clayton county, georgia county, georgia and incorporated areas community community ... lake city,...

CLAYTON COUNTY, GEORGIA AND INCORPORATED AREAS Community Community Name Number CLAYTON COUNTY 130041

(UNINCORPORATED AREAS) FOREST PARK, CITY OF 130042 JONESBORO, CITY OF 130043 LAKE CITY, CITY OF 130044 LOVEJOY, CITY OF 130658 MORROW, CITY OF 130045 RIVERDALE, CITY OF 130047

FLOOD INSURANCE STUDY NUMBER 13063CV000A

Effective: August 16, 2007

Clayton County

NOTICE TO FLOOD INSURANCE STUDY USERS

Communities participating in the National Flood Insurance Program have established repositories of flood hazard data for floodplain management and flood insurance purposes. This Flood Insurance Study (FIS) report may not contain all data available within the Community Map Repository. Please contact the Community Map Repository for any additional data. The Federal Emergency Management Agency (FEMA) may revise and republish part or all of this FIS report at any time. In addition, FEMA may revise part of this FIS report by the Letter of Map Revision process, which does not involve republication or redistribution of the FIS report. Therefore, users should consult with community officials and check the Community Map Repository to obtain the most current FIS report components. Initial Countywide FIS Effective Date: August 16, 2007

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TABLE OF CONTENTS

VOLUME I

1.0 INTRODUCTION ...........................................................................................................1

1.1 Purpose of Study........................................................................................................1

1.2 Authority and Acknowledgments ..............................................................................1

1.3 Coordination ..............................................................................................................3

2.0 AREA STUDIED .............................................................................................................4

2.1 Scope of Study ...........................................................................................................4

2.2 Community Description.............................................................................................6

2.3 Principal Flood Problems...........................................................................................6

2.4 Flood Protection Measures ........................................................................................7

3.0 ENGINEERING METHODS .........................................................................................7

3.1 Hydrologic Analyses..................................................................................................8

3.2 Hydraulic Analyses..................................................................................................20

3.3 Vertical Datum.........................................................................................................22

4.0 FLOODPLAIN MANAGEMENT APPLICATIONS ................................................23

4.1 Floodplain Boundaries .............................................................................................24

4.2 Floodways................................................................................................................25

5.0 INSURANCE APPLICATIONS ..................................................................................48

6.0 FLOOD INSURANCE RATE MAP ............................................................................48

7.0 OTHER STUDIES .........................................................................................................49

8.0 LOCATION OF DATA.................................................................................................49

9.0 BIBLIOGRAPHY AND REFERENCES ....................................................................49

TABLE OF CONTENTS (Continued)

VOLUME I

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FIGURES

Figures 1A - 1F - Frequency-Discharge, Drainage Area Curves ..................................................14 Figure 2 - Floodway Schematic .....................................................................................................47

TABLES

Table 1 - Summary of Discharges .................................................................................................10 Table 2 - Summary of Stillwater Elevations..................................................................................13 Table 3 - Manning’s “n” Values ....................................................................................................21 Table 4 - Vertical Datum Conversion............................................................................................23 Table 5 - Floodway Data ...............................................................................................................26 Table 6 - Community Map History................................................................................................50

EXHIBITS

Exhibit 1 - Flood Profiles

Beaver Dam Creek Panels 01P-03P Big Cotton Indian Creek Panels 04P-05P Camp Creek Panels 06P-09P Camp Creek Tributary Panels 10P-11P Conine Creek Panel 12P Conley Creek Panels 13P-14P Conley Creek Tributary Panel 15P Duffey Tributary Panel 16P East Tributary of Jester Creek Panel 17P Flint River Panels 18P-23P Flint River Tributary Panels 24P-25P Hurricane Creek Panels 26P-29P Jester Creek Panels 30P-36P Mud Creek Panels 37P-38P North Fork Jester Creek Panels 39P-41P Panther Creek Panels 42P-45P Pates Creek Panels 46P-48P Pine Creek Panel 49P Poole Creek Panel 50P Poole Creek Tributary Panel 51P Reeves Creek Panels 52P-54P Roberts Road Tributary Panels 55P-56P Shoal Creek Panel 57P Stratford Tributary Panels 58P-59P Stream A Panels 60P-61P Stream B Panels 62P-63P

TABLE OF CONTENTS (Continued)

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Exhibit 1 - Flood Profiles (Continued)

Stream BT Panel 64P Stream C Panels 65P-66P Stream CT Panels 67P-68P Stream CT-A Panel 69P Stream D Panel 70P Sullivan Creek Panels 71P-73P Swamp Creek Panels 74P-76P Tar Creek Panel 77P Upton Creek Panel 78P Wallis Creek Panels 79P-81P West Tributary of Jester Creek Panel 82P York Tributary Panel 83P

Exhibit 2 - Flood Insurance Rate Map Index

Flood Insurance Rate Map

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FLOOD INSURANCE STUDY CLAYTON COUNTY, GEORGIA AND INCORPORATED AREAS

1.0 INTRODUCTION

1.1 Purpose of Study

This Flood Insurance Study (FIS) revises and updates information on the existence and severity of flood hazards in the geographic area of Clayton County, including the Cities of Forest Park, Jonesboro, Lake City, Lovejoy, Morrow and Riverdale, and the unincorporated areas of Clayton County (referred to collectively herein as Clayton County), and aids in the administration of the National Flood Insurance Act of 1968 and the Flood Disaster Protection Act of 1973. This study has developed flood-risk data for various areas of the community that will be used to establish actuarial flood insurance rates and to assist the community in its efforts to promote sound floodplain management. Minimum floodplain management requirements for participation in the National Flood Insurance Program (NFIP) are set forth in the Code of Federal Regulations at 44 CFR, 60.3. Please note that the City of College Park is geographically located in both Clayton County and Fulton County, and the flood hazard information is included entirely in the Fulton County FIS report. Please see the Fulton County FIS report for flood hazard information for the City of College Park. In some states or communities, floodplain management criteria or regulations may exist that are more restrictive or comprehensive than the minimum Federal requirements. In such cases, the more restrictive criteria take precedence and the State (or other jurisdictional agency) will be able to explain them. The Digital Flood Insurance Rate Map (DFIRM) and FIS report for this countywide study have been produced in digital format. Flood hazard information was converted to meet the Federal Emergency Management Agency (FEMA) DFIRM database specifications and Geographic Information System (GIS) format requirements. The flood hazard information was created and is provided in a digital format so that it can be incorporated into a local GIS and be accessed more easily by the community.

1.2 Authority and Acknowledgments

The sources of authority for this FIS are the National Flood Insurance Act of 1968 and the Flood Disaster Protection Act of 1973.

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Information on the authority and acknowledgements for each jurisdiction included in this countywide FIS report, as compiled from their previously printed FIS reports, are shown below: Clayton County (Unincorporated Areas):

The hydrologic and hydraulic analyses for the original FIS report dated June 15, 1978 (Reference 1), were prepared by the U.S. Army Corps of Engineers (USACE), Savannah District, for the Federal Insurance Administration (FIA), under Inter-Agency Agreement Nos. IAA-H-2-73 and IAA-H-16-75, Project Order Nos. 1 and 2, respectively. The work was completed in December 1975. For the FIS report dated May 1, 1984 (Reference 2), the hydrologic and hydraulic analyses were prepared by the USACE, Savannah District, and additional information was obtained from the Clayton County Commissioners, Public Works Department. For the FIS report dated November 6, 1991 (Reference 3), the hydrologic and hydraulic analyses were prepared by the USACE, Mobile District, for the Federal Emergency Management Agency (FEMA), under Inter-Agency Agreement No. EMW-88-E-2739, Project Order No. 4, Amendment No. 1. The work was completed in November 1989. The hydrologic and hydraulic analyses for North Fork Jester Creek and Conine Creek were taken from the FIS for the City of Morrow, Georgia (Reference 4). For the FIS report dated November 20, 2000 (Reference 5), no hydrologic or hydraulic analyses were performed.

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Forest Park, City of: For the FIS report dated November 16, 1976 (Reference 6), the hydrologic and hydraulic analyses were performed by the USACE, Mobile District for the FIA, under Inter Agency Agreement Nos. IAA-H-2-73 and IAA-H-19-74, Project Order Nos. 13 and 15, respectively. The work, which was completed in October 1974, covered all flooding sources affecting the City of Forest Park.

Morrow, City of: For the FIS report dated August 16, 1982 (Reference 4), the hydrologic and hydraulic analyses were prepared by Mayes, Sudderth and Etheredge, Inc., for FEMA, under Contract No. H-6828. The work was completed in October 1981.

Riverdale, City of: For the FIS report dated November 6, 1991 (Reference 7), the hydrologic and hydraulic analyses were prepared by the USACE, Savannah District, for the FIA, under Inter-Agency Agreement No. IAA-H-7-76, Project Order No. 6. The work was completed in February 1977.

No previous FIS report was published for the Cities of Jonesboro, Lake City, and Lovejoy.

1.3 Coordination

The initial and final meeting dates for the previous FIS reports for Clayton County and its communities are listed in the following table:

Community FIS Date Initial Meeting Final Meeting

Clayton County (Unincorporated Areas)

June 15, 1978 May 1, 1984

November 6, 1991 November 20, 2000

May 15, 1974 ∗ ∗

June 23, 19991

October 17, 1975 ∗

November 27, 1990 ∗

Forest Park, City of November 1976 * March 25, 1975 Morrow, City of August 16, 1982 June 14, 1979 March 29, 1982 Riverdale, City of November 6, 1991 May 22, 1975 October 14, 1976 ∗Data not available 1Community was notified by letter that revision would be conducted

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The meetings held for the unincorporated areas of Clayton County were attended by representatives of FEMA, FIA, USACE, Clayton County, and Mayes, Sudderth, and Etheredge, Inc. For the City of Forest Park, a search for basic data was made at all levels of government. The city provided a large scale city map from which the base maps used in the report were taken. Contacts were made with city officials during the study in order to minimize all possible conflicts. The meetings held for the City of Morrow were attended by representatives of FEMA, city officials and Mayes, Sudderth, and Etheredge, Inc. The meetings held for the City of Riverdale were attended by representatives of the USACE, FIA and community officials. For this revision, a Scoping Meeting was held on October 28, 2004, and attended by representatives of Clayton County, the cities of Jonesboro, Lake City, Lovejoy, Morrow, and Riverdale, the Georgia Department of Natural Resources (DNR), and Greenhorne & O’Mara. The purpose of the meeting was to discuss the scope of the FIS. The final meeting was held on April 18, 2006, and was attended by representatives of Clayton County, FEMA, the Georgia DNR, PBS&J, and local communities.

2.0 AREA STUDIED

2.1 Scope of Study

This FIS covers the geographic area of Clayton County, Georgia, including the incorporated communities listed in Section 1.1. The areas studied by detailed methods were selected with priority given to all known flood hazards and areas of projected development or proposed construction. Precountywide Analyses The following streams were studied by detailed methods for the June 15, 1978, FIS report for Clayton County (Unincorporated Areas): Beaver Dam Creek, Big Cotton Indian Creek, Camp Creek, Conley Creek, Flint River, Hurricane Creek, Jester Creek, Mud Creek, Panther Creek, Pates Creek, Reeves Creek, Roberts Road Tributary, Sullivan Creek, Swamp Creek, Tar Creek, Upton Creek and Wallis Creek. Portions of the following streams were restudied by detailed methods for the May 1, 1984, revision for Clayton County (Unincorporated Areas): Conley Creek and Big Cotton Indian Creek.

