Step-by-step guide

When working in a region that is not covered by one of the standard rainfall theories provided within the program, a rainfall definition can be built. This is done by entering two pieces of information: the IDF curve or curves, and the dimensionless shape curve.

Two IDF curve graphs. The top one shows an IDF table for three different return periods of 2, 30, and 100 years, with the Average Intensity in mm/hr along the Y-axis and the Duration in minutes along the X-axis. The bottom graph shows a curve that represents Cumulative Depth Percentage over Time Percentage.

First, create a new rainfall event:

On the ribbon, Rainfall Pollutants tab, Rainfall panel, click Rainfall Manager.
In the Rainfall Manager toolbar, click New.

In the InfoDrainage interface, the open Rainfall Manager, with the New button called out with a red arrow; and in the background, the Plan View of the model used for this example.

Name the rainfall event. In this example, it is named “Test 1”.
Click Save.
Under Rainfall Manager Items, expand the IDF node to access the IDF library.
Since this example uses a series of curves, select Table IDF to create a table of events. For a single curve, Single RP IDF would be selected.

In the Rainfall Manager, under Rainfall Manager Items, IDF is expanded, and Table IDF is being selected.

Open the spreadsheet that contains the curve data.

This example uses data for the IDF curves for three storm durations, and temporal patterns for the dimensionless curve data. Start with the IDF data.

The data for this example in an open Excel spreadsheet, with IDF curve data for three storm durations, as well as the dimensionless curve data.

In the Rainfall Manager, with Table IDF selected, click Add (+).
Ensure that Rainfall Intensity is enabled.

Next, create columns for each of the three return periods:

In the table tools, click Add (+).
In the Add Return Period popup, in the Return Period (years) field, enter 2, for the 2-year return period.
Click OK.

In the Rainfall Manager, the settings for the new Table IDF item are active, and in the Add Return Period dialog, a value of 2 is entered, and OK is being selected.

Repeat steps 10 – 12 to add the 30-year and 100-year return periods.

To delete the 1-year return period, which is not needed for this example:

In the Rainfall Manager table, select the 1-years (mm/hr) column header.
Click Delete (-).
In the spreadsheet, select the data, making sure not to include the headers.

A zoomed-in view of a portion of the spreadsheet, showing that only the IDF curve data for the three storm durations is being selected.

Press Ctrl+C to copy the data to the clipboard.
Back in the Rainfall Manager, in the table, click the first cell under Duration.
Press Ctrl+V to paste the data.
In the Items list, right-click the new Table IDF item and select Rename.
Type “Test 1” to match the project name.

In the Rainfall Manager, under the Table IDF settings, the IDF curve data from the spreadsheet has been pasted into the table; and in the Items list, the new Table IDF item has been renamed to “Test 1”.

Next, enter the temporal pattern data, which again, is the dimensionless relationship data that defines the curve:

In the Rainfall Manager Items list, click Temporal Pattern.
In the toolbar, click Add (+).
Under Temporal Pattern, next to Label, enter a name, such as “Test 2”.
Expand the Profile Type drop-down and select Custom – Dimensionless.

In the Rainfall Manager, under Temporal Pattern, a “Test 2” item has been added. Also, in the Test 2 temporal pattern settings, the Profile Type drop-down is expanded, with Custom – Dimensionless selected.

Leave the Editable Column set to Cumulative.
In the spreadsheet, select and copy the Percentage time values, from a non-zero value, such as 5, through 100.

A zoomed-in view of a portion of the spreadsheet, showing that, under Temporal pattern, the Percentage time values from 5 to 100 are being selected.

In the Rainfall Manager table, under Time (%), paste the values.
From the spreadsheet, copy the data under Percentage depth.
In the table, under Cumulative (%), paste the values.

In the Test 2 temporal pattern settings, the Time (%) and Cumulative (%) data pasted into the table, with the Absolute (%) column populated.

Now, bring the IDF curve and the shape of the event together to create a series of user-defined rainfall events.

Under Rainfall Manager Items, expand the Design Storms node.
Select User Defined Rainfall.
Click Add (+).
In the Label field, type “User Defined Rainfall 1” to rename it.

