NARSAL - Metro Atlanta Area Land Cover Change

16-County Metro Atlanta Area
Land Cover Change (Pilot Project)

Canopy | Impervious Surface | Land Cover

Over the last decade, Metro Atlanta has experienced unprecedented population growth. This change in population has resulted in an increase in impervious surface and a decrease in forest canopy. Overall Metro Atlanta is accumulating 28 acres per day of impervious surface and losing 54 acres of canopy per day, resulting in a ten year loss of 196,921 acres of tree canopy and a gain of 103,273 acres of impervious surface.

Data from this project quantifies information about rates of change in the Metro Atlanta area over the last ten years. For every two acres of tree canopy that is lost, one acre of impervious surface is created. The loss of tree canopy and addition of impervious surfaces reduces the regions ability to absorb stormwater which leads to increases in flooding, soil erosion and sedimentation, and increases pollutants in waterways, thus limiting the ability of these natural systems to maintain clean water.

One initiative taken to address impacts on water resources specifically was the creation of the Metropolitan North Georgia Water Planning District. The District developed regional water plans for supply and conservation, stormwater management and wastewater management for the 16-county area.

This project was designed to create GIS data that will provide a consistent, uniform baseline to support the District goals to promote watershed protection by limiting impervious surfaces and preserving tree canopy. Data products for 2001 were developed for the National Land Cover Data Program and include the traditional land cover data and add impervious surface by percent pixel and tree canopy cover by percent pixel. These data are designed to build a national baseline. For this study we created three data products from 1992 imagery allowing an opportunity to look at change over time.

We mapped both the extent of tree canopy area and impervious surface area from Landsat TM and ETM+ imagery for both 1992 and 2001. The process used modifications of techniques developed by the USGS for the National Land Cover Data (NLCD) program. The map products are modeled results representing the percentage of an individual pixel that is either impervious area or canopy area. This new data will allow planners and decision makers to evaluate tree cover and impervious surface trends in the Water District over the decade from 1992-2001 using a reliable and consistent methodology employed across city and county lines. It may be most helpful in assessing which areas of their counties and watersheds have seen the greatest rates of change as they move forward in mitigating for stormwater impacts. The results of this study should also augment efforts to use watershed based planning approaches to manage growth, while protecting the region’s resources.

Comparison of Change in Canopy Between 1992 and 2001


Dark green indicates high canopy closure and light green indicates low canopy cover. White represents no canopy.	Comparison of canopy change by county

Comparison of Impervious Surface Between 1992 and 2001


Dark red represents a higher percentage of impervious surface and light red indicates a lower percentage of impervious surface. Black indicates pervious surface.	Comparison of impervious surface change by county

Comparison of Land Cover Change Between 1992 and 2001


Reds and pinks represent urban classes and shades of green represent forest classes.	Comparison of land cover change by county

Georgia Forestry Commission	United States Department of Agriculture

Funds for this project were provided by the Urban and Community Forestry Grant Program administered by the Georgia Forestry Commission.

The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, gender, religion, age, disability, political beliefs, sexual orientation, and marital or family status. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA’s TARGET Center at 202-720-2600 (voice and TDD).

To file a complaint of discrimination, write USDA, Director, Office of Civil Rights, Room 326-A, Whitten Building, 14th and Independence Avenue, SW, Washington, DC 20250-9410 or call 202-720-5964 (voice or TDD). USDA is an equal opportunity provider and employer.