CARROLL COUNTY, GEORGIA

Transcription

1 CARROLL COUNTY, GEORGIA AND INCORPORATED AREAS Community Name Community Number BOWDON, CITY OF CARROLL COUNTY (UNINCORPORATED AREAS) CARROLLTON, CITY OF MOUNT ZION, CITY OF *ROOPVILLE, CITY OF TEMPLE, CITY OF VILLA RICA, CITY OF *WHITESBURG, CITY OF *No Flood Hazard Areas Identified CARROLL COUNTY Effective: September 19, 2007 FLOOD INSURANCE STUDY NUMBER 13045CV000A

2 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. Selected Flood Insurance Rate Map panels for this community contain information that was previously shown separately on the corresponding Flood Boundary and Floodway Map panels (e.g., floodways, cross sections). In addition, former flood hazard zone designations have been changed as follows: Old Zone(s) Al through A30 B C New Zone AE X X Initial Countywide FIS Effective Date: September 19, 2007

3 TABLE OF CONTENTS 1.0 INTRODUCTION Purpose of Study Authority and Acknowledgments Coordination AREA STUDIED Scope of Study Community Description Principal Flood Problems Flood Protection Measures ENGINEERING METHODS Hydrologic Analyses Hydraulic Analyses Vertical Datum FLOODPLAIN MANAGEMENT APPLICATIONS Floodplain Boundaries Floodways INSURANCE APPLICATIONS FLOOD INSURANCE RATE MAP OTHER STUDIES LOCATION OF DATA BIBLIOGRAPHY AND REFERENCES...30 i

4 TABLE OF CONTENTS (Continued) FIGURES Figure 1 - Frequency Discharge, Drainage Area Curves... 9 Beulah Creek Figure 1A Beulah Creek Tributary Figure 1A Buffalo Creek Tributary No. 1 Figure 1B Buffalo Creek Tributary No. 2 Figure 1B Chandler s Spring Creek Figure 1C Curtis Creek Figure 1C Curtis Creek Tributary No. 1 Figure 1D Curtis Creek Tributary No. 2 Figure 1D Curtis Creek Tributary No. 3 Figure 1D Little Tallapoosa River Tributary Figure 1E Tanyard Branch Figure 1F Figure 2 - Floodway Schematic TABLES Table 1 - Streams Studied by Detailed Methods... 4 Table 2 - Streams Studied by Limited Detailed Methods... 4 Table 3 - Summary of Discharges... 7 Table 4 - Vertical Datum Conversion Table 5 - Floodway Data Table 6 - Community Map History EXHIBITS Exhibit 1 - Flood Profiles Beulah Creek Beulah Creek Tributary Buck Creek Buffalo Creek Buffalo Creek Tributary 1 Buffalo Creek Tributary 2 Chandler s Spring Creek Curtis Creek Curtis Creek Tributary 1 Curtis Creek Tributary 3 Little Tallapoosa River Little Tallapoosa River Tributary Sweetwater Creek Tanyard Branch Town Branch Panels 01P-02P Panels 03P-04P Panel 05P Panels 06P-09P Panel 10P Panel 11P Panels 12P-13P Panel 14P Panels 15P-17P Panel 18P Panels 19P-26P Panels 27P-30P Panel 31P Panels 32P-34P Panel 35P Exhibit 2 - Flood Insurance Rate Map Index Flood Insurance Rate Map ii

5 FLOOD INSURANCE STUDY CARROLL 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 Carroll County, including the Cities of Bowdon, Carrollton, Mount Zion, Roopville, Temple, Villa Rica, and Whitesburg; and the unincorporated areas of Carroll County (referred to collectively herein as Carroll County), and aids in the administration of the National Flood Insurance Act of 1968 and the Flood Disaster Protection Act of 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, Please note that the City of Bremen is geographically located in Carroll and Haralson Counties. The City of Bremen is not included in this FIS report. See the separately published FIS report and Flood Insurance Rate Map (FIRM) for floodhazard information. Please note that the City of Villa Rica is geographically located in Carroll and Douglas Counties. The flood-hazard information for the City of Villa Rica is included in its entirety in this FIS report. Please note that the Cities of Whitesburg and Roopville have no mapped flood hazard areas. 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 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

