- Project plans
- Project activities
- Legislation and standards
- Industry context
- Specialist wikis
Last edited 02 Feb 2021
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.
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%.
 Related articles on Designing Buildings Wiki
Featured articles and news
Government announces global innovation strategy.
An architectural biography. Book review.
The house where the future king of France lived.
The teacher, architectural technologist and mum offers her insights.
Careful planning needed as supply chain issues continue.
The sensitive conversion of a neglected Cornwall structure.
Plan stresses local involvement in city, town and village development.
Environment Agency publishes BAT guidance.
CLC guidance outlines carbon reduction priorities.
Making the most of a staycation.
Organisation urges G20 to revisit wind energy.
The historian spent much of his life compiling architectural resources.