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For the November 6, 1991, revision for Clayton County (Unincorporated Areas), the following streams were either revised or newly restudied by detailed methods: Camp Creek Tributary, Conine Creek, Flint River, Flint River Tributary, Jester Creek, North Fork Jester Creek, Shoal Creek, Smith Reservoir, Sullivan Creek. For the November 20, 2000, revision for Clayton County (Unincorporated Areas), the county boundary between Clayton County and Henry County was updated and Little Cotton Indian Creek was renamed to Big Cotton Indian Creek. The following flooding sources were studied by detailed methods in the City of Forest Park, November 16, 1976, FIS report: Conley Creek, Conley Creek Tributary, East Tributary of Jester Creek, Jester Creek, Pine Creek, Poole Creek, Poole Creek Tributary, and West Tributary of Jester Creek. The following streams were studied by detailed methods for the August 16, 1982, FIS report for the City of Morrow: Conine Creek, Duffey Tributary, North Fork Jester Creek, Stratford Tributary and York Tributary. The following streams were studied by detailed methods for the November 6, 1991, FIS report for the City of Riverdale: Camp Creek, Flint River, Stream A, Stream B, Stream BT, Stream C, Stream CT, Stream CT-A and Stream D. Countywide Analyses For this countywide analyses, the FIS report and FIRM were converted to countywide format, and the flooding information for the entire county, including both incorporated and unincorporated areas, is shown. Also, the vertical datum was converted from the National Geodetic Vertical Datum of 1929 (NGVD29) to the North American Vertical Datum of 1988 (NAVD88). In addition, the Universal Transverse Mercator coordinates, previously referenced to the North American Datum of 1927, are now referenced to the North American Datum of 1983. As part of Letter of Map Revision Case No. 99-04-101P, dated October 29, 1999, a 1-percent-annual-chance floodplain along the unnamed tributary to North Fork Jester Creek, between the Lake City corporate limits and the Norfolk Southern Railway, was studied by detailed methods. Approximate analyses were used to study those areas having low development potential or minimal flood hazards. The scope and methods of study were proposed to and agreed upon by FEMA and Clayton County.

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2.2 Community Description

Clayton County is located immediately south of Atlanta, in the northwest portion of Georgia. Clayton County is bordered by DeKalb County to the northeast, Fulton County to the northwest, Fayette County to the southwest, Henry County to the east, and Spaulding County to the south. Clayton County is the southernmost of the seven counties that comprise the Atlanta Regional Commission Planning Area. Administration of the county is performed by the Board of County Commissioners, with Jonesboro serving as the county seat. According to the U.S. Census Bureau, in 2000 the population for Clayton County and incorporated areas was 236,517 (Reference 8). The county has a land area of 146 square miles; approximately 37.4 percent of the land area (54.6 square miles) lies in the Ocmulgee River drainage basin, and the remaining 91.4 square miles lies in the Appalachicola River drainage basin. The Norfolk Southern Railway runs essentially along the ridge that separates these areas. The ridge between the Ocmulgee River basin and the Appalachicola River basin divides Clayton County approximately east and west. The major stream is the Flint River, which has its headwaters in the City of College Park, and flows through the William B. Hartsfield Airport. Clayton County’s mild climate consists of warm, humid summers and rather warm winters. The average annual precipitation is 50.2 inches with March being the wettest month. The mean temperatures range from a January low of 33 degrees Fahrenheit (ºF) to an July high of 89°F (Reference 9). The topography and floodplains of the streams studied by detailed methods vary from stream to stream and from the headwaters to the mouth of each stream. All streams except the Flint River are generally characterized by narrow, steep channels with narrow floodplains at the headwaters, but change to narrow streams with broad floodplains near the mouth. The Flint River above Lee’s Mill Road has a narrow floodplain. Downstream of Lee’s Mill Road, the floodplain becomes broad and swampy. Channel banks are low and are overtopped frequently.

2.3 Principal Flood Problems

The Flint River and its tributaries generally flow through flat, swampy areas. The floodplains are covered with natural brush and undergrowth, except where development has infringed on the floodplain. Such undergrowth tends to impede flood-flows along these streams. Streams in the eastern portion of the county, particularly Reeves and Pates Creeks, are very steep and rocky, and present a velocity hazard during floods. Flood damage in the past has mostly been sustained by roads, culverts, and public utilities. Minor flooding is attributed to beaver dams on many streams.

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The greatest flood for which data is available was the flood of November 10, 1966. Other great floods occurred on streams in the metropolitan area of Atlanta on December 7-10, 1919; April 30, 1963; and September 27, 2004. The 1919 floods resulted from a recorded 11.8 inches of rain on December 8 and 9, 1919. Due to the short stream lengths and urban uses of the watersheds, floods may occur on streams in Clayton County only a short time after intense rainfall begins. Previous studies have shown that the streams normally recede within 24 hours. Flood-producing storms may occur at any time during the year, but are more numerous in winter and spring. Winter storms are usually of the frontal type, lasting from 2 to 4 days and covering large areas. Summer storms are generally of a thunderstorm nature, with high rainfall intensities scattered over small areas. Within the City of Morrow, the restriction of North Fork Jester Creek caused by Interstate Highway 75 results in major ponding that enhances substantial mosquito infestation. In addition, siltation occurs in this area during significant floods, which contributes to a reduction in channel capacity which may ultimately raise future flood levels. In the City of Riverdale, the floodplain along Stream C has been slightly developed by residential housing, making some homes subject to flooding. The concentration of upstream runoff into Stream C is a major cause of flash flooding. Homes along Stream CT, upstream of Roundtree Road, and Stream B, upstream of Voyles Drive, are subject to flooding from small culverts and storm sewers beneath the streets and adjacent yards. Along Stream D, high velocity flows and small culverts create a flood hazard. Shallow flooding at the headwaters of Stream D is due to the fact that this area is relatively flat and there is no well defined stream channel.

2.4 Flood Protection Measures

Although there is no flood protection structures located in Clayton County, the floodplains along all streams within Clayton County are protected by the county zoning laws and the Sediment Control Resolution adopted by the County Commission in November 1973.

3.0 ENGINEERING METHODS

For the flooding sources studied by detailed methods in the community, standard hydrologic and hydraulic study methods were used to determine the flood hazard data required for this study. Flood events of a magnitude that are expected to be equaled or exceeded once on the average during any 10-, 50-, 100-, or 500-year period (recurrence interval) have been selected as having special significance for floodplain management

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and for flood insurance rates. These events, commonly termed the 10-, 50-, 100-, and 500-year floods, have a 10-, 2-, 1-, and 0.2-percent chance, respectively, of being equaled or exceeded during any year. Although the recurrence interval represents the long-term, average period between floods of a specific magnitude, rare floods could occur at short intervals or even within the same year. The risk of experiencing a rare flood increases when periods greater than 1 year are considered. For example, the risk of having a flood that equals or exceeds the 1-percent-annual-chance (100-year) flood in any 50-year period is approximately 40 percent (4 in 10); for any 90-year period, the risk increases to approximately 60 percent (6 in 10). The analyses reported herein reflect flooding potentials based on conditions existing in the community at the time of completion of this study. Maps and flood elevations will be amended periodically to reflect future changes. 3.1 Hydrologic Analyses

Hydrologic analyses were carried out to establish peak discharge-frequency relationships for each flooding source studied by detailed methods affecting the community.

The peak discharge-frequency relationships estimated using the U.S. Geological Survey (USGS) regression equations were adjusted to urbanization applying the relationships in the USGS Water Resources Investigation (WRI) Report 77-57 (Reference 10). Discharge-frequency relationships for Beaver Dam Creek, Big Cotton Indian Creek, Conley Creek, Flint River Tributary, Hurricane Creek, Panther Creek, Pates Creek, Reeves Creek, Roberts Road Tributary, Stream A, Stream B, Stream BT, Stream C, Stream CT, Stream CT-A, Stream D, Swamp Creek, Tar Creek, Upton Creek, and Wallis Creek were based on a statistical analysis for data obtained at all stream gages in the Metropolitan Atlanta area. The following tabulation lists gage records that were used in the log-Pearson Type III analysis:

Gage Location Length of Record (years)

South River at East Point 5 Yellow River near Snellville 26 Peachtree Creek at Northside Drive at Atlanta 10 South Utoy Creek Tributary at East Point 5 North Fork Camp Creek at Atlanta 5 South River at Atlanta 18 South River near Atlanta 18 Snapfinger Creek near Decatur 7 South Fork Peachtree Creek at Atlanta 7

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Peak discharge-frequency relationships along the Flint River were computed using rainfall-runoff models formulated with the USACE HEC-1 computer program (Reference 11) using the Soil Conservation Service (SCS) dimensionless unit hydrograph methodology. Peak discharge-frequency relationships were also formulated using the USGS regional regression equations (Reference 12). Rainfall depth-duration-frequency data were taken from Technical Paper No. 40 (Reference 13) and Hydro 35 (Reference 14). The rainfall loss rates were defined by the SCS curve number methodology. Storage-outflow relationships were derived using a USACE HEC-2 backwater model (Reference 15) for stream routings on the Flint River from the Hartsfield Airport boundary to the Clayton County boundary. Muskingum routings were used for Camp Creek, Flint River, Jester Creek, Mud Creek, and Sullivan Creek above the lower airport boundary. The hydrologic models computed the discharge-frequency relations in the basin for the 10-, 2-, 1-, and 0.2-percent-annual-chance floods. Unit hydrograph parameters were developed for 39 sub-basins in the Flint River basin for use in the USACE HEC-1 computer models (Reference 11). For areas outside the Hartsfield Airport, the SCS lag parameter was determined using stream length and land slope values measured from topographic maps. The SCS lag equation used related lag to stream length, land slope, and curve number. The point rainfall depth-duration relationship for the 0.2-percent-annual-chance rainfall was graphically extrapolated from the 10-, 2-, and 1-percent-annual-chance depth-duration data (References 13 and 14). For the Hartsfield Airport, the SCS time lag was determined from the time of concentration ,TC, for each airport sub-basin using the equation:

lag = 0.6 (TC) The times of concentration for the airport subbasins were provided by the airport engineers. The SCS curve numbers were used in both the lag computation and in defining the rainfall loss rate function. The SCS curve numbers for the sub-basins were determined by integrating soil group and land use for the land cover type and hydrologic conditions presented in Table 2-2 of Technical Release No. 55 (Reference 16). Soil group determinations were made from soil surveys (References 17 and 18). Land use determinations for areas outside the airport were made from aerial photos. Land use for the airport was taken from data provided by the airport engineers giving impervious (pavement) and pervious (grass) areas in each airport sub-basin. Rainfall depth-drainage area relationships were defined for a range of area sizes by applying area corrections to the point rainfall amounts.

