Before the Coosa River enters Alabama and becomes one of the most utilized waters of the state, its watershed is born in the northwestern corner of Georgia (and a small piece of Tennessee) as several vital tributaries, the Conasauga, Coosawattee, Oostanaula and Etowah rivers.
As these headwater mountain streams converge the emerging river flows southwest along the valleys of the Blue Ridge Mountains and Cumberland Plateau, into Alabama and southward towards Montgomery. The river’s mainstem flows for a total length of 286 miles before arriving just north of Montgomery. About 255 the Coosa River’s mainstem rests in Alabama (89% of the total river miles.) (GA DNR)
The Coos River was, at one time, considered a winding river. One of the most famous sayings about the Coosa is that its bends “touched every farm in the state.” (Jackson)
The Coosa River watershed covers an enormous area of about 10,200 square miles, of which roughly 4,500 square miles (46%) lie in Georgia, and 5,400 square miles (53%) lie in Alabama. Less than 130 square miles (1%) of the watershed occurs in Tennessee. (GA DNR)
The Upper Basin is characterized by mountainous terrain sloping down to rolling hills and plateaus.
The Coosa River watershed occupies 5 different physiographic regions, each lending a unique character to these sections of the basin. The majority of the basin is split between the Valley and Ridge and Piedmont provinces in the upper and middle sections. 34% of the basin lies in the Valley and Ridge physiographic province with altitudes ranging from 600 to 1,600 feet in this region. Another 34% of the basin lies in the Piedmont province.
Only 4% of the land area lies in the Blue Ridge province of North Georgia and Tennessee. At the opposite end of the basin approaching its convergence with the Tallapoosa, 8% of watershed lies in the Cumberland Plateau in Alabama with altitudes of 1,500 to 1,800. Only 2% lies in the Coastal Plain. (Corps)
The Coosa River mainstem is formed when the Oostanaula and Etowah Rivers converge near Rome, Georgia. The drainage area of the upper Coosa tributaries above Rome covers approximately 4,000 square miles. (Corps) The Coosa then flows 286 miles from Rome to north of Montgomery where it joins the Tallapoosa to form the Alabama River.
The river falls approximately 420 feet in 267 miles, or 1.6 feet per mile. (Corps)
Seven Alabama Power Company dams form continuous impoundments over nearly the entire length of the Coosa River, with each dam discharging into the upper end of the next downstream impoundment. The first of these seven dams is located 60 miles below Rome and the last one 19 miles above the confluence with the Tallapoosa River (see Hyrdrologic Modifications).
The Coosa River channel varies from 300 to 500 feet wide, with banks 25 feet high along the flood plain.
The Chattooga River is the largest tributary to the Coosa with a drainage area of 675 square miles. (Corps)
Flows in the Coosa are about 15,000 cfs at Rome, and 50,000 cfs near Gadsden. (Corps)
Average precipitation ranges from 52 to 64 inches annually. Rainfall is greater in the Coosa River Basin than anywhere in the nation with the exception of two areas in the northwest states of Washington and Oregon. (Rivers of AL)
The terrestrial vegetative communities of the Coosa begin with the Appalachian oak forests of north central Georgia. These headwater communities consist of dry slope species such as chestnut oak, northern red oak, white oak, pines, hickories, red maple and tulip poplar while more moisture rich sites are dominated by red maple, American beech, basswood, hickories, tulip poplar, white ash, and hemlock. Both subcanopies have mountain laurel, azaleas, and blueberries, while moist areas also have buckeye, spicebush, and hobblebush. (Corps)