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Improve understanding of return periods and flood probabilities.

A “100- year flood” is often mistakenly interpreted as a flood of a magnitude that will not occur again for another century. People need to understand that, in fact, it means that there is a 1 percent chance of a flood that size occurring every year. A risk-based approach to decision-making should be forward looking and include the lifespan of infrastructure and buildings. Similarly, flood events should not be characterized as “completely unexpected” or “never seen before”. Usually, flooded areas were often clearly identifiable hazard zones where such events had happened in the past. The frequency and severity of such floods will continue and likely increase in the future. Illustrative language is needed to highlight the consequences, including the frustrations and the irreplaceable losses when living through a flood.

PERC Reports