Sluice Gate

An example sluice gate with a broad crest is shown in the figure below.
Example Sluice Gate with Broad Crested Spillway

The equation for a free flowing sluice gate is as follows:

1)	$\begin{array}{l}\displaystyle Q=CWB \sqrt{2gH}\end{array}$

Symbol	Description	Units
$\begin{array}{l}H\end{array}$	Upstream energy head above the spillway crest ( $\begin{array}{l}Z_U - Z_{SP}\end{array}$ )
$\begin{array}{l}C\end{array}$	Coefficient of discharge, typically 0.5 to 0.7

When the downstream tailwater increases to the point at which the gate is no longer flowing freely (downstream submergence is causing a greater upstream headwater for a given flow), the program switches to the following form of the equation:

2)	$\begin{array}{l}\displaystyle Q=CWB \sqrt{2g3H}\end{array}$

Where: $\begin{array}{l}H=Z_U - Z_D\end{array}$

Submergence begins to occur when the tailwater depth above the spillway divided by the headwater energy above the spillway is greater than 0.67. (2) is used to transition between free flow and fully submerged flow. This transition is set up so the program will gradually change to the fully submerged Orifice equation (Radial Gates:3) when the gates reach a submergence of 0.80.