What is the 1 in 100 year flood?
There is no such flood as a “one hundred year flood”, even though this is a commonly used term in everyday language. All floods are different. We do not know when the next flood will occur, or how big it will be. But we can estimate what the likelihood (probability or chances) of a certain size flood are at a given location for a given period of time. So for example, if your area has had a (so called) “1 in 100 year” flood, it is a fallacy to think you will need to wait another 99 years before the next flood arrives. Floods do not happen like that. Some parts of Australia have received a couple of “1 in 100 year floods” in one decade. On average, if you live to be 70 years old and live at the same location at or below the “1 in 100 year” flood level, you have a better than even chance of experiencing a “1 in 100 year” flood in your lifetime. We should better refer to a flood that has a 1 in 100 chance of being equalled or exceed in any given year, or a flood that has a 1 in 10 chance o
