These rainfall curve distributions are typically developed based on statistical analyses of storm data for different durations. When developed properly for a specific location, these types of rainfall distributions provide the flexibility of modeling a variety of storms other than the standard 24-hour event.

The basic philosophy of this approach is that longer-duration storms are expected to behave differently than shorter-duration storms. For example, the most intense portion of a 24-hour storm is expected to differ from the most intense portion of a 1-hour storm.

Typically, these types of curves are dimensionless on both the X and Y axes, so they can be applied to a wide range of durations and rainfall depths. The following graph displays dimensionless rainfall curves established for different ranges of durations. To create a rainfall depth curve, select the curve for the desired duration. Then, multiply the X-axis by total storm duration and multiply the Y-axis by the total rainfall depth for that given duration.

Dimensionless Time and Depth Curve