The minimum Tc is applied only if you enter a Tc value for the subcat. You can even enter zero, but there must be at least one Tc segment in order for the minimum Tc to be applied.
The minimum Tc is normally used to avoid very small values (a few minutes). Since you have a significant Tc of...
At the water/media interface you would use an exfiltration outlet at 2 in/hr. Since the media is acting as an outlet control, the pond storage should include only the open space above the media. Any water below that point is not part of the same level-pool and ignored as far as the pond...
It is assumed that all the pond storage is interconnected so that it will fill from the bottom-up, always maintaining a level pool. The outlet devices, including exfiltration, regulate the flow of water out of the defined storage.
The problem with your setup is that you are attempting to...
If you set different routing for each device (primary, secondary, etc,) you will see a separate rating curve for each device. But a compound outlet will be displayed with a single composite curve.
Peter Smart
HydroCAD Software
www.hydrocad.net
As a rough approximation you could use a Vee weir with the vertical height of the sloped weir, and set the discharge multiplier to allow for the longer crest length (along the slope) Otherwise you may have to do the hydraulics for the sloped v-weir by hand and enter it into HydroCAD as a custom...
You would find it much easier to do the Tc calcs in HydroCAD. It's also an easy way to compare the different Tc options. There shouldn't be as much of a difference as you're running into with your hand calcs.
The most common approach, as recommended by NRCS, is to use a segment of sheet flow...
Since you have confirmed that at two separate programs provide a similar result for the SCS method, yes, I would trust that result. So this comes down to a matter of how you have chosen to model the area in question.
Give the size of the the watershed, I suspect that treating it as a single...
As you have found, those equations do not reflect a complete runoff calculation using the SCS method, as implemented in HydroCAD and other programs. You have used the equations for generating a single unit hydrograph, but this must be applied to each rainfall burst and not the total rainfall...
I see a weir/orifice in front, but cannot be sure what's inside. Perhaps a pipe? If so, outlets would be:
Device#1=Culvert, Routing=Primary
Device#2=Rect. Orifice at 45 deg, Routing=Device#1
For details see www.hydrocad.net/pond1.htm
Peter Smart
HydroCAD Software
www.hydrocad.net
I'm not surprised. There isn't much storage behind a check dam. They will cause a slight flow reduction based on increasing the overall "roughness" of the channel, but don't expect a big effect.
From www.hydrocad.net/checkdams.htm
As always, remember to use the simplest model that will...
When modeling any pond you need to provide complete storage data in order to get an accurate routing. Otherwise you will get get a "storage exceeded" warning and the pond behaves like a closed vault - not what you want with a check-dam.
I would go a foot or so above the crest. It depends how...
You need to define the storage up to the maximum WSE, whatever that may be. I suspect it's more than 1/10 foot above the crest.
I assume you have also defined the storage impounded by the check dam? You can generally just add another stage to that storage definition.
Peter Smart
HydroCAD...
Since you already have a weir to handle the overflow, you should NOT use automatic overflow. These are mutually exclusive.
A weir is more accurate, but make sure you define storage ABOVE the crest in order to handle the maximum WSE. Check the warning messages...
Peter Smart
HydroCAD...
Looks reasonable. But what is the objective for your HydroCAD model? As you can see from the hydrograph, the check-dams have very little effect on the inflow hydrograph. You have minimal storage, so the water than doesn't pass through the check dam simply passes over the top.
Also see...
Like all user preferences, the saved reports are stored in the registry only when you close HydroCAD. If the program is interrupted without doing a normal exit, settings are not saved.
Also be sure you are running HydroCAD 10.2-4b or later. Earlier versions would loose ALL saved reports after...
OK, that makes more sense. I would expect an actual box pipe to report both width and height. I suspect the word "Box" in your report was manually entered as part of the device name or the inlet geometry, rather than being automatically generated by HydroCAD.
Peter Smart
HydroCAD Software...
Since the report shows just one dimension, this suggests that it's a square box, but I would have to go back and reinstall 7.1 to know for sure.
Peter Smart
HydroCAD Software
www.hydrocad.net
