("Angle in Radian = between0.349 - 1.75 )
h
Cd
m3/s

Formula

q = 8/15 ×Cd/ ×(2g)1/2 ×tan(θ/2) ×h3/2

Where,
q = Flow Rate
Cd = Discharge Constant
θ = V - Notch Angle
g = gravity (9.81 m/s²)
h = Head on the Weir