Data presented here is reported in dimensionless (fractional) distributions both in time and rainfall depth space. The temporal axes starts at 0.0 and ends at 1.0 with a time step of 0.01. Duration Multipliers should be used in Drainage and Utilities to convert the dimensionless time to the desired rainstorm duration.

Quartile distributions are identified using the following notation:

• 1stQ—the first quartile time distribution
• 2ndQ—the second quartile time distribution
• 3rdQ—the third quartile time distribution
• 4thQ—the fourth quartile time distribution

Watershed area ranges are identified using the following notation:

• 00-10—point distributions (0 to 10 square miles)
• 10-50—intermediate distributions (10 to 50 square miles)
• 50-400—area distributions (50 to 400 square miles)

Exceedance probabilities are identified using the following notation:

• 50%—median distributions (for design storms)
• 10% - 90%—exceedance distributions (for analysis storms)
• 90% - 10%—exceedance distributions (for analysis storms)

Related Topics:

• Rainfall Time-Distribution Information "Rainfall Time-Distribution Information" on page 5-401
• Watershed Area
• Rainfall Duration
• Data Sources
• Bulletin 70/71 Data
• Circular 173 Data