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Can HydroCAD do this?

Can HydroCAD do this?

Can HydroCAD do this?

(OP)
I may be in a situation soon where I have to show an analysis to a reviewer of how much runoff reduction an infiltration system provides over the course of a year. I suspect I'll need to punch in a hyetograph for an entire year on a day by day basis, route it, and compare rainfall totals to volumes of runoff and volumes of infiltration.

The system is already designed in HydroCAD, the question is how to do 365 days worth of back to back storms in it, and where to get the data. Alternately, what other software could handle it. I'd like to avoid EPA-SWMM if I could, for headache reasons.

Ideas?

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com

RE: Can HydroCAD do this?

HydroCAD has no preset limit on the time span or number of time steps, so studies longer than the traditional 24 hours are certainly possible. However, for very long time spans you will probably want to use a larger time step, simply to control the memory and calculation requirements. For example, a step of 0.5 hours over 365 days would require a reasonable 17,520 ordinates.

In order to run for a full year, you will need to increase the default maximum time span of 999.9 hours.
1) Open the project
2) Open the Settings|Units screen
3) Click the CUSTOM button
4) Scroll down and check the "RealTime" parameter
5) Change the maximum value to 9999 hours (more than a year)
6) Click OK a couple of times.
Now you will be able to set a time span of slightly over a year. Remember to increase the time step for your initial test. You can always reduce it later depending on the speed and available memory in your PC.

Peter Smart
HydroCAD Software
www.hydrocad.net

RE: Can HydroCAD do this?

(OP)
Any idea where I could get a year's worth of rainfall data, and what format that would need to be ported into HydroCAD?

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com

RE: Can HydroCAD do this?

(OP)
Well, here's the data. (see attachment) I'm guessing the next step would be to convert that to a HydroCAD storm file using the incremental rainfall depth option?

Is there any way to set the unit up to be days, or at least have each data point be 24 hours worth? I don't relish entering 9000 numbers into a text file sideways.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com

RE: Can HydroCAD do this?

Your could use cumulative or incremental depth values. In either case you can paste the entire column into the HydroCAD rainfall editor, block out the values with a single "depth=" at the start, and use the "Reformat" button to break it into lines. For example:

depth=
1
2
3
4

becomes:

depth= 1 2 3 4

However - The SCS/NRCS procedure is a single-event model, where the initial abstraction is applied only once at the start of the storm. If you're trying to run a continuous simulation you may need a different runoff methodology.

Peter Smart
HydroCAD Software
www.hydrocad.net

RE: Can HydroCAD do this?

(OP)
If the initial abstraction is only being applied once, would that mean that the SCS procedure is producing a conservative (=higher) estimate of runoff volume than you'd expect in reality?

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com

RE: Can HydroCAD do this?

Yes, the single application of the initial abstraction will increase the predicted runoff.

Peter Smart
HydroCAD Software
www.hydrocad.net

RE: Can HydroCAD do this?

Not to butt in on your discussion, but how would HydroCAD handle the antecedent soil moisture with multiple storms? To what extent would infiltration be reduced?

RE: Can HydroCAD do this?

gbam - The AMC setting is used to adjust the curve number(s), which in turn changes the initial abstraction and runoff excess calculations. If you use AMC III (wet), all the CN values are increased and there will be less infiltration.

Peter Smart
HydroCAD Software
www.hydrocad.net

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