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Basic Node Modeling Question

Basic Node Modeling Question

Basic Node Modeling Question

I have a site that has a topographical high point in the center which drains into two separate drainage areas (wetland drainage ditches/swales).  The drainage areas are paralel to each other and run straight through the site.  

My question is, how detailed does the routing diagram need to be?  I delineated the drainage area in a great amount of detail on the topo map, however, I would end up with close to 40 nodes to define each drainage pattern.  Do I need a node for every change in slope?  Part of my problem is that the drainage area (or valley) receives drainage along the entire length of the site - do I need to stress about the channel length when the channel is receiving runoff along the entire length?

Any information or advice is greatly appreciated.  I am not a civil engineer and have little experience with this level of detail with the modeling and just want to get a reality check.

I have gone through the tutorial and manual and can not find any clear guidance on this topic.  

Thank you in advance.

RE: Basic Node Modeling Question

Your question really pertains to the use of the basic SCS/NRCS methodology, rather than HydroCAD itself.  You may want to review some of the general background material in the HydroCAD Owner's Manual and Training Manual, as well as the TR-55 manual, which has several examples concerning subcatchment delineation and Tc calculations.

As a general guideline, use the simplest model that will meet your design and modeling objectives.  It's possible that your site may have just two subcatchments, with each swale represented as a flow segment (channel flow) within the Tc calculation.

For a discussion of channel modeling options please see www.hydrocad.net/reach.htm

For general Tc issues see www.hydrocad.net/tc.htm

Also please see the general how-to at www.hydrocad.net/howto.htm

Peter Smart
HydroCAD Software

RE: Basic Node Modeling Question


How big is the site?  

You say you have little experience with this level of detail. I am not trying to be judgemental, but it concerns me that you have 40 nodes for 2 drainage areas.  I would typically expect 2 nodes for 2 drainage areas.  As Mr. Smart suggested, this sounds like a matter of becoming educated in SCS hydrology.

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