100-year flood
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A one-hundred year flood is calculated to be the maximum level of flood water expected to occur on average once every one hundred years. Sometimes, 500-year or 10,000-year floods are calculated (especially, in low lying countries, such as the Netherlands). The 100-year flood is sometimes referred to as the 1% flood, since there is a 1% chance of it occurring in any year. Based on the expected water level, an expected area of inundation may be mapped out according to elevation above sea level. This area figures very importantly in building permits, environmental regulations, and flood insurance.
10-year floods have a 10% chance of occurring in any given year; 50-year flood, 2% chance; 100-year, 1%; 500-year, 0.2%; and 1000-year, 0.1%.
The mathematical field of extreme value theory was created to model rare events such as 100-year floods for the purposes of civil engineering.
100-year floods caused by over a week of continuous heavy rains ravaged Europe in 2002.
References
- "[What is a 100 year flood?]". Boulder Area Sustainability Information Network (BASIN). URL accessed 2006-06-16.
See also
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