6 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 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: Carroll County, Georgia (Unincorporated Areas) City of Carrollton The hydrologic and hydraulic analyses for the December 15, 1990, FIS report (Reference 1) were performed by Post, Buckley, Schuh & Jernigan, Inc. (the Study Contractor), for the Federal Emergency Management Agency (FEMA), under Contract No. EMW-87-C This work was completed in June The hydrologic and hydraulic analyses for the December 1976 FIS report (Reference 2) were performed by the U.S. Army Corps of Engineers (USACE), Mobile District, for the Federal Insurance Administration, under Inter-Agency Agreement No. IAA-H-16-75, Project Order No. 19. This work, which was completed in November 1976, covered all significant flooding sources affecting the City of Carrollton. The hydrologic and hydraulic analyses and redelineations for this countywide FIS report were performed by PBS&J, for the Georgia Department of Natural Resources (DNR), under Contract No. EMA-2005-CA-5211 with FEMA. This work was completed in June The hydrologic and hydraulic analyses for the limited detailed studies for Keaton Creek, Keaton Creek Tributary 2, and Town Branch in this FIS report were performed by the Georgia Department of Natural Resources (DNR) under contract number EMA-2005-GR-5369 with FEMA. The work was completed in April

7 1.3 Coordination The initial and final meeting dates for the previous FIS reports for Carroll County and its communities are listed in the following table: Community FIS Date Initial Meeting Final Meeting Carroll County (Unincorporated Areas) December 15, 1990 October, 1986 January 25, 1990 City of Carrollton December 1976 January 21, 1975 August 3, 1976 The meetings were attended by the study contractor, FEMA, and community officials. The initial meetings were held to discuss the nature and purpose of the proposed FIS. The final meetings were held to review the results of the FIS. For this countywide FIS report, a scoping meeting was held on October 18, 2004, with representatives from the Georgia DNR, Greenhorne and O Mara, FEMA, and the communities. The purpose of this meeting was to discuss the scope of the FIS. The results of the study were reviewed at the final meeting held on October 2, 2006, and attended by representatives of the City of Bowdon, City of Carrollton, City of Temple, City of Villa Rica, Town of Roopville, Carroll County, Georgia DNR, and PBS&J. All problems raised at the meeting have been addressed. 2.0 AREA STUDIED 2.1 Scope of Study This FIS covers the geographic area of Carroll 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 through October 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 the communities. For this FIS report, the FIS report and FIRM were converted to countywide format, and 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 (NGVD) to the North American Vertical Datum (NAVD). In addition, the Universal Tranverse Mercator coordinates, previously referenced to the North American Datum of 1927, are now referenced to the North American Datum of In addition, Beulah Creek, Buffalo Creek, Buffalo Creek Tributary 1, Chandler s Spring Creek, Curtis Creek, Curtis Creek Tributary 1, Curtis Creek Tributary 3, Little 3

8 Tallapoosa River from approximately 320 feet downstream of State Highway 166 to approximately 4,090 feet upstream of West Hickory Level Road, and Tanyard Branch were redelineated using 2 foot digital topographic data provided by the City of Carrollton (Reference 3) and 20 foot spacing digital elevation models provided by Carroll County (Reference 4). Town Branch was redelineated using 2 foot digital topographic data provided by Douglas County (Reference 5). The following table represents the streams that are studied by detailed methods for Carroll County. The limits of detailed study are shown on the FIRM panels and on the Flood Profiles (Exhibit 1). Table 1 Streams Studied by Detailed Methods Beulah Creek Curtis Creek Tributary 1 Beulah Creek Tributary Curtis Creek Tributary 3 Buck Creek Little Tallapoosa River Buffalo Creek Little Tallapoosa River Tributary Buffalo Creek Tributary 1 Sweetwater Creek Buffalo Creek Tributary 2 Tanyard Branch Chandler s Spring Creek Town Branch Curtis Creek The areas studied by limited detailed methods were selected with priority given to all known flood hazards and areas of projected development or proposed construction through June The streams studied by limited detailed methods are presented in the following table. Table 2 Streams Studied by Limited Detailed Methods Stream Keaton Creek Keaton Creek Tributary 2 Town Branch Reach Description From county boundary to approximately 3,500 feet upstream of Daniel Road From approximately 4,200 feet upstream of Tyson Road to approximately 2,100 feet upstream of Liberty Road North From the Limit of Detailed Study to approximately 500 feet upstream of Walker Street 2.2 Community Description Carroll County, established in 1826 from lands acquired by a treaty signed with the Cherokee and Creek Indian Nations, was named for Charles Carroll, a signer of the Declaration of Independence. According to the U.S. Census Bureau, in 2000 the population for Carroll County was 87,268. Since 1990 the county has experienced a 22.2% population increase (Reference 6). Carroll County, encompassing approximately 500 square miles, is situated in west-central Georgia on the Georgia-Alabama state line, some 50 miles west of Atlanta, approximately 85 miles north of Columbus, and 95 miles south of Chattanooga, Tennessee. It is bordered on the north by Haralson and Paulding Counties; on the east by Douglas and Fulton Counties; on the south by Coweta 4

