BROOKS COUNTY, GEORGIA AND INCORPORATED AREAS

Transcription

1 BROOKS COUNTY, GEORGIA AND INCORPORATED AREAS COMMUNITY NAME COMMUNITY NUMBER BROOKS COUNTY (UNINCORPORATED AREAS) MORVEN, CITY OF QUITMAN, CITY OF Brooks County EFFECTIVE: September 2, 2009 Federal Emergency Management Agency FLOOD INSURANCE STUDY NUMBER 13027CV000A

2 NOTICE TO FLOOD INSURANCE STUDY USERS Communities participating in the National Flood Insurance Program (NFIP) have established repositories of flood hazard data for floodplain management and flood insurance purposes. This Flood Insurance Study (FIS) may not contain all data available within the repository. It is advisable to contact the community repository for any additional data. Part or all of this FIS may be revised and republished at any time. In addition, part of this FIS may be revised by the Letter of Map Revision process, which does not involve republication or redistribution of the FIS. It is, therefore, the responsibility of the user to consult with community officials and to check the community repository to obtain the most current FIS components. Initial Countywide FIS Effective Date: September 2, 2009 i

3 TABLE OF CONTENTS Page 1.0 INTRODUCTION Purpose of Study Authority and Acknowledgements 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 APPLICATION FLOOD INSURANCE RATE MAP OTHER STUDIES LOCATION OF DATA BIBLIOGRAPHY AND REFERENCES 13 ii

4 TABLE OF CONTENTS continued Page FIGURES Figure 1 - Floodway Schematic 9 TABLES Table 1 Summary of Discharges 5 Table 2 Floodway Data Table 10 Table 3 - Community Map History 14 Exhibit 1 Flood Profiles EXHIBITS Jefferson Street Ditch Panel 01P Little River Panel 02P Okapilco Creek Panel 03P Withlacoochee River Panels 04P 06P Exhibit 2 - Flood Insurance Rate Map Index Flood Insurance Rate Map iii

5 1.0 INTRODUCTION FLOOD INSURANCE STUDY BROOKS COUNTY, GEORGIA AND INCORPORATED AREAS 1.1 Purpose of Study This Flood Insurance Study revises and updates information on the existence and severity of flood hazards in the geographic area of Brooks County, including the Cities of Morven and Quitman; and the unincorporated areas of Brooks County (referred to collectively herein as Brooks 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 Town of Barwick and the City of Pavo are geographically located in Brooks and Thomas Counties. The flood-hazard information for these counties are for information only. See Thomas County Flood Insurance Study report and Flood Insurance Rate Map. 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. 1.2 Authority and Acknowledgments The sources of authority for this Flood Insurance Study are the National Flood Insurance Act of 1968 and the Flood Disaster Protection Act of For the Brooks County FIS, dated September 15, 1981, the hydrologic and hydraulic analyses were performed by the U.S. Army Corps of Engineers, Jacksonville District, for the Federal Emergency Management Agency, under Interagency Agreement No. IAA-H-979, Project Order No. 5. This study was completed in July For the City of Quitman FIS, dated October 1, 1981, the hydrologic and hydraulic analyses were performed by the U.S. Army Corps of Engineers, Jacksonville District, for the Federal Emergency Management Agency, under Interagency Agreement No. IAA-H-9-79, Project Order No. 5. This study was completed in July For this countywide FIS, new hydrologic and hydraulic analyses were prepared by Watershed Concepts for the Georgia Department of Natural Resources (DNR), under Contract No This study was completed in August 2008 The coordinate system used for the production of this FIRM is NAD 1983 State Plane Georgia West FIPS Corner coordinates shown on the FIRM are in latitude and longitude referenced to the UTM projection, NAD 83. Differences in the datum and spheroid used in the production of FIRMs for adjacent counties may result in slight positional differences in map features at the county boundaries. These differences do not affect the accuracy of information shown on the FIRM. 1

