dear all,
please do Civilstorm support design using SCS unit hydrograph not only rational method since the rational method gives oversized pipes because it designs on peak flow
note that I am using civilstrom SS4
BR,
Rasha Yehia
If I understand your question correctly then , CivilStorm supports design using Unit Hydrograph, EPA-SWMM Runoff, ILSAX, time-Area & User defined Methods. Whereas if you are designing using GVF-Rational StormCAD solver you will have option of Unit Hydrograph or Rational method.
To understand oversizing in StormCAD please have a look at this support solution.
communities.bentley.com/.../10402.why-is-stormcad-over-designing-the-conduits-during-a-design-run-on-a-system-with-very-shallow-slopes.aspx
Regards,
Sushma Choure
Bentley Technical Suppport
As Sushma mentioned, if you use one of the other available solvers in CivilStorm (SWMM and Implicit dynamic) you can indeed model other runoff methods. If you open the Sample1 model included with CivilStorm for example (located in the Samples folder within the CivilStorm installation folder) you will see that the catchments are configured with the SCS Unit HydroGraph Method. I've added a screenshot at the bottom of this message.
However, if by "design" you mean automated pipe/inlet design - this is a GVF-Rational only feature in CivilStorm. As you mentioned, it designs based on the rational method which simulates peak flows. This is a standard practice in many locations for pipe sizing. If you would like to override the rational method and enter your own peak flows (for example peak from a SCS method runoff hydrograph), you can use the "Flow (Additional Carryover)" field in the properties of your catchbasins.
Jesse DringoliTechnical Support Manager, OpenFlowsBentley Communities Site AdministratorBentley Systems, Inc.
Answer Verified By: Sushma Choure
thanks for you Jesse and Sushma,
but Jesse mentioned that I can use peak flow of SCS unit hydrograph in rational method.
the question is how to make this applicable for automated design.
or how can I use additional carryover flow in civilstorm for design,i mean where I can enter this value of carryover to represent Peak flow?
or the alternative is to design manually each conduit using values of carryover additional flow?
thanks Again
Hi Rasha,
My suggestion would basically replace the rational method with user defined flows. Meaning, you would not have catchments in the model (so no runoff calculations) but rather enter the desired peak flows directly into the catchbasins (and those peak flows could be based on an external calculation from the SCS method for example). You can then set the calculation model to Design in the calculation options and it will size the pipes and inlets as it normally would, except it would be using the user-defined flows that you enter instead of flows calculated from the catchments using the rational method.
When you have the active numerical solver set to GVF Rational, you'll see the additional carryover flow field in the catchbasin properties:
thanks Jesse I got your nice idea