question on modeling

[tsli001]

I had other question regarding modeling. Why do people set up up a 'reach' in Hydro CAD setup as a 'total flow', whats the purposed of it? Was it try to cheat it on archieving flow has been reduce?

thanks.

 

[psmart]

Can you clarify your question?


Peter Smart
HydroCAD Software

http://www.hydrocad.net

 

[tsli001]

Let me tell you the whole story. A site has been study,two anaylsis points were established, and two reach 'A' & 'B' was added in the model to represent those two points. One day, a person is interested to know what is the total 'Run Off' leave the site under the model. So, the person believe adding one 'reach' call the 'total flow'and rout 'A' & 'B' reach to the 'total flow' reach, so the added readch can tell the person what is the 'run off' volume. But I think the reason why people but set up the situation like this is just want to make it so people believe the design model has less flot under the Pre vs post condition, and there is nothing to do with telling poeple the what is the 'Run off' volume leave the site. So, what do you think about me opinion on this?

 

[psmart]

You seems to have two threads on the same topic. You'll do better if you keep everything in a single thread...


Peter Smart
HydroCAD Software

http://www.hydrocad.net

 

[PSVT]

I think that I understand the situation. This is more of a policy question than a Hydrocad technical question. But I will comment anyway.

The two study points drain to different receiving waters, and the report seeks to quantify the total site runoff to the two different discharge points. In my opinion, routing them both to the same reach is not appropriate since the peaks can be offset. In this situation, I prefer to sum the two peaks numerically. This does not necessarily reflect reality , but at least it provides for a maximum possible peak discharge leaving the site (like a forced coincident peaking)

I must add that only do this when it is appropriate and it is understood by all parties involved what we are trying to achieve with the modeling. I would be interested in any input on this that others may have.

 

[tnuboston]

you can model reaches in different ways. one way is to provide actual physical contraints for the reach that causes the reach to influence the peak flows. the second way is simply to model a "dummy reach", which is a reach with no physical constraints. this "dummy reach" allows you a simple way to sum the peak flows from the contributing watersheds/basins/ponds etc while accounting for offset tc's.