(PONDPACK) - Modeling an inlet box with a Cipoletti weir on the side

Question

I am trying to model a trapezoidal weir on the side of an inlet box. In my composite outlet structure I am using a riser, a culvert and a weir. The max headwater is set to the top of the pond at 885 feet. The inlet box has a top elevation of 882 ft. I'm using the "outlet structure (riser)" component to model the weir at the top of the box which is 51 feet with an area of 123.8 feet. I am using a separate weir to model the irregular weir on the side of the box which will have an elevation of 872.67. When I try to compute the rating curve for the composite outlet structure, I get an error message saying that top of the weir needs to be equal to the max HW of 885. 
 Am I using the correct approach to model this scenario? Can this trapezoidal weir be modeled within the Riser component of the composite outlet structure instead of using a separate weir?

Sushma Choure · Answer

Hello Luis, 
 Top of your weir in the cross section table is equal to the maximum headwater of the upstream pond and not above it and the maximum tailwater is less than or equal to the maximum headwater. Once you correct it, error message should no longer appear. See below link for details. 
 User Notification: Cross section maximum elevation is above the maximum headwater elevation 
 Below is an example of modeling riser control structure for pond. 
 
 If you are modeling weir element separately you could specify its dimension, on / off conditions etc. 
 As a reference have a look at sample model - Pre and Post Pond Design located at C:\Program Files (x86)\Bentley\PondPack\Samples. 
 
 Here is information for modeling riser control structure for your reference. 
 Modeling Riser Pond Outlet Structures