Under drain Outlet allows the flows through a Stormwater Controls under drain to be routed to another location. The outlet is only available for Stormwater Controls that provide an under drain, an even then only if it has been turned on.
The outlet type will be chosen by default for the first outlet added when an Under drain is present in the Stormwater Control. It can however be selected from the drop down list
The actual parameters for the under drain are entered as part of the Stormwater Control dimensions, a Porous Paving is shown below as an example:
The parameters are as follows:
Height Above Base - Height of the invert of the pipe above the base of the system.
Diameter - Defines the diameter of the pipe/s.
No of Barrels - Represents the number of pipes.
Friction Scheme - Specifies the formula used to calculate velocity and time of travel. Select from: Manning's, and Colebrook-White. The variable below the combo box depends on the option selected.
n - Manning’s n roughness value. Used by the Manning Formula equation to calculate the velocity and therefore time of travel when using the Manning's option.
Roughness - Colebrook-White roughness value. Used by the Colebrook-White Formula equation to calculate the velocity and therefore time of travel when using the Colebrook-White option.
Release Height - Height above the invert of the under drain pipe at which the water is released. This is commonly used to create a saturated zone.