name | Text of up to 10 characters. Blanks are not allowed. This is in order to preserve the tabular printout, which can be read back into the program. |
Qb# | Added or Carryover flow. This can reference a carryover flow computed on an "InletOnGrade" line. |
Q# | Flow in section. This can reference a flow computed on a "Qcia" line. |
S | Slope of the curb, longitudinal. |
n | Manning's roughness coefficient. Suggested values are given with the Open Channel formulas. |
W | Width of the gutter. This should be zero if there is no gutter. However, if an inlet is referencing this curb, this value is needed as the width of the local depression (if applicable), so Sw should be set equal to Sx instead. |
Sw | Cross slope of the gutter. |
Sx | Cross slope of the pavement or lane beyond the gutter. |
lw | Width of the lane beyond the gutter. When added to "W", this is also the allowable spread. If a large number is given, the program will limit the computation to the width achievable with a 6" curb and the given cross-slopes. |
T | Spread, or width of water surface, from the curb |
d | Depth of water from the curb bottom. |
Eo | Percentage of frontal flow, or flow in the gutter portion of the cross-section. |
W/T and Sw/Sx | These are just intermediate values given only because they are asked for in VDOT tables. |
The formulas and nomenclature of the Federal Highway Administration's Hydraulic Engineering Circular No. 12 (HEC-12) are used, with further clarification in Hydraulic Engineering Circular No.22 (HEC-22). The referenced formulas are listed below.
dw = wSw
T = d/Sw
Qw = (0.56/n) Sw1.67 S0.5 T2.67
Ts = (d - dw) / Sx
T = w + Ts
Qs = (0.56/n) Sw1.67 S0.5 Ts2.67
swx = Sw/Sx
tw = T/w
v1 = swx/(tw-1)
v2 = (1+v1)2.67
Eo = 1/[1+swx/(v2-1)]
Q = Qs/(1-Eo)