City of Atlanta CDP

Current Conditions

All of Atlanta is located within the Atlanta Plateau, and is part of the greater Georgia Piedmont Province of the Southern Piedmont Region of the United States.  One of the most striking features of Atlanta is the valley of the Chattahoochee River, which runs along its northwestern boundary.  The valley ranges in depth from 150 to 400 feet and from two to five miles in width from rim to rim.

Topography

Rolling to hilly and broad, smooth uplands characterize the general surface features of the City.  The largest areas, with slopes of 15 percent or greater, are located in the north, southwest, and southeast quadrants of the City.  Elevations in Atlanta range from 960 to 1,050 feet above sea level.

Geology

Schist, biotite, gneiss, and other metamorphic rock underlie the majority of the Piedmont Plateau.  Augen gneiss, hornblende gneiss, granite intrusions and other igneous rocks underlie the remainder. These rock formations have weathered thousands of years, interacting with various biological processes, to form the soils found in Atlanta.

Soil Types

The soils in Atlanta are generally red in color and, with the exception of those found in flood-plain areas, are well drained.  These soils were formed from metamorphic and igneous rocks and range in texture from stony, gravelly and sandy loams to clay loams.  Much of the original topsoil has been eroded away, leaving red clay subsoil exposed in some areas.

Six soil associations are found in Atlanta.  They are grouped into three categories according to type, location, and use limitations:

1.   Nearly level soils on bottomlands and low stream terraces:

• Congaree-Chewacla-Wickham: Drainage is moderately good along the Chattahoochee River but somewhat poor along small streams.  Relief is mostly level or nearly level, although some slopes are undulating.

These soils lie along the Chattahoochee River and along the City's larger streams and creeks.  Because of the flooding hazard, the major soils in these associations have severe limitations if used for utility construction or residential, recreational, commercial or light industrial development.  These areas should be limited to suitable wildlife habitat and supporting hardwood stands.

2.   Gently sloping and moderately sloping soils of uplands:

• Cecil-Floyd-Appling:  Drainage ranges from good to excessive.
• Floyd-Cecil-Madison:  Deep to moderately deep soils that are well to somewhat excessively drained.
• Appling-Cecil:  Deep to moderately deep soils that are well to somewhat excessively drained.

In most areas, limitations are slight for residential and park/recreational development and moderate because of clay for commercial and light industrial development, roads and septic tank drainage fields.  However, in the few areas where Louisburg soils predominate, depth to bedrock is very shallow, ranging from a few inches to three feet in depth.

3.   Strongly sloping and steep soils of uplands:

• Madison-Louisa: Well-drained to excessively drained soils.
• Cecil-Lockhart:  Soil drainage is good to excessive in most places, although it is excessive in some steep areas.

Soils in these associations are located primarily along portions of the major stream banks.  Limitations are moderate for residential, park and road constructions on slopes less than 15 percent and severe for all uses on slopes 15 to 40 percent.  Development in these areas is also limited by adverse soil properties.

Steep Slopes

Slopes in Atlanta range from nearly level to 60 percent.  The steeper slopes (greater than 15 percent) are generally located in north, southwest, and southeast quadrants of the City.  Some of these areas are heavily forested or covered with other forms of protective vegetation.  Additional protection of slopes greater than 15 percent is anticipated as development pressure in the City increases.

Sensitive Plant And Animal Habitats

Rare plants, animals, and natural habitats are particularly vulnerable to the effects of development and should be recognized and protected to the extent possible.  The following includes a list of sensitive plants and animals, and a brief description of their habitats.

Plants

1. Moccasin Flower, Pink Ladyslipper
2. Golden Slipper, Yellow Ladyslipper: Primarily found in rich, moist, hardwood coves and forests.
3. Bay Star-vine; Climbing Magnolia, Weld Jarsparilla: Typically found twining over understory trees shrubs in rich, alluvial woods, and on lower slopes near streams.
4. Granite Stonecrop, Dwarf Stonecrop: Found growing among moss in partial shade under large, open-grown eastern red cedar (Juniperus virginians) trees on granite outcrops.
5. False Hellebore, Ozark Bunchflower: Found in moist, hardwood dominated woods, usually in small clumps on terraces along streams.
6. Piedmont Barren Strawberry: Found in rocky, acidic woods along streams with mountain laurel (Kalmia latifolia), also in drier, upland oak-hickory-pine woods.

