100-year event
A 100-year event (or 100-year return period event) is an event that occurs (or is exceeded) on average once in every one hundred years (such as a storm, flood or rainfall event). This can also be expressed as 1 in 100 or 1:100.
For example, a 100-year storm is a storm that is likely to occur once every hundred years.
A ‘return period’ is an estimate of the likelihood of a particular event occurring. The return period of a rainfall event is the average time between events of at least a given magnitude.
Events can also be described by their ‘probability of occurrence’ (or frequency of occurrence) which is expressed as a percentage, or as 1 divided by the return period. The probability of occurrence of a 100-year event is 1%.
The ‘critical duration’ is the duration of the event for a specified return period event.
Ref CIRIA. 2015. C753. The SuDS Manual.
[edit] Related articles on Designing Buildings Wiki
Featured articles and news
Access control in buildings.
MASTRO project – lifecycle costing and assessment.
Five things to consider before installing solar panels.
New conservation building for the Louvre completed.
A balance between character and climate.
Mimetic architecture
Bamboo pavilion built at London South Bank Uni.
Bringing in an expert.
Why the lowest price isn't sustainable.
The Most Economically Advantageous Tender.
Pipe dream or possibility?