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Flood-inundation maps for Sweetwater Creek from above the confluence of Powder Springs Creek to the Interstate 20 bridge, Cobb and Douglas Counties, Georgia

Scientific Investigations Map 3220

Prepared in cooperation with Cobb County, Georgia
By:

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Abstract

Digital flood-inundation maps for a 10.5-mile reach of Sweetwater Creek, from about 1,800 feet above the confluence of Powder Springs Creek to about 160 feet below the Interstate 20 bridge, were developed by the U.S. Geological Survey (USGS) in cooperation with Cobb County, Georgia. The inundation maps, which can be accessed through the USGS Flood Inundation Mapping Science Web site at http://water.usgs.gov/osw/flood_inundation/, depict estimates of the areal extent and depth of flooding corresponding to selected water levels (stages) at the USGS streamgage at Sweetwater Creek near Austell, Georgia (02337000). Current stage at this USGS streamgage may be obtained at http://waterdata.usgs.gov/ and can be used in conjunction with these maps to estimate near real-time areas of inundation. The National Weather Service (NWS) is incorporating results from this study into the Advanced Hydrologic Prediction Service (AHPS) flood-warning system (http://water.weather.gov/ahps/). The NWS forecasts flood hydrographs at many places that commonly are collocated at USGS streamgages. The forecasted peak-stage information for the USGS streamgage at Sweetwater Creek near Austell (02337000), which is available through the AHPS Web site, may be used in conjunction with the maps developed in this study to show predicted areas of flood inundation. A one-dimensional step-backwater model was developed using the U.S. Army Corps of Engineers Hydrologic Engineering Centers River Analysis System (HEC–RAS) software for Sweetwater Creek and was used to compute flood profiles for a 10.5-mile reach of the creek. The model was calibrated using the most current stage-discharge relations at the Sweetwater Creek near Austell streamgage (02337000), as well as high-water marks collected during annual peak-flow events in 1982 and 2009. The hydraulic model was then used to determine 21 water-surface profiles for flood stages at the Sweetwater Creek streamgage at 1-foot intervals referenced to the streamgage datum and ranging from just above bankfull stage (12.0 feet) to approximately 1.2 feet above the highest recorded water level at the streamgage (32.0 feet). The simulated water-surface profiles were then combined with a geographic information system digital elevation model—derived from contour data (8-foot horizontal resolution), in Cobb County, and USGS National Elevation Dataset (31-foot horizontal resolution), in Douglas County—to delineate the area flooded for each 1-foot increment of stream stage. The availability of these maps, when combined with real-time information regarding current stage from USGS streamgages and forecasted stream stages from the NWS, provides emergency management personnel and residents with critical information during flood-response activities, such as evacuations and road closures, as well as for post-flood recovery efforts.

Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Flood-inundation maps for Sweetwater Creek from above the confluence of Powder Springs Creek to the Interstate 20 bridge, Cobb and Douglas Counties, Georgia
Series title:
Scientific Investigations Map
Series number:
3220
Year Published:
2012
Language:
English
Publisher:
U.S. Geological Survey
Publisher location:
Reston, VA
Contributing office(s):
Georgia Water Science Center
Description:
v, 10 p.; maps (col.); PDF and JPG Downloads of Sheets 1-21: 27 x 36 inches; Downloads Directory
First page:
i
Last page:
10
Country:
United States
State:
Georgia
County:
Cobb County;Douglas County
Other Geospatial:
Sweetwater Creek
Online Only (Y/N):
Y
Additional Online Files(Y/N):
Y