What is the probable maximum flood (PMF)?
The PMF is the largest flood that could possibly occur. It is a very rare and improbable flood. Despite this, a number of historical floods in Australia have approached the magnitude of a PMF. Every property potentially inundated by a PMF will have some flood risk, even if it is very small. Other properties may have an extreme risk to life at the PMF where buildings could be washed away with little or no warning, and people trapped inside would most likely perish. The NSW Government Floodplain Development Manual requires all possible floods up to and including the PMF to be considered in floodplain planning. It states: “The PMF … provides an upper limit of flooding and associated consequences … . It is used for emergency response planning purposes to address the safety of people.” History has shown that extreme flood events can and do happen (e.g.