9 and Heard Counties; and on the west by Cleburne and Randolph Counties, Alabama. The County is served by Interstate Highway 20, U.S. Highway 27, and State Highway 1, 5, 16, 61, 78, 100, 101, 113, and 166. It is also served by the Norfolk Southern Railway. Carroll County s mild climate consists of mild winters and warm summers. The average temperature is 59 degrees Fahrenheit ( o F) with an average annual rainfall of 53 inches and negligible snowfall. The wettest month is March with an average of 6.22 inches of precipitation while September is the driest with an average of 3.21 inches (Reference 7) 2.3 Principal Flood Problems Several streams, including the Little Tallapoosa River, Buffalo Creek, and Bethel Creek are subject to flooding during any month. Most of the major flood problems existing in the county are in low-lying agricultural areas. Historical records indicate that flooding has been caused by tropical storms from the Gulf of Mexico, frontal activity, and prolonged occurrences of low pressure areas. The floodplains are covered with natural brush and undergrowth except for a subdivision development which has encroached on the portion of the floodplain downstream of King s Bridge Road. The undergrowth tends to impede floodflows along the river, particularly below Alabama Street. The City of Carrollton s waste stabilization pond and portions of its 5 million gallon per day, extended aeration plant are subject to flooding by the Little Tallapoosa River. 2.4 Flood Protection Measures Fourteen Soil Conservation Service (SCS) flood-retarding structures and Lake Carroll attenuate flood flows along the Little Tallapoosa River. Richland s Lake and SCS flood retarding structures also attenuate flood flows in upper portions of Buffalo and Curtis Creeks. 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 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 5

10 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. For the Little Tallapoosa River and Buffalo Creek, the discharge-frequency relationships were determined by using U.S. Geological Survey (USGS) regional regression equations (Reference 8). For areas where significant urbanization has occurred, these discharges were adjusted using established procedures (Reference 9). A detailed discussion of the methodology used in the hydrologic analysis is presented in Hydrology Study for Unincorporated Carroll County (Reference 10). For Town Branch, the flood-flow frequency data was developed using the Golden-Price methodology (Reference 11). This technique incorporates an urbanization factor into the Sauer-Golden method (Reference 12), which was developed to predict floods in rural watersheds of Georgia. The Sauer method was used because it considers urbanization effects, resulting in consistently conservative flood predictions. For all other detailed streams, discharges were analyzed by two methods. First, hydrologic models of the Little Tallapoosa River, including Curtis Creek and Buffalo Creek Basins, were prepared to simulate rainfall-runoff relationships in the determination of flood hydrographs resulting from the 10-, 2-, 1-, and 0.2- percent-annual chance storms on these streams. Historical streamflow records are available for the Little Tallapoosa River at the Carrollton water treatment plant. The period of record at the gage is 1936 through Runoff from 73 percent of the square mile gaged drainage area is affected by the construction of 14 flood retarding reservoirs built over the period from May 1958 to June The streamflow record is non-homogeneous because of the construction of the reservoirs and cannot be used in the statistical estimation of flood flow frequency for the stream. Hydrologic models were also prepared to determine the attenuation of runoff caused by culvert restrictions on Curtis Creek Tributary 3 and Beulah Creek Tributary. All hydrologic models were developed using the USACE HEC-1 Flood Hydrograph Package (Reference 13). 6

