2016 Rainfall IFD Data System

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How to use the design rainfall system

The new design rainfalls (including the Intensity-Frequency-Duration (IFD) design rainfalls) are retrieved through location-based searches using the following method.

  1. Acknowledge and accept the conditions of use and the coordinates caveat. You must agree with these conditions in order to proceed.
  2. Enter your location information in the Search panel. To choose a type of location coordinate, select on of the following:
    • Decimal degrees: Fill in your latitude and longitude. Whilst the system will accept both positive and negative degree values, it will assume a southern latitude and an eastern longitude as the coordinates are only valid over Australia.
    • Degrees, Minutes, Seconds: Fill in your latitude and longitude as degrees, minutes and seconds. Take note of the degrees sign information above.
    • Easting, Northing, Zone: Fill in your easting, northing, and zone.
  3. If desired, enter text into the label field which will be printed on the generated design rainfalls, to help you identify your results.
  4. 'Map Preview' will show the submitted location on a map for you to review.
  5. Select 'Submit' once you are happy with the location. The default table will be displayed.
  6. Select the probability range applicable for your project.
    • Very Frequent - 12 EY to 0.2 EY
    • IFDs (Frequent and Infrequent) - 50% AEP to 1% AEP
    • Rare - 1-in-100 to 1-in-2000 AEP

    Find out more about the probability terminology here

  7. Update the standard and non-standard durations to suit your analysis requirements.
  8. Select 'Update' to apply these changes.
  9. The design rainfall values for the location have now been extracted. You can view it as a table, or a chart (graph of data). The date of issue is included for reference.
  10. The 'Reset' button will remove any user-specified modifications and return to the default settings.

Downloading design rainfalls

Design rainfalls can be downloaded and printed in several formats.

Download as CSV: Allows the user to download the table as a CSV text file.

Download as PNG: Allows the user to download the chart as a PNG image file.

Print Screen: Opens a print dialogue on a separate screen.

You also have the choice of saving the table or graph first and then printing those files directly.


Units

The new design rainfalls are displayed in units of depth in millimetres (mm) by default. There is an option to change the units if you require design rainfall values in intensity, in millimetres per hour (mm/h). This functionality is located on the web page above the table or chart on the right-hand side.

Rainfall depth and rainfall intensity are related as follows:

  • intensity (mm/h) = depth (mm) / duration (hours)
  • depth (mm) = intensity (mm/h) x duration (hours)

  • Labelling

    Enter any information desired into the label field to help you identify your selected location. This label will be displayed on the exported chart image heading and the .csv file header.


    Non-standard Durations

    User-defined non-standard durations may be rounded. The rounded value will be displayed in the Design Rainfall table. The rounded value shown in the results table is the value used in calculations, and therefore may differ slightly from the entered value.

    Note: this option is not available for Rare design rainfalls.