Flood events are referred to in terms of their Annual Exceedance Probability (AEP). The AEP is a measure of the likelihood that a flood of a given magnitude will occur once or more within any given year. The AEP is expressed as either a “one in X” value (e.g. 1:200) or as a percentage (e.g. 1:200 equates to 0.5%).

The table below summarises the return periods discussed in this report, and the equivalent AEP of these events.

Return Period |
Annual Exceedance
Probability (AEP) |
---|

1 in 2 year |
(Q2) 50% |

1 in 5 year |
(Q5) 20% |

1 in 20 year |
(Q20) 5% |

1 in 100 year |
(Q100) 1% |

1 in 200 year |
(Q200) 0.5% |

1 in 500 year |
(Q500) 0.2% |

1 in 1000 year |
(Q1000) 0.1% |

### Brothock Meadows

### Hercules Den

### St Vigeans