modeling a weir / pipe diversion combination 1

[ssast]

Hi,

I have an existing 6'x6' storm pipe, which I would like to divert a portion of flow from to a proposed detention basin. I would like to place a 14" high x 8" wide weir at invert(136.28') of the existing 6'x6' pipe and place a 12" diversion pipe immediately upstream of the weir - that way the weir would force smaller storm events to flow into the 12" diversion pipe and then to the detention basin, and allow larger storm events to continue over the proposed weir and into the existing 6'x6' pipe. (Please see attached scanned sketch of the proposed diversion)

This is how I would like to model it in HydroCAD:

I have my subcatchement draining directly to the diversion (Pond 1-which I have modeled as a catch basin with insignificant storage). The outlets from pond 1 are as follows:


Device # Invert Description Routing
1 136.28' 12" Diversion pipe Secondary
2 138.00' Ex. 6x6' RCP Main Primary
3 136.28' 14" high internal weir Device 2


Would this be the correct? I have modeled the 12" diversion pipe as secondary and routed to the detention basin. The Weir is routed to the Ex. 6'x6' pipe,which is modeled as primary and linked directly to the outfall.

I have modeled the weir as a custom weir, but I do not have the option to put the 8" weir breadth in - would it be incorrect to model it as a broad crested weir, where I have the option of inputting the 8" crest breadth?

I would really appreciate any advice/comments you have regarding the way I am modeling this.

Thanks!

 

[psmart]

Your approach seems reasonable, but the invert elevations in your example don't seem to be correct. I suspect you want the diversion pipe near the bottom of the 6x6 pipe (about 135.2'), rather than at the crest of the weir. And the elevation for the 6x6 pipe should be 14" below the weir crest (about 135.1).

Peter Smart
HydroCAD Software

http://www.hydrocad.net