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The synthetic depth-duration-frequency rainfall data were used in the USACE HEC-1 computer model (Reference 11) to define the peak flood frequency relationships for streams in the Flint River study area. Peak discharges obtained from the USACE HEC-1 model were compared to the USGS regional regression equations to verify the reasonableness of the computed peak flood discharge estimates. Peak discharge-frequency relationships were computed for Camp Creek Tributary, Shoal Creek, and Smith Reservoir, using the regional study methodologies applied for the upper Flint River. The USGS methodology presented in WRI 83-4203 (Reference 19) was used to adjust the regional regression estimates for urbanized areas. The equations in WRI 83-4203 use drainage area, percent impervious area, and stream slope as the independent variables in estimating flood discharges. Hydrologic analyses of North Fork Jester Creek and Conine Creek were based on the USGS regional regression equations presented in WRI 78-137 (Reference 20) which relate discharge to drainage area for natural streams in various physiographic provinces in Georgia. The WRI 78-137 regression equation results were adjusted for urbanization. For Duffey Tributary, Lake Spivey, Stratford Tributary, and York Tributary, hydrologic analyses were based upon utilization of the regional regression equations presented in WRI 78-137 (Reference 20) relating discharge to drainage area for natural streams in various physiographic provinces in Georgia. For Conley Creek, Conley Creek Tributary, East Tributary of Jester Creek, Jester Creek, Pine Creek, Poole Creek, Poole Creek Tributary, and West Tributary of Jester Creek, in the City of Forest Park flood-flow frequency data were taken from regionalized frequency curves developed by the USACE for the Atlanta Metropolitan Area. Peak discharge-drainage area relationships for all streams studied by detailed methods are shown in Table 1.

Table 1 - Summary of Discharges

Peak Discharges (cubic feet per second)

FLOODING SOURCE AND LOCATION

DRAINAGE AREA

(square miles)

10-Percent-Annual-Chance

2-Percent-Annual- Chance


0.2-Percent-Annual-Chance

BEAVER DAM CREEK See Figures 1A

and 1B

BIG COTTON INDIAN CREEK See Figures 1A

and 1B

Table 1 - Summary of Discharges (Continued)

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DRAINAGE AREA

(square miles)





CAMP CREEK See Figure 1C CAMP CREEK TRIBUTARY

At the confluence with Camp Creek

3.70 1,200 1,800 2,100 2,900

At West Fayetteville Road / State Highway 314

3.42 1,000 1,600 1,800 2,500

At Bethsaida Road 1.90 800 1,200 1,400 1,900 At upstream county boundary 0.93 400 700 800 1,200

CONINE CREEK At the confluence with North

Fork Jester Creek 1.23 732 1,094 1,259 1,674

CONLEY CREEK See Figure 1D

CONLEY CREEK TRIBUTARY See Figure 1D DUFFEY TRIBUTARY

At the confluence with York Tributary

0.13 191 285 332 443

EAST TRIBUTARY OF JESTER CREEK

See Figure 1D

FLINT RIVER See Figure 1F

At downstream county boundary 159.68 9,600 16,400 18,300 23,900 Just downstream of the

confluence of Shoal Creek 136.98 9,900 17,100 19,000 25,200

Just downstream of the confluence of Hurricane Creek

126.04 10,300 16,800 18,700 24,500

Just downstream of the confluence of Swamp Creek

72.44 8,500 13,900 15,600 20,100

Just downstream of the confluence of Camp Creek

68.03 8,400 13,600 15,300 19,600

Just upstream of the confluence of Camp Creek

47.98 6,600 10,200 11,500 14,800

Just downstream of the confluence of Jester Creek

39.18 7,800 11,800 13,700 17,800

Just upstream of the confluence of Jester Creek

27.22 5,900 8,700 9,800 12,700

At Upper Riverdale Road 23.41 7,600 12,000 13,500 17,200 Just downstream of the

confluence of Mud Creek 19.99 7,300 10,600 11,900 14,900

Just downstream of the confluence of Sullivan Creek

11.99 5,100 7,300 8,200 10,100

FLINT RIVER TRIBUTARY

At the confluence with Flint River 2.24 900 1,400 1,600 2,200 At State Highway 85 1.36 700 1,000 1,200 1,600 Approximately 2,450 feet

upstream of West Lees Mill Road

0.50 500 700 800 1,100

HURRICANE CREEK See Figures 1A

and 1B


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DRAINAGE AREA

(square miles)





JESTER CREEK

At the confluence with Flint River 11.96 3,100 4,600 5,200 6,800 At U.S. Interstate Highway 19 /

41/ State Highway 3C / Tara Boulevard

11.62 3,100 4,500 5,200 6,700

Just downstream of the confluence of North Fork Jester Creek

8.61 2,700 3,900 4,500 5,800

Just upstream of the confluence of North Fork Jester Creek

3.57 1,500 2,300 2,600 3,400

At Morrow Road 2.21 1,200 1,800 2,000 2,700 Just upstream of Windsor Drive 1.48 1,000 1,400 1,700 2,200

MUD CREEK See Figures 1A and 1B

NORTH FORK JESTER CREEK

At Morrow Industrial Boulevard 4.27 1,691 2,462 2,799 3,636 Just downstream of Interstate

Highway 75 / State Highway 401

2.46 1,218 1,780 2,030 2,649

Just upstream of Morrow Road 1.59 939 1,377 1,574 2,061

PANTHER CREEK See Figures 1A and 1B

PATES CREEK See Figures 1A

and 1B

PINE CREEK See Figure 1D POOLE CREEK See Figure 1D POOLE CREEK TRIBUTARY See Figure 1D REEVES CREEK See Figures 1A

and 1B

ROBERTS ROAD TRIBUTARY See Figures 1A

and 1B

SHOAL CREEK

At the confluence with Flint River 9.13 1,600 2,600 3,000 4,200 STRATFORD TRIBUTARY

Approximately 200 feet downstream of Harbin Wood Drive

0.34 333 493 570 756

Approximately 625 feet downstream of Mural Circle

0.22 205 305 354 473

STREAM A See Figure 1E

STREAM B See Figure 1E

STREAM BT See Figure 1E


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DRAINAGE AREA

(square miles)





STREAM C See Figure 1C

STREAM CT See Figure 1C

STREAM CT-A See Figure 1F

STREAM D See Figure 1F SULLIVAN CREEK

At the confluence with Flint River 6.01 2,200 3,300 3,800 4,800 Just downstream of Interstate

Highway 285 / State Highway 407

4.17 2,100 3,000 3,400 4,500

SWAMP CREEK See Figures 1A

and 1B

TAR CREEK See Figures 1A

and 1B

UPTON CREEK See Figures 1A

and 1B

WALLIS CREEK See Figures 1A

and 1B

WEST TRIBUTARY OF JESTER CREEK

See Figure 1D

YORK TRIBUTARY

Approximately 250 feet downstream of Meadowbrook Lane

0.31 338 501 579 767

Approximately 260 feet upstream of Meadowbrook Lane

0.13 159 237 276 369

Stillwater elevations for lakes studied in detail within Clayton County are shown in Table 2.

Table 2 - Summary of Stillwater Elevations

Water Surface Elevations (Feet NAVD881)

Flooding Source 10-Percent-

Annual-Chance 2-Percent-

Annual-Chance 1-Percent-

Annual-Chance 0.2-Percent-

Annual-Chance SMITH RESERVOIR

805.8

806.3

806.5

806.9

LAKE SPIVEY 784.72 785.52 786.12 786.72

1North American Vertical Datum of 1988 2Elevations for Lake Spivey were taken from the Henry County, Georgia profile for Rum Creek.

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3.2 Hydraulic Analyses

Analyses of the hydraulic characteristics of flooding from the sources studied were carried out to provide estimates of the elevations of floods of the selected recurrence intervals. Users should be aware that flood elevations shown on the FIRM represent rounded whole-foot elevations and may not exactly reflect the elevations shown on the Flood Profiles or in the Floodway Data Table in the FIS report. Flood elevations shown on the FIRM are primarily intended for flood insurance rating purposes. For construction and/or floodplain management purposes, users are cautioned to use the flood elevation data presented in this FIS report in conjunction with the data shown on the FIRM. Cross sections for all flooding sources studied by detailed methods were obtained from field surveys. All bridges, dams, and culverts were field surveyed to obtain elevation data and structural geometry. Cross sections for the backwater analyses were field surveyed at selected intervals to model conveyance of the valley; they were also field surveyed just upstream and downstream of bridges and culverts in order to compute the significant backwater effects of such structures. Four-foot contour interval topographic mapping was photogrammetrically derived from aerial surveys (Reference 21) and are utilized to supplement the surveyed cross sections for select flooding sources. For the May 1, 1984, FIS report for the unincorporated areas of Clayton County, the USACE, Savannah District, provided HEC-2 computer printouts (Reference 15) revising the water surface profiles and correcting the flood delineations for Conley Creek. The analysis supersedes the information presented in the USACE, Savannah District, Flood Plain Information report completed in 1968 (Reference 22). For the restudy of Big Cotton Indian Creek included in the May 1, 1984, FIS report for the unincorporated areas of Clayton County, the Clayton County Commissioners, Public Works Department surveyed the Mill Pond Dam and found the elevation to be approximately 7 feet lower than was previously reported in the June 15, 1978, FIS report for the unincorporated areas of Clayton County. A review of the HEC-2 program used for Big Cotton Indian Creek revealed that data for the dam had not been included in the model. Instead, input data held the WSELs upstream and downstream of the dam at a constant value. Since detailed channel cross sections were not available in the area of the dam, calculations of weir flow were used with the correct dam elevation to revise the water surface profiles for the stream reach. Starting WSELs for Big Cotton Indian Creek, Camp Creek, Conine Creek, Duffey Tributary, Flint River, Flint River Tributary, Hurricane Creek, North Fork Jester Creek, Panther Creek, Stratford Tributary, Stream C, Stream CT, Tar Creek, Upton Creek and York Tributary were developed by the slope-area

21

method. Water-surface profiles for Pates Creek, Stream B and Stream D were started at critical depth. Starting WSELs for Beaver Dam Creek, Roberts Road Tributary, Sullivan Creek, Swamp Creek, and Wallis Creek were taken from computed profile elevations of the Flint River. Starting WSELs for Stream A and Stream BT were taken from the computed profile elevations of Camp Creek and Stream B, respectively. Starting WSELs for Reeves Creek were taken from a USACE Floodplain Information Report in adjacent Henry County (Reference 23). Starting elevations for Conley Creek were taken from the Floodplain Information Report completed in 1968 by the USACE, Savannah District (Reference 22). Starting WSELs for Mud Creek and Jester Creek were obtained from a Floodplain Information Report completed in 1969 by the USACE, Mobile District (Reference 24). Channel roughness factors (Manning’s “n”) used in the hydraulic computations were chosen by engineering judgment and based on field observations of the stream channels and overbank floodplain areas. The channel and overbank “n” values for all streams studied by detailed methods are shown Table 3.