11 The flood discharges for the remaining streams studied by detailed methods were determined by the use of preliminary flood frequency relations for urban streams, as recommended by the USGS (Reference 14). All computations included consideration of the percentage of watersheds developed or zoned for development as determined by field reconnaissance and by study of the City of Carrollton Zoning Map (Reference 15). For Keaton Creek, Keaton Creek Tributary 2, and Town Branch, which were studied by limited detailed methods, the peak discharge for the 1-percent-annualchance flood was estimated using the regression equations published in USGS Fact Sheet (Reference 16). Peak discharge-drainage area relationships for streams studied in detail in Carroll County are shown in Table 3. Table 3 - Summary of Discharges Peak Discharges (cubic feet per second) Flooding Source and Location Beulah Creek Drainage Area (square miles) See Figure 1A 10-Percent- Annual-Chance 2-Percent- Annual-Chance 1-Percent- Annual-Chance 0.2-Percent- Annual-Chance Beulah Creek Tributary At the confluence with Beulah Creek See Figure 1A Buck Creek Approximately 19,550 feet upstream of the confluence with Possum Branch ,700 3,850 4,700 5,800 Buffalo Creek At Laurel Road 15.8 N/A N/A 5,345 7,191 Just upstream of Buffalo ,350 5,849 Creek Road Approximately 500 feet 8.3 N/A N/A 3,316 4,215 downstream of Martin Cemetery Road Approximately 2,100 feet downstream of Hayes Mill Road ,000 1,400 Buffalo Creek Tributary 1 Buffalo Creek Tributary 2 Chandlers Spring Creek Curtis Creek Curtis Creek Tributary 1 Curtis Creek Tributary 2 See Figure 1B See Figure 1B See Figure 1C See Figure 1C See Figure 1D See Figure 1D 7

12 Table 3 - Summary of Discharges (Continued) Peak Discharges (cubic feet per second) Flooding Source and Location Curtis Creek Tributary 3 Drainage Area (square miles) See Figure 1D 10-Percent- Annual-Chance 2-Percent- Annual-Chance 1-Percent- Annual-Chance 0.2-Percent- Annual-Chance Little Tallapoosa River At State Highway ,607 9,586 10,797 13,584 At confluence of Buck Creek ,419 7,890 8,916 11,255 Approximately 800 feet 73.1 N/A N/A 7,280 9,223 upstream of McKenzie Bridge Road Just upstream of confluence of Hominy Creek 53.1 N/A N/A 6,065 7,708 Little Tallapoosa River Tributary Tanyard Branch Town Branch Downstream of Lake Val-Do-Mar See Figure 1E See Figure 1F 3.1 1,088 1,668 1,927 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 the flooding sources studied by detailed methods were obtained from field surveys and aerial photography (Reference 17). All bridges, dams, and culverts were field surveyed to obtain elevation data and structural geometry. Channel roughness factors (Manning s n ) used in the hydraulic computations, were chosen by engineering judgment and based on field observations of the streams and floodplain areas. The roughness values for the channels ranged from to Roughness values for overbank areas ranged from 0.02 to Water-surface elevations (WSELs) of floods of the selected recurrence intervals were computed using the USACE HEC-2 step-backwater computer program (Reference 18). Flood profiles were drawn showing the computed WSELs to an accuracy of 0.5 foot for floods of the selected recurrence intervals. 8

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19 Starting WSELs for Buck Creek, Buffalo Creek, Little Tallapoosa River, and Town Branch were established using the slope-area method. Starting WSELs for Beulah Creek, Chandler s Spring Creek, Curtis Creek, Little Tallapoosa River Tributary, and Tanyard Branch were taken from computed profile elevations of the Little Tallapoosa River. Starting WSELs for Beulah Creek Tributary were taken from computed profile elevations for Beulah Creek. Starting WSELs for Buffalo Creek Tributary 1 and Buffalo Creek Tributary 2 were taken from computed high-water elevations of Richards Lake. Starting WSELs of Curtis Creek Tributary 1 were taken from computed high-water elevations of Lake Carroll. WSELs for Curtis Creek Tributary 3 were started at critical depth. For this study, cross sections for portions of Keaton Creek, Keaton Creek Tributary 2, and Town Branch, which were studied by limited detailed methods, were obtained using digital topography and field surveys. The 1-percent-annual-chance WSELs were computed using the USACE s HEC-RAS hydraulic model, version (Reference 19). Limited detailed and detailed studied streams may include a "profile base line" on the maps. This "profile base line" provides a link to the flood profiles included in the FIS report. The detailed studied stream centerline may have been digitized or redelineated as part of this revision. The "profile base lines" for these streams were based on the best available data at the time of their study and are depicted as they were on the previous FIRMs. In some cases where improved topographic data was used to redelineate floodplain boundaries, the "profile base line" may deviate significantly from the channel centerline or may be outside the special flood hazard area. 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 NGVD. With the finalization of the NAVD, many FIS reports and FIRMs are being prepared using NAVD as the referenced vertical datum. All flood elevations shown in this FIS report and on the FIRM are referenced to NAVD. Structure and ground elevations in the community must, therefore, be 15

