On rainfall and reservoirs re: Hurricane Florence

A photo of the eye of Hurricane Florence taken from space by European Space Agency astronaut Alexander Gerst.

(Editor’s Note: We have received several calls from media and concerned citizens related to our operations and posture as Hurricane Florence makes her way toward the East Coast. Below is a consolidation of our responses to these questions as of Sept. 12.)

The Savannah District remains at normal operations. This includes the District’s three hydropower dams and their associated reservoirs.

We have no plans at this time for any pre-releases of water from the reservoirs. The Corps bases its releases on current conditions, not on predictions that may or may not happen.

The long-standing, fully-vetted plans allow for quickly changing release rates based on changing conditions. These release rates are first met by increasing the amount of water passed through the dam and generating additional electricity.

If conditions require increasing releases beyond the capacity to generate electricity, the Corps can pass water through the spillway gates. Water managers do not anticipate the need for spillway releases at this time, but are prepared to make changes as conditions dictate.

Hartwell Lake slightly exceeds its “full summer pool” at 660.70 feet above mean sea level (ft‑msl). Nearly 5 feet of flood storage remain at Hartwell Lake.

Russell Lake is at 471.90 ft-msl, or 3 feet below its full pool level. In addition to this 3 feet it has 5 more feet of flood storage.

Thurmond Lake remains at 327.33 ft-msl, which is more than 2 feet below full summer pool but currently must remain there due to ongoing gate repairs. The repairs should be at a point by Friday where work can be suspended. This will allow water managers to use the remaining 2-plus feet plus an additional 5 feet of flood storage, should it become necessary.

Below the Thurmond Dam, the most downstream of the Corps’ dams, the Savannah River is uncontrolled. Rainfall and tributaries to the Savannah below Thurmond Dam can cause local flooding and flash floods.

Experts with the Savannah District monitor these downstream conditions carefully in order to manage water releases from the Thurmond Dam. The Corps strives to avoid contributing to downstream flooding with releases from Thurmond Dam.

Below Thurmond Dam no one has control of the Savannah River. In high water events, the Stevens Creek Dam and the New Savannah Bluff Lock & Dam (NSBL&D) become ineffective at any type of water control.

As the river level and flow approach the top of the gates at the NSBL&D, operators raise the gates in order to prevent the tremendous river flow from damaging or destroying the gates. The NSBL&D does not now have, nor has it ever had, a flood reduction capability. Operators raise the gates out of the way to preserve them.

The Savannah District remains prepared to assist other Districts and the national recovery team to get the region back on its feet. This may include recovery missions such as debris removal and providing emergency power to critical locations.

Under its own authority, the Corps of Engineers works with the National Oceanic and Atmospheric Administration (NOAA) and the U.S. Coast Guard to ensure harbors re-open quickly after a storm. The Savannah District owns and operates boats to survey the District’s two deep-water harbors for damage and debris.

~ Billy Birdwell, Corporate Communications Office

About U.S. Army Corps of Engineers Savannah District

The U.S. Army Corps of Engineers Savannah District oversees a multimillion dollar military construction program at 11 Army and Air Force installations in Georgia and North Carolina. We also manage water resources across the Coastal Georgia region, including maintenance dredging of the Savannah and Brunswick harbors; operation of three hydroelectric dams and reservoirs along the upper Savannah River; and administration of an extensive stream and wetland permitting and mitigation program within the state of Georgia. Follow us on Twitter @SavannahCorps and on Facebook.com/SavannahCorps
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