Within the Lake Worth Drainage District (LWDD) boundary, some homes and businesses are constructed in areas known as the 1 in 100-year flood plain but have experienced multiple floods in the same year. The assumption that if their area has experienced a 1 in 100-year flood, then for the next 99 years they do not have to worry about flooding is not correct. While it’s unlikely that two large storms will happen in close succession, history has demonstrated that it is possible.
Confused by the term 1 in 100-year flood, many people begin to wonder what their flood risk really is. The definition of a 1 in 100-year flood is a flood that has a 1% chance of occurring in any given year. Understanding your flood risk can be a complex process, but the hydrologists at the U.S. Geological Survey (USGS) are striving to communicate risk more effectively, in part by transitioning away from the term 1 in 100-year flood and instead referencing multiple year flooding probabilities. For example, a home in the 1 in 100-year flood plain, may be better understood as a home with a 26% chance it will flood over the course of a 30-year mortgage. Providing a clearer understanding of the probability of flood risk allows decisions to be made to better protect people and buildings.
The USGS has published a flyer discussing in detail the probability of flood risk. You can download a copy at https://pubs.usgs.gov/gip/106/pdf/100-year-flood-handout-042610.pdf