Flood Frequency & Return Interval: 100-Year Analysis

[Varanus]

if in 100 years of records you have had floods in five of those years is the flood frequency 5 per 100 years ?

and would the flood return interval be every 20 years?

 

[HallsofIvy]

Yes, the frequency is 5/100= 1/20 years per flood. There will be an average of one flood every 20 year but that is only an average.