Why are we still using 100 to 1000-year rainfall designations of events? False security is not productive.

Why are we still using 100 to 1000-year rainfall designations of events? False security is not productive.

The South Carolina Department of Natural Resources has posted online its report, Tropical Cyclone Florence in South Carolina.

Florence came to the North Carolina and South Carolina coast in September of 2018 causing widespread flooding.  The SCDNR report includes maps showing the extent of the devastation in our state.

The report cites Loris as receiving the most flooding:  “The highest rainfall measured in South Carolina from Hurricane Florence was 23.63” from a CoCoRaHS station (Loris 2.9 WSW) in Horry County. This site exceeded the 1000-year return interval mark for 4-day rainfall accumulation.”

According to the report: “Hurricane Florence’s slow march across the region added insult to injury, as portions of Dillon, Florence, Georgetown, Horry, Marion, and Williamsburg counties experienced their third 100-year rainfall event since 2015.”

In three years, parts of coastal South Carolina received three 100-year rainfall events plus a 1000-year event!

We need new terminology to talk about the severity of rainfall events. The terminology weather and insurance experts have been using since 1973 is completely misleading and gives a false sense of security.

A FiveThirtyEight analysis of the issue by Maggie Koerth-Baker in 2017 said this:

That’s no surprise to experts, who say the concept of the “100-year flood” is one of the most misunderstood terms in disaster preparedness. In the wake of catastrophic flooding on the Texas coast, the media has been workinghard to explain the termturning out dozens of articles explaining that a “100-year flood” is not a flood that you should expect to happen only once every 100 years. Instead, it refers to a flood that has a 1 percent chance of happening in any given year. Over the course of a 30-year mortgage, a house in a 100-year floodplain has a 26 percent chance of being inundated at least once.1

The odds of being impacted by a 100-year to 1000-year flood are increasing every year due to climate change.

Recognizing what is going on and the cause is desperately needed to focus the public’s and our elected leaders’ attention on taking action to address this crisis that literally threatens our nation’s and the whole world’s future.