FLOOD-INUNDATION MAPS FOR PEACHTREE CREEK FROM THE NORFOLK SOUTHERN RAILWAY BRIDGE
TO THE MOORES MILL ROAD NW BRIDGE, ATLANTA, GEORGIA

by Jonathan W. Musser

2012

Scientific Investigation Map 3189

Abstract:

Digital flood-inundation maps for a 5.5-mile reach of the Peachtree Creek from the Norfolk
Southern Railway bridge to the Moores Mill Road NW bridge, were developed by the U.S.
Geological Survey (USGS) in cooperation with the City of Atlanta, 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
Peachtree Creek at Atlanta, Georgia (02336300) and the USGS streamgage at Chattahoochee
River at Georgia 280, near Atlanta, Georgia (02336490). Current water level (stage) at
these USGS streamgages 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 Peachtree Creek, 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 HEC–RAS software for a 6.5-mile
reach of Peachtree Creek and was used to compute flood profiles for a 5.5-mile reach of the
creek. The model was calibrated using the most current stage-discharge relations at the
Peachtree Creek at Atlanta, Georgia, streamgage (02336300), and the Chattahoochee River at
Georgia 280, near Atlanta, Georgia, streamgage (02336490) as well as high water marks
collected during the 2010 annual peak flow event. The hydraulic model was then used to
determine 50 water-surface profiles. The profiles are for 10 flood stages at the Peachtree
Creek streamgage at 1-foot intervals referenced to the streamgage datum and ranging from
just above bankfull stage (15.0 feet) to approximately the highest recorded water level at
the streamgage (24.0 feet). At each stage on Peachtree Creek, five stages at the
Chattahoochee River streamgage, from 26.4 feet to 38.4 feet in 3-foot intervals, were used
to determine backwater effects. The simulated water-surface profiles were then combined with
a geographic information system digital elevation model—derived from Light Detection and
Ranging (LiDAR) data having a 0.3-foot vertical and 16.4-foot horizontal resolution—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, provide emergency management personnel
and residents with critical information during flood response activities, such as evacuations
and road closures as well as for postflood-recovery efforts.

DISCLAIMERS:

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement 
by the U.S. Government.

Although this information product, for the most part, is in the public domain, it also contains copyrighted 
materials as noted in the text.  Permission to reproduce copyrighted items for other than personal use must 
be secured from the copyright owner.

Although these data have been processed successfully on a computer system at the U.S. Geological Survey, 
no warranty expressed or implied is made regarding the display or utility of the data on any other system, 
or for general or scientific purposes, nor shall the act of distribution constitute any such warranty. The U.S. 
Geological Survey shall not be held liable for improper or incorrect use of the data described and/or 
contained herein.

This data base, identified as SIM 3189, has been approved for release and publication by the Director of the 
USGS.  Although this database has been subjected to rigorous review and is substantially complete,
the USGS reserves the right to revise the data pursuant to further analysis and review. Furthermore, it is 
released on condition that neither the USGS nor the United States Government may be held liable
for any damages resulting from its authorized or unauthorized use.

CONTENTS:

This report consists of fifty map sheets, each with data files and metadata

To access the data:

The data files can be downloaded via the web from http://pubs.usgs.gov/sim/3189

The National Weather Service (NWS) Advanced Hydrological Prediction Service (AHPS) web pages for the gage
location mentioned in this report is as follows:
Peachtree Creek at Atlanta: AANG1, http://water.weather.gov/ahps2/hydrograph.php?wfo=ffc&gage=aang1

The main product is a Portable Document Format (.pdf) map and pamphlet which requires Adobe Acrobat 
for viewing. Acrobat software runs on a variety of systems, and is available for download free of charge 
from Adobe at http://www.adobe.com.

To access the inundation layers and depth grids, ArcGIS 9.3 is prefered, older versions may also work.