Table 3 - Manning’s “n” Values

Stream Channel “n” Overbank “n”

Beaver Dam Creek 0.045-0.070 0.055-0.150 Big Cotton Indian Creek 0.045-0.070 0.055-0.150 Camp Creek 0.045-0.055 0.10-0.12 Camp Creek Tributary 0.045-0.055 0.075-0.120 Conine Creek 0.045-0.055 0.075-0.120 Conley Creek 0.045-0.070 0.055-0.150 Conley Creek Tributary * * Duffey Tributary 0.055 0.075-0.11 East Tributary of Jester Creek * * Flint River 0.045-0.055 0.10-0.12 Flint River Tributary 0.045-0.055 0.10-0.12 Hurricane Creek 0.045-0.070 0.055-0.150 Jester Creek 0.045-0.055 0.075-0.120 Mud Creek 0.045-0.070 0.055-0.150 North Fork Jester Creek 0.045-0.055 0.075-0.120 Panther Creek 0.045-0.070 0.055-0.150 Pates Creek 0.045-0.070 0.055-0.150 Pine Creek * * Poole Creek * * Poole Creek Tributary * * Reeves Creek 0.045-0.070 0.055-0.150 Roberts Road Tributary 0.045-0.070 0.055-0.150 Shoal Creek 0.045-0.055 0.075-0.120 Stratford Tributary 0.055 0.075-0.11 Stream A 0.045-0.055 0.06-0.15 Stream B 0.045-0.055 0.06-0.15 * Data not available

Table 3 - Manning’s “n” Values (Continued)

22

Stream Channel “n” Overbank “n”

Stream BT 0.045-0.055 0.06-0.15 Stream C 0.045-0.055 0.06-0.15 Stream CT 0.045-0.055 0.06-0.15 Stream CT-A 0.045-0.055 0.06-0.15 Stream D 0.045-0.055 0.06-0.15 Sullivan Creek 0.045-0.055 0.075-0.120 Swamp Creek 0.045-0.070 0.055-0.150 Tar Creek 0.045-0.070 0.055-0.150 Upton Creek 0.045-0.070 0.055-0.150 Wallis Creek 0.045-0.070 0.055-0.150 West Tributary of Jester Creek * * York Tributary 0.055 0.075-0.11 * Data not available

Locations of selected cross sections used in the hydraulic analyses are shown on the Flood Profiles (Exhibit 1). For stream segments for which a floodway was computed (Section 4.2), selected cross section locations are also shown on the FIRM (Exhibit 2). The hydraulic analyses for this study were based on unobstructed flow. The flood elevations shown on the Flood Profiles (Exhibit 1) are thus considered valid only if hydraulic structures remain unobstructed, operate properly, and do not fail.

3.3 Vertical Datum

All FIS reports and FIRMs are referenced to a specific vertical datum. The vertical datum provides a starting point against which flood, ground, and structure elevations can be referenced and compared. Until recently, the standard vertical datum in use for newly created or revised FIS reports and FIRMs was the NGVD29. With the finalization of the NAVD88, many FIS reports and FIRMs are being prepared using NAVD88 as the referenced vertical datum. All flood elevations shown in this FIS report and on the FIRM are referenced to NAVD88. Structure and ground elevations in the community must, therefore, be referenced to NAVD88. It is important to note that adjacent communities may be referenced to NGVD29. This may result in differences in Base Flood Elevations (BFEs) across the corporate limits between the communities. The average conversion factor that was used to convert the data in this FIS report to NAVD88 was calculated using the National Geodetic Survey’s VERTCON online utility (Reference 25). The data points used to determine the conversion factor are listed in Table 4, “Vertical Datum Conversion”.

23

Table 4 - Vertical Datum Conversion

Quad Name

Corner Latitude Longitude Conversion from NGVD29

to NAVD88

Riverdale NW 33.63 -84.50 0.164 feet Riverdale NE 33.63 -84.38 0.203 feet Jonesboro NE 33.63 -84.25 0.177 feet Jonesboro SE 33.50 -84.25 0.095 feet Riverdale SE 33.50 -84.38 0.102 feet Hampton SW 33.38 -84.38 0.046 feet AVERAGE 0.131 feet

For more information on NAVD88, see the FEMA publication entitled Converting the National Flood Insurance Program to the North American Vertical Datum of 1988 (FEMA, June 1992), or contact the Vertical Network Branch, National Geodetic Survey, Coast and Geodetic Survey, National Oceanic and Atmospheric Administration, Silver Spring, Maryland 20910 (Internet address http://www.ngs.noaa.gov). Temporary vertical monuments are often established during the preparation of a flood hazard analysis for the purpose of establishing local vertical control. Although these monuments are not shown on the FIRM, they may be found in the Technical Support Data Notebook associated with the FIS report and FIRM for this community. Interested individuals may contact FEMA to access these data.

4.0 FLOODPLAIN MANAGEMENT APPLICATIONS

The NFIP encourages State and local governments to adopt sound floodplain management programs. Therefore, each FIS provides 1-percent-annual-chance (100-year) flood elevations and delineations of the 1- and 0.2-percent-annual-chance (500-year) floodplain boundaries and 1-percent-annual-chance floodway to assist communities in developing floodplain management measures. This information is presented on the FIRM and in many components of the FIS report, including Flood Profiles, Floodway Data Table, and Summary of Stillwater Elevations Table. Users should reference the data presented in the FIS report as well as additional information that may be available at the local map repository before making flood elevation and/or floodplain boundary determinations.

24

4.1 Floodplain Boundaries

To provide a national standard without regional discrimination, the 1-percent-annual-chance flood has been adopted by FEMA as the base flood for floodplain management purposes. The 0.2-percent-annual-chance flood is employed to indicate additional areas of flood risk in the community. For each stream studied by detailed methods, the 1- and 0.2-percent-annual-chance floodplain boundaries have been delineated using the flood elevations determined at each cross section. For Camp Creek, Camp Creek Tributary, Flint River, Flint River Tributary, Jester Creek, Shoal Creek, and Sullivan Creek the boundaries between cross sections were interpolated using topographic maps at a scale of 1:4,800, with a contour interval of 4 feet (Reference 21). For Conine Creek, Duffey Tributary, North Fork Jester Creek, Stratford Tributary and York Tributary, the boundaries between cross sections were interpolated using topographic maps at a scale of 1:2,400, with a contour interval of 5 feet (Reference 4). Between cross sections for Conley Creek Tributary, East Tributary of Jester Creek, Pine Creek, Poole Creek, Poole Creek Tributary, West Tributary of Jester Creek, and the portions of Conley Creek and Jester Creek within the City of Forest Park corporate limits, the boundaries were interpolated using topographic maps at a scale of 1:24,000, with a contour interval of 10 feet (Reference 26). For Stream A, Stream B, Stream BT, Stream C, Stream CT, Stream CT-A, Stream D and the portions of Flint River and Flint River Tributary that are within the corporate limits of the City of Riverdale, the boundaries between cross sections were interpolated using USGS quadrangle maps enlarged to a scale of 1:7,200, with a contour interval of 10 feet (Reference 27). For Beaver Dam Creek, Big Cotton Indian Creek, Conley Creek, Hurricane Creek, Mud Creek, Panther Creek, Pates Creek, Reeves Creek, Roberts Road Tributary, Swamp Creek, Tar Creek, Upton Creek and Wallis Creek the boundaries between cross sections were interpolated using topographic maps at a scale of 1:12,000, with a contour interval of 10 feet (Reference 28).

The 1- and 0.2-percent-annual-chance floodplain boundaries are shown on the FIRM (Exhibit 2). On this map, the 1-percent-annual-chance floodplain boundary corresponds to the boundary of the areas of special flood hazards (Zones A, AE, and AO), and the 0.2-percent-annual-chance floodplain boundary corresponds to the boundary of areas of moderate flood hazards. In cases where the 1- and 0.2-percent-annual-chance floodplain boundaries are close together, only the 1-percent-annual-chance floodplain boundary has been shown. Small areas within the floodplain boundaries may lie above the flood elevations but cannot be shown due to limitations of the map scale and/or lack of detailed topographic data. For the streams studied by approximate methods, only the 1-percent-annual-chance floodplain boundary is shown on the FIRM (Exhibit 2).

25

For streams studied by approximate methods within the unincorporated areas of Clayton County the floodplain boundaries were determined using Flood Prone Area Maps furnished by SCS and USGS maps (References 29-32). The Flood Prone Area Maps were prepared by several methods. Floodplain boundaries along some streams depict the inundation of past floods as estimated from photographs and/or high-water marks. Other floodplain boundaries were estimated from regional relations between drainage area and depth of a relatively large flood. For streams studied by approximate methods within the City of Morrow, the flood boundaries were determined from Flood Hazard Boundary Maps prepared by Gannett-Fleming for FEMA dated May 24, 1974, and revised July 30, 1976 (Reference 33). For streams studied by approximate methods within the City of Riverdale, the flood boundaries were determined through field observation and the use of USGS topographic maps at a scale of 1:24,000, with a contour interval of 10 feet (Reference 27).

4.2 Floodways

Encroachment on floodplains, such as structures and fill, reduces flood-carrying capacity, increases flood heights and velocities, and increases flood hazards in areas beyond the encroachment itself. One aspect of floodplain management involves balancing the economic gain from floodplain development against the resulting increase in flood hazard. For purposes of the NFIP, a floodway is used as a tool to assist local communities in this aspect of floodplain management. Under this concept, the area of the 1-percent-annual-chance floodplain is divided into a floodway and a floodway fringe. The floodway is the channel of a stream, plus any adjacent floodplain areas, that must be kept free of encroachment so that the 1-percent-annual-chance flood can be carried without substantial increases in flood heights. Minimum Federal standards limit such increases to 1 foot, provided that hazardous velocities are not produced. The floodways in this study are presented to local agencies as minimum standards that can be adopted directly or that can be used as a basis for additional floodway studies. The floodways presented in this FIS report and on the FIRM were computed for certain stream segments on the basis of equal-conveyance reduction from each side of the floodplain. Floodway widths were computed at cross sections. Between cross sections, the floodway boundaries were interpolated. The results of the floodway computations have been tabulated for selected cross sections (Table 5). In cases where the floodway and 1-percent-annual-chance

FLOODING SOURCE FLOODWAY 1-PERCENT-ANNUAL-CHANCE-FLOOD WATER SURFACE ELEVATION

CROSS SECTION DISTANCE1 WIDTH (FEET)

SECTION AREA

(SQUARE FEET)

MEAN VELOCITY (FEET PER SECOND)

REGULATORY (FEET NAVD)

WITHOUT FLOODWAY (FEET NAVD)

WITH FLOODWAY (FEET NAVD)

INCREASE (FEET)

BEAVER DAM CREEK A 5,000 140 536 1.8 802.7 802.7 803.7 1.0 B 7,000 65 140 6.6 812.7 812.7 813.0 0.3 C 7,525 25 165 5.0 814.8 814.8 815.8 1.0 D 8,025 215 516 1.6 818.2 818.2 819.2 1.0 E 8,625 80 401 1.9 818.4 818.4 819.3 0.9 F 9,100 50 90 8.6 819.2 819.2 819.6 0.4 G 9,600 80 202 3.2 821.9 821.9 822.9 1.0 H 10,075 16 71 8.0 822.6 822.6 823.6 1.0 I 11,118 25 104 5.1 829.7 829.7 829.7 0.0 J 11,618 20 52 9.0 832.9 832.9 832.9 0.0 K 12,368 35 130 3.4 836.6 836.6 837.6 1.0 L 13,368 15 45 7.0 842.8 842.8 843.1 0.3 M 15,568 12 33 1.5 856.7 856.7 857.7 1.0

