The recent flooding in the midwest prompted a visit to this thread.
Some of my relatives live in Cedar Falls, Iowa.
The town was well-prepared, and endured the problem well.
(My relatives live at the highest point in town, and weren't directly affected.)
News coverage has highlighted some finger-pointing concerning two 500-year floods occurring during a 15 year interval and insufficient levees.
In this thread, the topic of estimating risk was addressed a few times:
Quote:
Originally Posted by The Reaper
The intent of this thread is to discuss Disaster Preparedness and assist members of PS.com with their personal disaster planning.
Disaster Analysis
Frequency of Occurrence:
• Highly likely (Near 100% probability in the next year)
• Likely (Between 10% and 100% probability in the next year, or at least one chance in the next 10 years)
• Possible (Between 1% and 10% probability in the next year, or at least one chance in the next 100 years)
• Unlikely (Less than 1% probability in the next 100 years)
|
Quote:
Originally Posted by mugwump
|
Risk-estimation can be difficult due to the misnomers used to describe the probability of a major event and the non-intuitive nature of probability.
In the case of the recent flooding, it has been called a "500-year" flood.
What does this mean?
According the the USGS:
http://www.usgs.gov/newsroom/article.asp?ID=1963
"...a 0.2 percent chance - 1 in 500 - of happening in any given year in a particular location."
What does that mean?
How safe are we for X years to come? (not as safe as you think)
A "500-year" flood happened in 1993.
What are the odds of at least one more "500-year" flood occurring in the next 15 years?
1 - ((1-.002)^15) = 0.0296, or about 1 in 34.
In other words, the second "500-year" flood occuring in next 15 years is more likely than a person winning on their first spin at the roulette wheel.
There is a reason the Netherlands protects populated areas against a "10,000-year" flood.
Buy flood insurance if it is warranted. Don't delay preparations.
Thanks for the thread, TR.
It has given me much to consider in protecting my own clan.