Resolve example 5.4.3 with a discharge of 10,000 cfs and a downstream water surface elevat...

Resolve example 5.4.3 with a discharge of 10,000 cfs and a downstream water surface elevation of 123.5 ft.

EXAMPLE 5.4.3

For the compound cross-section at river mile 1.0 shown in Figure 5.4.2, determine the energy correction factor α. The discharge is Q = 11,000 cfs and the water surface elevation is 125 ft.

SOLUTION

Step 1 Compute the cross-sectional areas of flow for the left overbank (L), channel (C), and right overbank (R):

Step 2 Compute the hydraulic radius for L, C, and R:

Step 3 Compute the conveyance factor for L, C, and R:

Step 4 Compute totals At and K1:

Step 5 Compute K3/A2 and :

Step 6 Use equation (5.4.24) to compute α:

Figure 5.4.2 Cross-section and reach length data for example 5.4.3 (from Hoggan (1997)).