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Southeastern Floodplains and Low Terraces

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About the Southeastern Floodplains and Low Terraces

The Southeastern Floodplains and Low Terraces are a region consisting of numerous discontinuous pieces of floodplain and bottomlands in the southeastern United States, ranging from North Carolina through South Carolina, Georgia, the Florida panhandle, into Alabama and Mississippi. The region includes the floodplains of major rivers and adjacent terraces and bottomlands, including ponds, swamps, and oxbow lakes. These rivers are slow-moving and tend to flow southeast throughout most of this region, although they flow more straight south and a few even southwest towards the southwestern most portion of this region.

This region is underlain by alluvial deposits including sand, clay, and gravel. The larger rivers here tend to originate in the higher-elevation piedmont, they bring more mineral-rich sediment down from the piedmont. These floodplains are characterized as "brownwater" floodplains, contrasting with the more mineral-poor "blackwater" floodplains of smaller rivers and streams whose watersheds are entirely contained within the coastal plain.

Original forest cover included bottomland oak forests, with swamp chestnut oak (Quercus michauxii), water oak (Quercus nigra), willow oak (Quercus phellos) alongside red maple (Acer rubrum), green ash (Fraxinus pennsylvanica), green ash (Fraxinus pennsylvanica), shagbark hickory (Carya ovata), and bitternut hickory (Carya cordiformis). There were also river swamp forests of bald cypress (Taxodium distichum), pond cypress (Taxodium ascendens), water tupelo (Nyssa aquatica), and swamp tupelo (Nyssa biflora). Towards the south of this region, southern floodplain forests also contained atlantic white cedar (Chamaecyparis thyoides) and sweetbay magnolia (Magnolia virginiana), especially on more acidic soils, along with laurel oak (Quercus laurifolia).

This region is mostly left as swamp forest, with a forest composition similar to its original state. There is some cropland and pastureland in the better-drained higher terraces around the margins of this area, and in the south of this region, there are some pine plantations on the terraces as well. This region cuts through a number of smaller cities and metro areas, but is mostly undeveloped and sparsely populated due to being flood-prone.

This region is surrounded by different regions in different areas. In North Carolina it is mostly surrounded by the Rolling Coastal Plain, except in the south of that state where it is surrounded by the Atlantic Southern Loam Plains, which extend through South Carolina into Georgia. The most upstream portion of this region in South Carolina is surrounded by the Sand Hills, which also extends into Georgia; in Georgia an intermediate region, the Coastal Plain Red Uplands, also surrounds part of this region. In Alabama, this region cuts through many regions, starting inland, the Fall Line Hills, the Blackland Prairie, the Flatwoods/Blackland Prairie Margins (also in Mississippi), the Southern Hilly Gulf Coastal Plain, the Buhrstone/Lime Hills, and the Southern Pine Plains and Hills.

Downstream, this region is bordered by two separate regions: in the north, south through South Carolina, the Mid-Atlantic Floodplains and Low Terraces, and from Georgia south and west into Mississippi, the Floodplains and Low Terraces.

References

1. Griffith, G.E., Omernik, J.M., Comstock, J.A., Lawrence, S., Martin, G., Goddard, A., Hulcher, V.J., and Foster, T. "Ecoregions of Alabama and Georgia (color poster with map, descriptive text, summary tables, and photographs)", U.S. Geological Survey, Reston, VA (2001) Web.