Surface Water - Alabama Department of Environmental Management

Methodology
The southern section of the BWC Basin Group lies below the Fall Line within the
Southeastern Plains (65) Ecoregion.
The Piedmont (45) Ecoregion comprises a transitional area between the mostly
mountainous ecoregions of the Ridge and Valley (67) Ecoregion to the northwest and the
relatively flat coastal plain to the southeast. A small portion of the Cahaba River CU lies
within the Southern Inner Piedmont (45a) subecoregion. The landscape is a rolling to hilly
and mostly forested, with major forest types of oak-pine and oak-hickory, and some
loblolly-shortleaf pine. Open areas are mostly in pasture, although there are some small
areas of cropland. Streams in this subecoregion tend to be low- to moderate-gradient
streams with cobble, gravel, and sandy substrates.
The southern half of the Black Warrior and Cahaba River basins lie within the
Southeastern Plains (65) Ecoregion. The Ecoregion is characterized by irregular plains
with broad interstream areas. Natural vegetation is mostly oak-hickory-pine and southern
mixed forest. The soils of the region are sands, silts, and clays. Elevations and relief are
less than the Ridge and Valley (67) and Southwestern Appalachians (68) Ecoregions.
The Blackbelt region of the extreme southern portion of the Black Warrior River Basin
is composed of two subecoregions of the Coastal Plain: the Blackland Prairie (65a) and the
Flatwoods/Blackland Prairie Margins (65b). Because the regions are narrow and
intermingled, many streams drain through portions of both subecoregions. The elevations
in these regions range from 150-250’ in the Blackland Prairie to 100-400’ in the
Flatwoods/Blackland Prairie margins. The soils are primarily clays and loams that weather
into nutrient-rich soils that can bake hard in summers and become very adhesive when wet.
Streams in this region usually erode to chalk bedrock and are noted for variable flows and
high rates of runoff during storms. In summers, many smaller streams will go dry, and
flow in larger streams becomes quite low. The natural vegetation of the Blackland Prairie,
consisting of sweetgum, post oak, red cedar, and bluegrass prairie, has been transformed to
cropland and pasture, with small patches of mixed hardwoods. Aquaculture, primarily
pond-raised catfish, has increased in recent years. The Flatwoods are comprised of a
mostly-forested lowland area of little relief, formed primarily on dark, massive marine clay.
The Lower Black Warrior River CU lies mainly within the Fall Line Hills (65i)
subecoregion. Unlike other regions of the BWC, streams located within the Fall Line Hills
flow year round due to extensive sand and gravel aquifers in the region (Mettee et al.
1996). Riverine wetlands are characteristic of the subecoregion. Within the BWC, the Fall
Line Hills is a transition zone between the Coastal Plain and the Southwestern
Appalachians. It is mostly forested terrain of oak-hickory-pine on hills with 200-400 foot
relief. Longleaf pine is being reintroduced in many areas.
The Southeastern Floodplains and Low Terraces (65p) comprise a riverine ecoregion
of large sluggish rivers and backwaters with ponds, swamps, and oxbow lakes. River
swamp forests of bald cypress, water tupelo, and oak-dominated bottomland hardwood
forests provide important wildlife corridors and habitat. In Alabama, cropland is typical on
the higher, better-drained terraces, while hardwoods cover the floodplains.
The Ridge and Valley (67) Ecoregion consists of a series of folded and faulted parallel
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