Surviving a 100 Year Flood Doesn't Mean 99 Years of Safety
The recent flooding in Houston could be considered a 1-in-100-year event, but that label is a misnomer in that it can mislead people into thinking that such flooding literally happens once every 100 years and that they will thus be safe for 99 years out of 100. The U.S. government has used the label to suggest that a flood of that severity has a 1 percent chance of happening in any given year, not that it could happen only once per century. However, the label does not take into account other conditions that can alter those probabilities, such as climate change, El Niño, and La Niña. "That's why the 100-year event is such a moving target, especially in an urban environment. Someone builds a couple of parking lots, and you just turned a 100-year event into a 70-year event because of the impervious surfaces," says Chuck Watson, director of research and development at Enki Research. Weather Research Center founder Jill Hasling suggests that residents of places like Houston that get more than one flood per year buy flood insurance. "If you are not in the flood zone, buy it anyway; it will just be cheaper," she said.