Compound Weir Discharge

A mathematical model for computing the discharge over a compound weir was developed by separating the weir shape into geometrical elements, computing the discharge through each element using well-known equations for weirs and orifices, and summing the individual discharges through each element. The method was checked and the discharge coefficients were evaluated by a physical model. The accuracy obtained was well within practical needs. The results obtained suggest that similar methods can be used for related practical applications. The weir modeled was U shaped in plan. When linearized the shape was a high level trapezoid superimposed on a low level trapezoid. To prevent overbank flow from dropping into the channel and eroding the channel banks near the spillway, the low weir was sized to have a capacity equal to that of the approach channel at bank-full dishcarge.