Ocoee River geological history

The Ocoee River corridor has been the scene of three significant rock slides over the past 12 months. The largest one of course brought fame and notoriety to the Ocoee River and Southeastern Tennessee. Many questions have been asked about the rock slide and the geology of the area in general. The following exerpts are from a website hosted by the US Geological Survey department and are specific to the Ocoee River Gorge. The site contains more broad range information on the geographic timeline and can be viewed at  http://pubs.usgs.gov/gip/ocoee2/ This site covers a timeline that goes back to the early fossil record until present day where Whitewater Rafting is the popular draw to the area. Geology students from around the country travel to the Ocoee River Gorge each and every year to study the strata and timeline of the rocks. 

“This web page showcases a brochure that tells the geologic story of the rocks exposed along the Ocoee River in Polk County, east Tennessee. The brochure was prepared by the USGS, in cooperation with Forest Service and Tennessee Valley Authority (TVA), to highlight the geology along a popular stretch of the Ocoee River.

TVA produces maps in cooperation with the USGS. TVA operates three dams on the lower Ocoee River to produce hydroelectric power and manages the flow of water in the river.

The Ocoee River area attracts thousands of visitors every year and includes the Ocoee Whitewater Center in the Cherokee National Forest, site of the 1996 Olympic Canoe/Kayak Slalom competition.
US Highway 64 follows the Ocoee River through the gorge, east of the town of Cleveland, Tennessee. Many interesting rocks can be seen from the highway in roadcuts and in the river bed starting near Ocoee Dam No. 1 (Parksville Dam). East of Ocoee Dam No. 3, the Ocoee River turns south and Highway 64 continues east to Ducktown.

460 to 240 million years ago

Rocks buckled into folds and large blocks of rock slid over each other along the Great Smoky fault. Heat and pressure increased due to these collisions and transformed sedimentary rocks into metamorphic rocks. For example, shale became slate. These events built the present-day Appalachian Mountains. Light and dark gray bands in the rocks that we see along the Ocoee River Gorge today originally were layers of sediments that were deformed during this era. The lighter colored layers are coarser grained and harder than the darker colored layers. The hard, coarse grained layers form ledges that make many of the rapids in the river.

Erosion by westward flowing water created the dramatic landscape and deep gorges along the Ocoee River and its tributaries. The Ocoee River Gorge cuts across the northeast trend of the Appalachian Mountains and has exposed a cross section through the rocks. The first dam (Ocoee Dam No. 1 or Parksville Dam) was completed on the Ocoee River to generate hydroelectric power. This dam created Lake Ocoee (Parksville Lake). USGS began monitoring the flow along the Ocoee River. The Great Smoky fault intersects the Earth’s surface near Ocoee Dam No. 1 (Parksville Dam). Faults and folds formed when older rocks were shoved over younger rocks during a continental collision more than 240 million years ago. The fault marks the boundary between two physiographic provinces: the Valley and Ridge province to the west and the Blue Ridge province to the east. Landforms are different on either side of the fault because rocks on the east side are more resistant to weathering and erosion than the younger rocks to the west. The fault is no longer active.

The great power of this river has been harnessed at three points to generate electricity. At Ocoee Dam No. 3, water from the Ocoee No. 3 Lake is diverted to Powerhouse (PH) No. 3 through a tunnel cut through the rock on the west side of the river. The river channel between the dam and the powerhouse normally carries only local flow and, when necessary, flood releases from the lake. A 1,500 ft (457 m) long stretch in this segment of the river was modified to create the Ocoee Whitewater Center, the site of the 1996 Olympic Canoe/Kayak Slalom competition. TVA can release water at Ocoee Dam No. 3 to provide flow for the whitewater course. Unlike a natural stream, most of the flow in this segment of the river can be turned on and off. Downstream, the water is used again as it is diverted through a flume from Ocoee No. 2 Dam to PH No. 2.
The rate of water released for competitions at the Ocoee Whitewater Center is about 1,400 cubic feet per second (628,320 gallons per minute, or 39.6 cubic meters per second). As you consider the amount of turbulence and whitewater that this discharge provides, you might imagine the awesome power of this river when in flood – on November 19, 1906, an estimated discharge of 62,000 cubic feet per second (27,800,000 gallons per minute, or 1,756 cubic meters per second) passed the gaging station site just downstream from PH No. 2.

The USGS operates stream-gaging stations along the Ocoee River in cooperation with the Tennessee Valley Authority (TVA) and the Tennessee Ocoee Development Agency. Stream flow data have been collected continuously since 1913 at the gaging station site shown in the photo and on the map (station 03563000 near the former village of Emf, TN). Another recently installed submerged sensor at Slam Dunk (one of the named natural bedrock ledges that forms an eddy in the channel at the Ocoee Whitewater Center) transmits data continuously to TVA. Data from these stations enable TVA to determine discharge rates and maintain flow within a specified range along the canoe/kayak competition course.”