For normal stormwater flow modeling the XPRafts Storms database is a database of average recurrence interval, storm duration and rainfall data.

Design Storm

This option accepts an average intensity in conjunction with a dimensionless temporal pattern usually in the form provided in ARR 1987 for design storm events.

Average Recurrence Interval

The Average Recurrence Interval (ARI) is the interval in years at which, on average, the storm will re-occur.

Average Intensity

The average Intensity is the average rainfall intensity which is obtained by dividing the total rainfall depth by the total storm duration. The units of rainfall intensity are mm/h (SI Units).

Temporal Pattern Reference

The Temporal Pattern Reference is the name of the associated storm temporal pattern from the Temporal Pattern database.

AR R Standard Zone

This option allows for the eight standard temporal pattern zones defined in Volume 2 of Australian Rainfall & Runoff (1987)

Rainfall Distribution

This option is used as an alternative to the Design Storm option when entering real (historical) storm data. The unit of rainfall is millimeters.

Variable Time Step

This option allows rainfall data to be entered in uneven time steps. It is used when longer events of days, weeks or months are being simulated and it is used in conjunction with the “Rainfall Distribution” option. The time interval is in minutes and the rainfall amount is in millimeters.


The duration is the total storm duration in minutes. The duration is used to calculate the interval used in the temporal pattern of the design and also the interval for the Rainfall Distribution option if a variable time step is not selected.