PondPack Help - Chicago Storm Distributions

Jeff,

Could you elaborate on what your "Chicago storm distribution" consists of? If it is a dimensionless depth curve (time vs. fraction) or time-depth curve, you can enter these into Pondpack using the catalog explorer (View > Catalog explorer.) For example, right click on the "custom" rainfall curve catalog, choose "add rainfall curve" and then select the type and enter the data. Then, you can similarly create a new design storm catalog, use the curve you created and enter in the rainfall depth. Refer to the internal help documentation for elaboration on creating a rainfall curve and design storm. 

If the "Chicago storm distribution" is actually a custom unit hydrograph (T/tc vs. Q/Qp), you can create that under the "unit hydrograph catalog", which is near the bottom of the catalog explorer. You can then select the custom unit hydrograph in the "options" button of the subarea properties.

If the "Chicago storm distribution" is actually a special hydrograph method itself, different from the SCS method, then I'm fairly confident that Pondpack does not currently support it. Pondpack only support the SCS, Santa Barbara, modified rational and Q/Qp template hydrograph methods.

Based on some clarification, other forum contributors may be able to give you some further insight.

As for additional learning materials - we have training classes available, both online and classroom based. Contact your Bentley Account manager for details on that, or check http://www.bentley.com/en-US/Training/

There are also sample models available for you to look at, under the installation folder. For example, C:\Program Files\Bentley\Pondpack\Samples\Bobcat.ppw

Regards,

Jesse Dringoli

Technical Support

Jesse,

Firstly, thank you very much for your reply!

To elaborate a little on chicago storm distributions - Essentially an IDF curve gives you an average intensity for a design storm of given duration/return period. The Chicago method takes that constant intensity and gives it a "peaked" shape over the duration of the storm which more closely models actual rainfall patterns. I believe it can be entered into Pondpack the same as an SCS type curve (i.e time and depth fraction), however I'm trying to figure out if I have converted the IDF storms to the appropriate Chicago storm depth fractions. Hopefully that helps clarify things a little bit...but while I'm here, I may as well ask the next question on my clipboard!

I understand Ponpack can handle oversized horizontal underground pipes as a detention method. I have navigated through the pipe-volume window, and was wondering if I could get a little more clarification on what some of the variables are, such as barrel length, # of barrels, slice width, and vertical increment? Is there anything special that must be done during the analysis to return these volume calculcations, or do you simply run the program as you would designing a pond, and simply change the volume option to "pipe'?

 Again, thank you for the help!

Jeff 

Thanks for the clarification on the Chicago storm. It does indeed sound like you'll need to convert it to a typical rainfall curve for the SCS method.

As for the pipe pond - you would configure your pond to be a pipe by selecting "pipe" as the volume type in the pond node properties. Pondpack internally converts that to an elevation/volume curve to use in the calculation, which you can see if you click the graph tab of the pipe pond and click compute > volume. Here are the definitions of the pipe attributes, per the Pondpack internal help:

Upstream Invert - Set the elevation for Upstream Invert of pipe.

Downstream Invert - Set the elevation for Downstream Invert of pipe.

Barrel Length - Set the length of barrel (not the plan length).

Diameter - Set the inside Diameter of pipe.

Number of Barrels - Set the number of pipes (with same configuration) used for this storage.

Slice Width - Set the incremental Slice Width perpendicular to top and bottom sides of pipe. This is similar to looking at a roll of coins with the thickness of one coin being the incremental slice width. In general, the smaller the slice width, the more precise the computations. The computation speed slows down with smaller increments since one computation is performed for each step increment.

Vertical Increment - Water surface step increment for computing cumulative volume in the pipe. Computations start at the downstream pipe invert and step by the vertical increment. If the upstream invert elevation does not fall on an exact increment, then it is added to the end of the rating table.

If you have additional technical questions on the pipe pond, I'd recommend emailing Support@bentley.com

Jeff,

Yes, I would probably enter this as a 'Dimensionless Depth Curve'  in PondPack (like the SCS curves).

The parameters you need for this type of curve are:

End time - sounds like 24 hrs in your case
Increment - depends on what you Chigago temporal pattern looks like...it might have a data point every 5, 15, 60 mins...
Start time - usually zero

Then, for each time value you need to enter a depth fraction based on your Chicago pattern.

Next you have to add this Rainfall Curve to a Design Storm collection. The Design Storm parameters are mostly self explanatory (and you can take a look at an example like Bobcat Creek under the Stormsrnq folder for help), but it is important to set the rainfall depth correctly. So in your case it would be 24 hrs multiplied by your IDF curve intensity for the 24 hr storm.

If you are still not sure you have it right, maybe you can post the Chicago storm information you have. Somtimes I have seen this given in the form of equations, other times in a curve of intensity vs. time or depth vs. time...so the format of your data will determine the steps you need to take to get this into PondPack.

Regards,

Mal Sharkey
Product Manager
Bentley