AutoCAD Civil 3D - Stormwater

AutoCAD Civil 3D - Stormwater

Active Member
Posts: 7
Registered: ‎04-12-2012
Message 1 of 4 (551 Views)
Accepted Solution

Simple Stormwater Routing in SSA

551 Views, 3 Replies
06-04-2012 01:35 PM

I'm trying to make a direct comparrison of a SSA Routing (Basin Runoff to Pond with outfall to a weir / orifice tied to a junction followed by a pipe and then the outfall.  For some reason the peak flows generated discharging into the pond are excessive, while the flows generated from the basin (~3 acres in area) ruonoff are very reasonable.  Perhaps someone may be able to offer some feedback. 


Again the scenario being modeled is very basic / straightforward.


Thanks in advance for anyones feedback.



Active Contributor
Posts: 32
Registered: ‎12-05-2011
Message 2 of 4 (542 Views)

Re: Simple Stormwater Routing in SSA

06-05-2012 04:55 AM in reply to: carlirwin3430

There are a few things I noticed in taking a quick look at your model. You should take a look a the elevations and the storage curve you have set up. Your first entry should be a depth of '0' and increase from there. In the Storage Node dialog box you set invert elevations and in the Storage Curve inputs you have to enter "depths". 


It looks like somthing is wrong with the weir link. The water surface elevation in your basin has not reached the crest elevation the the weir but it is flowing 45cfs. Also, you are not getting any rating curves forthe weir.


I would either try recreating the weir link or starting the model over. It is a fairly simple model with few inputs.

Active Member
Posts: 7
Registered: ‎04-12-2012
Message 3 of 4 (539 Views)

Re: Simple Stormwater Routing in SSA

06-05-2012 06:14 AM in reply to: rdbrennan48
Thanks for the feedback. Updated the storage component, adding a depth of "0" as suggested. Also, re-input the weir, however, still getting excessive flows over the weir. I'm also not getting a weir rating curve for some reason. Again I have developed a simple model for comparison with another proprietary model. Any additional help is greatly appreciated. Thanks, Carl Carl H. Irwin, P.E. Advantage Engineering, Inc. 3914 Flatiron Loop, #102 Wesley Chapel, Fl. 33544 Ph. 813/267-8976 Fax 813/994-5265 To help the families of our fallen soldiers consider donating $10 to the Navy SEAL Foundation. Text the word SEAL to 90999 and a one-time $10 charge will be added to your wireless bill. You will receive a text asking to confirm your donation.
Posts: 2,909
Registered: ‎05-13-2005
Message 4 of 4 (538 Views)

Re: Simple Stormwater Routing in SSA

06-05-2012 06:58 AM in reply to: carlirwin3430

Carl -


Here are a couple of tips:


1.) Invert of the pond is currently at zero.  The weir is at elevation 12.  This is why the rating curve does not calculate.  Edit the Pond Invert to 9.5.


2.) Review the Analysis options and change the Routing time step from 30 seconds to 1 sec.  Change the Reporting time from 5 minutes to 1 minute.


3.) Change the Lenghtening time step to 15 seconds.


The model will run and be stable. 

Matthew Anderson, PE
Product Manager
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