CHAPTER 7 - WEIRS

14. Velocity of Approach Corrections

If the traditional standard weirs need correction for excessive velocity
of approach, then their limits, as expressed in the previous sections,
have been exceeded. Velocity cannot be effectively corrected by adjusting
head alone as done with older procedures. Recognizing this limitation is
probably the reason for the development of the Kindsvater equations and
methods, which account for velocity of approach caused by allowing partial
contraction. Thus, Kindsvater methods will directly recalibrate most
rectangular and triangular weirs with excess approach velocity. Correcting
a Cipoletti weir reading is more difficult, and (1/4)*h*_{1}
must be added to the crest length to approximate a rectangular overflow
opening. Then, the Kindsvater-Carter relationship is used to calculate
discharge for both the fully contracted discharge case and the partially
contracted case, causing the excess velocity of approach to determine the
correction discharge ratio to apply to the Cipoletti table or equation
value for discharge.