1Feet above confluence with Flint River

FLOODWAY DATA

TAB

LE 5

FEDERAL EMERGENCY MANAGEMENT AGENCY

CLAYTON COUNTY, GA AND INCORPORATED AREAS

BEAVER DAM CREEK



SECTION AREA

(SQUARE FEET)





INCREASE (FEET)

BIG COTTON INDIAN CREEK

A 101,700 175 1,302 4.0 749.6 749.6 750.6 1.0 B 103,620 175 1,252 4.3 757.1 757.1 758.1 1.0 C 106,220 160 1,088 4.8 769.8 769.8 770.6 0.8 D 109,145 540 4,389 1.2 785.3 785.3 786.3 1.0 E 111,220 425 3,445 1.2 790.1 790.1 791.1 1.0 F 113,620 265 696 5.8 792.1 792.1 793.1 1.0 G 114,760 605 2,241 1.7 796.2 796.2 797.2 1.0 H 116,920 170 738 3.0 808.4 808.4 808.7 0.3 I 118,820 330 1,478 1.5 810.5 810.5 811.5 1.0

1Feet above confluence with South River

FLOODWAY DATA

TAB

LE 5



BIG COTTON INDIAN CREEK



SECTION AREA

(SQUARE FEET)





INCREASE (FEET)

CAMP CREEK A 944 856/3802 11,024 0.5 794.6 N/A N/A N/A B 3,564 182/952 1,829 3.3 795.6 N/A N/A N/A C 7,364 372 3,456 1.7 802.8 802.8 803.8 1.0 D 10,514 467 3,059 2.0 807.4 807.4 808.3 0.9 E 15,660 146/1002 918 5.3 813.8 813.8 814.8 1.0 F 17,130 310/2662 2,198 2.2 814.8 814.8 815.8 1.0 G 19,632 300/1302 1,586 2.9 816.3 816.3 817.2 0.9 H 21,160 620/3022 4,406 1.1 820.6 820.6 820.8 0.2 I 23,600 270/1902 892 4.9 821.5 821.5 822.0 0.5 J 26,200 400/2252 2,090 1.9 826.7 826.7 827.7 1.0 K 28,300 360/122 1,476 2.6 828.8 828.8 829.8 1.0 L 29,100 50 339 11.4 831.0 831.0 831.7 0.7 M 31,630 160 902 3.3 836.9 836.9 837.8 0.9 N 33,622 330 1,279 2.3 840.5 840.5 841.5 1.0 O 35,464 50 242 10.9 847.8 847.8 847.8 0.0 P 37,370 180 480 5.5 849.0 849.0 849.1 0.1 Q 39,430 230 1,081 2.0 854.3 854.3 855.3 1.0 R 41,600 150 516 4.5 858.5 858.5 859.2 0.7 S 43,700 80 314 5.9 864.0 864.0 865.0 1.0 T 44,400 40 212 8.8 865.1 865.1 866.1 1.0 U 45,845 40 204 7.9 871.1 871.1 872.1 1.0 V 48,000 40 146 9.2 873.6 873.6 874.4 0.8

1Feet above confluence with Flint River 2Total width/width within county

FLOODWAY DATA

TAB

LE 5



CAMP CREEK



SECTION AREA

(SQUARE FEET)





INCREASE (FEET)

CAMP CREEK TRIBUTARY

A 585 118 419 5.0 835.6 833.32 834.3 1.0 B 1,532 197 1,375 1.5 841.2 841.2 842.1 0.9 C 2,170 127 909 2.3 841.6 841.6 842.5 0.9 D 2,920 38 307 5.9 842.1 842.1 842.9 0.8 E 3,525 95 720 2.5 844.0 844.0 844.5 0.5 F 3,950 176 740 2.4 844.5 844.5 845.0 0.5 G 4,800 146 860 2.1 845.8 845.8 846.5 0.7 H 5,520 63 215 8.4 849.0 849.0 849.4 0.4 I 6,730 145 676 2.1 854.7 854.7 855.3 0.6 J 7,830 132 360 3.9 865.6 865.6 866.3 0.7 K 8,170 232 1,136 1.2 866.6 866.6 867.5 0.9 L 9,380 73 225 6.2 868.2 868.2 868.7 0.5 M 9,700 61 197 7.1 871.8 871.8 871.8 0.0 N 10,330 117 787 1.0 873.9 873.9 874.3 0.4

1Feet above confluence with Camp Creek 2Elevation computed without consideration of backwater effects from Camp Creek

FLOODWAY DATA

TAB

LE 5



CAMP CREEK TRIBUTARY


CROSS SECTION DISTANCE WIDTH (FEET)

SECTION AREA

(SQUARE FEET)





INCREASE (FEET)

CONINE CREEK A 2101 49 331 3.8 862.2 859.12 860.1 1.0 B 5201 161 1,004 1.3 862.2 859.62 860.5 0.9 C 8751 411 1,859 0.7 869.5 869.5 870.5 1.0 D 1,8001 388 4,427 0.3 869.5 869.5 870.5 1.0 E 2,5601 207 2,226 0.6 869.5 869.5 870.5 1.0 F 3,4901 141 639 2.0 869.6 869.6 870.5 0.9 G 3,8001 135 752 1.7 870.0 870.0 870.9 0.9 CONLEY CREEK A 29,6803 9174 5,132 0.9 793.0 793.0 793.7 0.7 B 30,7603 3004 1,643 2.8 793.8 793.8 794.3 0.5 C 32,2953 700/4205 2,937 1.6 796.4 796.4 797.4 1.0 D 34,1753 540/2105 1,177 3.9 798.8 798.8 799.7 0.9 E 34,9333 500/3605 1,992 2.2 807.3 807.3 807.3 0.0 F 36,8703 55 395 8.9 812.6 812.6 813.1 0.5 G 38,5003 300 919 2.9 822.9 822.9 823.0 0.1 H 41,2503 40 292 8.2 833.5 833.5 834.4 0.9 I 42,2003 75 324 7.1 837.0 837.0 837.6 0.6 J 42,6603 105 469 4.9 838.7 838.7 838.7 0.0 K 43,3103 95 352 6.1 842.3 842.3 843.2 0.9 L 43,6203 95 422 1.8 844.2 844.2 845.2 1.0 M 44,7003 185 813 2.5 847.5 847.5 848.5 1.0

1Feet above confluence with North Fork Jester Creek 4This width is beyond county boundary 2Elevation computed without consideration of backwater effects from North Fork Jester Creek 5Total width/width within county 3Feet above confluence with South River

FLOODWAY DATA

TAB

LE 5



CONINE CREEK - CONLEY CREEK



SECTION AREA

(SQUARE FEET)





INCREASE (FEET)

DUFFEY TRIBUTARY A 3251 22 65 5.1 850.1 850.1 851.1 1.0 B 7151 12 35 9.5 857.0 857.0 857.2 0.2 C 1,0551 53 76 4.4 866.1 866.1 867.0 0.9 FLINT RIVER A 3,1002 345 / 2703 3,155 5.8 757.7 757.7 758.3 0.6 B 4,3202 287 / 1753 3,201 5.7 760.7 760.7 761.7 1.0 C 5,0602 266 / 1253 3,357 5.5 761.8 761.8 762.7 0.9 D 7,4402 571 / 3203 8,139 2.2 764.3 764.3 765.2 0.9 E 10,1602 1,027 / 9353 11,803 1.6 765.2 765.2 766.2 1.0 F 13,2802 933 / 1303 11,199 1.6 765.9 765.9 766.9 1.0 G 15,3602 966 / 653 11,297 1.6 766.4 766.4 767.4 1.0 H 17,4702 756 / 4553 8,559 2.1 766.9 766.9 767.8 0.9 I 18,9802 362 / 1553 4,622 4.0 768.2 768.2 769.2 1.0 J 19,0802 541 / 1503 6,055 3.0 768.9 768.9 769.9 1.0 K 21,9502 2,224 / 7803 26,120 0.7 769.9 769.9 770.9 1.0 L 24,6012 1,325 / 1,0603 12,367 1.5 770.4 770.4 771.3 0.9 M 30,3202 1,061 / 4603 9,360 2.0 773.0 773.0 773.9 0.9 N 32,1812 312 / 03 3,199 5.9 775.2 775.2 775.9 0.7 O 35,8002 399 5,435 3.5 779.4 779.4 780.3 0.9 P 35,9342 374 3,485 5.5 779.9 779.9 780.9 1.0 Q 36,9002 396 6,367 3.0 781.1 781.1 782.0 0.9

1Feet above confluence with York Tributary 2Feet above county boundary 3Total width / width within county

FLOODWAY DATA

TAB

LE 5


CLAYTON COUNTY, GA AND INCORPORATED ARES

DUFFEY TRIBUTARY - FLINT RIVER



SECTION AREA

(SQUARE FEET)





INCREASE (FEET)

FLINT RIVER (CONTINUED)

R 38,640 452 7,047 2.7 781.8 781.8 782.7 0.9 S 40,130 1,173 17,453 1.1 782.4 782.4 783.4 1.0 T 42,061 300 4,193 4.5 782.7 782.7 783.6 0.9 U 45,545 1,832 27,974 0.7 783.9 783.9 784.9 1.0 V 48,240 1,809 25,469 0.7 784.0 784.0 785.0 1.0 W 54,070 1,638 / 1,2102 21,438 0.9 784.2 784.2 785.2 1.0 X 56,625 547 / 1472 7,005 2.7 784.7 784.7 785.7 1.0 Y 59,330 311 / 2852 3,353 5.6 785.8 785.8 786.8 1.0 Z 61,100 1,620 / 602 12,967 1.5 787.2 787.2 788.1 0.9 AA 63,581 1,650 / 4552 17,555 1.1 788.2 788.2 789.1 0.9 AB 69,130 401 / 3102 3,954 3.9 790.4 790.4 791.2 0.8 AC 70,580 1,265 / 1,1752 10,484 1.5 791.6 791.6 792.5 0.9 AD 71,500 1,074 / 6002 8,877 1.7 792.3 792.3 793.1 0.8 AE 73,830 802 9,525 1.2 795.6 795.6 796.3 0.7 AF 75,300 406 4,744 2.4 796.0 796.0 796.7 0.7 AG 78,000 1,263 15,622 0.7 796.6 796.6 797.4 0.8 AH 78,285 1,148 13,573 0.8 796.7 796.7 797.5 0.8 AI 80,520 647 5,407 2.1 797.3 797.3 798.0 0.7 AJ 82,710 663 6,532 1.8 798.9 798.9 799.7 0.8 AK 84,330 636 5,614 2.0 800.0 800.0 800.8 0.8 AL 86,100 843 6,605 1.7 801.1 801.1 801.9 0.8

