All three lakes were above full pool and approaching the top of their flood storage elevations, the corps said. Releases at Thurmond Dam were pushed from 25,000 to 37,000 cubic feet per second at noon Wednesday.
“Combined with localized inflows below Thurmond dam, the river flow near Augusta could reach flows as high as 45,000 (cubic feet per second),” the corps said, adding that those flows could increase the river level along downtown Augusta to 117 feet above sea level – or three feet above the area’s normal full pool.
The increases were made necessary by heavy rains and also the potential for more precipitation from Tropical Storm Chantal, which has been downgraded to a tropical wave but still could spawn torrential rains.
“Last night’s rain event contributes to the extraordinary volume of rainfall observed in the last 10 days, approaching nearly 600 percent of average for this time of year,” the corps said.
Potentially hazardous conditions resulting from high water and increased flows include floating debris, submerged retaining walls and higher river velocity downstream of Thurmond Dam. Additional flooding is also expected in the New Savannah Bluff Lock and Dam Park and at Fury’s Ferry.
Because of the high water, which is expected to persist for several weeks, the 28th annual Augusta Southern Nationals dragboat races, which had been scheduled for July 19-21, were canceled Wednesday over safety concerns.
The races are typically held when the river’s flow is about 7,000 cubic feet per second, but current flows are 40,000 cubic feet per second and the Army Corps of Engineers forecast indicates high water will persist for the next several weeks.
The river’s rise Wednesday pushed its elevation above the point where New Savannah Bluff Lock and Dam helps regulate the pool along downtown Augusta, said Shawn Rosenquist, a research scientist with the Southeastern Natural Sciences Academy.
“When it gets to that point, it’s less like a reservoir downtown and more like a river,” he said, and subsequent increases in elevation will be equal above and below the dam.
Although rivers and streams are overflowing, the Augusta Canal’s water levels are expected to stay roughly the same when the river floods, said Dayton Sherrouse, the Canal Authority’s executive director.
“It’s still a balancing act,” he said.
Most of the canal’s flow comes in from the headgates that adjoin the river, but three main tributaries – Rae’s, Reed and Rock creeks – all empty into the canal downstream from those headgates. So if those creeks are flooding and adding flow to the canal, the headgates are adjusted to allow less river water and maintain a relatively steady flow, he said.
Meanwhile, the corps closed most boat ramps and courtesy docks – and some campgrounds and recreation areas – at Lake Hartwell because of rising floodwaters.
At Lake Russell, all beaches were closed and electric power was removed from a gas dock and 80 slip docks in Beaver Dam.
Although the accelerated releases from Thurmond Dam are being conducted through the turbines and not the spillway gates, corps officials still plan to hold their scheduled floodgate tests this week at all three dams.
In both Augusta and Columbia County, flash flooding was reported Wednesday as new storms dumped 2 to 3 additional inches of rain in the already saturated area.
Mie Lucas, of the Richmond County Emergency Management Office, advised residents to stay away from Lock and Dam Park, which is flooded, and also advised that the new Baurle Boat Ramp below New Savannah Bluff is under water and unusable.
People near Butler Creek, in the Windsor Spring and Meadowbrook area, should monitor conditions and make any necessary preparations for flooding, she said. Affected areas include Salem Arms, Caddenwoods, Rosier Road on the Butler Creek side and Elliott Boulevard.
Riverwalk Augusta’s lower walking paths and marina will remain closed until it is deemed safe to access those areas.
People are strongly encouraged not to go into any area that has standing water.
In Columbia County, floodwaters submerged streets and intersections, sinkholes were reported in two subdivisions and two houses were struck by lightning, said Pam Tucker, the director of Columbia County’s Emergency & Operations Division.