20 referenced to NAVD. It is important to note that adjacent communities may be referenced to NGVD. 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 NAVD was calculated using the National Geodetic Survey s VERTCON online utility (Reference 20). The data points used to determine the conversion are listed in Table 4. Table 4 Vertical Datum Conversion Conversion from Quad Name Corner Longitude Latitude NGVD to NAVD Tallapoosa South SW Tallapoosa South SE Bremen SE Bowdon East SW Bowdon East SE Temple NE Temple SE Villarica NE Villarica SE Carrollton SE Hulett SE Average For more information on NAVD, see the FEMA publication entitled Converting the National Flood Insurance Program to the North American Vertical Datum of 1988 (Reference 21), or contact the Vertical Network Branch, National Geodetic Survey, Coast and Geodetic Survey, National Oceanic and Atmospheric Administration, Silver Spring, Maryland (Internet address 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 16

21 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. 4.1 Floodplain Boundaries To provide a national standard without regional discrimination, the 1-percentannual-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. Between cross sections, the 1-percent-annual-chance floodplain boundaries for the portions of Little Tallapoosa River located in the unincorporated areas of Carroll County were interpolated using topographic maps at a scale of 1:4,800, with a contour interval of 4 feet (Reference 22). The 1-percent-annual-chance floodplain boundaries for Beulah Creek Tributary, Buck Creek, Buffalo Creek Tributary 2, and Little Tallapoosa River Tributary, were interpolated using a USGS map enlarged to a scale of 1:9,600, with a contour interval of 20 feet (Reference 23). The 1-percent-annual-chance floodplain boundary for Town Branch was interpolated using a USGS topographic map at a scale of 1:24,000, with a contour interval of 20 feet (Reference 24). The 1-percent-annual-chance floodplain boundaries for Beulah Creek, Buffalo Creek, Buffalo Creek Tributary 1, Chandler s Spring Branch, Curtis Creek, Curtis Creek Tributary 1, Curtis Creek Tributary 3, Tanyard Branch, and the portion of Little Tallapoosa River within the corporate limits of the City of Carrollton were interpolated using digital topographic maps with a contour interval of 2 feet (Reference 25). 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 and AE), 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 17

22 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-annualchance floodplain boundary is shown on the FIRM (Exhibit 2). For this countywide FIS report, for the streams studied by limited detailed methods, Keaton Creek, Keaton Creek Tributary 2, and Town Branch, the boundaries between cross sections were interpolated using topographic maps at a scale of 1:800, with a contour interval of 2 feet (Reference 26). 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 floodplain boundaries are either close together or collinear, only the floodway boundary has been shown. 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 WSEL 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. Floodways were not computed for portions of Beulah Creek, Buffalo Creek, and Little Tallapoosa River. 18

23 FLOODING SOURCE CROSS SECTION DISTANCE WIDTH (FEET) FLOODWAY SECTION AREA (SQUARE FEET) MEAN VELOCITY (FEET PER SECOND) REGULATORY (FEET NAVD) 1-PERCENT-ANNUAL-CHANCE FLOOD WATER SURFACE ELEVATION WITHOUT FLOODWAY (FEET NAVD) WITH FLOODWAY (FEET NAVD) INCREASE (FEET) BEULAH CREEK A 1, , B 1, , C 6, , , , BEULAH CREEK TRIBUTARY A , , , B , , , C , , , D 1, , , , E 1, , , , BUCK CREEK A 19, , , , , B 19, , , , , Feet above confluence with Little Tallapoosa River 3 Feet above confluence with Beulah Creek 2 Elevation computed without consideration of backwater effects from Little Tallapoosa River 4 Feet above confluence with Possum Branch TABLE 5 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA CARROLL COUNTY, GA AND INCORPORATED AREAS BEULAH CREEK BEULAH CREEK TRIBUTARY BUCK CREEK

