Defined model

Exceed a 1% annual flood threshold

Probability:
1%
Odds:
1 to 99
dBan
−20 dBan

At the defined location, the threshold has one modelled annual exceedance for every 99 years without one, on average. The 1% annual chance does not promise one flood every 100 years.

Calculation

p = 0.01 for the defined location, threshold, and year

Assumptions

The threshold belongs to a particular location. Homes and waterways at other locations have different risks.

Sources

  1. USGS: floods and recurrence intervals