136—Southern Piedmont

This MLRA (shown in orange in the figure above) is in North Carolina (29 percent), Georgia (27 percent), Virginia (21 percent), South Carolina (16 percent), and Alabama (7 percent). It makes up about 64,395 square miles (166,865 square kilometers). It includes the cities of Auburn, Alabama; Atlanta, Georgia; Greenville, South Carolina; Charlotte, Raleigh, and Winston-Salem, North Carolina; and Richmond and Arlington, Virginia. Interstate 85 runs from Auburn, Alabama, to Greensboro, North Carolina, in this MLRA. Other interstate highways in this area are, from south to north, Interstates 75, 20, 26, 40, 64, 66, and 95. The MLRA includes the Talladega National Forest and Horseshoe Bend National Military Park in Alabama; Kennesaw Mountain National Battlefield Park, the Oconee National Forest, and parts of the Chattahoochee National Forest in Georgia; King’s Mountain National Military Park, Cowpens National Battlefield, and Sumter National Forest in South Carolina; parts of the Pisgah and Uwharrie National Forests and Guilford C.H. National Military Park in North Carolina; Appomattox Courthouse National Historic Park, Fort Pickett, Fredericksburg, and Spotsylvania National Military Park, and Quantico Marine Corps Combat Development Command in Virginia; and Thomas Jefferson’s home in Monticello, Virginia. The farm of Hugh Hammond Bennett, the “father of soil conservation,” is in this MLRA. Bennett designed many of the early conservation practices to address the severe erosion that historically occurred in this area. A number of State forests and State parks are throughout the area.

Physiography

Almost all of this area is in the Piedmont Upland Section of the Piedmont Province of the Appalachian Highlands. A very small part of the MLRA, in central North Carolina, is in the Atlantic Plain Division. A very small part in the Roanoke, Virginia, area is on the eastern edge of the Blue Ridge Province of the Appalachian Highlands. This MLRA is a rolling to hilly upland with a well defined drainage pattern. Streams have dissected the original plateau, leaving narrow to fairly broad upland ridgetops and short slopes adjacent to the major streams. The valley floors are generally narrow and make up about 10 percent or less of the land area. The associated stream terraces are minor. Elevation ranges from 330 to 1,310 feet (100 to 400 meters).

The extent of the major Hydrologic Unit Areas (identified by four-digit numbers) that make up this MLRA is as follows: Edisto-Santee (0305), 18 percent; Chowan-Roanoke (0301), 14 percent; Apalachicola (0313), 10 percent; Pee Dee (0304), 10 percent; Ogeechee-Savannah (0306), 10 percent; Alabama (0315), 9 percent; Altamaha-St. Marys (0307), 9 percent; Lower Chesapeake (0208), 9 percent; Neuse-Pamlico (0302), 5 percent; Cape Fear (0303), 5 percent; and Potomac (0207), 1 percent. Some of the major rivers in this MLRA are, from north to south, the Roanoke, Cape Fear, Savannah, Altamaha, Chattahoochee, and Alabama Rivers. These rivers typically form within the Piedmont Province and flow east and south across the Coastal Plain Province and empty into the Atlantic Ocean or Gulf of Mexico. Reaches of the Rappahannock, Rivanna, and Roanoke (Staunton) Rivers have been designated National Wild and Scenic Rivers in Virginia.

Geology

Precambrian and Paleozoic metamorphic and igneous rocks underlie almost all of this MLRA. The dominant metamorphic rock types include biotite gneiss, schist, slate, quartzite, phyllite, and amphibolite. The dominant igneous rock types are granite and metamorphosed granite. Some gabbro and other mafic igneous rocks also occur, and diabase dikes are not uncommon. The Carolina Slate terrane occurs just east of an imaginary centerline in this MLRA. It consists of metamorphic rocks with some metavolcanics and metasediments. Scattered graben basins, which are bounded by faults where the ground between the faults has dropped down, occur from South Carolina to south of Charlottesville and Richmond, Virginia. These basins have Triassic and Jurassic siltstone, shale, sandstone, and mudstone. River valleys have recent alluvium and few terraces.