24 FLOODING SOURCE CROSS SECTION DISTANCE 1 WIDTH (FEET) BUFFALO CREEK A-G 2 FLOODWAY SECTION AREA (SQUARE FEET) MEAN VELOCITY (FEET PER SECOND) REGULATORY (FEET NAVD) 1-PERCENT-ANNUAL-CHANCE FLOOD WATER SURFACE ELEVATION WITHOUT FLOODWAY (FEET NAVD) WITH FLOODWAY (FEET NAVD) INCREASE (FEET) H 41, , I 42, , J 42, K 43, , , , L 45, , , , , M 46, , , , , N 46, , , , , O 46, , , , , P 48, , , , Q 48, , , , R 49, , , , , S 49, , , , , T 50, , , , U 50, , , , V 51, , , , , W 51, , , , , X 56, , , , Feet above confluence with Little Tallapoosa River 2 No floodway computed TABLE 5 FEDERAL EMERGENCY MANAGEMENT AGENCY CARROLL COUNTY, GA AND INCORPORATED AREAS FLOODWAY DATA BUFFALO CREEK

25 FLOODING SOURCE CROSS SECTION DISTANCE WIDTH (FEET) FLOODWAY SECTION AREA (SQUARE FEET) MEAN VELOCITY (FEET PER SECOND) REGULATORY (FEET NAVD) 1-PERCENT-ANNUAL-CHANCE FLOOD WATER SURFACE ELEVATION WITHOUT FLOODWAY (FEET NAVD) WITH FLOODWAY (FEET NAVD) INCREASE (FEET) BUFFALO CREEK (CONTINUED) Y 57, , , , BUFFALO CREEK TRIBUTARY 1 A 1, , , , B 2, , , , BUFFALO CREEK TRIBUTARY 2 A , , , B , , , Feet above confluence with Little Tallapoosa River 2 Feet above Strickland Road 3 Feet above confluence with Richards Lake TABLE 5 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA CARROLL COUNTY, GA AND INCORPORATED AREAS BUFFALO CREEK BUFFALO CREEK TRIBUTARY 1 BUFFALO CREEK TRIBUTARY 2

26 FLOODING SOURCE CROSS SECTION DISTANCE WIDTH (FEET) FLOODWAY SECTION AREA (SQUARE FEET) MEAN VELOCITY (FEET PER SECOND) REGULATORY (FEET NAVD) 1-PERCENT-ANNUAL-CHANCE FLOOD WATER SURFACE ELEVATION WITHOUT FLOODWAY (FEET NAVD) WITH FLOODWAY (FEET NAVD) INCREASE (FEET) CHANDLER S SPRING CREEK A 2, , B 2, C 3, , , , D 4, , , , CURTIS CREEK A 3, B 3, CURTIS CREEK TRIBUTARY 1 A , , , , B 1, , , , C 2, , , , D 3, , , , E 5, , , , F 5, , , , Feet above confluence with Little Tallapoosa River 2 Elevation computed without consideration of backwater effects from Little Tallapoosa River 3 Feet above confluence with Curtis Creek TABLE 5 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA CARROLL COUNTY, GA AND INCORPORATED AREAS CHANDLER S SPRING CREEK CURTIS CREEK CURTIS CREEK TRIBUTARY 1

27 FLOODING SOURCE CROSS SECTION DISTANCE WIDTH (FEET) FLOODWAY SECTION AREA (SQUARE FEET) MEAN VELOCITY (FEET PER SECOND) REGULATORY (FEET NAVD) 1-PERCENT-ANNUAL-CHANCE FLOOD WATER SURFACE ELEVATION WITHOUT FLOODWAY (FEET NAVD) WITH FLOODWAY (FEET NAVD) INCREASE (FEET) CURTIS CREEK TRIBUTARY 3 A , , , , B , , , LITTLE TALLAPOOSA RIVER A , B 3, ,457 10, C 4, , D 6, , E 6, , F 8, , G 10, ,375 10, H 17, , I 20, , J 21, , K 25, , L 32, , Feet above confluence with Curtis Creek 2 Feet above limit of detailed study (limit of detailed study is approximately 300 feet downstream from State Highway 166) TABLE 5 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA CARROLL COUNTY, GA AND INCORPORATED AREAS CURTIS CREEK TRIBUTARY 3 LITTLE TALLAPOOSA RIVER

