Horizontal,
sharp edged weirs (Bazins formula)

Q =
0.66 x cB x (2g)^{0.66} x H^{1.5}
where;
Q =
water flow rate, m^{3}/sec
B =
width of the weir, metres*
c = discharge
coefficient, average 0.62
g =
gravitational constant, 9.81
H = Height of the water
over the weir, measured behind the weir edge, m
*
Note’; if the weir is narrower than the channel feeding it,
shorten B by 0.2xH

Broad
crested (flat topped) weirs

Q =
0.35 x B x (2g)^{0.5} x H^{1.5}
where;
Q =
water flow rate, m^{3}/sec
B =
width of the weir, metres
g =
gravitational constant, 9.81
H = h
x (V2)/2g where, h = height of the water over the weir at the
discharge edge of the weir, m
V =
velocity of the stream across the weir crest, m/sec

V
notch, sharp edged weirs

Q =
0.266 x cB x (2g)^{0.5} x H^{1.5}
where;
Q =
water flow rate, m^{3}/sec
B =
width of the weir at the flowing rate
c = discharge
coefficient, average 0.62
g =
gravitational constant, 9.81
H =
Height of the water over the weir, measured behind the weir edge, m