1Feet above county boundary 2Total width / width within county

FLOODWAY DATA

TAB

LE 5



FLINT RIVER



SECTION AREA

(SQUARE FEET)





INCREASE (FEET)


AM 86,630 259 1,571 7.3 801.4 801.4 802.2 0.8 AN 87,780 1,042 7,673 1.5 804.4 804.4 804.8 0.4 AO 89,255 1,114 8,384 1.4 804.9 804.9 805.4 0.5 AP 90,580 1,057 7,211 1.6 805.4 805.4 806.0 0.6 AQ 93,360 388 3,028 3.8 807.2 807.2 808.0 0.8 AR 94,500 447 3,683 3.1 808.5 808.5 809.3 0.8 AS 95,530 146 1,355 0.1 810.7 810.7 811.6 0.9 AT 96,490 634 6,214 2.2 815.5 815.5 815.9 0.4 AU 97,571 209 2,415 4.1 816.3 816.3 816.8 0.5 AV 99,175 699 7,006 1.4 817.2 817.2 817.7 0.5 AW 100,370 238 2,049 4.8 817.9 817.9 818.4 0.5 AX 101,500 751 7,613 1.3 819.5 819.5 820.1 0.6 AY 102,710 444 4,199 2.3 820.0 820.0 820.9 0.9 AZ 104,370 537 4,550 2.2 821.5 821.5 822.3 0.8 BA 104,860 154 1,217 8.1 822.0 822.0 822.8 0.8 BB 106,760 753 7,747 1.3 824.8 824.8 825.3 0.5 BC 107,940 1,195 11,847 0.8 825.1 825.1 825.7 0.6 BD 109,050 753 7,617 1.3 825.4 825.4 825.9 0.5 BE 110,670 748 4,259 2.3 826.6 826.6 827.2 0.6 BF 111,650 1,169 6,690 1.5 828.3 828.3 828.9 0.6 BG 113,110 531 3,110 4.3 831.4 831.4 832.0 0.6

1Feet above county boundary

FLOODWAY DATA

TAB

LE 5



FLINT RIVER



SECTION AREA

(SQUARE FEET)





INCREASE (FEET)


BH 113,410 624 4,411 3.1 832.6 832.6 833.4 0.8 BI 114,020 575 4,811 2.8 834.2 834.2 835.0 0.8 BJ 115,650 855 5,897 2.0 836.4 836.4 837.2 0.8 BK 117,010 891 6,969 1.7 838.0 838.0 838.8 0.8 BL 118,510 922 6,163 1.9 839.0 839.0 839.7 0.7 BM 119,220 505 3,754 3.2 840.5 840.5 841.3 0.8 BN 121,650 274 2,255 5.3 847.6 847.6 848.4 0.8 BO 123,520 152 1,995 6.0 853.1 853.1 853.9 0.8 BP 124,450 506 5,648 2.1 855.2 855.2 856.1 0.9 BQ 125,530 747 7,139 1.1 855.9 855.9 856.7 0.8 BR 126,040 264 1,253 6.5 855.9 855.9 856.7 0.8 BS 127,510 309 2,432 3.4 859.9 859.9 860.1 0.2 BT 130,520 187 1,935 4.2 875.8 875.8 876.0 0.2 BU 132,800 211 1,520 5.4 884.1 884.1 884.4 0.3 BV 133,700 139 1,143 7.2 886.9 886.9 887.0 0.1 BW 134,350 115 1,031 8.0 889.8 889.8 890.4 0.6

1Feet above county boundary

FLOODWAY DATA

TAB

LE 5



FLINT RIVER



SECTION AREA

(SQUARE FEET)





INCREASE (FEET)

FLINT RIVER TRIBUTARY

A 2,975 118 571 2.8 848.1 848.1 849.0 0.9 B 3,820 80 262 6.1 851.7 851.7 852.3 0.6 C 5,420 70 390 3.1 859.8 859.8 860.6 0.8 D 6,900 50 265 4.5 864.5 864.5 865.4 0.9 E 7,100 91 398 3.0 866.3 866.3 867.0 0.7 F 7,275 193 2,439 0.5 870.9 870.9 871.5 0.6 G 8,525 51 131 9.2 871.1 871.1 871.1 0.0 H 9,000 81 275 2.9 874.5 874.5 874.5 0.0 HURRICANE CREEK A 3,400 170 597 3.2 783.4 782.02 783.0 1.0 B 8,648 40 264 6.2 801.3 801.3 802.3 1.0 C 12,771 230 1,025 1.3 814.3 814.3 815.3 1.0 D 13,371 190 635 1.7 814.7 814.7 815.7 1.0 E 13,971 200 254 2.1 815.7 815.7 816.7 1.0 F 15,446 250 1,293 0.6 829.8 829.8 830.8 1.0 G 15,946 43 170 3.7 829.8 829.8 830.8 1.0 H 17,446 35 93 4.1 834.4 834.4 835.4 1.0 I 19,396 35 93 4.1 840.6 840.6 841.2 0.6 J 20,405 35 157 1.7 853.1 853.1 854.1 1.0 K 21,722 30 110 1.9 864.5 864.5 865.5 1.0 L 22,945 25 70 1.9 880.4 880.4 881.4 1.0

1Feet above confluence with Flint River 2Elevation computed without consideration of backwater effects from Flint River

FLOODWAY DATA

TAB

LE 5



FLINT RIVER TRIBUTARY - HURRICANE CREEK



SECTION AREA

(SQUARE FEET)





INCREASE (FEET)

JESTER CREEK A 860 562 3,332 1.6 815.8 812.62 813.6 1.0 B 2,205 443 2,567 2.0 815.8 814.22 814.9 0.7 C 3,120 588 2,848 1.8 815.8 815.02 815.7 0.7 D 3,455 110 634 8.2 815.8 815.62 816.2 0.6 E 3,680 193 1,292 4.0 817.5 817.5 817.6 0.1 F 3,900 101 809 6.4 818.6 818.6 819.3 0.7 G 5,330 383 4,031 1.3 823.3 823.3 824.0 0.7 H 6,320 363 2,245 2.3 823.6 823.6 824.4 0.8 I 7,530 259 2,317 1.9 824.9 824.9 825.8 0.9 J 8,390 91 673 6.7 825.4 825.4 826.4 1.0 K 9,925 411 1,781 2.5 828.7 828.7 829.5 0.8 L 11,150 249 1,396 3.2 832.7 832.7 833.6 0.9 M 12,170 289 1,509 3.0 835.4 835.4 836.2 0.8 N 13,590 529 2,882 1.6 837.7 837.7 838.5 0.8 O 14,920 574 2,539 1.0 839.6 839.6 840.3 0.7 P 16,100 507 3,674 0.7 848.0 848.0 848.8 0.8 Q 16,750 480 2,974 0.9 848.2 848.2 849.0 0.8 R 17,620 211 458 5.7 849.2 849.2 849.7 0.5 S 18,495 420 1,666 1.2 853.8 853.8 854.5 0.7 T 19,147 553 3,338 0.6 860.1 860.1 860.9 0.8 U 19,950 57 455 4.4 860.1 860.1 860.9 0.8 V 20,750 370 5,038 0.4 870.9 870.9 871.7 0.8

1Feet above confluence with Flint River 2Elevation computed without consideration of backwater effects from Flint River

FLOODWAY DATA

TAB

LE 5



JESTER CREEK



SECTION AREA

(SQUARE FEET)





INCREASE (FEET)

JESTER CREEK (CONTINUED)

W 21,400 498 5,022 0.4 870.9 870.9 871.7 0.8 X 21,970 216 1,648 1.2 870.9 870.9 871.7 0.8 Y 22,575 344 2,125 0.9 871.2 871.2 871.9 0.7 Z 23,380 129 794 2.5 874.4 874.4 875.4 1.0 AA 24,370 65 425 4.7 875.9 875.9 876.7 0.8 AB 25,450 41 258 7.7 879.1 879.1 879.6 0.5 AC 26,500 246 1,286 1.3 884.0 884.0 884.7 0.7 AD 27,040 154 972 1.7 884.8 884.8 885.6 0.8 MUD CREEK A 1,100 891 6,969 1.7 838.02 N/A N/A N/A B 2,050 922 6,163 1.9 839.02 N/A N/A N/A C 2,700 410 1,460 2.5 839.6 836.03 837.0 1.0 D 4,750 120 578 6.2 844.1 844.1 844.6 0.5 E 6,150 220 646 4.3 851.0 851.0 852.0 1.0 F 6,900 140 810 3.2 854.4 854.4 854.7 0.3 G 9,950 100 476 5.5 862.8 862.8 863.8 1.0 H 12,400 40 462 5.1 876.0 876.0 876.6 0.6 I 14,300 180 1,410 1.6 877.0 877.0 878.0 1.0 J 15,700 40 287 7.9 878.6 878.6 879.6 1.0 K 16,800 130 337 6.5 884.2 884.2 885.2 1.0

1Feet above confluence with Flint River 3Elevation computed without consideration of backwater effects from Flint River 2Elevation computed with consideration of flooding controlled by Flint River

FLOODWAY DATA

TAB

LE 5



JESTER CREEK - MUD CREEK



SECTION AREA

(SQUARE FEET)





INCREASE (FEET)


A 3,115 63 559 5.0 854.1 854.1 854.2 0.1 B 3,920 42 352 8.0 856.2 856.2 856.7 0.5 C 4,660 54 483 5.8 859.7 859.7 860.5 0.8 D 5,295 53 527 5.3 861.5 861.5 862.5 1.0 E 6,000 51 473 4.3 863.1 863.1 864.0 0.9 F 6,650 168 1,373 1.5 863.8 863.8 864.7 0.9 G 7,000 101 1,218 1.7 867.3 867.3 867.4 0.1 H 8,020 33 356 5.7 867.3 867.3 867.5 0.2 I 8,900 424 2,805 0.7 867.4 867.4 868.3 0.9 J 9,080 135 829 1.9 868.1 868.1 868.5 0.4 K 10,720 375 894 1.8 869.3 869.3 870.3 1.0 L 11,885 105 653 2.4 871.4 871.4 872.0 0.6 M 12,600 22 169 9.3 871.8 871.8 872.7 0.9 N 13,060 132 372 4.2 877.9 877.9 878.2 0.3 O 13,170 129 445 3.5 879.6 879.6 879.6 0.0 P 14,510 75 343 4.6 884.7 884.7 885.4 0.7

1Feet above confluence with Jester Creek

FLOODWAY DATA

TAB

LE 5






SECTION AREA

(SQUARE FEET)





INCREASE (FEET)

PANTHER CREEK A 6,5401 545 4,377 1.0 751.8 751.8 752.3 0.5 B 9,0901 240 1,397 3.0 756.8 756.8 756.8 0.0 C 11,6901 295 2,022 2.0 761.9 761.9 762.9 1.0 D 13,7401 70 532 7.1 767.6 767.6 768.6 1.0 E 16,4401 200 1,735 2.1 775.7 775.7 776.7 1.0 F 19,3401 280 1,710 1.2 782.0 782.0 782.9 0.9 G 20,7401 85 667 3.0 786.5 786.5 787.5 1.0 H 22,4151 130 822 2.3 792.3 792.3 793.3 1.0 I 25,3151 345 2,190 0.8 799.2 799.2 799.6 0.4 J 26,7401 85 409 2.6 806.0 806.0 806.9 0.9 K 29,0401 85 526 2.0 817.2 817.2 818.2 1.0 PATES CREEK A 40,2302 42 319 6.7 785.2 785.2 786.2 1.0 B 44,2572 26 210 7.5 800.2 800.2 801.2 1.0