6 1.3 Coordination 2.0 AREA STUDIED For the Brooks County FIS, dated September 15, 1981, county officials, the U.S. Department of Agriculture (USDA), Soil Conservation Service (SCS), and the U.S. Geological Survey (USGS), were contacted during the course of this study. Available maps, flood data, rainfall data, and technical publications were obtained. A pre-contract consultation and coordination meeting to explain the nature and purpose of a Flood Insurance Study, to give a detailed presentation of Flood Insurance Study procedures, and to discuss the areas in Brooks County which would be included in the Flood Insurance Study was held in Quitman, Georgia, on November 14, Representatives from the U.S. Army Corps of Engineers (COE), FEMA, and local officials and residents of Brooks County attended. On May 6, 1981, the results of the study were reviewed at a final coordination meeting attended by representatives of the COE, FEMA, and residents and officials of Brooks County. For the City of Quitman FIS, dated October 1, 1981, county officials, the U.S. Department of Agriculture (USDA), Soil Conservation Service (SCS), and the U.S. Geological Survey (USGS), were contacted during the course of this study. Available maps, flood data, rainfall data, and technical publications were obtained. A pre-contract consultation and coordination meeting to explain the nature and purpose of a Flood Insurance Study, to give a detailed presentation of Flood Insurance Study procedures, and to discuss the areas in Brooks County which would be included in the Flood Insurance Study was held in Quitman, Georgia, on November 14, Representatives from the U.S. Army Corps of Engineers (COE), FEMA, and local officials and residents of the City of Quitman attended. On May 6, 1981, the results of the study were reviewed at a final coordination meeting attended by representatives of the COE, FEMA, and residents and officials of City of Quitman. For this revision, an initial Consultation Coordination Officer s (CCO) meeting is held with representatives of the communities, FEMA, and the study contractors to explain the nature and purpose of the FIS, and to identify the streams to be studied by detailed methods. A final CCO meeting is held with representatives of the communities, FEMA, and the study contractors to review the results of the study. For this countywide FIS, the initial CCO meeting was held on February 28, 2007, and a final CCO meeting was held on November 7, The meetings were attended by representatives of the communities, the Southwest Georgia Regional Development Center, the Georgia Department of Natural Resources (GADNR), FEMA, and the Study Contractor. All problems raised at that meeting have been addressed in this study. 2.1 Scope of Study This Flood Insurance Study covers the geographic area of Brooks County, Georgia, including the incorporated communities listed in Section

7 For the Brooks County FIS, dated September 15, 1981, floods caused by the overflow of the Withlacoochee River, Little River, Jefferson Street Ditch and Okapilco Creek were studied in detail. The detail study area was determined and agreed upon at the pre-contract consultation and coordination meeting on November 14, The areas studied by detailed methods were selected with priority given to all known flood hazard areas, and areas of projected development or proposed construction through August For the City of Quitman FIS, dated October 1, 1981, floods caused by the overflow of the Okapilco Creek and the Jefferson Street Ditch were studied in detail. The detail study area was determined and agreed upon at the pre-contract For this revision, no new detailed studies have been performed as part of this countywide study. Approximate analyses were used to study those areas having a low development potential or minimal flood hazards. The scope and methods of study were proposed to, and agreed upon, by FEMA, the Georgia Department of Natural Resources (GADNR), Brooks County, and the Study Contractor. 2.2 Community Description Brooks County and its county seat, Quitman, are located in southwest of Georgia. The county is bounded on the north by Colquitt County, Georgia and Cook County, Georgia, on the east by Lowndes County, Georgia, on the south by Jefferson County, Florida and Madison County, Florida, and on the west by Thomas County, Georgia. The population of Brooks County was 16,450. The land area of the county covers 498 square miles (1,298 square kilometers), of which, 494 square miles (1,278 square kilometers) of it is land and 4 square miles (11 square kilometers) of it is water (Reference 1). Brooks County was created December 11, 1858 from portions of Lowndes and Thomas counties by an act of the Georgia General Assembly named in honor of Preston Brooks. 2.3 Principal Flood Problems The major flooding sources in Brooks County are the Withlacoochee River and Little River, which runs along the eastern border of the county and Okapilco Creek, which flows through in the middle of the county. 2.4 Flood Protection Measures Flood protection measures are not known to exist within the study area. 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, 3

