People often think it's impossible that a location can get hit by multiple 500 year floods in a single decade. But it's actually more common than you think.

The odds of two 500 year flood hitting a location twice in a decade is 1 in 5,101. Long odds but not impossible by any stretch of the imagination. 500 year floods are a lot more common than people realize. Indeed the odds of a single 500 year flood in a decade are 1 in 51. 

It is actually more likely a home will get hit by four 500 year floods in a decade then the home owner will strike it rich by buying a power ball ticket.

R is wonderful for statistical analysis.