2017年7月4日 · A key result is that we can’t use the simple relationship ARI = 1/AEP for frequent events. So, for example, the 50% AEP event is not the same as the 2-year ARI event. Example calculations. For an ARI of 5 years, what is the AEP? For an AEP of 50%, what is the ARI?

The term Annual Exceedance Probability (AEP) will be used for design events (rainfalls and floods) including and rarer (less frequent) than those with a 10% AEP. AEPs are to be expressed as an exceedance probability using percentage probability; for example a design rainfall will be described as having a 1% AEP.

Annual Exceedance Probability (AEP) is the probability of a certain sized flood occurring in a single year. For example, a 0.5 per cent AEP flood has a 0.5 per cent, or 1-in-200 chance of occurring in any year. AEP is the inverse of ARI, where large, infrequent floods have a low AEP and smaller, more frequent floods have a higher AEP.

ARI and AEP. The Average Recurrence Interval (ARI) and the Annual Exceedance Probability(AEP) are both a measure of the rarity of a rainfall event. What is ARI? ARI is defined as: "The average, or expected, value of the periods between exceedances of a given rainfall total accumulated over a given duration."

Historically the peak over threshold method has been used to derive average recurrence intervals, while the annual maxima method has been used to derive annual exceedance probabilities. Conversion between these can be done using the Langbein’s formula (Langbein, 1949) and its inverse: \mathrm {AEP} = 1 - \exp (-1/\mathrm {ARI}) AEP = 1− exp(−1/ARI)

... change from ARI to AEP has caused a slight change to the design rainfall regarding the level of service provided by councils. For example, infrastructure that is designed for a 1 : 5 year...

2020年10月5日 · Annual exceedance probability (AEP): the probability or likelihood of an event occurring or being exceeded within any given year, usually expressed as a percentage. The table below lists the probability terminology used for the 2016 design rainfalls and shows in bold the standard EY and AEP values for which design rainfalls are available.

The Average Recurrence Interval (ARI) is replaced by Average Exceedance Probability (AEP) in the 2019 version of ARR (ie. 1% AEP replaces 1 in 100 year ARI). Using the Bureau of Meteorology IFD data, a 7-coefficient natural log polynomial regression is used to derive a depth of rainfall for a specific AEP and duration. DepthP = e(C0 + C1 ln(T ...

The following table shows the equivalent AEP for ARIs ranging from 1-100 years. The Extreme Precipitation Monitor displays exceedances for ARIs between 1 and 100 years and AEPs between 4% and 1%. This product is generated with the WPC's Days 1-3 Quantitative Precipitation Forecasts (QPFs) for the 6-, 24-, and 72-hr periods.

Calculate an ARI To determine the rarity of a rainfall event for the chosen co-ordinates, enter the Rainfall Total in millimetres and the duration, in minutes, over which the rain fell. The Average Recurrence Interval(ARI) and Average Exceedance Probability(AEP) will be given.