the composite hydraulic radius is calculated as the total area divided by the total
wetted perimeter.
For the alpha method:
k
∑ R i C i Ai
Ri
R = i=1
k
∑ C i Ai
Ri
i=1
For the conveyance, equal velocity, and total force methods:
k
∑A
i
i=1
R=
k
∑P
i
i=1
where:
k = the number of panels
i = the panel number
R = the composite hydraulic radius
_
Ri = Ai / Pi
Ci = the panel Chezy roughness coefficient
Ai = the panel cross-sectional area
Pi = the wetted perimeter
The composite roughness coefficient, n , is calculated using the composite R in
the Manning equation:
2 1 k
3 S 2 ∑ Ai
1.486 R
i=1
n=
Q
where:
S = energy slope
Q = total discharge
89
Chapter 6
Input Requirements and Program Output for SAM.hyd
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