8 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 100-year flood (1-percent chance of annual 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 approximate methods affecting the community. For the Brooks County FIS, dated September 15, 1981, hydrologic analyses were carried out to establish peak discharge-frequency relationships for floods of the selected recurrence intervals for the Withlacoochee River, Little River, and Okapilco Creek. Peak discharges were determined by regression equations determined by the USGS and published in a report titled Floods in Georgia, Magnitude and Frequency and dated October 1979 (Reference 3) For the City of Quitman FIS dated October 1, 1981, hydrologic analyses were carried out to establish peak discharge-frequency relationships for floods of the selected recurrence intervals for the Okapilco Creek and the Jefferson Street Ditch. Peak discharges for the Okapilco Creek were determined by regression equations determined by the USGS and published in a report titled Floods in Georgia, Magnitude and Frequency and dated October 1979 (Reference 3) Peak discharges for the Jefferson Street Ditch were determined by the COE rainfall Model HEC-1 (Reference 4) Rainfall-frequency estimates were obtained from U.S. Weather Bureau Technical Paper 40 (Reference 5) and the National Oceanic and Atmospheric Administration Technical Memorandum NWS HYDRO-35 (Reference 6) Rainfall-frequency estimates are as follows: Duration 10-Percent- Annual-Chance 2-Percent- Annual-Chance Rainfall -Inches 1-Percent- Annual-Chance 0.2-Percent- Annual-Chance 10 minutes minutes hour hours The amount of rainfall that will run off (rainfall excess) from a particular basin is less than the rainfall due to soil permeability, vegetation cover, and other characteristics. To estimate the rainfall excess, the SCS has developed Runoff Curve Number (Reference 7) which relates rainfall to direct runoff. The Runoff Curve Numbers were used to calculate the infiltration losses based on the soil type and land use. 4

9 The rainfall-frequency estimates and the SCS runoff curve number procedure were incorporated into the HEC-1 computer model to determine the routed peak discharges at selected points along the Jefferson Street Ditch. Some flows are attenuated in the downstream direction due to storage effects in the overbank areas. The peak discharge-drainage area relationships for the selected recurrence intervals are presented in Table 1, Summary of Discharges. Flooding Source and Location Drainage Area (Square Miles) Table 1. Summary of Discharges Peak Discharges (cfs) 10-Percent- Annual-Chance 2-Percent- Annual-Chance 1-Percent- Annual-Chance 0.2-Percent- Annual-Chance JEFFERSON STREET DITCH At Jefferson Street At Railroad At Boundary Street LITTLE RIVER At mouth ,500 26,200 32,700 49,000 OKAPILCO CREEK At U.S. Highway ,925 9,635 11,140 15,000 WITHLACOOCHEE RIVER At U.S. Highway 84 1,480 19,100 34,700 42,700 62,000 For this revision, discharges for Zone A studies were developed using Region 4 regression equations for rural areas in Georgia (Reference 2) contained in the USGS report. Drainage areas along streams were determined using a flow accumulation grid developed from the USGS 10 meter digital elevation models and corrected National Hydrologic Data (NHD) stream coverage. Flow points along stream centerlines were calculated using the regression equations in conjunction with accumulated area for every 10 percent increase in flow along a particular stream. 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 wholefoot elevations and may not exactly reflect the elevations shown on the Flood Profiles or in the Floodway Data tables in the FIS report. For construction and/or floodplain management purposes, users are encouraged to use the flood elevation data presented in this FIS in conjunction with the data shown on the FIRM. 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 Flood Insurance Rate Map (Exhibit 2) 5

