Why the May 2010 flood won’t happen again in our lifetime

NASHVILLE, Tenn. (WSMV) - This week marks 14 years since the Nashville flood that claimed dozens of lives and caused more than $2 billion in damage.

Back-to-back record-breaking rains fell on Saturday, May 1, and again on Sunday, May 2, causing widespread flash flooding and river flooding across much of the Mid State in 2010.

Cars were submerged in flood waters on I-24 in Nashville during the May 2010 flood.

The storm killed 18 people in Middle Tennessee and at least 27 in all of Tennessee, Kentucky and Mississippi. Property damage exceeded $2 billion throughout three states and helped prompt a Presidential Disaster Declaration for many counties in West and Middle Tennessee.

Several rainfall records in the Nashville area were broken during the rain event. Nashville experienced its all-time rainiest day and third-rainiest day consecutively, totaling 13.57 inches collectively. They broke National Weather Service records dating back to the early 1870s.

In addition to the heavy rain, the Cumberland River swelled to unprecedented levels, causing much of the flooding disaster throughout downtown Nashville and surrounding areas that the river runs through. By May 4, 2010, the rain caused the river to rise well above flood stage (40 feet) to nearly 52 feet. To put that into perspective, the river would be around 20 feet on an average day in May.

We now refer to what happened as a 1,000-year flood – that means there was a .1% chance of it occurring in any given year, so we likely won’t see a flood as drastic as that again in our lifetime, thankfully.

However, the “1,000-year flood” label, used by the National Centers for Environmental Information, is a bit misleading. One might believe that a 1,000-year flood actually occurs once every 1,000 years. It doesn’t, necessarily. A major flood like this could happen twice in 10 years, or it might not happen for another 10,000 years. The reference is to a statistical measure — 1 in 1,000. It means that there is a 1 in 1,000, or 0.1%, chance that such a rain event or flood will occur in any given year.

Since the Nashville flood, the city has spent thousands of dollars to ensure this won’t happen again. Twelve new gauges were established just within Davidson County with a focus on the Cumberland River at locations that experienced major flooding and in the headwaters of the tributaries around Nashville. The National Weather Service also set minor, moderate, and major flood stages for each of these gauges along with specific impacts of what gets flooded and at what level.