Endangered Wildlife

"Endangered" species are those in danger of extinction throughout a significant portion of its range.  The federal Endangered Species Act of 1973 and Georgia’s Rules offer protection for endangered species, for the Department of Natural Resources (DNR) beginning at 391-4-13.02.  Four endangered species may live in the Atlanta Region:

1. The Indiana bat, a nocturnal insectivore, lives in caves in the winter and may live outside caves from April through October.
2. The red-cockaded woodpecker is endangered because it only nests in pine trees over sixty years old, which are infected with a fungus called red heart disease.
3. Peregrine falcons migrate long distances and usually live on cliffs over water, but in Atlanta they have nested on tall towers and buildings
4. Southern bald eagles usually live in inland waterways and estuaries, however they have been spotted nesting in tall trees in undisturbed Piedmont wetlands and lake shores.

Major Parks, Recreation, And Conservation Areas

The City has approximately 3, 200 acres of parkland that represents 3.78 percent of the city’s total geographic area.  Atlanta parkland comprises a wide variety of natural resource areas and environmental functions.  Eighty-five percent of City parks are located along streams in floodplain and wetland areas, in areas with steep and rocky topography, or in other environmentally sensitive areas.  Part of the City park inventory includes four nature preserves: North Camp Creek, Cascade Springs, Daniel Johnson, and the Outdoor Activity Center.  In addition to City holdings, the National Park Service operates the Chattahoochee National Recreation Area that extends from Buford Dam in Gwinnett County south to Peachtree Creek in the City of Atlanta.

Scenic Views And Sites

The City has not identified to date any scenic views or sites requiring special management.

Prime Agriculture And Forest Lands

Prime agricultural and forest land is generally classified as those areas whereby the soils and topography are conducive to growth.  As a result of increased urbanization, neither of these land-use types can be found in any great quantity within the Atlanta City limits.  The City is, however, focused on protecting urban forest areas in each quadrant of the city as a legacy for future generations.

Hydrology And Watersheds

The annual rainfall in Atlanta varies from thirty-two to sixty-eight inches per year with an average of forty-eight inches. Evaporation and transpiration account for approximately 30 inches of rainfall, resulting in about 18 inches annually available for streamflow and percolation to groundwater.  The land is traversed with numerable streams, creeks, springs and ravines.  Atlanta's geographic location is unique in several ways; it is one of the only cities to be located on a subcontinental divide and it is one of the few metropolitan areas in the United States to be over one thousand feet in elevation.  DeKalb Avenue, Spring Street, and Peter Street are on the ridge line which divides Atlanta's major drainage basins, the Chattahoochee and South River (the Ocmulgee), which drain into the Gulf of Mexico and Atlantic Ocean respectively.

Atlanta's roadway network and resulting development patterns are directly shaped by its watershed topography.  Atlanta is the meeting point for ten stream drainage basins, which supply two distinctly-separate River basins -- the Chattahoochee River and the Ocmulgee River.  Table 11.1 ‘Atlanta Watersheds, including the Chattahoochee River Basin, the Ocmulgee River Basin, and their Tributary Streamway’ provides a detailed description of the locations and components of these watersheds. 

On the West and North sides of the City, the Chattahoochee River is supplied by seven stream drainage basins: Long Island Creek, Nancy Creek, Peachtree Creek, Proctor Creek, Sandy Creek, Utoy Creek, and Camp Creek basins.  In the Southeast section of the City, three stream drainage basins supply the Ocmulgee River:  Sugar Creek, Intrenchment Creek, and the South River.

Each stream drainage basin watershed is bounded by ridgelines and plateaus, which cradle floodplain valleys where the headwaters of several tributary creeks originate in springs.  These springwaters flow into the principal creek, which finally flows through a streamway corridor and floodplain to supply the river.

From Atlanta’s earliest days, the network of its major arterial roads has followed the ridgeline network bordering the river and stream basins.  The relationship between Atlanta’s stream basin ridgeline system and the roadway framework is shown by Table 11.1 ‘Atlanta Watersheds, including the Chattahoochee River Basin, the Ocmulgee River Basin, and their Tributary Streamway’.

The two continental plates that comprise each river basin interface in the heart of the Central Business District (CBD).  This boundary runs along a ridge line which originates east of Atlanta, travels westward to enter the City along what is now DeKalb Avenue, crosses Woodruff Park to Forsyth Street, and then arches to the southwest, paralleling Spring Street and Peters Street.