10 For the Brooks County FIS, dated September 15, 1981, each jurisdiction within Brooks County had a previously printed FIS report describing each jurisdiction's hydraulic analyses. Those analyses not revised for this countywide FIS have been compiled from the FIS reports and are summarized below. 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. For all flooding sources studied by detailed methods, roughness coefficients (Manning s n ) for the computations were estimated on the basis of field inspections of flood plain areas. The roughness coefficients ranged from 0.05 for the main channel to 0.15 for the overbank areas. The acceptability of all assumed hydraulic factors, cross sections, and hydraulic structure data was checked by computations that duplicated historic flood water profiles where available. Water-surface elevations of floods of the selected recurrence intervals were computed through use of the COE HEC-2 computer program (Reference 6). Flood profiles were drawn showing computed water-surface elevations to an accuracy of 0.5 foot for floods of the selected recurrence intervals (Exhibit I). Starting water-surface elevations for the Okapilco Creek were based on the slope-area method. Starting water-surface elevations for Withlacoochee River were based on gage analysis at U.S. Highway 84 Starting watersurface elevations for Little River were based on the computed water-surface elevations of the receiving stream (Withlacoochee River). For the City of Quitman FIS, dated October 1, 1981, each jurisdiction within Brooks County had a previously printed FIS report describing each jurisdiction's hydraulic analyses. Those analyses not revised for this countywide FIS have been compiled from the FIS reports and are summarized below. 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. For all flooding sources studied by detailed methods, roughness coefficients (Manning s n ) for the computations were estimated on the basis of field inspections of flood plain areas. The roughness coefficients ranged from 0.05 for the main channel to for the overbank areas. The acceptability of all assumed hydraulic factors, cross sections, and hydraulic structure data was checked by computations that duplicated historic flood water profiles where available. Water-surface elevations of floods of the selected recurrence intervals were computed through use of the COE HEC-2 computer program (Reference 8). Flood profiles were drawn showing computed water-surface elevations to an accuracy of 0.5 foot for floods of the selected recurrence intervals (Exhibit I). Starting water-surface elevations for the Okapilco Creek were based on the slope-area method.starting water-surface elevations for the Jefferson Street Ditch were based on the computed water-surface elevations of the receiving stream (Okapilco Creek). For this revision, floodplains were delineated using automated approximate methods. Floodplains were mapped to include backwater effects that govern each flooding source near its downstream extent. Floodplains were reviewed for accuracy and adjusted as necessary. 6

11 The hydraulic analyses for this study were based on unobstructed flow. The flood elevations shown on the profiles 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 National Geodetic Vertical Datum of 1929 (NGVD 29). With the finalization of the North American Vertical Datum of 1988 (NAVD 88), many FIS reports and FIRMs are being prepared using NAVD 88 as the referenced vertical datum. The average datum shift for Brooks County, Georgia is feet. Flood elevations shown in this FIS report and on the FIRM are referenced to NAVD 88. These flood elevations must be compared to structure and ground elevations referenced to the same vertical datum. It is important to note that adjacent counties may be referenced to NGVD 29. This may result in differences in base flood elevations across county lines. For information regarding conversion between the NGVD and NAVD, visit the National Geodetic Survey website at TUwww.ngs.noaa.govUTH, or contact the National Geodetic Survey at the following address: Vertical Network Branch, N/CG13 National Geodetic Survey, NOAA Silver Spring Metro Center East-West Highway Silver Spring, Maryland (301) 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. To assist in this endeavor, each FIS report provides 1-percent-annual-chance floodplain data, which may include a combination of the following: 10-, 2-, 1-, and 0.2-percent-annual-chance flood elevations; delineations of the 1- and 0.2-percent-annual-chance floodplains; and a 1-percent-annual-chance floodway. This information is presented on the FIRM and in many components of the FIS report, including Flood Profiles, Floodway Data tables, and Summary of Stillwater Elevation tables. Users should reference the data presented in the FIS report as well as additional information that may be available at the local community 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-percent annual chance (100-year) flood has been adopted by FEMA as the base flood for floodplain management 7

