# 100-Year Flood

A 100-Year Flood is a flood event that has 1% probability of occurring in any time period of 1 year.

**Counter-Example(s):**- a flood with a 26 percent chance of occurring in 30 years

**See:**Random Event, Statistical Analysis, Flood Risk Map

## References

### 2015

- (Wikipedia, 2016) ⇒ ttps://www.wikiwand.com/en/100-year_flood Retrieved 2016-07-02
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**one-hundred-year flood**is a flood event that has a 1% probability of occurring in any given year. The 100-year flood is also referred to as the 1% flood, since its annual exceedance probability is 1%. For river systems, the 100-year flood is generally expressed as a flowrate. Based on the expected 100-year flood flow rate, the flood water level can be mapped as an area of inundation. The resulting floodplain map is referred to as the 100-year floodplain. Estimates of the 100-year flood flowrate and other streamflow statistics for any stream in the United States are available.Areas near the coast of an ocean or large lake also can be flooded by combinations of tide, storm surge, and waves Maps of the riverine or coastal 100-year floodplain may figure importantly in building permits, environmental regulations, and flood insurance.

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### 2007

- (Bell et al., 2007) ⇒ H. M. Bell, G. A. Tobin (2007). “Efficient and effective? The 100-year flood in the communication and perception of flood risk" , Environmental Hazards - Elsevier, 7(4), 302-311, [doi:10.1016/j.envhaz.2007.08.004]
- This paper presents a synopsis of several terms used to describe US policy’s benchmark flood and a preliminary study of how such terms are interpreted. Questionnaire surveys were conducted in a flood prone community with residents living in and out of official flood plains. Comparable questions regarding uncertainty, perceived need for protection, and concern were asked in connection with four descriptive methods: a 100-year flood; a flood with a 1 percent chance of occurring in any year; a flood with a 26 percent chance of occurring in 30 years; and a flood risk map. Statistical analysis and qualitative observation showed a disjuncture between understanding and persuasion, potential problems with the 26 percent chance method, and a preference for concrete references in describing risk.