Alabama Landscapes

The Valley and Ridge

Coosa River System

The Coosa River system drains some 5,350 sq. miles in Alabama, most of it in the Valley and Ridge.  It enters Alabama in Cherokee County and flows SW until it passes into the Piedmont north of Lay Lake dam.  Several main tributaries flowing from the Cumberland Plateau join the Coosa near Gadsden.  These include Little River, Big and Little Canoe Creeks and Big Wills Creek. 

The Coosa river and its valley can be divides into three main areas in the Valley and Ridge (FigureCR1).

Figure CR1.  Drainage and valley types of the of the Coosa River.  Red: ridges, purple lines topographic profile (see Figure CR2) 

North and east of Hoakes Bluff (Etowah County) the river flows in a wide flat valley that is cut into the Cambrian Conasauga Formation (area 1 on Figure CR1 and profile 1 on Figure CR2).  Most of the valley floor is covered in alluvium (material deposited by the river), resulting in a floodplain up to 15 miles wide.   Near Gadsden, the river is extremely sinuous (S = 2.7) with meanders of amplitude of 2 miles and wavelengths of 5 miles (Figure CR3).  

Figure CR3 Coosa River near Gadsden, Etowah County. (Image © Mike Neilson)

A large part of the valley is filled by Weiss Lake, a 30,200 acre impoundment behind Weiss Dam built in 1961 by Alabama Power.

Figure CR2.  Topographic profiles across the Coosa Valley.  (Profile locations shown on Figure CR1)

The valley narrows and deepens along the St. Clair/Calhoun County line (Area 2 on Figure Cr1 and profile 2 on Figure CR2), where the river cuts through more resistant shale and sandstone of the northern edge of the Coosa Ridges.  The valley is V-shaped, with virtually no flatlands Neeley Henry dam is built at the southern edge of the ridges (Figure CR4).  Neeley Henry lake covers 11,200 acres and backs up water almost to Gadsden (Etowah County)

Figure CR4.  Sandstone ridge, Neely Henry Dam. Calhoun Co. This resistant sandstone caused the valley to narrow and made a suitable place to locate a dam.  Neely Henry Dam was built in 1966. (Image © Mike Neilson)

To the south, the valley widens to about 20 miles near Pell City (St. Clair County) and begins to meander again, but is not as sinuous as near Gadsden. ( In the vicinity of Childersburg, the river has a S  of 1.6: Area 3 on Figure CR and profile 3 on Figure CR2)  The underlying dolomites of the Knox Group contain varying amounts of chert and the river strikes ledges of more resistant rocks along its course.  Logan Martin dam south of Pell City (Figure CR5) was built on one of these ledges.

Figure CR5. Logan Martin Dam. St. Clair/Talladega Counties  Built in 1964, the dam impounds 11,200 acres of water.(Image © Mike Neilson)

South of Lay Lake dam, the Coosa flows on metamorphic rocks of the Piedmont section. (Area 4, Figure CR1).

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