Climate

The average annual precipitation is 37 to 45 inches (940 to 1,145 millimeters) at the northern end of this area, is 45 to 60 inches (1,145 to 1,525 millimeters) at the southern end, and is as much as 75 inches (1,905 millimeters) in a small, high-elevation area in northeastern Georgia. The precipitation generally is evenly distributed throughout the year. It is lowest in autumn. Most of the rainfall occurs as high-intensity, convective thunderstorms during the growing season. Significant moisture also comes from the movement of warm and cold fronts across the MLRA from November to April. High amounts of rain can occur during hurricanes at the same time of the year. Snowfall typically is light. The average annual temperature is 53 to 64 degrees F (12 to 18 degrees C). The freeze-free period averages 230 days and ranges from 185 to 275 days. Both the mean annual temperature and length of the freeze-free period increase from north to south and with decreasing elevation.

Water

Following are the estimated withdrawals of freshwater by use in this MLRA:

Public supply—surface water, 11.1%; ground water, 1.1%
Livestock—surface water, 0.7%; ground water, 0.2%
Irrigation—surface water, 0.5%; ground water, 0.1%
Other—surface water, 83.9%; ground water, 2.5%

The total withdrawals average 12,720 million gallons per day (48,145 million liters per day). This MLRA ranks third among all of the MLRAs in total amount of water used. About 4 percent is from ground water sources, and 96 percent is from surface water sources. Precipitation, perennial streams, rivers, and lakes provide an abundance of good-quality, soft surface water throughout this MLRA. Small farm ponds are important sources of water for livestock. Industry and thermoelectric power plants use most of the surface water in this area. Toxins, nutrients, and sediment are the primary contaminants in the water. Fecal coliform contamination from point and nonpoint sources is a problem in South Carolina.

Ground water supplies are relatively small, but shallow and deep wells in the crystalline bedrock aquifer are the principal sources of water for domestic use in the area. The water is drawn from joints, fractures, and bedding planes in the crystalline rocks. It generally is soft, but it can be hard or very hard, depending on the type of rock from which the well is drawing its water. High concentrations of manganese and iron can be a problem in some wells. Naturally high levels of radiation in the ground water in this MLRA can cause radon gas problems in basements.

Soils

The dominant soil orders in this MLRA are Ultisols, Inceptisols, and Alfisols. The soils in the area dominantly have a thermic soil temperature regime, a udic soil moisture regime, and kaolinitic or mixed mineralogy. They are shallow to very deep, generally well drained, and loamy or clayey. Hapludalfs (Enon and Wilkes series), Hapludults (Badin, Nason, and Tatum series), and Kanhapludults (Appling, Cecil, Georgeville, Herndon, Madison, Pacolet, and Wedowee series) formed in residuum on hills and ridges. Dystrudepts (Chewacla series) formed in alluvium on flood plains. Udults in the Rhodic subgroup (Davidson, Hiwassee, and Lloyd series) formed in old alluvium on stream terraces or in residuum derived from mafic rocks.

Biological Resources

The uplands in this area generally support a mixture of hardwoods and pine. Loblolly pine, slash pine, white oak, red oak, gum, yellow-poplar, and sycamore are the principal species. Pine is dominant on eroded sites. Hardwoods or mixed stands of pine and hardwoods are on slightly eroded soils and the flood plains along streams. The understory includes dogwood, honeysuckle, pinehill bluestem, and briars.

Some of the major wildlife species in this area are white-tailed deer, cottontail, squirrel, bobwhite quail, and mourning dove.

Land Use

Following are the various kinds of land use in this MLRA:

Cropland—private, 9%
Grassland—private, 11%
Forest—private, 58%; Federal, 2%
Urban development—private, 15%
Water—private, 3%
Other—private, 2%

Most of this area is in small farms, but a sizable acreage is controlled by forest products companies. Although most of the land was once cultivated, much has reverted to mixed stands of pine and hardwoods. Most of the open areas are used as pasture, but some crops, such as soybeans, corn, cotton, and wheat and other small grains, are grown in these areas. Tobacco is grown to a lesser extent. Dairy cattle and poultry are important locally. Rural land adjacent to the major cities is being converted to residential development and associated urban development. This land use conversion is occurring rapidly in the corridor called the Piedmont Crescent, which extends from Atlanta, Georgia, to Raleigh, North Carolina.

The major soil resource concerns are water erosion and the increasing conversion of prime farmland and farmland of statewide importance to urban uses. Conservation practices on cropland generally include conservation tillage, crop residue management, field borders, vegetative wind barriers, and nutrient and pest management.

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