Jonathan W. Musser 20190312 Vector Digital Data Set (Polygon) and raster digital data https://doi.org/10.5066/P9KKB3H2 The digital flood-inundation maps included in this data release were developed for a 16.4-mile reach of the Yellow River from 0.5-mile upstream of River Drive to Centerville Highway (Georgia State Route 124), Gwinnett County, Georgia (Ga.) to depict estimates of the areal extent and depth of flooding corresponding to selected water levels (stages) at two U.S. Geological Survey (USGS) streamgages in the mapped area. The maps for the 9.0-mile reach from 0.5-mile upstream of River Drive to Stone Mountain Highway (US Route 78) are referenced to the Yellow River, near Snellville, Georgia (Ga.; station 02206500), and the maps for the 7.4-mile reach from Stone Mountain Highway to Centerville Highway are referenced to the streamgage Yellow River at Ga. 124, near Lithonia, Ga. (02207120). Real-time stage information from these streamgages can be used with these maps to estimate near real-time areas of inundation. The forecasted peak-stage information for the USGS streamgages Yellow River, near Snellville, Ga. (02206500), and Yellow River at Ga. 124, near Lithonia, Ga. (02207120), can be used in conjunction with the maps developed for 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 Center's River Analysis System (HEC-RAS) software for the Yellow River and was used to compute flood profiles for this 16.4-mile reach of the Yellow River. The hydraulic model was then used to simulate 16 water-surface profiles at 1.0-foot (ft) intervals at the Yellow River near Snellville, Ga. streamgage and 17 water-surface profiles at 1.0-ft intervals at the Yellow River near Lithonia, Ga. streamgage. At the Yellow River near Snellville, Ga. streamgage, the profiles ranged from a stage of 18.0 ft, which is 819.1 ft above the North American Vertical Datum of 1988 (NAVD 88), to a stage of 33.0 ft, which is 834.1 ft above NAVD 88. At the Yellow River at Ga. 124, near Lithonia, Ga. streamgage, the profiles ranged from the National Weather Service action stage of 13.0 ft, which is 732.5 ft above NAVD 88, to a stage of 29.0 ft, which is 748.5 ft above NAVD 88. 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-ft horizontal resolution to delineate the area flooded at each 1.0-ft interval of stream stage for each streamgage. Information about the study, floods, and methods used can be found in the USGS Scientific Investigations Report 2019-5009 online at https://doi.org/10.3133/sir20195009. This dataset was created to support the development of flood-peak inundation maps for the Yellow River in Gwinnett County, Georgia. Geographic Information System (GIS) shapefiles represent the modeled flood inundation extents of a 9.0-mile reach of the Yellow River from 0.5-mile upstream of River Drive to Stone Mountain Highway, and a 7.4-mile reach of the Yellow River from Stone Mountain Highway to Centerville Highway, Gwinnett County, Georgia. These flood inundation extents are for 1.0-foot intervals referenced to the water surface elevation and ranging from stage 18.0 to 33.0 feet (water surface elevation 819.1 to 834.1 feet) for streamgage 02206500, and stage 13.0 to 29.0 feet (water surface elevation 7325 to 748.5 feet) for streamgage 02207120. The flood-inundation maps will be used on the U.S. Geological Survey Flood Inundation Mapper website. GIS raster files represent the inundation depths corresponding to each flood extent elevation value for each of the two river extents. 20190312 publication date Complete None planned -84.0969 -84.0573 33.8952 33.7727 USGS Thesaurus floods river reaches stream discharge geospatial analysis None high-water marks flood-inundation maps flooded area USGS Metadata Identifier USGS:5bec4656e4b0b3fc5cf91437 Common geographic areas Georgia Gwinnett County None. Please see 'Distribution Info' for details. None. Users are advised to read the data set's metadata thoroughly to understand appropriate use and data limitations. U.S. Geological Survey, Southeast Region Jonathan W Musser Hydrologist mailing address

1770 Corporate Drive Suite 500

Norcross GA 30093 United States 678-924-6675 678-924-6710 jwmusser@usgs.gov Gwinnett County Environment as of Metadata Creation: Microsoft [Unknown] Version 6.2 (Build 9200); Esri ArcGIS 10.5.1 (Build 7367) Service Pack N/A (Build N/A) No formal attribute accuracy tests were conducted. No formal logical accuracy tests were conducted. Data set is considered complete for the information presented, as described in the abstract. Users are advised to read the rest of the metadata record carefully for additional details. A formal accuracy assessment of the horizontal positional information in the data set has not been conducted. A formal accuracy assessment of the vertical positional information in the data set has either not been conducted, or is not applicable. Gwinnett County 2015 Raster Digital Data Set obtained from Gwinnett County Gwinnett County Digital and/or Hardcopy Resources 2015 publication date Source Input 1 Source information used in support of the development of the data set. A HEC-RAS model was created and calibrated to the flow and streamgage height. The resulting inundated area was exported to ArcGIS and refined for publication. 20180801 Vector G-polygon 2 State Plane Coordinate System 1983 1002 0.9999 -84.16666666666667 30.0 2296583.333333333 0.0 coordinate pair 0.6096 0.6096 survey feet North_American_Datum_1983 GRS_1980 6378137.0 298.257222101 North American Vertical Datum of 1988 0.5 feet Attribute values Depth of Water 0.5 feet Attribute values The entity and attribute information provided here describes the tabular data associated with the data set. Please review the detailed descriptions that are provided (the individual attribute descriptions) for information on the values that appear as fields/table entries of the data set. The entity and attribute information was generated by the individual and/or agency identified as the originator of the data set. Please review the rest of the metadata record for additional details and information. U.S. Geological Survey GS ScienceBase mailing address

Denver Federal Center, Building 810, Mail Stop 302

Denver CO 80225 United States 1-888-275-8747 sciencebase@usgs.gov Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty. Inundated areas shown should not be used for navigation, regulatory, permitting, or other legal purposes. The U.S. Geological Survey provides these maps "as-is" for a quick reference, emergency planning tool but assumes no legal liability or responsibility resulting from the use of this information. Vector Digital Data Set (Polygon) https://doi.org/10.5066/P9KKB3H2 None. No fees are applicable for obtaining the data set. 20200827 Jonathan W Musser U.S. Geological Survey, Southeast Region Hydrologist mailing address

1770 Corporate Drive Suite 500

Norcross GA 30093 United States 678-924-6675 678-924-6710 jwmusser@usgs.gov FGDC Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998