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In large part, this latter characteristic represents a general lack of under- 
standing of the relative ease and cost savings to be gained by further sub- 
division of the Level Il categories and polygons into Level lll or IV areas. 
Too often, such jurisdictions as we are considering here confuse the need for 
very large scale cadastral information with the need for medium-to-small 
scale thematic information on land use and land cover patterns and trends. 
Both types of information are typically needed, and neither one will suffice 
for the other. In spite of this existing situation, several examples of 
applications are possible. 
The Atlanta Metropolitan Region is an excellent example of a dynamic urban 
region. As the southeastern hub of the ''Sun Belt'', the Atlanta area is ex- 
periencing rapid population change and industrial growth, with attendant 
changes in land use patterns. Foresight on the part of the Georgia State 
Geologist has resulted in the production of a group of up-to-date maps for 
the Atlanta Metropolitan Region at a scale of 1:100,000. The group of maps 
includes a special 1:100,000-scale topographic map centered on Atlanta and 
encompassing 6,000 square miles surrounding the central city. Also included 
is a land use and land cover map at 1:100,000 to match the new topographic 
base, as well as land use and land cover maps at a scale of 1:24,000 covering 
the central city. The State Geologist is using these materials in conjunction 
with other data on engineering soils properties, geologic hazards zones, and 
similar data to define earth science constraints on development in the region. 
The Atlanta Regional Commission is using the maps and data for a land use 
change analysis being conducted for its 8-county jurisdiction. Certain types 
of Level Ill data were supplied to the Commission for its use in this analysis. 
The 1:24,000, 1:100,000, and 1:250,000-scale land use maps and data prepared 
for the Atlanta Metropolitan Region are being used in the USGS Chattahoochee 
River Quality Assessment Study. Area measurements from the maps are being 
related to measurements of yearly sediment loadings and other pollutants. Sub- 
basins which are characteristically urban, agricultural, or forested are being 
analyzed for the impacts of non-point source pollutants on the main stream of 
the Chattahoochee River. 
The amount of stormwater runoff generated by a particular rainfall event de- 
pends to a great extent on the degree of urbanization, e.g. impervious cover, 
within the drainage basin. By relating impervious cover measured from aerial 
photographs to USGS land use and land cover maps, an index of imperviousness 
for each of the land use and land cover categories can be developed. Current 
research is focusing on Peachtree Creek, a tributary of the Chattahoochee 
River, encompassing a large portion of the Atlanta urban area. While the 
procedure for arriving at the index should be transferable to other urban areas, 
transferability of particular indices of imperviousness is probably limited to 
those areas similar to Atlanta. 
A cooperative agreement has been drawn up with San Mateo (California) County 
for the production of Level Ill land use and land cover data for that county. 
The USGS is interested in this particular project as a demonstration of the 
technique of subdividing Level || categories into more finite Level Ill cate- 
gories, which are being derived from a combination of remotely sensed data 
and data collected by field surveys.