12 purposes. The 0.2-percent annual chance (500-year) flood is employed to indicate additional areas of flood risk in the community. For each stream studied in detail, the 100-year and 500 year floodplain boundaries have been delineated using the flood elevations determined at each cross section. For each stream studied by approximate methods, the 1-percent-annualchance floodplain boundaries have been delineated using interpolation using 5-foot topographic mapping developed from USGS DEM data. The 100- and 500-year floodplain boundaries are shown on the Flood Insurance Rate Map (Exhibit 2). On this map, the 100-year floodplain boundary corresponds to the boundary of the areas of special flood hazards (Zones A and AE,), and the 500-year floodplain boundary corresponds to the boundary of areas of moderate flood hazards. In cases where the 100- and 500-year floodplain boundaries are close together, only the 100-year 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 100-year floodplain boundary is shown on the Flood Insurance Rate Map (Exhibit 2). 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 study 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 are tabulated for selected cross sections (see Table 2, Floodway Data ). In cases where the floodway and 100-year floodplain boundaries are either close together or collinear, only the floodway boundary is shown. Floodways are computed on the basis of equal-conveyance reduction from each side of the floodplain. Floodway widths are computed at cross sections. Between cross sections, the floodway boundaries are interpolated. The results of the floodway computations are tabulated for selected cross sections. In cases where the floodway and 1-percent-annualchance floodplain boundaries are either close together or collinear, only the floodway boundary is shown. Encroachment into areas subject to inundation by floodwaters having hazardous velocities aggravates the risk of flood damage and heightens potential flood hazards by further increasing velocities. To reduce the risk of property damage in areas where the stream velocities are high, the community may wish to restrict development in areas outside the floodway. 8

13 Near the mouths of streams studied in detail, floodway computations are made without regard to flood elevations on the receiving water body. Along streams where floodways have not been computed, the community must ensure that the cumulative effect of development in the floodplain will not cause more than a 1.0-foot increase in the BFEs at any point within the community. 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 1. Figure 1. Floodway Schematic 5.0 INSURANCE APPLICATION 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 rate zone that corresponds to the 100-year floodplains that are determined in the Flood Insurance Study by approximate methods. Because detailed hydraulic analyses are not performed for such areas, no base (100-year) flood elevations (BFEs) or depths are shown within this zone. Zone AE Zone AE is the flood insurance rate zone that corresponds to the 100-year floodplains that are determined in the Flood Insurance Study by detailed methods. Whole-foot BFEs derived from the detailed hydraulic analyses are shown at selected intervals within this zone. 9

14 BASE FLOOD WATER SURFACE ELEVATION FLOODING SOURCE FLOODWAY INCREASE WITH FLOODWAY (NAVD) WITHOUT FLOODWAY (NAVD) REGULATORY (NAVD) MEAN VELOCITY (FEET PER SECOND) SECTION AREA (SQUARE FEET) DISTANCE 1 WIDTH (FEET) CROSS SECTION JEFFERSON STREET DITCH A 3, B 3, C 4, D 4, E 5, Feet above mouth FLOODWAY DATA FEDERAL EMERGENCY MANAGEMENT AGENCY JEFFERSON STREET DITCH BROOKS COUNTY, GA (AND INCORPORATED AREAS) TABLE 2

15 BASE FLOOD WATER SURFACE ELEVATION FLOODING SOURCE FLOODWAY INCREASE WITH FLOODWAY (NAVD) WITHOUT FLOODWAY (NAVD) REGULATORY (NAVD) MEAN VELOCITY (FEET PER SECOND) SECTION AREA (SQUARE FEET) DISTANCE 1 WIDTH (FEET) CROSS SECTION OKAPILCO CREEK A 15,840 1,205 9, B 17,176 1,385 8, C 19, , D 21,170 1,324 9, E 21, , F 23,881 1,553 10, G 26,289 1,647 11, H 27, , I 28,575 1,657 10, J 29,953 1,518 12, K 32,145 1,471 10, L 33,883 1,387 13, M 34, , N 35,006 1,554 14, O 36,807 1,549 6, Feet above mouth FLOODWAY DATA FEDERAL EMERGENCY MANAGEMENT AGENCY OKAPILCO CREEK BROOKS COUNTY, GA (AND INCORPORATED AREAS) TABLE 2

16 BASE FLOOD WATER SURFACE ELEVATION FLOODING SOURCE FLOODWAY INCREASE WITH FLOODWAY (NAVD) WITHOUT FLOODWAY (NAVD) REGULATORY (NAVD) MEAN VELOCITY (FEET PER SECOND) SECTION AREA (SQUARE FEET) CROSS SECTION DISTANCE 1 WIDTH (FEET) 2 WITHLACOOCHEE RIVER A , B 1, , C 5, , D 9, , E 13, , F 17, , G 24, , H 28, , I 33, , J 39, , K 43, , L 49, , M 54, , LITTLE RIVER A 1, , B 5, , C 9, , D 15, , E 19, , F 23, , Feet above County Road 136 for Withlacoochee River and feet above the mouth for Little River 2 Total width FLOODWAY DATA FEDERAL EMERGENCY MANAGEMENT AGENCY WITHLACOOCHEE RIVER-LITTLE RIVER BROOKS COUNTY, GA (AND INCORPORATED AREAS) TABLE 2

