If the J. Strom Thurmond Dam collapsed, anyone living in a subdivision named after a body of water should know their homes are likely in the path of deluge.
The homes in such neighborhoods as Jones Creek, River Island, Creekwalk, Rivershyre, Forest Creek, and many others along the tributaries of the Savannah River would be among those inundated as water from Clarks Hill lake gushes downstream from a dam failure.
“It’s like a little clue,” Columbia County Emergency an Operations Division Pam Tucker said.
Tucker recently updated the county’s Emergency Evacuation Plan for Dam Failure and Flooding. The plan addresses the number of people and homes that would be affected by the dam failure, arrival and peak time of the flood waters, as well as evacuation plans, reception centers and emergency shelters.
One of the reasons Lisa Elmore and her family bought their Stratford home was its proximity to the Savannah River. The home is less than 500 feet from the riverbank, which puts it squarely in the inundation area listed in the plan.
“I’m not surprised that would be the case,” Elmore said of her home’s inclusion in the inundation area. While she can’t see the river from her home because of a stand of trees, her family can easily reach the water through a trail.
Elmore’s subdivision isn’t listed in the county flood plain, where flash flooding is likely. Flood insurance wasn’t mandatory when Elmore purchased the home.
After heavy rains a couple of years ago, Elmore said water stood in the wooded area behind her home, but never came close. A dam failure would be a different story.
But the chances of such a disaster are slim.
“The dam is not designed to collapse,” said Billy Birdwell, spokesman for the U.S. Corps of Engineers Savannah District. “The fear of that happening, it shouldn’t exist in people’s minds. The dam is not going to collapse.”
One of the missions of the dam, built between 1946 and 1954, was flood risk reduction downstream. It was designed with earthquakes, heavy rain and other possible threats to its stability in mind, Birdwell said.
“It would take something really catastrophic,” Birdwell said, such as a nuclear explosion.
In the event of other threatening situations, dam personnel would execute plans such as water releases to ease flooding downstream, Birdwell said.
“(The Corps has) lots of plans to prevent it from ever getting this bad to begin with,” Tucker said.
On the slim chance that “an alien race came down and beamed the dam out of existence,” at the current lake level of about 319 feet above sea level, more than 817 billion gallons of water would pour downstream, Birdwell said.
Despite the extremely slim odds the dam will fail, Tucker said planning for the worst-case scenario is a must.
“This is highly unlikely, but the fact that the dam exists just means we need to have a plan,” Tucker said.
She last updated the plan in 2005, and a lot has changed since then. The number of people in the inundation area doubled from 6,535 in 2005 to 13,700 people, living at 5,249 addresses, Tucker said. Every individual address, street and subdivision is listed in the plan that soon will be available on the county Web site.
The flood damage would be constrained within the 30802, 30809 and 30907 ZIP codes.
“The water (would) back up these creeks and streams,” Tucker said.
Flood water would back up into Lloyd Creek, which is only 1.67 miles from the dam; Kiokee Creek, Euchee Creek, Betty’s Branch, Jones Creek and Stevens Creek before rushing into Richmond County. Such a flood would peak more than nine hours after the flooding begins.
Corps officials reexamined county topography and other factors and adjusted the estimated arrivals times of the water at the tributaries. The water would hit Lloyd Creek six minutes after a dam failure. That time was estimated to be 30 minutes in the 2005 plan. Flood waters are expected to reach Kiokee Creek in 22 minutes; Betty’s Branch in 32 minutes; Germany Island in 42 minutes; Jones Creek in an hour and 15 minutes; and Stevens Creek in an hour and 25 minutes.
Tucker presented the plan to officials in Harlem and Grovetown on March 11, assuring them the cities are in no danger of flooding from dam failure, but their support would likely be a part of the emergency response.
“I have faith that this is not going to happen,” Tucker told Harlem officials. “This is worst-case scenario.”
Tucker said she expects county officials to approve the plan at the Tuesday, Feb. 26 Emergency Services Committee meeting. The plan should be available on the county Web site by March 3.