The probability that events such as floods, wind storms or tornadoes will occur is often expressed as a return period. You may hear about that if you are one who learn about environment, hydrology, water resource, climate change and other related.
Return Period, the inverse of probability (generally expressed in %), it gives the estimated time interval between events of a similar size or intensity.For example, the return period of a flood might be 100 years; otherwise expressed as its probability of ocurring being 1/100, or 1% in any one year. This does not mean that if a flood with such a return period occurs, then the next will occur in about one hundred years' time - instead, it means that, in any given year, there is a 1% chance that it will happen, regardless of when the last similar event was. Or, put differently, it is 10 times less likely to occur than a flood with a return period of 10 years (or a probability of 10%).
