This report has been prepared as part of a program of water-resources investigations, under the provisions of a cooperative agreement between the Highway Division, Department of Transportation, State of Georgia, and the U.S. Geological Survey. The Highway Division plans modification of the bridge crossing of North Fork Peachtree Creek at Interstate 85 and the addition of frontage roads and bridges upstream and downstream of Interstate 85, DeKalb County, Ga.
The purpose of the study was to determine the flood characteristics for North Fork Peachtree Creek in the vicinity of Interstate 85 in relation to (1) major changes that have occurred since 1956 and (2) the effects of the proposed highway modifications and additions in the vicinity of the Interstate 85 crossing. Analyses of flow characteristics for the 50- and 100year floods were made for the following conditions:
- Natural conditions before construction of Interstate 85 (1952).
- Conditions after construction of Interstate 85 but prior to construction of Century Center, an office complex downstream from Interstate 85 (1968).
- Present conditions (1975) after construction of Interstate 85 and Century Center.
- Conditions for proposed bridge modification and highway additions, assuming that both frontage road bridges will be constructed higher than the 100-year flood.
In addition, the study included backwater computations, area of opening under high water, and average velocity at the proposed Interstate 85 bridge opening for both the 50- and 100-year floods.
All elevations referred to in this report are to highway datum, which is mean sea level.
