Skip to main content

Why Rare Storms Occur so Frequently and What to Do About It

Buy Article:

$17.50 plus tax (Refund Policy)

Or sign up for a free trial


Many people wonder why our cities have experienced so many X-year (fill in the blank for X) recurrence interval storms recently. The public has a hard time believing us when we report the third 10-year recurrence interval storm in seven years. We don't understand it ourselves. Do the statistics experts who develop precipitation frequency estimates really know what they are talking about? This paper identifies three reasons for the perceived higher than expected frequency of rare storms: 1) thinking regionally instead of considering just a single point, 2) rounding to the nearest X-year storm instead of using a threshold, and 3) ignoring storm duration. Numerical testing shows 71 to 700 percent increase in the perceived frequency of rare storms attributed to these reasons. Suggestions are offered for possible changes to rare storms classification to reduce public misperception.

Keywords: 100-year storm; Precipitation frequency; Rainfall frequency; Recurrence-interval

Document Type: Research Article


Publication date: 2011-01-01

More about this publication?
  • Proceedings of the Water Environment Federation is an archive of papers published in the proceedings of the annual Water Environment Federation® Technical Exhibition and Conference (WEFTEC® ) and specialty conferences held since the year 2000. These proceedings are not peer reviewed.

    WEF Members: Sign in (right panel) with your IngentaConnect user name and password to receive complimentary access.
  • Subscribe to this Title
  • Membership Information
  • About WEF Proceedings
  • WEFTEC Conference Information
  • Ingenta Connect is not responsible for the content or availability of external websites
  • Access Key
  • Free ContentFree content
  • Partial Free ContentPartial Free content
  • New ContentNew content
  • Open Access ContentOpen access content
  • Partial Open Access ContentPartial Open access content
  • Subscribed ContentSubscribed content
  • Partial Subscribed ContentPartial Subscribed content
  • Free Trial ContentFree trial content
Cookie Policy
Cookie Policy
Ingenta Connect website makes use of cookies so as to keep track of data that you have filled in. I am Happy with this Find out more