17 Zone X Zone X is the flood insurance rate zone that corresponds to areas outside the 500-year floodplain, areas within the 500-year floodplain, areas of 100-year flooding where average depths are less than 1 foot, areas of 100-year flooding where the contributing drainage area is less than 1 square mile, and areas protected from the 100-year flood by levees. No BFEs or depths are shown within this zone. 6.0 FLOOD INSURANCE RATE MAP The Flood Insurance Rate Map is designed for flood insurance and floodplain management applications. For flood insurance applications, the map designates flood insurance rate zones as described in Section 5.0. 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 100-year floodplains used in the hydraulic analyses. The countywide Flood Insurance Rate Map presents flooding information for the entire geographic area of Brooks County. Previously, Flood Insurance Rate Maps were prepared for each incorporated community and the unincorporated areas of the County identified as flood-prone. This countywide Flood Insurance Rate Map 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 3, Community Map History. 7.0 OTHER STUDIES This report either supersedes or is compatible with all previous studies published on streams studied in this report and should be considered authoritative for the purposes of the NFIP. 8.0 LOCATION OF DATA Information concerning the pertinent data used in the preparation of this FIS can be obtained by contacting FEMA, Federal Insurance and Mitigation Administration, Koger Center - Rutgers Building, 3003 Chamblee Tucker Road, Atlanta, Georgia Future revisions may be made that do not result in the republishing of the Flood Insurance Study report. To ensure that any user is aware of all revisions, it is advisable to contact the map repository of flood hazard data located in the community. 9.0 BIBLIOGRAPHY AND REFERENCES 1. U.S. Department of Commerce, Bureau of the Census, 2000 Census, Fact Sheet, Brooks County, Georgia. 2. U.S. Department of the Interior, U.S. Geological Survey, The National Flood-Frequency Program Methods for Estimating Flood Magnitude and Frequency in Rural and Urban Areas in Georgia, August

18 COMMUNTIY NAME INITIAL IDENTIFICATION FLOOD HAZARD BOUNDARY MAP REVISIONS DATE FIRM EFFECTIVE DATE FIRM REVISIONS DATE Brooks County February 3, 1978 March 15, 1982 (Unincorporated Areas) Morven, City of September 2, 2009 September 2, 2009 Quitman, City of March 29, 1974 December 26, 1975 April 1, 1982 FEDERAL EMERGENCY MANAGEMENT AGENCY BROOKS COUNTY, GA AND INCORPORATED AREAS COMMUNITY MAP HISTORY TABLE 3

19 3. U.S. Geological Survey, Floods in Georgia, Magnitude and Frequency, October U.S. Army Corps of Engineers, Jacksonville District, Stream Cross Sections Continental Aerial Surveys, Inc., Alcoa, Tennessee. Compiled by photo grammetric methods from aerial photography of January 24, Weather Bureau, U.S. Department of Commerce, Washington, D.C., Rainfall Frequency Atlas of the United States, Technical Report No. 40, May NOAA National Weather Service, HYDRO 35, Five- to 60-Minute Precipitation Frequency for the Eastern and Central United States, June U.S. Department of Agriculture, Soil Conservation Service, National Engineering Handbook Section 4, Hydrology, 1964, revised U.S. Army Corps of Engineers, Hydrologic Engineering Center, Davis, California, Generalized Computer Program HEC-2, Water-Surface Profiles, November Federal Emergency Management Agency, Flood Insurance Study, Brooks County and Unincorporated Areas, Georgia, Washington, D.C., September 15, Federal Emergency Management Agency, Flood Insurance Study, City of Quitman, Georgia, Washington, D.C., October 1,

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