Expert on flooding in Nashville, Illinois: 'Nashville dam performed as it was designed'

NASHVILLE, Il. (KMOX) - As the rain poured down Tuesday morning, hundreds of people were evacuated from homes and businesses in the Southern Illinois town of Nashville, which is a little over an hour away from St. Louis

Waters overtopped the dam system regulating the town's reservoir, leading to some streets in the area being flooded and about 200 residents needing to be evacuated. One woman needed to be rescued.

Amanda Cox, Director of the WATER Institute at Saint Louis University and an associate professor of civil engineering joined KMOX's Total Information AM Wednesday to discuss the flooding and says that while there were some initial reports of the Nashville Reservoir Dam failing, that wasn't necessarily accurate as the dam didn't fail.

"The categorization of failure isn't quite accurate because the dam itself didn't fail, the emergency spillway was activated." said Cox. "Although there were some material that's removed when it is activated, the dam itself, the primary dam, is still in place and secured. It did perform the way it was designed to function."

Cox says the role of a emergency spillway is that once water gets up to a certain level at the principal spillway, the emergency spillway will push material away so it can release the water through the emergency spillway.

"Once water starts to spill over (from principal spillway), it creates a channel for it to go through," said Cox. "I can't tell how common it is for dams to have emergency spillways, but it a very well known type of emergency outlet."

Cox said that a failure of dam would've meant the water would've overtopped the primary dam, causing it to head to the town of Nashville at a more quicker pace and more destructive velocity.

"The dam didn't fail, and like I said, if it did fail, it would've been more catastrophic and more damaging," said Cox. "I know people were evacuated so it might not have impacted loss of life, but the way it performed was it allowed them enough time to get people out and once the water is released, it's not as abrupt. It just going through a designed spillway."

Cox says the correct wording should've been 'a breach or activation of the emergency spillway' rather than 'failure of the dam was imminent.'

"The damn did performed as it was designed, but unfortunately this was just a really large event," said Cox. "The term failure isn't really a good characterization of it. It was really the spillway was overtopped. The damn itself was not."