engineering Calculations

FIGURE 9. Branching pipes.

38.7(0.833)^264 (70/8000)^0513 = 2.10 ft^3 /s (59.455 L/s). Similarly, Q 2 = 1.12 ft^3 /s (31.710
L/s) and q 3 = 0.83 ft^3 /s (23.499 L/s); Q 2 + Q 3 = 1.95 < Q 1. The assumed value of hFl is ex-
cessive.

4. Make another assumption for hF1 and the corresponding
   revisions
   Assume hFl = 66 ft (20.1 m). Then ^ 1 = 2.10(66/7O)^0513 = 2.04 ft^3 /s (57.757 L/s). Simi-
   larly, Q 2 = 1.18 ft
   3
   /s (33.408 L/s); ft = 0.85 ft
   3
   /s (24.065 L/s). G 2 + 6s = 2.03 ft
   3
   /s
   (57.736 L/s). These results may be accepted as sufficiently precise.

UNIFORM FLOW IN OPEN CHANNEL-

DETERMINATION OF SLOPE

It is necessary to convey 1200 ft^3 /s (33,974.6 L/s) of water from a dam to a power plant in

a canal of rectangular cross section, 24 ft (7.3 m) wide and 10 ft (3.0 m) deep, having a

roughness coefficient of 0.016. The canal is to flow full. Compute the required slope of

the canal in feet per mile (meters per kilometer).

Calculation Procedure:

1. Apply Eq. 22
   Thus, A = 24(10) - 240 ft^2 (22.3 m^2 ); wetted perimeter = WP = 24 + 2(10) = 44 ft
   (13.4 m); R = 240/44 = 5.45 ft (1.661 m); V = 1200/240 = 5 ft/s (152.4 cm/s); s =
   [nV/(1.486R2/3)]^2 - [0.016 x 5/(1.486 x 5.452/3)]^2 = 0.000302; slope = 0.000302(5280
   ft/mi) = 1.59 ft/mi (0.302 m/km).

REQUIRED DEPTH OF CANAL FOR

SPECIFIED FLUID FLOW RATE

A trapezoidal canal is to carry water at 800 ft

3

/s (22,649.7 L/s). The grade of the canal is

0.0004; the bottom width is 25 ft (7.6 m); the slope of the sides is I^1 A horizontal to 1 ver-