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Scientific Investigations Map 3226

Prepared in cooperation with Gwinnett County, Georgia

Flood-Inundation Maps for Suwanee Creek from the Confluence of Ivy Creek to the Noblin Ridge Drive Bridge, Gwinnett County, Georgia

Jonathan W. Musser

ABSTRACT

Thumbnail of and link to report PDF (2 MB)

Digital flood-inundation maps for a 6.9-mile reach of Suwanee Creek, from the confluence of Ivy Creek to the Noblin Ridge Drive bridge, were developed by the U.S. Geological Survey (USGS) in cooperation with Gwinnett 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 Suwanee Creek at Suwanee, Georgia (02334885). 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 Suwanee Creek at Suwanee (02334885), 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 Suwanee Creek and was used to compute flood profiles for a 6.9-mile reach of the creek. The model was calibrated using the most current stage-discharge relations at the Suwanee Creek at Suwanee streamgage (02334885). The hydraulic model was then used to determine 19 water-surface profiles for flood stages at the Suwanee Creek streamgage at 0.5-foot intervals referenced to the streamgage. The profiles ranged from just above bankfull stage (7.0 feet) to approximately 1.7 feet above the highest recorded water level at the streamgage (16.0 feet). 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 5.0-foot horizontal resolution—to delineate the area flooded for each 0.5-foot increment of stream stage.

The availability of these maps, when combined with real-time stage information from USGS streamgages and forecasted stream stage 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.

August 7, 2012

For additional information contact:
Director, Georgia Water Science Center
U.S. Geological Survey
3039 Amwiler Rd.
Suite 130
Atlanta, GA 30360-2824
http://ga.water.usgs.gov/

Part or all of this report is presented in Portable Document Format (PDF); the latest version of Adobe Reader or similar software is required to view it. Download the latest version of Adobe Reader, free of charge.

Contents

Abstract

Introduction

Purpose and Scope

Study Area Description

Previous Studies

Constructing Water-Surface Profiles

Hydrologic and Steady Flow Data

Topographic and Bathymetric Data

Energy Loss Factors

Model Calibration and Performance

Development of Water-Surface Profiles

Inundation Mapping

Suwanee Creek, Georgia, Flood-Inundation Maps on the Internet

Disclaimer for Flood Inundation Maps

Uncertainties and Limitations Regarding Use of Flood Inundation Maps

Summary

References Cited



Map Sheets

You can view the map sheets either as high-resolution JPG images or as downloadable PDF files.
The JPG images are about 4 Megabytes in size, and the PDF files are about 18 Megabytes.

Sheet number reference based on stages (water-surface elevations) at the Suwanee Creek at Suwanee, Ga. (02334885) streamgage.
[Values 7.0-16.0 represent stage heights, in feet above gage datum. Values in parentheses (916.9-925.9) represent elevation in feet above North American Vertical Datum of 1988]

Stream stages and (water-surface elevations) at Suwanee Creek at Suwanee, Georgia, streamgage 02334885), with reference to corresponding map-sheet numbers in this report.
Suwanee Creek at Suwanee, Georgia
Stage
(Water-surface elevation)
7.0
(916.9)
7.5
(917.4)
8.0
(917.9)
8.5
(918.4)
9.0
(918.9)
9.5
(919.4)
10.0
(919.9)
10.5
(920.4)
11.0
(920.9)
11.5
(921.4)
Sheet number 1
JPG
PDF
2
JPG
PDF
3
JPG
PDF
4
JPG
PDF
5
JPG
PDF
6
JPG
PDF
7
JPG
PDF
8
JPG
PDF
9
JPG
PDF
10
JPG
PDF
Stage
(Water-surface elevation)
12.0
(921.9)
12.5
(922.4)
13.0
(922.9)
13.5
(923.4)
14.0
(923.9)
14.5
(924.4)
15.0
(924.9)
15.5
(925.4)
16.0
(925.9)
(925.9)
Sheet number 11
JPG
PDF
12
JPG
PDF
13
JPG
PDF
14
JPG
PDF
15
JPG
PDF
16
JPG
PDF
17
JPG
PDF
18
JPG
PDF
19
JPG
PDF
 

Suggested citation:

Musser, J.W., 2012, Flood-inundation maps for Suwanee Creek from the confluence of Ivy Creek to the Noblin Ridge Drive bridge, Gwinnett County, Georgia: U.S. Geological Survey Scientific Investigations Map 3226, 8 p. pamphlet, 19 sheets; available online at http://pubs.usgs.gov/sim/3226/.

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