1Feet above confluence with Big Cotton Indian Creek 2Feet above mouth

FLOODWAY DATA

TAB

LE 5



PANTHER CREEK - PATES CREEK



SECTION AREA

(SQUARE FEET)





INCREASE (FEET)

REEVES CREEK A 29,5991 63 320 6.5 795.3 795.3 796.2 0.9 B 32,6451 142 674 2.4 806.8 806.8 807.8 1.0 C 36,1581 42 240 5.6 824.7 824.7 825.7 1.0 D 36,2611 118 517 2.6 825.7 825.7 826.7 1.0 E 38,3611 65 294 3.4 832.8 832.8 833.8 1.0 F 40,2111 74 189 3.7 840.3 840.3 841.1 0.8

ROBERTS ROAD TRIBUTARY

A 8002 184 385 1.1 804.2 804.2 805.2 1.0 B 8602 217 1,065 0.4 804.2 804.2 805.2 1.0 C 1,3102 8 33 11.5 808.6 808.6 809.2 0.6 D 2,7802 6 23 9.6 822.7 822.7 823.3 0.6 SHOAL CREEK A 3102 85 466 6.4 775.9 771.13 772.1 1.0

1Feet above confluence with Little Cotton Indian Creek 2Feet above confluence with Flint River 3Elevation computed without consideration of backwater effects from Flint River

FLOODWAY DATA

TAB

LE 5


CLAYTON COUNTY, GA AND INCORPORATED AREAS REEVES CREEK - ROBERTS ROAD TRIBUTARY -

SHOAL CREEK



SECTION AREA

(SQUARE FEET)





INCREASE (FEET)

STRATFORD TRIBUTARY

A 01 33 81 7.0 843.3 843.3 843.6 0.3 B 1151 24 109 5.3 845.0 845.0 846.0 1.0 C 2801 27 120 4.7 849.4 849.4 849.5 0.1 D 6301 33 135 4.2 851.2 851.2 851.8 0.6 E 1,0201 34 150 3.8 853.1 853.1 853.8 0.7 F 1,5601 20 42 8.4 857.0 857.0 857.0 0.0 G 1,9651 19 80 4.4 862.2 862.2 862.7 0.5 H 2,1301 27 55 6.5 863.6 863.6 864.3 0.7 I 2,2301 60 209 1.7 867.2 867.2 867.2 0.0 J 2,8801 11 41 8.5 872.3 872.3 872.3 0.0 K 3,2501 31 89 4.0 880.3 880.3 881.3 1.0 L 3,4001 123 166 2.1 882.3 882.3 882.6 0.3 STREAM A A 4502 18 40 8.6 854.0 854.0 854.0 0.0 B 1,3802 27 88 3.9 868.4 868.4 868.4 0.0 C 2,7602 41 65 2.8 894.0 894.0 894.0 0.0 D 3,1602 94 264 0.7 909.2 909.2 909.2 0.0 E 3,7632 97 236 0.6 912.9 912.9 912.9 0.0

1Feet above limit of detailed study (limit of detailed study is approximately 200 feet downstream of Harbin Wood Drive) 2Feet above confluence with Camp Creek

FLOODWAY DATA

TAB

LE 5



STRATFORD TRIBUTARY - STREAM A



SECTION AREA

(SQUARE FEET)





INCREASE (FEET)

STREAM B A 5,2721 19 76 6.9 851.3 851.3 851.3 0.0 B 5,4751 20 92 5.7 852.2 852.2 852.2 0.0 C 5,6821 60 205 2.6 854.4 854.4 854.5 0.1 D 5,9641 60 307 1.7 855.0 855.0 856.0 1.0 E 6,4641 32 84 6.3 855.6 855.6 856.3 0.7 F 6,7191 38 51 3.7 862.0 862.0 862.0 0.0 G 7,0191 28 37 5.1 866.9 866.9 866.9 0.0 H 7,4041 50 45 4.2 876.5 876.5 876.5 0.0 I 7,9041 11 23 6.5 880.0 880.0 880.0 0.0 J 8,3251 13 24 5.9 886.9 886.9 886.9 0.0 K 8,5861 50 79 1.8 891.2 891.2 891.2 0.0 L 9,0111 50 64 2.2 897.4 897.4 897.4 0.0 STREAM BT A 1802 60 186 1.8 862.1 861.23 862.1 0.9 B 6802 60 188 1.8 870.2 870.2 870.6 0.4 C 1,2002 19 45 7.5 871.5 871.5 871.7 0.2 D 1,8002 25 88 3.2 875.8 875.8 875.8 0.0

1Feet above confluence with Stream C 2Feet above confluence with Stream B 3Elevation computed without consideration of backwater effects from Stream B

FLOODWAY DATA

TAB

LE 5



STREAM B - STREAM BT



SECTION AREA

(SQUARE FEET)





INCREASE (FEET)

STREAM C A 7,3501 75 105 3.9 865.0 865.0 865.0 0.0 B 7,5291 85 492 0.7 870.8 870.8 871.0 0.2 C 7,7621 185 322 1.1 870.8 870.8 871.0 0.2 D 8,5851 17 41 7.4 875.6 875.6 876.4 0.8 E 9,2411 182 395 0.6 880.5 880.5 880.7 0.2 F 9,9101 93 68 2.9 887.1 887.1 887.5 0.4 G 10,2511 55 37 4.4 889.3 889.3 889.3 0.0 H 10,9751 35 37 4.4 900.4 900.4 900.4 0.0 STREAM CT A 7112 247 309 2.0 857.7 857.7 857.7 0.0 B 9852 458 771 0.8 863.8 863.8 863.8 0.0 C 2,5652 61 309 2.0 875.5 875.5 875.5 0.0 D 3,9202 11 128 9.3 899.6 899.6 899.6 0.0 E 4,1252 30 58 4.4 901.6 901.6 901.6 0.0 F 4,7802 84 84 3.1 914.2 914.2 914.2 0.0 STREAM CT-A A 1953 500 2,790 0.0 904.9 904.9 904.9 0.0 B 3133 440 1,980 0.0 904.9 904.9 904.9 0.0 C 6033 310 900 0.1 906.0 906.0 906.0 0.0

1Feet above confluence with Flint River 2Feet above confluence with Stream C 3Feet above confluence with Stream CT

FLOODWAY DATA

TAB

LE 5



STREAM C - STREAM CT - STREAM CT-A



SECTION AREA

(SQUARE FEET)





INCREASE (FEET)

STREAM D A 1311 98 84 1.8 892.7 892.7 892.7 0.0 B 3341 9 18 8.4 894.1 894.1 894.1 0.0 C 6001 96 58 1.5 902.5 902.5 902.5 0.0 SULLIVAN CREEK A 1,1002 295 1,472 2.5 860.1 857.43 858.4 1.0 B 2,8102 44 330 11.2 862.2 862.2 862.8 0.6 C 3,9002 53 446 8.3 866.4 866.4 866.8 0.4 D 5,0002 40 298 12.4 871.6 871.6 872.6 1.0 E 6,4002 154 1,151 3.2 878.7 878.7 879.1 0.4 F 7,2902 46 335 11.0 880.1 880.1 880.4 0.3 G 8,2302 62 345 10.7 888.9 888.9 889.8 0.9 H 8,9802 30 294 12.6 893.1 893.1 893.9 0.8 I 9,3152 133 883 4.2 897.2 897.2 897.3 0.1 J 10,8402 73 509 7.3 900.4 900.4 900.8 0.4 K 11,8502 51 485 7.0 905.4 905.4 905.6 0.2 L 12,3002 80 660 5.2 908.5 908.5 908.9 0.4 M 13,9602 344 518 6.6 918.5 918.5 918.9 0.4

1Feet above Taylor Road 2Feet above confluence with Flint River 3Elevation computed without consideration of backwater effects from Flint River 4Floodway width located in Area Not Included

FLOODWAY DATA

TAB

LE 5



STREAM D - SULLIVAN CREEK



SECTION AREA

(SQUARE FEET)





INCREASE (FEET)

SWAMP CREEK A 6501 549 4,560 0.4 790.0 N/A N/A N/A B 4,2101 32 236 7.0 793.1 793.1 794.1 1.0 C 4,2791 148 437 3.8 794.3 794.3 794.9 0.6 D 4,5271 285 516 3.2 805.3 805.3 806.3 1.0 E 7,0701 87 317 5.2 806.7 806.7 807.4 0.7 F 8,7071 279 1,068 1.6 812.2 812.2 813.2 1.0 G 10,8571 135 488 3.4 821.5 821.5 822.4 0.9 H 10,9581 42 277 6.0 824.1 824.1 824.9 0.8 I 12,9071 162 705 2.4 831.4 831.4 832.4 1.0 J 14,8571 74 283 5.9 844.2 844.2 845.0 0.8 TAR CREEK A 4,0502 125 708 8.0 779.2 779.2 780.2 1.0 B 6,1402 40 207 9.1 791.3 791.3 792.3 1.0 UPTON CREEK A 2,5003 200 424 2.2 806.0 806.0 807.0 1.0 B 5,3503 27 143 6.0 817.4 817.4 818.4 1.0

1Feet above confluence with Flint River 2Feet above confluence with Big Cotton Indian Creek 3Feet above Double Bridge Road

FLOODWAY DATA

TAB

LE 5



SWAMP CREEK - TAR CREEK - UPTON CREEK



SECTION AREA

(SQUARE FEET)





INCREASE (FEET)

WALLIS CREEK A 3,2101 20 91 12.8 792.3 792.3 792.3 0.0 B 5,8801 65 314 3.5 801.7 801.7 802.7 1.0 C 8,5751 25 84 6.0 809.8 809.8 810.7 0.9 D 10,5601 25 77 6.6 825.7 825.7 825.8 0.1 E 13,0751 30 54 0.4 853.5 853.5 853.5 0.0 F 13,7701 9 44 7.0 862.0 862.0 862.0 0.0 G 15,2741 9 20 8.4 878.8 878.8 878.8 0.0 YORK TRIBUTARY A 02 24 84 6.9 836.0 836.0 836.5 0.5 B 1452 15 53 10.8 840.6 840.6 840.6 0.0 C 2602 200 1,838 0.3 850.1 850.1 850.5 0.4 D 4552 101 565 0.5 850.1 850.1 850.5 0.4 E 6012 88 344 0.8 851.2 851.2 851.6 0.4 F 1,0952 15 36 7.8 851.4 851.4 851.6 0.2 G 1,3302 11 45 6.1 856.7 856.7 857.6 0.9 H 1,7002 34 43 6.4 864.9 864.9 865.0 0.1

1Feet above confluence with Flint River 2Feet above limit of detailed study (limit of detailed study is approximately 190 feet downstream of Meadowbrook Lane)

FLOODWAY DATA

TAB

LE 5



WALLIS CREEK - YORK TRIBUTARY

47

floodplain boundaries are either close together or collinear, only the floodway boundary has been shown. On Pates Creek, no floodway is applicable through Orr’s Lake. Above Orr’s Lake, the steep stream and overbank slopes convey hazardous velocity flows for the base flood and, thus no floodway is shown. In the City of Forest Park, floodways were not included due to the velocities produced by the steep gradients of the streambeds in order to pass the base flood. Under natural conditions, channel velocities range from 5 feet to 13 feet per second. Floodplain encroachments would increase velocities even more. Therefore, the floodways were considered to be the limits of the 1-percent-annual-chance floodplain boundaries (Reference 6). The area between the floodway and 1-percent-annual-chance floodplain boundaries is termed the floodway fringe. The floodway fringe encompasses the portion of the floodplain that could be completely obstructed without increasing the water surface elevation of the 1-percent-annual-chance flood more than 1 foot at any point. Typical relationships between the floodway and the floodway fringe and their significance to floodplain development are shown in Figure 2.