In the Rainfall Manager Items, the Design Storms node is expanded, and a new User Defined Rainfall item has been created. And under the User Defined Rainfall 1 settings, in the Label field, a new name is entered and highlighted in red.

Click OK to close the Rainfall Manager.
Reopen the Rainfall Manager.

Closing and reopening the Rainfall Manager enables the library to update. The User Defined Rainfall 1 Design Storm remains active, and on the Storms tab, the Create From IDF tool is now available.

In the reopened Rainfall Manager, the still-active User Defined Rainfall 1 Design Storm is highlighted in the Items list, and on the Storms tab, the new Create From IDF tool is highlighted in red.

Click Create From IDF.
In the User Defined Rainfall From IDF popup, select From Library.
Expand the drop-down and select the Test 1 IDF curve.

The return period information appears.

Expand the Return Period drop-down and select 30-years.

In the User Defined Rainfall From IDF popup, the Return Period drop-down is expanded, with 30-years being selected.

Click OK.
In the Label field, add “30 years” to the name for easier identification.
Press ENTER to accept the change.
In the table, in the Temporal Pattern column, expand each drop-down and select Test 2.
Enable Use for all rows.

In the Storms table for the User Defined Rainfall 30 years item, Use is selected, and the Temporal Pattern is set to Test 2 for all nine rows.

This means that these nine rainfall events will be used with the Temporal Pattern set to Test 2.

Click the Temporal Patterns tab to double-check that it displays the data entered.

On the Temporal Patterns tab, the Test 2 Label is highlighted in red, and the relevant data is displayed in the table.

Click the Increase Rainfall tab.

Adding in an aspect of climate change could be done here.

On the Increase Rainfall tab, Use is selected and highlighted in red next to the Increase Rainfall (%) field, where a value can be entered.

Click Save to save the rainfall definition.
Click OK to close the Rainfall Manager.

NOTE: this same rainfall later can be reused later, if needed.

Now, run an analysis using the data:

On the ribbon, Analysis tab, Criteria panel, click Analysis Criteria.

In the Analysis Criteria dialog box, the User Defined Rainfall 30 years set of curves is now available, and crucially, there are nine rainfall events matching the nine chosen.

The Analysis Criteria dialog box showing the new rainfall data, with User Defined Rainfall 30 years selected, and the Number of Storms highlighted to show 9 rainfall events.

Click OK.
As a best practice, on the ribbon, click Validate.
In the Validate dialog box, click OK.
On the ribbon, click Go.

NOTE: Since the model used in this example is small—40 manholes and 40 pipes—and only 9 storms are used, this does not take long to process, but a larger model may take longer.

Once the simulation is finished, the Stormwater Controls Summary appears.

The Stormwater Controls Summary displays a table of results for the rainfall analysis.

However, the results can be viewed in several different ways:

Close the summary.
On the ribbon, click the Results tab.
As an example, in the Item Results, expand the Inflows drop-down and select S29-DA.

In the graph, flows entering or leaving an inflow area, or flows entering a manhole can be reviewed. Specific rainfall events can also be selected.

On the ribbon, Results tab, Item Results panel, the Inflows drop-down is highlighted in red. Below the ribbon is the Results window, where a new flow graph shows the results of the user-defined rainfall. In the Flow Graph, the Rainfall and Total Inflow for the selected area show as bell curves, with Flow in L/s and Rainfall in mm/hr along the Y-axis, and Time in minutes along the X-axis.

In the Event Selection panel, expand the Select Event drop-down and choose a different rainfall event, such as 240.
In the graph, deselect the Total Inflow to see only the Rainfall.

On the ribbon, Event Selection panel, in the Select Event drop-down, the selected event is highlighted in red. Below, in the Results window is the Flow Graph. The Total Inflow option is deselected, while the Flow Graph shows the stepped bell curve shape of the rainfall for the selected event, with Rainfall in mm/hr along the Y-axis, and Time in minutes along the X-axis.

In this case, because it is a 1-in-30-years storm, 240-minute event, the maximum intensity is a little more than 26 millimeters per hour.

Creating rainfall data for determining temporal patterns is a straightforward process, provided the IDF curve and shape curve data for the area of interest is available.

Conducting a Quick Storage Estimate

Video quiz

Which of the following is NOT critical for calculating an appropriate pond size?