28 FLOODING SOURCE CROSS SECTION DISTANCE 1 WIDTH (FEET) FLOODWAY SECTION AREA (SQUARE FEET) MEAN VELOCITY (FEET PER SECOND) REGULATORY (FEET NAVD) 1-PERCENT-ANNUAL-CHANCE FLOOD WATER SURFACE ELEVATION WITHOUT FLOODWAY (FEET NAVD) WITH FLOODWAY (FEET NAVD) INCREASE (FEET) LITTLE TALLAPOOSA RIVER (CONTINUED) M 33, , N 34, , O 36, , P 36, , Q 38, , R 40, , S 41, , T 43, , U 44, , V 46, , W 48, , X 49, , Y 50, , Z 51, , AA 52, , AB 54, , Feet above limit of detailed study (limit of detailed study 300 feet downstream from State Highway 166) TABLE 5 FEDERAL EMERGENCY MANAGEMENT AGENCY CARROLL COUNTY, GA AND INCORPORATED AREAS FLOODWAY DATA LITTLE TALLAPOOSA RIVER

29 FLOODING SOURCE CROSS SECTION DISTANCE WIDTH (FEET) FLOODWAY SECTION AREA (SQUARE FEET) MEAN VELOCITY (FEET PER SECOND) REGULATORY (FEET NAVD) 1-PERCENT-ANNUAL-CHANCE FLOOD WATER SURFACE ELEVATION WITHOUT FLOODWAY (FEET NAVD) WITH FLOODWAY (FEET NAVD) INCREASE (FEET) LITTLE TALLAPOOSA RIVER (CONTINUED) AC 56, , AD-AP 2 LITTLE TALLAPOOSA RIVER TRIBUTARY A 3, , , , B 4, , , , C 4, , , , D 5, , , , SWEETWATER CREEK A /96 5 1, Feet above limit of detailed study (limit of detailed study 300 feet downstream from State Highway 166) 2 No floodway computed 3 Feet above confluence with Little Tallapoosa River 4 Feet above County Boundary 5 Total width/width within county TABLE 5 FEDERAL EMERGENCY MANAGEMENT AGENCY CARROLL COUNTY, GA AND INCORPORATED AREAS FLOODWAY DATA LITTLE TALLAPOOSA RIVER LITTLE TALLAPOOSA RIVER TRIBUTARY SWEETWATER CREEK

30 FLOODING SOURCE CROSS SECTION DISTANCE WIDTH (FEET) FLOODWAY SECTION AREA (SQUARE FEET) MEAN VELOCITY (FEET PER SECOND) REGULATORY (FEET NAVD) 1-PERCENT-ANNUAL-CHANCE FLOOD WATER SURFACE ELEVATION WITHOUT FLOODWAY (FEET NAVD) WITH FLOODWAY (FEET NAVD) INCREASE (FEET) TANYARD BRANCH A 1, , B 1, , C 2, D 2, E 3, , , , F 4, , , , G 5, , , , TOWN BRANCH A 13, B 15, , , , C-E 4 1 Feet above confluence with Little Tallapoosa River 2 Elevation computed without consideration of backwater effects from Little Tallapoosa River 3 Feet above confluence with Mud Creek 4 No floodway computed TABLE 5 FEDERAL EMERGENCY MANAGEMENT AGENCY CARROLL COUNTY, GA AND INCORPORATED AREAS FLOODWAY DATA TANYARD BRANCH TOWN BRANCH

31 Figure 2 - Floodway Schematic 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, wholefoot BFEs derived from the detailed hydraulic analyses are shown at selected intervals within this zone. 27

32 Zone X Zone X is the flood insurance risk zone that corresponds to areas outside the 0.2-percentannual-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. 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 Carroll 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, Community Map History. 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, Koger Center Rutgers Building, 3003 Chamblee Tucker Road, Atlanta, Georgia

33 COMMUNITY NAME INITIAL IDENTIFICATION FLOOD HAZARD BOUNDAY MAP REVISION DATE FIRM EFFECTIVE DATE FIRM REVISION DATE Bowdon, City of November 15, 1974 August 8, 1975 December 19, 1975 June 17, 1986 September 19, 2007 Carroll County (Unincorporated Areas) August 11, 1978 None December 15, 1990 September 19, 2007 Carrollton, City of May 24, 1974 January 23, 1976 April 3, 1978 September 19, 2007 Mount Zion, City of July 1, 1977 None September 1, 1987 September 19, 2007 Roopville, City of* September 19, 2007 None September 19, 2007 None Temple, City of April 11, 1975 None September 18, 1987 September 19, 2007 Villa Rica, City of June 27, 1975 None September 1, 1986 September 19, 2007 Whitesburg, City of* September 19, 2007 None September 19, 2007 None * No flood hazard areas identified TABLE 6 FEDERAL EMERGENCY MANAGEMENT AGENCY CARROLL COUNTY, GA AND INCORPORATED AREAS COMMUNITY MAP HISTORY Table 1 - Community Map History 29