Figure 2 - Floodway Schematic

48

5.0 INSURANCE APPLICATIONS

For flood insurance rating purposes, flood insurance zone designations are assigned to a community based on the results of the engineering analyses. These zones are as follows: Zone A Zone A is the flood insurance risk zone that corresponds to the 1-percent-annual-chance floodplains that are determined in the FIS by approximate methods. Because detailed hydraulic analyses are not performed for such areas, no BFEs or base flood depths are shown within this zone. Zone AE Zone AE is the flood insurance risk zone that corresponds to the 1-percent-annual-chance floodplains that are determined in the FIS by detailed methods. In most instances, whole-foot BFEs derived from the detailed hydraulic analyses are shown at selected intervals within this zone. Zone AO Zone AO is the flood insurance risk zone that corresponds to the areas of 1-percent-annual-chance shallow flooding (usually sheet flow on sloping terrain) where average depths are between 1 and 3 feet. Average whole-foot base flood depths derived from the detailed hydraulic analyses are shown within this zone. Zone X Zone X is the flood insurance risk zone that corresponds to areas outside the 0.2-percent-annual-chance floodplain, areas within the 0.2-percent-annual-chance floodplain, areas of 1-percent-annual-chance flooding where average depths are less than 1 foot, areas of 1-percent-annual-chance flooding where the contributing drainage area is less than 1 square mile, and areas protected from the 1-percent-annual-chance flood by levees. No BFEs or base flood depths are shown within this zone.

6.0 FLOOD INSURANCE RATE MAP

The FIRM is designed for flood insurance and floodplain management applications. For flood insurance applications, the map designates flood insurance risk zones as described in Section 5.0 and, in the 1-percent-annual-chance floodplains that were studied by detailed methods, shows selected whole-foot BFEs or average depths. Insurance agents use the zones and BFEs in conjunction with information on structures and their contents to assign premium rates for flood insurance policies.

49

For floodplain management applications, the map shows by tints, screens, and symbols, the 1- and 0.2-percent-annual-chance floodplains, floodways, and the locations of selected cross sections used in the hydraulic analyses and floodway computations. The countywide FIRM presents flooding information for the entire geographic area of Clayton County. Previously, FIRMs were prepared for each incorporated community and the unincorporated areas of the County identified as flood-prone. This countywide FIRM also includes flood-hazard information that was presented separately on Flood Boundary and Floodway Maps, where applicable. Historical data relating to the maps prepared for each community are presented in Table 6.

7.0 OTHER STUDIES

This report either supersedes or is compatible with all previous studies on streams studied in this report and should be considered authoritative for purposes of the NFIP.

8.0 LOCATION OF DATA

Information concerning the pertinent data used in the preparation of this study can be obtained by contacting FEMA, Federal Insurance and Mitigation Division, 3003 Chamblee-Tucker Road, Atlanta, Georgia 30341.

9.0 BIBLIOGRAPHY AND REFERENCES

1. Federal Insurance Administration, Flood Insurance Study, Clayton County, Georgia (Unincorporated Areas), U.S. Department of Housing and Urban Development, June 15, 1978.

2. Federal Emergency Management Agency, Flood Insurance Study, Clayton

County, Georgia (Unincorporated Areas), May 1, 1984.

3. Federal Emergency Management Agency, Flood Insurance Study, Clayton County, Georgia (Unincorporated Areas), November 6, 1991.

4. Federal Emergency Management Agency, Flood Insurance Study, City of

Morrow, Clayton County, Georgia, Flood Insurance Study Report August 16, 1982; Flood Insurance Rate Map, February 16, 1983.

COMMUNITY NAME

INITIAL IDENTIFICATION

FLOOD HAZARD BOUNDAY MAP REVISION DATE

FIRM EFFECTIVE DATE

FIRM REVISION DATE

Clayton County (Unincorporated Areas) October 31, 1975 None June 15, 1978

May 1, 1984 November 6, 1991

September 20, 1996 November 20, 2000

August 16, 2007

Forest Park, City of May 31, 1974 None May 16, 1977 August 16, 2007

Jonesboro, City of August 16, 2007 None August 16, 2007 None

Lake City, City of May 31, 1974 May 14, 1976 September 4, 1986 August 16, 2007

Lovejoy, City of August 16, 2007 None August 16, 2007 None

Morrow, City of May 24, 1974 July 30, 1976 February 16, 1983 August 16, 2007

Riverdale, City of June 14, 1974 January 30, 1976 February 15, 1978 January 7, 1983

November 6, 1991 August 16, 2007

TAB

LE 6



COMMUNITY MAP HISTORY

Table 1 - Community Map History

51

5. Federal Emergency Management Agency, Flood Insurance Study, Clayton County, Georgia (Unincorporated Areas), November 20, 2000.

6. Federal Insurance Administration, Flood Insurance Study, City of Forest Park,

Clayton and Fulton Counties, U.S. Department of Housing and Urban Development, Flood Insurance Study Report, November 16, 1976; Flood Insurance Rate Map, May 16, 1977.

7. Federal Insurance Administration, Flood Insurance Study, City of Riverdale,

Clayton County, Georgia, U.S. Department of Housing and Urban Development, November 6, 1991.

8. U.S. Census Bureau, American FactFinder, Clayton County, Georgia, 2000.

Retrieved October 26, 2005, from http://factfinder.census.gov.

9. The Weather Channel, Monthly Averages for Jonesboro, Georgia. Retrieved November 29, 2005, from http://www.weather.com.

10. U.S. Geological Survey, Water Resources Investigations 77-57, USGS

Preliminary Flood Frequency Relations for Urban Streams, Metropolitan Atlanta, Georgia, U.S. Department of the Interior, August 1977.

11. Hydrologic Engineering Center, HEC-1 Flood Hydrograph Package, Davis,

California, U.S. Army Corps of Engineers, September 1981, revised January 1985.

12. U.S. Geological Survey, Water Resources Investigations 88-4085, Flood

Frequency Relations for Urban Streams in Georgia, U.S. Department of the Interior, 1988.

13. National Weather Service, Rainfall Frequency Atlas of the United States, 30-

Minute to 24-Hour Durations, 1- to 100-Year Return Periods, Technical Paper No. 40, U.S. Department of Commerce, 1961.

14. National Oceanographic and Atmospheric Administration, National Weather

Service, Technical Memorandum NWS Hydro-35, Five- to 60-Minute Precipitation Frequency for the Eastern and Central United Sates, Silver Spring, MD, U.S. Department of Commerce, National Climatic Center, June 1977.

52

15. Hydrologic Engineering Center, HEC-2 Water-Surface Profiles, Davis, California, U.S. Army Corps of Engineers, April 1984.

16. Soil Conservation Service, Technical Release No. 55, Urban Hydrology for Small

Watersheds, U.S. Department of Agriculture, January 1975.

17. Soil Conservation Service, Soil Survey of Fulton County, Georgia, U.S. Department of Agriculture, 1958.

18. Soil Conservation Service, Soil Survey of Clayton, Fayette, and Henry Counties,

Georgia, U.S. Department of Agriculture, 1979.

19. U.S. Geological Survey, Water Resources Investigations 83-4203, Flood Frequency Relations for Urban Streams in Metropolitan Atlanta, Georgia. U.S. Department of the Interior, 1983

20. U.S. Geological Survey, Water Resources Investigations Report 78-137, Floods in

Georgia, Magnitude and Frequency, U.S. Department of the Interior, October 1979.

21. U.S. Army Corps of Engineers, Mobile District, Topographic Maps, Scale

1:4,800, Contour Interval 4 feet: Clayton County, Unincorporated Areas, Georgia, January 1989.

22. U.S. Department of the Army, Corps of Engineers, Savannah District, Flood Plain

Information, Metropolitan Atlanta, Conley Creek-South River, Georgia, July 1968.

23. U.S. Department of the Army, Corps of Engineers, Savannah District, Flood Plain

Information, Little Cotton Indian Creek, Henry County, Georgia, June 1975.

24. U.S. Department of the Army, Corps of Engineers, Mobile District, Flood Plain Information, Metropolitan Atlanta, Georgia, Upper Flint River, Mud Creek and Jester Creek, January 1969.

25. National Geodetic Survey, VERTCON-North American Vertical Datum

Conversion Utility. Retrieved September 21, 2005, from http://www.ngs.noaa.gov/.

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26. U.S. Geological Survey, 7.5-Minute Series Topographic Maps, Scale 1:24,000,

Contour Interval 10 feet: Southwest Atlanta, Southeast Atlanta, Riverdale, and Jonesboro, U.S. Department of the Interior, various dates.

27. U.S. Geological Survey, 7.5 Minute Series Topographic Maps, Scale 1:24,000,

Contour Interval 10 feet: Riverdale, Georgia, U.S. Department of the Interior, Photorevised 1973.

28. Clayton County Planning Commission, Topographic Maps, Scale 1:12,000,

Contour Interval 10 feet: Clayton County, Georgia, revised January 1973.

29. Soil Conservation Service, 7.5-Minute Series Flood-Prone Area Maps, Scale 1:24,000, Contour Interval 10 feet: Jonesboro, Georgia, U.S. Department of Agriculture, April 1974.

30. Soil Conservation Service, 7.5-Minute Series Flood-Prone Area Maps, Scale

1:24,000, Contour Interval 20 feet: Stockbridge, Georgia, U.S. Department of Agriculture, April 1974.

31. U.S. Geological Survey, 7.5-Minute Series Flood-Prone Area Maps, Scale

1:24,000, Contour Interval 10 feet: Riverdale, Georgia, U.S. Department of the Interior, 1969.

32. U.S. Geological Survey, 7.5-Minute Series Flood-Prone Area Maps, Scale

1:24,000, Contour Interval 20 feet: Brooks, Georgia 1969; Fayetteville, Georgia 1969; Griffin North, Georgia 1974; Hampton, Georgia, 1973, U.S. Department of the Interior, various dates.

33. Mayes, Sudderth & Etheredge, Inc., Flood Plain Study, City of Morrow, Georgia,

June 1980.

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