The headwaters for several creeks in the Chattahoochee River Basin and the Ocmulgee River Basin originate within a fifteen-block radius of the "Five Points" intersection. 

Waters from these springs are currently routed to the storm sewer system that carries the water to the rivers via outfall pipes, which feed the creeks. 

Water Supply Watersheds

Water supply watersheds are subject to the Department of Natural Resources’ Rules for Environmental Planning Criteria.  The Department of Natural Resources defines water supply watersheds as the areas of land that drain to a public drinking water supply intake. The City’s public drinking water supply intake is located on the Chattahoochee River just north of Peachtree Creek and the portion of the City that falls within the boundaries of its water supply watershed is the Chattahoochee River drainage basin north of Peachtree Creek.

Wetlands

Wetlands are subject to the Department of Natural Resources’ Rules for Environmental Planning Criteria.  Freshwater wetlands are defined by federal law as those areas that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, and that under normal circumstances do support a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs and similar areas.  According to the National Wetlands Inventory conducted by the US. Fish and Wildlife Service, wetlands within Atlanta occur generally in the areas along the Chattahoochee River and the City's major streams and creeks, though some non-stream corridor wetlands do exist in the City.  Currently, the US Fish and Wildlife Service National Wetland Inventory Maps are the best source of information available on the location of wetlands in the City.

Groundwater Recharge Areas

Groundwater recharge areas are subject to the Department of Natural Resources’ Rules for Environmental Planning Criteria.  Recharge is the process by which precipitation infiltrates soil and rock to add to the volume of water stored in pores and other openings within them.  Most of northern Georgia is underlain by crystalline rocks with complex geologic character and with little or no porosity within the rocks themselves.  Significant recharge areas in the crystalline rock terrain of northern Georgia are found in areas that have thick soils or saprolite and relatively low (less than 8 percent) slopes.  These conditions are not present in the City.

Flood Plains

Flood plains serve three major purposes:  (1) natural water storage and conveyance, (2) water quality maintenance, and (3) ground water recharge.  The Federal Emergency Management Agency (FEMA) has identified and mapped areas in Atlanta that are prone to flooding.  These maps constitute the flood hazard district maps for the City and have been incorporated into and made a part of the City's official zoning map as described in Section 16.02.004 of the City's zoning ordinance.  Development in these areas is carefully monitored to protect the functional integrity of flood plains as well as the health, safety and property of the City's residents.  Additional management of the 100-year floodplain is anticipated as flooding frequency increases due to watershed development.

Protected River Corridors

Protected river corridors are subject to the Department of Natural Resources’ Rules for Environmental Planning Criteria.  The Chattahoochee River Corridor is protected by the Metropolitan River Protection Act (MRPA), which is described later in the Natural Resources section of the CDP.  The Chattahoochee River Corridor is the region’s most significant natural feature.  It is unrivaled in the State for historic and cultural significance and is rich in animal and plant diversity.  These characteristics make reclaiming the corridor for environmental enhancement and public benefit desirable.  Invasive infrastructure and plants and adverse land uses have irreparably altered the natural ecology of the corridor south of Peachtree Creek.  Proposed development threatens the corridor north and south of Peachtree Creek.  Several plans and initiatives by the City of Atlanta, the Region, the State, and the National Parks Service are focused on further protecting and preserving the Chattahoochee River Corridor.

Streams

Atlanta’s streams and drainageways ( Map 11.1 ‘City of Atlanta Major Streams’) are potentially the City’s most valuable natural resources.  Unfortunately, the City’s streams suffer from litter, pollution, and hydrologic impacts due to stormwater runoff from impervious surfaces.  Several efforts are underway to reclaim and protect Atlanta’s streams and watersheds including the Metro Atlanta Urban Watershed Initiative (MAUWI) and the Greenway Acquisition Project, both described later in the Natural Resources section of the CDP.    

Air Quality

Air quality within the Atlanta metropolitan area does not meet federal standards for hydrocarbons and photochemical emissions.  Within the City, the primary source of emissions is automobile exhaust.  The U.S. Environmental Protection Agency (EPA) classifies the City, and the entire metropolitan Atlanta region, as having a non-attainment status for ozone.

• Back to Top

• Previous
• Next