In most cases, drainage engineers design facilities for future rainfall events (not actual gauged storms). Rainfall distributions provide a way to model statistically predicted events of various magnitudes. These distributions are sometimes referred to as synthetic storms, since they are not actual gauged events.

Rainfall distributions fall into two categories:

• Dimensionless Depth—The Y-axis for these distributions range from 0.0 to 1.0 (0% to 100%) of total rainfall depth. The total storm duration is defined on the X-axis, in units of time.
• Dimensionless Depth and Time—These are similar to dimensionless depth curves, except that the X-axis is also dimensionless.

Related Topics:

• Gauged (Time Versus Depth)"Gauged (Time versus Depth)" on page 5-389
• Dimensionless Depth: SCS Distributions"Dimensionless Depth: SCS Distributions" on page 5-395
• Modeling Storms with SCS Distributions"Modeling Storms with SCS Distributions" on page 5-397
• Dimensionless Depth and Time"Dimensionless Depth and Time" on page 5-398
• Synthetic Rainfall Tables"Synthetic Rainfall Tables" on page 5-400