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Drainage Design: Truly
Understand What 'Year Event' Really Means
Anthony O. Righellis, P.E.
Overview
Hydrologic analysis and results are statistically based. The term 'year
event' is the common way to express the hydrologic magnitude of precipitation
and runoff quantities, but it does not tell the entire story. What does it
really mean?
Discussing drainage and flood issues with the general public and policymakers
sometimes needs more than thinking just in terms of 'year event'. Its
brevity in expression does not illustrate important considerations. One
such is that the 100-year event has only a 63% chance of happening in 100
consecutive years yet can occur more than once in a single year.
Three other primary expressions are 'probability', 'service level', and
'expected occurence'. There is a direct relationship between these terms
and 'year event'. All are important to understand and doing so can help an
engineer to better grasp situations and relate the impact of their work to
others. This course relates the four terms with discussion, formulas, and
examples.
The student must take a
multiple-choice quiz at the end of this course to earn PDH credits.
Specific Knowledge or Skill Attained
This course teaches the following specific knowledge and
skills:
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Definitions of the
terms Probability, Year Event, Service Level, and Expected Occurrence
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Relationships
between the four terms
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Methods for
calculating Probability, Year Event, Service Level, and Expected Occurrence
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The positive and
negative perceptions associated with each term by the non-technical public
Course
Click on the following PDF attachments to review
"Drainage Design: Truly Understand What 'Year Event' Really Means".
"Drainage Design: Truly Understand What 'Year Event' Really Means" (99
KB)
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