34 9.0 BIBLIOGRAPHY AND REFERENCES 1. Federal Emergency Management Agency, Flood Insurance Study, Carroll County, Georgia, Washington, D.C., December 15, Federal Insurance Administration, Flood Insurance Study, City of Carrollton, Carroll County, Georgia, Washington, D.C., Flood Insurance Study report, December 1976; Flood Insurance Rate Map, April 3, City of Carrollton, Georgia, Digital Topographic Data, City of Carrollton, Carroll County, Georgia, Contour Interval 2 feet, February Carroll County, Georgia, Digital Elevation Models, Carroll County, Georgia, Spacing of 20 feet, February Douglas County, Georgia, Digital Topographic Data, Douglas County, Georgia, Contour Interval 2 feet, March/April U.S. Census Bureau, American FactFinder, Carroll County, Georgia, Retrieved May 1, 2006, from 7. The Weather Channel, Monthly Averages for Carroll County. Retrieved May 1, 2006, from 8. U.S. Department of the Interior, U.S. Geological Survey, Water Resources Investigation , Floods in Georgia, Magnitude and Frequency; Techniques for Estimating the Magnitude and Frequency of Floods in Georgia, McGlone Price, October U.S. Geological Survey, Water Supply Paper 2207, Flood Characteristics of Urban Watersheds in the United States, Techniques for Estimating Magnitude and Frequency of Urban Floods, V.B. Saur, W.O. Thomas, Jr., V.A. Stricker, and K.V. Wilson, Post, Buckley, Schuh & Jernigan, Inc., Hydrology Study for Unincorporated Carroll County, Atlanta, Georgia, March U.S. Geological Survey, Open File Report 77-57, Preliminary Flood-Frequency Relations for Urban Streams in Metropolitan Atlanta, Georgia, Golden, H.G., Golden, H.G. and Price, McGlone, Flood Frequency Analysis for Small Natural Streams in Georgia, July

35 13. U.S. Army Corps of Engineers, Hydrologic Engineering Center, HEC-1, Flood Hydrograph Package, Computer Program 723-X , Users Manual, January U.S. Geological Survey, Preliminary Flood Frequency Relations for Urban Streams, Metropolitan Atlanta, Georgia, Doraville Georgia, October 10, City of Carrollton, City Engineering Department, City of Carrollton Zoning Map, April U.S. Geological Survey, The National Flood-Frequency Program-Methods for Estimating Flood Magnitude and Frequency in Rural and Urban Areas in Georgia, USGS Fact Sheet , August Woolpert Consultants, Aerial Photographs, Carroll County Georgia, Scale 1:14,400: Mobile, Alabama, March U.S. Army Corps of Engineers, Hydraulic Engineering Center, HEC-2 Water Surface Profiles, Generalized Computer Program 723-X6-L202A, Davis, California, April Hydrologic Engineering Center, HEC-RAS River Analysis System, Version 3.1.3, U.S. Army Corps of Engineers, Davis, California, May National Geodetic Survey, VERTCON-North American Vertical Datum Conversion Utility. Retrieved April 1, 2006, from Federal Emergency Management Agency, Converting the National Flood Insurance Program to the North American Vertical Datum of 1988, June Woolpert Consultants, Topographic Maps, Carroll County, Georgia, Scale 1:4800, Contour Interval 4 feet: Mobile, Alabama, U.S. Geological Survey, 15-Minute Series Topographic Maps, Scale 1:62,500, Contour Interval 20 feet: Carrollton, Georgia, U.S. Geological Survey, 7.5 Minute Topographic Maps: Villa Rica, Georgia Carroll County, Georgia, Digital Topographic Data, Carroll County, Georgia, Contour Interval 2 feet, Photo Science Geospatial Solutions, LiDAR data and Aerial Photographs, Scale 1:800, Contour Interval 2 feet: Douglas County, Georgia,

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