TM 5820-4/AFM 885, Chap 4
APPENDIX D
NOTATION
Drainage area, acres, total area of clear opening, or cross-sec-
A
tional area of flow, ft2.
Allowable headwater depth, ft.
AHW
Width, ft.
B
c
Coefficient.
Height of culvert barrel, ft.
D
Depth or thickness of grate, ft.
d
Critical depth, ft.
dc
Infiltration rate, in/hr.
F
g
Depth of water, ft.
H
Headloss due to friction, ft.
Hf
Headwater, ft.
Distance from culvert invert at the outlet to the control eleva-
hO
tion, ft.
Rainfall intensity, in/hr.
I
Hydraulic gradient.
i
K
Constant.
Coefficient.
Ke
k
Coefficient of permeability.
Length of slot or gross perimeter of grate opening, or length, ft.
L
Adjusted length, ft.
L1
Length of spiral, ft. (nonsuperelevated channel).
Ls
Length of spiral, ft. (superelevated channels).
Lt
Manning's roughness coefficient.
n
Discharge or peak rate of runoff, cfs.
Q
Hydraulic radius, ft.
R
Radius of curvature center line of channel, ft.
RC
s
Slope of energy gradient, ft/ft.
so
Slope of flow line, ft/ft.
Top width at water surface, ft.
T
Tailwater, ft.
v
Mean velocity of flow, ft/sec.
Discharge velocity in Darcy's law, ft/sec.
v
Depth of water, ft.
Y
D-1
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