What's at stake when dam floodgates open during massive rainstorms

Yahoo

26-03-2025

During a massive rainstorm, water must make it through the Catawba River System from Lake James in the mountains to Lake Wateree, north of Columbia.
Duke Energy manages how quickly water flows through using its hydroelectric dam system.
Channel 9′s Michelle Alfini got an inside look at one of the dams and explains what's at stake when the energy company opens the floodgates.
'It's taken some time to get over all the stress that everybody went through here,' said resident Tom Davis, who lives on Riverside Drive.
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Davis is still rebuilding his home nearly six months after the floodwaters from Hurricane Helene inundated the neighborhood. He is one of the few planning to stick around.
'It destroyed a village is what it did,' Davis said.
Riverside Drive is downstream from Mountain Island Lake, but the water that rose through the neighborhood came from much farther upstream.
Duke Energy opened the floodgates at Cowans Ford Dam on Lake Norman shortly after 5 p.m. on Sept. 27, 2024.
READ MORE: Residents monitor river levels after floodgates to dam open
Voluntary evacuations downstream became mandatory, and Riverside Drive was underwater for days.
It was the second time in five years floodwaters forced Davis out of his home. He doesn't believe the fault lies only with Mother Nature but with how Duke Energy managed its dams.
'You knew the hurricane was coming out of the Gulf,' Davis said. 'You had plenty of time to prepare for it.'
Duke Energy owns a series of hydroelectric plants along the Catawba River system.
The system starts at Lake James in McDowell County and flows down to Lake Wateree in South Carolina.
Duke Energy is responsible for moving water through the system to generate electricity and manage local water supplies as a part of its licensing agreement with the Federal Energy Regulatory Commission.
If a lake gets too high, it can flood nearby homes and damage the hydroelectric powerhouses.
If it gets too low, it can threaten power output and drinking water resources.
'Absolute total loss': Evacuees return to homes along Catawba River
'This system, the Catawba-Wateree, was not built for flood management; it was built for power generation and for our infrastructure, so the margins that we have are a lot less,' said Bryan Walsh, the vice president for Central Operational Services.
Duke Energy took Alfini to the top of Cowans Ford Dam to show her how the water in Lake Norman must sit to comply with their license.
The lake enters a drought stage at about five feet below the gates. It can damage the infrastructure if the water overtops them.
'Water would come on top of the gate,' said Aaron Dale, the director of Operations for Renewables. 'It would take debris with it, and that debris could potentially bind up into the chains into the mechanisms and compromise its ability to be operated. That's why we don't go above 100 at a gated spillway.'
Duke Energy says that's what officials are weighing as they decide about when and where to move water ahead of a storm.
A report sent to the Federal Energy Regulatory Commission after the storm shows Duke Energy had started to lower the levels at Lake Hickory on Sept. 26, 2024.
The report does not show any significant change in Lake Norman's water levels until after Helene.
'To move too far in advance can have two effects,' Dale said. 'One, you're either too dry in some places after the fact, or you can send water to the incorrect place. You might send it to a reservoir that gets hit much harder.'
Even the best forecasts can only provide about 24 to 72 hours of notice of flood concerns on the river system, and any decisions about moving water must be made with the whole system in mind, according to Duke Energy.
That's not good enough for Davis.
'I've been on this property for 52 years,' he said.
Davis said his home has seen significant flooding twice: in 2019 when the dam opened and after Helene.
After the 2019 flood, about a dozen of his neighbors took buyouts from FEMA or Mecklenburg County to move to higher ground.
Davis said he has heard that about 40 homes are bailing out.
'People never came back,' he said.
However he is staying for now, but he expects the floodgates to open again.
'Their problem is solved because everybody's gone,' he said.
Duke Energy filed a report to federal regulators detailing Helene preparations and response along the Catawba-Wateree River System.
Earlier this year, officials responded and requested updates on how the utility will rebuild its own damaged infrastructure.
It did not mention any of the damage to communities, such as Riverside Drive, or request any additional information on pre-storm actions.
VIDEO: 'Absolute total loss': Evacuees return to homes along Catawba River