How to incorporate NOAA Atlas 14 rainfall distributions?

  Product(s): PondPack, CivilStorm, SewerGEMS, StormCAD
  Version(s): CONNECT Editiion, V8i
  Area: Layout and Data Input


How can NOAA 14 rainfall information be incorporated into the Storm-Sewer products and PondPack to simulate catchment runoff?


You can obtain cumulative rainfall depth data for a range of events from the NOAA Atlas 14 website. In Pondpack, CivilStorm or SewerGEMS, this would be used to construct a Time-Depth storm event and use it with the unit hydrograph method for example. This website does not provide data in the proprietary XML format used by the Bentley products, but that information can be entered in the Bentley product and exported to the engineering library if needed for future models.

Note: Starting with the CONNECT Edition Update 3 (version release of the Storm-Sewer products, it is now possible to import NOAA Atlas 14 storm data into a User-Defined IDF curve for use in StormCAD or the GVF-Rational solver. See the workflow below on how to do this.

For SewerGEMS, CivilStorm, and PondPack using Time-Depth storms

Here are the steps to obtain this information, as of June 2017:

1) Navigate to the link above, select your state and click "load"

2) Select your station from the list and click the "supplementary information" tab.

3) Under "Temporal Distributions", select your duration and click Submit

4) Download and open the CSV file and determine how the information is configured. See below two cases:

Configuration #1 - explicit time:


Configuration #2 - dimensionless time

5) Locate the desired quartile (such as First) and percentage or occurrence (such as 90%). For case #1 (explicit time), it would be the data below the column with header for the desired percent occurrence. For case #2 (dimensionless time) it would be the data in the row that has the percentage of occurrence shown on the far left side. See highlights above for 90% occurrence for the first quartile.

6) For case #1 (explicit time), copy the desired column of cumulative percentages and note the duration (such as 24 hr) and increment (such as 0.5 hr). For case #2 (dimensionless time), note the cumulative percentages (row of data in the highlighted example above) and respective percentage of duration values. As an example, using the image above, the cell within the red highlight with a value of 7.4 has a percentage of duration above it (the row with "percent of duration" on the left side) of 8.3. So, this means that at 8.3% of the total duration (1.992 hours for a 24 hour duration) the cumulative depth is 7.4% of the total depth.

7) In the OpenFlows product, open the Engineering Libraries (Components tab > Engineering Libraries), right-click Dimensionless Rainfall Curves and create new library. After you create the library, right-click on it and "Add Item." Highlight the new item, and on the right side, select "Time" as the dimensionless time type for case #1, or "Dimensionless Time" for case #2.

8) Click the ellipsis (...) button next to the "Dimensionless Depth Collections" field. Click the yellow pencil button, enter the end time (such as 24 hr for case #1) and increment (such as 0.5 hr) to match what you saw in step 6.

For case #2, the Increment is taken from the "percent of duration" header row in example above. (In the example data, the increment is a repeating decimal and needs to be entered very precisely, such as 0.083333333, or else the end time of 1.0 should be adjusted slightly to be an even multiple of the increment as entered.) The end time for distribution with dimensionless time is typically 1.0.

9) Click OK. For case #1 (explicit time), you can paste in the column of percentages from step 6 (starting from 0 and ending at 100) using CTRL+V

For case #2 (dimensionless time) the data in the NOAA source spreadsheet is contained in a row. You could type or paste in the values one by one, or first convert this row to a column in Excel and copy from there.


10) Click OK, close the Engineering Library Manager, open the Storm Events manager.

11) Follow the steps in the below article, adding a new "Time-Depth" event: How do I import a return event for a dimensionless curve from the engineering libraries?

Note: You can saved your Storm Event to the Enginerring Libraries, as mentioned here: Reusing storm events across multiple projects and computers.

StormCAD or the GVF-Rational Solver with IDF curves

Starting with the CONNECT Edition Update 3 (version release of the Storm-Sewer products, NOAA Atlas 14 data can now be imported into the Storm Data manager as a User-Defined IDF Table. Create a new User-Defined IDF Table storm event, then click the Import button at the top of the Storm Data manager to import a CSV file.\

Note: The NOAA Atlas 14 data will need to saved using intensity data rather than depth.

As with the Time-Depth method, you can saved your Storm Event to the Enginerring Libraries, as mentioned here: Reusing storm events across multiple projects and computers.

See Also

Reusing storm events across multiple projects and computers

How to create storm events using NRCS's six regional rainfall distributions for California