Backwater Calculations for Parallel Bridges

The backwater calculation for parallel bridges (depicted in Figure 9-16) requires the application of a coefficient. The chart in Figure 9-17 relates the value of the backwater adjustment coefficient (μ) to the ratio of the out-to-out dimension of the parallel bridges to the width of a single embankment (see Figure 9-18). Determine the backwater head calculation for a parallel bridge with Equation 9-11.
EquationObject274328
Equation 9-11.
where:
  • h
     = total backwater head (ft. or m)
  • μ = backwater adjustment coefficient (see Figure 9-17)
  • h
    1
    = backwater head for one bridge as discussed in the
    Bridge Flow Class
    subsection above.
    Parallel Bridges (click in image to see full-size image)
    Figure 9-16. Parallel Bridges
    Parallel Bridges Backwater Adjustment (click in image to see full-size image)
    Figure 9-17. Parallel Bridges Backwater Adjustment
    Definition of Parameters (click in image to see full-size image)
    Figure 9-18. Definition of Parameters