How can I model in PondPack storm events with different return periods and durations using the dimensionless rainfall curves from NOAA? For example, 100yr-1h-1stQuartile-10percentile, 100yr-24h4thQuartile-90percentile, 2yr-1hr1stQuartile-10percentile, and so on..... I already created the dimensionless rainfall curves and exported into the Engineering Libraries.
Hello Jose,
Once you have created the storms, you would apply these to scenarios through the Rainfall Runoff alterative and the Global Storm Events manager. You will want to have scenarios created for the different storm events would will be using (2 year, 100 year, etc.). Each of these scenarios will have a unique rainfall runoff alternative.
Once you have created these and have them assigned, go to Components > Global Storm Events. You will see each of the Rainfall Runoff alternatives listed there and a column for the storm event. Click in the cell and choose the appropriate storm for the scenario. Below is an example of this from one of the sample files that come with PondPack:
These sample files may be useful to see the general setup of scenarios and alternatives for a model. You can find the sample files by going to C:\Program Files (x86)\Bentley\PondPack\Samples.
Regards,
Scott
Thanks Scott,
I have a follow up question.
Before creating the scenarios and alternatives; in the Storm Data Window, how do I differentiate, for example between a 100-yr, 1-hr 1stQuartile, 10%(percentile) event from a 100-yr, 24-hr, 1stQ, 90%??
The number of scenarios you would want would be related to the number of storm events you want to model. If you want to model both the 100-year 1-hour storm and the 100-year 24-hour storm, I would recommend having two scenarios.
Just to add - each of the storms would be a separate storm item in the Storm Event Group, and you can label them accordingly:
(See: How can I apply a rainfall depth or intensity to a dimensionless curve to create a storm event? )
You would then assign each storm to its own scenario as Scott mentioned. The "Create new Pre/Post Scenarios" wizard can potentially help with creation of the necessary scenarios and alternatives.
Jesse DringoliTechnical Support Manager, OpenFlowsBentley Communities Site AdministratorBentley Systems, Inc.
Answer Verified By: José Díaz
Scott,
In the attached screenshot , how do I create a second 100-year event with a 24-hour duration. I'm stuck trying to figure that out.
DOCX
Jose, see my previous reply and the article I linked to, which explains how to construct a storm event based on available (or user-entered) dimensionless distributions. After creating the storm event group, on the right side you would choose to create a new storm, and choose the "...from dimensionless" option, select the distribution, then enter the label, depth, and duration. The included Huff distributions are both dimensionless time and time so you can apply any depth and duration, but some distributions like the SCS Types are not dimensionless time and are locked at 24 hours.
Thanks Jesse,
I got it know!
Just one last question (maybe).
Is it possible to assigned the time increment for the time-depth graph generated from the dimensionless curve?
For Example, for a 1hr storm pond pack use 5 min and I need it to be 2 min
Jose,
The increment of the generated storm appears to be based on the number of rows in the dimensionless curve. For example for the "Cir173" dimensionless rainfall curve library, each curve has 100 rows, so the generated storm event has 100 rows. Therefore a 24 hour duration storm has 1440 minutes / 100 = 14.4 minute increments.
Why do you need the storm to have a specific increment if the storm event is already created for you? If the Output increment in the calculation options is less than 5 minutes, interpolation will be used and the calculated results from model elements will still be at the smaller timestep.
Its a requirement/guideline from the regulatory agency:
24-hr storm duration -- 30 min interval
12-hr storm duration -- 15 min interval
6-hr storm duration -- 10 min interval
1-hr storm duration -- 2 min interval
Ok, but when they say that you must have a 2 minute "interval", does that specifically mean that you need to be able to report the data input of the storm event in 2 minute increment, or does it mean that they need to be able to see hydraulic results like catchment runoff in 2 minute increments, or something else?
If you really need to see the input storm event in 2-minute increment, you would either need to: