§TU0oc mam 1.2o9=o1oo67 noon INSURANCE A ST U D Y i CITY OF FORT PAYNE, ALABAMA n: KALB COUNTY M _ Library lexas Aéifvl University FEB Z8 T980 DEEOSITORY NOVEMBER 1979 FEDERAL EMERGENCY MANAGEMENT AGENCY FEDERAL "INSURANCE ADMINISTRATION COMMUNITY NUMBER - 010067 TABLE OF CONTENTS Page ‘INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1 Purpose of Study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. l 1.2 Coordination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1 1.3 Authority and Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1 AREA STUDIED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2 2.L Scope of Study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2 2.2 Community Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2 2.3 Principal Flood Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5 2.4 Flood Protection Measures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5 ENGINEERING METHODS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5 3.1 Hydrologic Analyses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 6 3.2 Hydraulic Analyses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 10 FLOOD PLAIN MANAGEMENT APPLICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . .. ll 4.1 Flood Boundaries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. l1 4.2 Floodways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 11 INSURANCE APPLICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. l9 5.1 Reach Determinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 19 5.2 Flood Hazard Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 19 5.3 Flood Insurance Zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 22 5.4 Flood Insurance Rate Map Description . . . . . . . . . . . . . . . . . . . . . .. 22 _OTHER STUDIES . . . . ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 23 LOCATION OF DATA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 23 BIBLIOGRAPHY AND REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 23 TABLE OF CONTENTS (COnt'd) Page FIGURES Figure l - Vicinity Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3 Figure 2 — Floodway Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . . . . .. 12 TABLES Table l — Summary of Discharges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 7 Table 2 — Floodway Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. I3 Table 3 — Flood Insurance Zone Data . . . . . . . . . . . . . . . . . . . . Q . . . . . . . . . . . .. 20 EXHIBITS Exhibit l — Flood Profiles Big wills Creek OlP—O4P Little Wills Valley Branch O5P Davis Gap Creek O6P—O7P Dye Creek O8P—lOP Beeson Branch llP—l3P Beeson Branch Tributary l4P Sulphur Springs Branch l5P—l6P Sulphur Springs Tributary A l7P Allen Branch l8P—l9P Exhibit 2 — Flood Boundary and Floodway Map Index Flood Boundary and Floodway Map PUBLISHED SEPARATELY: Flood Insurance Rate Map Index Flood Insurance Rate Map ii 1.0 FLOOD INSURANCE STUDY INTRODUCTION 1.1 Purpose of Study The purpose of this Flood Insurance Study is to investigate the existence and severity of flood hazards in the City of Fort Payne, De Kalb County, Alabama, and to aid in the administration of the National Flood Insurance Act of 1968 and the Flood Disaster Protec- tion Act of 1973. Initial use of this information will be to convert Fort Payne to the regular program of flood insurance by the Federal Insurance Administration. Further use of the information will be made by local and regional planners in their efforts to promote sound land use and flood plain development. Coordination Streams requiring detailed study were identified at a meeting attended by representatives of the study contractor, the Federal Insurance Administration, and the City of Fort Payne in October 1976. The priority of the study had been set by the State Coordinator at the annual priority meeting. The U.S. Geological Survey was contacted to obtain data for this study. The results of this study were reviewed at a final community coordina- tion meeting held on March 9, 1979. Attending the meeting were repre- sentatives of the Federal Insurance Administration, the study contractor, and the city. No problems were raised at the meeting. Authority and Acknowledgments The source of authority for this Flood Insurance Study is the National Flood Insurance Act of 1968, as amended. The hydrologic and hydraulic analyses for this study were performed by the U.S. Army Corps of Engineers for the Federal Insurance Adminis- tration, under Inter—Agency Agreement No. IAA—H—lO—77, Project Order No. 13. This work, which was completed in October 1978, covered all significant flooding sources affecting the City of Fort Payne. 2.9 AREA STQQLQQ 2.1 Scope of Study This Flood Insurance Study covers the incorporated area of the City of Fort Payne, De Kalb County, Alabama. The area of study is shown on the Vicinity Map (Figure l). Floods caused by the overflow of Big Wills Creek from the most down- stream corporate limits of Fort Payne to the most upstream corporate limits, were studied in detail. The tributaries to Big Wills Creek that were studied in detail are Allen Branch, Sulphur Springs Branch, Sulphur Springs Tributary A, Beeson Branch, Beeson Branch Tributary, Dye Creek, Davis Gap Creek, and the upper end of Little Wills Valley Branch. Flooding on Bear Creek, Little Bear Creek, the upstream portions of Little Wills Valley Branch, Davis Gap Creek, Dye Creek, Beeson Branch, Beeson Branch Tributary, Sulphur Springs Branch, Sulphur Springs Tributary A, and several minor tributaries was studied by approximate methods. Approximate methods of analyses were used to study those areas having a low development potential or a minimal flood hazard. Those areas studied by detailed methods were chosen with consider- ation given to all proposed construction and forecasted development through 1983. Community Description The City of Fort Payne is located in central De Kalb County, in northeastern Alabama. Fort Payne is surrounded by unincorporated areas of De Kalb County and is situated approximately 96 miles northeast of the City of Birmingham, Alabama, between Lookout Mountain and Sand Mountain. The business district is located in Little Wills Valley and Railroad Valley. According to the census, the population of Fort Payne was 8433 in 1970 (Reference 1). Big Wills Creek flows southwest through Big Wills Valley along the northwestern corporate limits of Fort Payne and eventually into the Coosa River near the City of Gadsden, Alabama. It has a drainage area of 75.8 square miles just upstream of the confluence of Little Wills Valley Branch, which is 16,800 feet downstream of the lower corporate limits. Little Wills Valley Branch flows southwest through Little Wills Valley, out of the corporate limits, and then west into Big Wills Creek. The drainage area of Little Wills Valley Branch above the Southern Railway is l.7 square miles. “E2 525:, I: 5E 5 l 1 l I ._< fizz; E2 B C5 w Q v =owmbn=mE =< 00:952- 1:25"- w._ ‘W . Mslzcgfi / ~ , 1 @523. .0 _ M/Q/ ._ , 5 _ r 0|. & ...~ o; / m >£§Q /_ emmww J _. 7 \/:\_ Q? .,;....._l ___x.>f . . w “zézgwm .4 Q, /,_ . . \\.~ __...\..§A.\...wo _ j _ _ , .. \\\\‘ \ \\~..Ro\mnu r __ ~ \ \ .- _ , \@w-\\», @ . = .. + _\ , \ Davis Gap Creek, also a tributary flowing southwest into Big Wills Creek, is 3.3 miles in length and has a drainage area of 3.1 square miles. Dye Creek flows southwest through the business district of Fort Payne along the Southern Railway, and then flows west along State Highway 35 into Big wills Creek. It is 3.4 miles in length and has a drainage area of 4.8 square miles. Beeson Branch flows generally west along the northern limits of the Fort Payne business district and into Big Wills Creek. Its largest tributary is Beeson Branch Tributary, which flows southwest along the Southern Railway into Beeson Branch. Beeson Branch is 3.7 miles long and has a drainage area of 5.1 square miles. Sulphur Springs Branch flows northwest along 49th Street into Big Wills Creek. Sulphur Springs Tributary A flows north into Sulphur Springs Branch near the intersection of 49th Street North and Gault Avenue. Sulphur Springs Branch is 3.1 miles long and has a drainage area of 3.8 square miles. Allen Branch flows west through Allen Branch Reservoir, which is the city's water supply reservoir, into Big Wills Creek. Allen Branch is 4.3 miles long and has a drainage area of 5.9 square miles. Approximately 20 percent of the area inside the corporate limits has been developed, with the remainder of land being vacant or wooded. Within the flood plains studied, development consists of single- family residences, private businesses, and a variety of industries. The majority of development is adjacent to Gault Avenue. Fort Payne is served by a network of primary and secondary highways, including State Highway 35, U.S. Highway ll, and Interstate Highway 59, and also Southern Railway's main line connection between the Cities of Birmingham, Alabama, and Chattanooga, Tennessee. The soils of Fort Payne are primarily of the Allen and Hermitage Series. Soils of the Allen Series in the area are well—drained, sandy loams to sandy clay loams, characterized by a yellowish—brown to reddish—brown color. The soils of the Hermitage Series are well- drained and moderately fine—textured silty clay loams. Runoff is slow to medium and the moisture—holding capacity is moderate for these soils. They are dark brown to dark reddish—brown in color. The forest in and around Fort Payne consists of mixed hardwood and pine trees (Reference 2). Fort Payne has a temperate climate. The area has complete seasonal cycles, with mild spring and fall seasons. The variety of weather patterns is caused by changes between cool northern highs and more humid movements from the Gulf of Mexico. The average annual temper- ature at Valley Head, the nearest station, is 59.9°F, with July being the warmest month, and January being the coolest. Over a 25-year period of record, the average annual precipitation at Fort Payne is nearly 52 inches. Principal Flood Problems No stream gage records are available for the drainage basins within the corporate limits. Flood—producing storms may occur at any time of the year, but are more numerous during the winter and spring. Winter storms are generally of the frontal type, lasting from 2 to 4 days and covering large areas. Summer storms are usually of the thunderstorm type with high rainfall intensities over small areas. Although there have been no disastrous floods in the past that caused loss of life or great property damage, the business district of Fort Payne has experienced local flash flooding along the tri- butaries to Big Wills Creek due to severe thunderstorms over the watershed. Flood Protection Measures The only reservoir in the drainage basins studied is llen Branch Reservoir, located near the mouth of Allen hransn- Although the reservoir was not designed for flood protection, but rather for water supply to Fort Payne, the floodflow reduction resulting from the flood storage is significant and was considered in this s enlargement was done in l976 by the City of Port Payne from 5th Street North to Street South. This is the stream cross sections obtained by field surveys The channel enlargement was designed to contain the l0—year flood. Further channel enlargement is planned by the city from 2nd Street South to the mouth of Dye Creek. This further enlargement was not considered in this study as it is still in the planning stage. Some channel on Dye Creek reflected by this study. Z T1 Ll for ENGINEERING METHODS For the flooding sources studied in detail 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 which are expected to be equalled or exceeded once on the average during any l0—, 50-, l00—, or 500—year period (recurrence interval) have been selected as having special significance for flood plain management and for flood insurance premium rates. These events, commonly termed the 10-, 50-, 100-, and 500—year floods, have a l0, 2, l, and 0.2 percent chance, respectively, of being equalled 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 l year are considered. For example, the risk of having a flood which equals or exceeds the l00—year flood (1 percent chance of annual occurrence) in any 50-year period is approximately 40 percent (4 in 10), and, for any 90-year period, the risk increases to approximately 60 percent (6 in l0). The analyses reported here reflect flooding potentials based on conditions existing in the community at the time of completion of this study. Maps and flood eleva- tions will be amended periodically to reflect future changes. 3.1 Hydrologic Analyses Hydrologic analyses were carried out to establish the peak discharge- frequency relationships for floods of the selected recurrence inter- vals for each stream studied in detail in the community. A regional frequency study developed by the U.S. Army Corps of Engineers for Big Wills Creek was used to estimate the peak dis- charges for each stream studied in detail (Reference 3). The U.S. Soil Conservation Service unit hydrograph method, as described in the National Engineering Handbook, (Reference 4), was used to verify the results from the regional frequency study. Stream discharges developed from the regional frequency study were estimated by fitting the regional frequency statistics with a log- normal distribution (log—Pearson Type III distribution with a skew of zero) using the methods outlined by the U.S. Water Resources Council (Reference 5). Stream discharges on Dye Creek were significantly affected by urbani— zation. The effect of urbanization on the natural discharges was estimated by the method described in the U.S. Geological Survey publication, An Approach to Estimating Flood Frequency for Urban Areas in Oklahoma (Reference 6). It was assumed that 100 percent of the Dye Creek area had storm sewers. The percentage of imper- vious area was determined from aerial photographs at scales of l:24,000 and l:l2,000 (Reference 7), and topographic maps at a scale of l:24,000, with a contour interval of 2O feet (Reference 8). Flood hydrographs were computed and routed through the Allen Branch Reservoir to determine the effects of reservoir regulation on the discharges of Allen Branch. The flood hydrographs were computed and routed using the U.S. Army Corps of Engineers unit hydrograph option (Reference 9). Synthetic rainfall for this model was developed using U.S. Weather Bureau Technical Paper No. 40 (Reference 10). Peak discharge-drainage area relationships for Big Wills Creek, Little Wills Valley Branch, Davis Gap Creek, Dye Creek, Beeson Branch, Beeson Branch Tributary, Sulphur Springs Branch, Sulphur Springs Tributary A, and Allen Branch are shown in Table l. These relationships reflect the effects of urbanization on Dye Creek and reservoir regulation on Allen Branch. 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Water—surface elevations of floods of the selected recurrence intervals‘ were computed through use of the U.S. Army Corps of Engineers HEC—2 step—backwater computer program (Reference ll). Cross sections for the backwater analyses of the streams studied in detail were obtained from field surveys. All bridges and culverts were surveyed to obtain elevation data and structural geometry. Locations of selected cross sections used in the hydraulic analyses are shown on the Flood Profiles (Exhibit l). For stream segments for which a floodway is computed (Section 4.2), selected cross section locations are also shown on the Flood Boundary and Floodway Map (Exhibit 2). 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 flood plain areas. Channel roughness factors varied from 0.050 to 0.060; overbank roughness factors varied from 0.060 to 0.l40. Starting water—surface elevations for all the streams studied in detail were calculated using the slope—area method. The flood profiles for Davis Gap Creek, Dye Creek, Beeson Branch, Sulphur Springs Branch, and Allen Branch reflect backwater from Big Wills Creek. Flood profiles were drawn showing computed water—surface elevations to an accuracy of 0.5 foot for floods of the selected recurrence intervals (Exhibit l). For those areas studied by approximate methods, depths were deter- mined by examining flood depths on streams studied by detailed methods and applying these to streams of comparable slope and drainage area. 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. All elevations are referenced to the National Geodetic Vertical Datum of l929 (NGVD). Elevation reference marks used in the study are shown on the maps. l0 FLOOD PLAIN MANAGEMENT APPLICATIONS A prime purpose of the National Flood Insurance Program is to encourage State and local governments to adopt sound flood plain management pro- grams. Each Flood Insurance Study, therefore, includes a flood boundary map designed to assist communities in developing sound flood plain management measures. 4.1 Flood Boundaries In order to provide a national standard without regional discrimina- tion, the lOO—year flood has been adopted by the Federal Insurance Administration as the base flood for purposes of flood plain manage- ment measures. The 500—year flood is employed to indicate additional areas of flood risk in the community. For each stream studied in detail, the boundaries of the lOO— and 500—year floods have been delineated using the flood elevations determined at each cross section; between cross sections, the boundaries were interpolated using topographic maps enlarged to a scale of l:l2,000, with a contour interval of 20 feet (Reference 8). For the areas studied by approximate methods, boundaries were determined using topographic maps enlarged to a scale of l:l2,000, with a contour interval of 2O feet (Reference 8), and flood eleva- tions previously determined. In cases where the lOO— and 500—year flood boundaries are close to- gether, only the lOO—year flood boundary has been shown. Flood boundaries for the lOO— and 500—year floods are shown on the Flood Boundary and Floodway Map (Exhibit 2). Small areas within the flood boundaries may lie above the flood elevations and, therefore, not be subject to flooding; owing to limitations of the map scale and/or lack of detailed topographic data, such areas are not shown. Floodways Encroachment on flood plains, such as artificial fill, reduces the flood—carrying capacity and increases flood heights, thus increasing flood hazards in areas beyond the encroachment itself. One aspect of flood plain management involves balancing the economic gain from flood plain development against the resulting increase in flood hazard. For purposes of the National Flood Insurance Program, the concept of a floodway is used as a tool to assist local communities in this aspect of flood plain management. Under this concept, the area of the lOO—year flood is divided into a floodway and a floodway fringe. The floodway is the channel of a stream, plus any adjacent flood plain areas, that must be kept free of encroachment in order that the lOO—year flood be carried without substantial increases in ll flood heights. As minimum standards, the Federal Insurance Adminis- tration limits such increases in flood heights to l.O foot, provided that hazardous velocities are not produced. The floodways presented in this study were computed on the basis of equal conveyance reduction from each side of the flood plain. The results of these computations were tabulated at selected cross sections for each stream segment for which a floodway was computed (Table 2). For Allen Branch Reservoir, the floodway was delineated as the shoreline of the reservoir. As shown on the Flood Boundary and Floodway Map (Exhibit 2), the floodway boundaries were determined at cross sections; between cross sections, the boundaries were interpolated. In cases where the floodway and lOO—year flood boundaries are close together, only the floodway boundary has been shown. The area between the floodway and the boundary of the lOO—year flood is termed the floodway fringe. The floodway fringe thus encompasses the portion of the flood plain that could be completely obstructed without increasing the water—surface elevation of the lOO—year flood more than l.O foot at any point. Typical relationships between the floodway and the floodway fringe and their significance to flood plain development are shown in Figure 9 LINE AB IS THE FLOOD ELEVATION BEFORE ENCROACHMENT. LINE CD ZS THE FLOOD ELEVATION AFTER ENCROACHMENT. ‘SURCHARGE IS NOT TO EXCEED 'I.O FOOT (FIA REQUIREMENT) OR LESSER AMOUNT IF SPECIFIED BY STATE. << 10&YEARFLOODPLAHd >% FLOODWAY FLOODWAY -<(-——- ——-—->-4—- F -_.____—> - FRINGE-l LOODWAY 4' FRINGE Tl STREAM CHANNEL I FLOODELEVATKWIWHEN CONHNEDVWTHWJFLOODWAY __<_ ENCROACHMENT \\\ ENCROACHMENT _“_ __L_ ,. ii? \\ I '1: —::iii1i* '§ A ,_ __ _____§.~12¢_':2R_@_E__,_ i. AREACDFFLOOD_1AH4THATCOULD as oseo FOR DEVELOP RAISING GROUND FLOOD ELEVATION BEFORE ENCROACHMENT ON FLOOD PLAIN Figure 2. 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This process includes the determination of reaches, Flood Hazard Factors, and flood insurance zone designations for each flooding source studied in detail affecting the City of Fort Payne. 5.1 Reach Determinations Reaches are defined as lengths of watercourses having relatively the same flood hazard, based on the average weighted difference in water~surface elevations between the i0— and l00—year floods. This difference does not have a variation greater than that indicated in the following table for more than 20 percent of the reach: Average Difference Between 10- and 100-year Floods Variation Less than 2 feet 0.5 foot 2 to 7 feet 1.0 foot 7.1 to 12 feet 2.0 feet More than 12 feet 3.0 feet The locations of the reaches determined for the flooding sources of the City of Fort Payne are shown on the Flood Profiles (Exhibit 1) and summarized in Table R. 5.2 Flood Hazard Factors The Flood Hazard Factor (FHF) is the Federal Insurance Administra- tion device used to correlate flood information with insurance rate tables. FHF are on FHFs Correlations between property damage from floods and their used to set actuarial insurance premium rate tables based from O05 to 200. The FHF for a reach is the average weighted difference between the 10- and 100-year flood water-surface elevations expressed to the nearest one—half foot, and shown as a three-digit code. For example, if the difference between water—surface elevations of the 10- and l00—year floods is 0.7 foot, the FHF is 005; if the difference is 1.4 feet, the FHF is O15; if the difference is 5.0 feet, the FHF is 050. when the difference between the 10- and 100-year water- surface elevations is greater than 10.0 feet, accuracy for the FHF is to the nearest foot. =22”; 22:5 ._==.:_;.:_<=z== =22: ==mum.=u=<: 2m: .555 59523 .5 m_>=_._a=<: 5;; 3:; WFPZQHZQ 3:; 2m <~<= u==~ ~Q=<==m=_===A& _.=u @.<= H=_ ._< .5: 5:: 3 Eu =¢=E§=mEu< @2552: 35am» Ew§¢3w>w= 25E: oz< w_,__..,.._5: é Ewzhfifio TABLE3 uoom umwumwz ow wwwcsom wmmnw>< ©wucmHw3 Hwcmm mmz wumm m0cmusmcH ©ooHm m N H mmz wwm mwH~m> mm mH@ m.@ m.o| @.H| Qooo H numwm nocmum mmQHM@m HD£@HDw mmz wwm mwHum> ~< oHo w.o m.o| H.H| >ooo.mooo H Qumwm >Hmu§QHMB socmum Qomwwm mmz mwm mmHum> ¢< omo m.H m.o| o.m| >ooo.mooo H Qumwm socmnm comwmm mmz wwm mwHum> >4 mmo >.@ m.H| m.m| @ooo.mooo m Qumwm mmz wwm mwHum> mm oHo w.o m.o| m.H| @ooo_mooo N momwm mwz wwm wwHum> ¢< omo w.H @.@| m.H| wooo.mooo H somwm xwwuu m>Q mmz mom mwHum> w< omo ~.~ w.o| ~.~| Hooo H somwm xwwuu mmw mH>mQ mmz wwm mwH~m> ~< oHo §.@ m.@| H.H| Hooo N Qomwm mmz wwm mwHHm> @< omo @.@ m.o| w.~| Hooo H somwm socmum >@HH@> wHHHB mHuuHH ans www wwH~m> ¢¢ owe m.H @.@| ~.~| Hose N nomwm wooo\mooo mmz wwm m@H~m> @< QMQ @.~ @.@| ~.m| .~@@@_H@@@ H numwm xwwuu mHHH3 mHm 2:62 9mm“: moeumm AmmEToomv Ammmwlomv QEETQHV 0N5 ww OOH m 2894515 MZON Qmawmm OZANAHw OOOHM Amdmw QOHV 0H Zimgmm HqmzMHM $2.55 zwié‘ zflkwwmaw magma” $233M 5E M23 mnwzfiawzm mg: raw mdwm 72mm: a? @522... n5 :,m§t_<$@. HBLEIi hi. p(ah ummmmmz uw @w©mD0m> mmm»m>¢ finwzndwz aocmm mmz wpmm wocmunmqw wooflmq ~ N - - H »::, .1: _ Q m w ~ . W M U H ~ mm: mwm w@HH@> Q4 QNQ m.H @.@, ¢.H| wgoo H sommm Qocmum GQHHQ mmz mwm mm@~@> mm Qflo @.@ m.@| m.H| w@@@ m Qumwm mwz wwm m@H~@> mm mma ¢.@ ~.@| ¢.m| ¢@@@ N Qomwm mm: wmm m@H~m> mm @~@ w.@ v.@| ~.m| ¢@@@ H Quwwm Q %MMMDQHHH mmcqmmm uflmmfifim , Am¢mw|o@mVAmmqm mzow omNQM Zones A2—A7 Flood Insurance Zones After the determination of reaches and their respective Flood Hazard Factors, the entire incorporated area of the City of Fort Payne was divided into zones, each having a specific flood potential or hazard. Each zone was assigned one of the following flood insurance zone designations: Zone A: Special Flood Hazard Areas inundated by the lOO-year flood, determined by approximate methods; no base flood elevations shown or Flood Hazard Factors determined. Special Flood Hazard Areas inundated by the lOO-year flood, determined by detailed methods; base flood elevations shown, and zones subdivided according to Flood Hazard Factors. Zone B: Areas between the Special Flood Hazard Areas and the limits of the 500—year flood, including areas of the 500—year flood plain that are protected from the lOO-year flood by dike, levee, or other water control structure; also areas subject to certain types of lOO- year shallow flooding where depths are less than l.O foot; and areas subject to lOO-year flooding from sources with drainage areas less than l square mile. Zone B is not subdivided. Zone C: Areas of minimal flooding. The flood elevation differences, Flood Hazard Factors, flood insur- ance zones, and base flood elevations for each flooding source studied in detail in the community are summarized in Table 3. Flood Insurance Rate Map Description The Flood Insurance Rate Map for the City of Fort Payne is, for insurance purposes, the principal result of the Flood Insurance Study. This map (published separately) contains the official delineation of flood insurance zones and base flood elevation lines. Base flood elevation lines show the locations of the expected whole—foot water—surface elevations of the base (lOO-year) flood. This map is developed in accordance with the latest flood insurance map preparation guidelines published by the Federal Insurance Administration. 22 Q O 0 OTHER STUDIES A Flood Plain Information report covering portions of Big Wills Creek was completed by the U.S. Army Corps of Engineers in May 1974 (Reference 12). Estimated discharges for the lOO—year flood developed for the present study vary somewhat from those presented in the Flood Plain Information report. The basic reason for these differences is that the present study utilizes a more systematic method of station selection and a greater number of stations with longer periods of record to estimate the regression equations. The results of this study supersede those shown in the Flood Plain Information report. Flood boundary delineations for this study supersede the Federal Insur- ance Administration's Flood Hazard Boundary Map (Reference 13). This study is authoritative for the purposes of Insurance Program; data presented herein either with all previous determinations. the National Flood supersede or are compatible ‘LOCATION OF DATA Survey, hydrologic, hydraulic, and other pertinent data used in this study can be obtained by contacting the office of the Federal Insurance Administration, Regional Director, l37l Peachtree Street, N.F., Atlanta, Georgia 30309. BIBLIOGRAPHY AND REFERENCES l. U.S. Department of Commerce, Bureau of the Census, Final Report PC(l)-A2, 1970 Census_9f Population,_Number of InhabitantsL_Alabama, Washington, D.C., 1971 2. U.S. Department of Agriculture, Soil Conservation Service,_§pil_ Survey, DeKalb County, Alabama! September 1958 3. U.S. Department of Army, Corps of Engineers, Big Wills Creek Flood Frequency Analysis, May 1976 4. U.S. Department of Agriculture, Soil Conservation Service, fl§tional_ Engineering Handbook, Section 4, "Hydrology," l972 5. U.S. Water Resources Council, "Guidelines for Determining Floodflow Frequency", Bulletin 17, March 1976 6. U.S. Department of the Interior, Geological Survey, Water Resources Investiqatiwn 23-74 , .A,n,l_.lérp.r_o.acb...Estimating.,ElQQ-1ueri§ifa fer. Urban Areas in Oklahoma, l974 23 U.S. Department of Agriculture, Soil Conservation Service, Aerial Photographs, Fort Payne, Alabama, Scales l:24,000 and l:l2,000, October 1973 U.S. Department of the Interior, Geological Survey, 7.5—Minute Series Topographic Mapsl Scale 1:24,000, Contour Interval 20 feet: Dugout Valley Alabama (1975); Fort Payne, Alabama (1946), Photorevised (1970), Chavies, Alabama (1946), Photorevised (1970) U.S. Department of the Army, Corps of Engineers, Hydrologic Engineer- ing Center, Computer Program 723—X6—L2010, HEC—l Flood Hydrograph Package, Davis, California, January 1964 with updates U.S. Department of Commerce, Weather Bureau, Technical Paper 40, Rainfall Frequency Atlas of the United States, Washington, D.C., May 1961 U.S. Department of the Army, Corps of Engineers, Hydrologic Engineer- ing Center, Computer Program 723—X6—L202A, HEC—2 Water-Surface Profiles, Davis, California, December 1968 with updates —————————— --, Mobile District, Flood Plain Information, Big Wills Creek, Vicinity of Fort Payne, Alabama, May 1974 U.S. Department of Housing and Urban Development, Federal Insurance Administration, Flood Hazard Boundary Map, City of Fort Payne, Alabama, Scale l:l2,000, November l, 1974 24 ELEVATION (FEET NGVDI 830 820 810 800 790 780 770 760 16,000 18,000 20,000 22,000 24,000 26,000 28,000 30,000 32,000 34,000 STREAM DISTANCE IN FEET ABOVE CONFLUENCE WITH LITTLE WILLS VALLEY BRANCH LEGEND 500-YEAR FLOOD IOU-YEAR FLOOD SO-YEAR FLOOD IO-YEAR FLOOD ST REAIVIBED CROSS SECTION LOCATION 36,000 38,000 40,000 42,000 m u; a: _.| Lu — Lu u- n: Q u a: a- 3 ' -—l a — Q = 3 u! Lb E I- Z LIJ E O- 3 4 LU a “ Q I~ 2.2m; 22>‘ =§§2 @111 ‘J 2< - 5 l: E a I-— CC <11 O. LU Q IIIP ELEVATION (FEET NGVD) 860 850 840 830 820 810 800 42,000 44,000 46,000 48,000 50,000 52,000 54,000 56,000 58,000 60,000 STREAM DISTANCE IN FEET ABOVE CONFLUENCE WITH LITTLE WILLS VALLEY BRANCH LEGEND 500-YEAR FLOOD TOO-YEAR FLOOD 50-YEAR FLCOD IO-YEAR FLOOD STFIEAIVIBED CROSS SECTION LOCATION 62,000 64,000 66,000 68,000 FLIIIID PROFILES BIG WILLS CREEK DEPARTMENT 0F HOUSING AND URBAN DEVELOPMENT an? B} "FEE? FKIFIE", AL in: KALB 004 UIZI ELEVATION (FEET NGVDI 900 890 880 870 850 840 68,000 70,000 72,000 74,000 76,000 78,000 80,000 82,000 84,000 86,000 STREAM DISTANCE II\I FEET ABOVE CONFLUENCE WITH LITTLE WILLS VALLEY BRANCH LEGEND SOD-YEAR FLOOD IOU-YEAR FLOOD 50-YEAR FLCOD IO-YEAR FLOOD STREAMBED CROSS SECTION LOCATION 88,000 90,000 92,000 94,000 (I) - 5 2' u; ‘i. Z c Q l: m Q- -l 2 Z ¢ g Z $ d i u- Z |-— Z LU 2 LL LIJ 3 2' i. DELI-r E152 m_‘§>- gs- s< Em U <|,_ én: 52$ an. s an. 51 ‘U “E 2 [us KALB 004 0IiI' ELEVATION (FEET NGVD) 840 830 820 810 800 790 780 770 760 500 1000 1500 2000 2500 3000 3500 STREANHNSTANCEINFEETABOVEMOUTH 4000 4500 5000 LEGEND SOOYEARFLOOD 100YEARFLOOD SOYEARFLCOD 10YEARFLOOD STREAMBED CROSSSECTWON LOCQTWON 5500 6000 6500 v‘: Lil E:i _| g; =- 5 ‘=5 Il- II: =~ s Ill g1) c i c Z —l a u. r- Z LLI 2 Q- B _| < QEuI 5E2 <§.'~Z>'.__ réfié D2 9 Z <8E3 (s: < 22:2 5; 3 L1- ::_5 zg c1__ LL- __ I§Z "-1: 21>- z ‘I LU E Q a- I < & LU D 06F ELEVATION (FEET NGVD) 840 830 820 810 800 790 780 770 760 500 1000 1500 2000 2500 3000 3500 STREAM[NSTANCEINFEETABOVEMOUTH 4000 4500 LEGEND 500YEARFLOOD 100YEARFLOOD 50YEARFLCOD 10YEARFLOOD STREAMBED CROSSSECTWON LOCNHON 5000 5500 6000 6500 v‘: u-I E _| u; - 5 ‘=, CL. ll: a. g lll (15 1:5 5;: c < —l a u. l- Z LLI s LL 8 _| LLI a “ “Eu; §§Z 1g.‘é><'._. C I ='én.3 ‘=2 Z (vii: as 3 cl: ct 2:EE C=D a: 53H- ::_5 zg c>._ Ll- ._. 18c H % 2w- E ‘I E u l- I <1 O. LLI D 06F ELEVATION (FEET NGVDI 890 880 870 860 850 840 830 6,500 7,000 7,500 8,000 8,500 9,000 9,500 STREAM DISTANCE IN FEET ABOVE MOUTH ,11' < 3 I L9 :1: "I 10,000 10,500 FI.000 PIIUFILES DAVIS GAP CREEK LEGEND 500-YEAR FLOOD ‘IOU-YEAR FLOOD ‘SO-YEAR FLOOD IO-YEAR FLOOD STREAMBED CROSS SECTION LOCATION DEPARTMENT 0F HOUSING AND URBAN DEVELOPMENT CITY 0E FORT PAYNE, AI. (n: mu co) 07P ELEVATION (FEET NGVD) 860 850 840 830 820 810 800 790 500 1000 1500 O5 LO >- 4 . 3 :1: ‘2 :1: ii‘ <._ m‘ 2000 2500 3000 3500 STREAM[NSTANCE|NFEETABOVEMOUTH 4000 4500 LEGEND 500YEARFLOOD 100YEARFLOOD 50- YEARFLOOD TGYEARFLOOD STREAMBED CROSSSECTWON LOCATION 5000 5500 6000 6500 (ID u; _| u- E G=D LL] II: ll: Q- $ Lu Q >n (=5 I:I {=5 _| u... r- Z LU s O- g -J > < 35m“ 2'0: 22 5.15:"? = ca 3.- Qgfl-Z Z 'I"I}IE‘1" AL [DE KALB 00.] IIP ELEVAT|ON’(FEET NGVD) 920 910 900 890 880 870 860 6,500 7,000 7,500 8,000 8,500 9,000 9,500 10,000 10,500 STREAM DISTANCE IN FEET ABOVE MOUTH 11,000 LEGEND — SOOYEARFLOOD 100YEARFLOOD BOYEARFLOOD 10YEARFLOOD STREAMBED CROSS SECTION LOCATION 11,500 12,000 12,500 13,000 FLUUD PRUFHIS BEESUN BRANCH DEPARTMENT 0F HOUSING AND URBAN DEVELOPMENT _J < E Lb; g2 E2 E cp < 3 F“ g2 ~51 lfil-l- 15L!- 33$ ‘U 31> t:: L3 10: KALB coq IIZP ELEVATION (FEET NGVDI 930 920 910 900 13,000 13,500 14,000 STREAM DISTANCE IN FEET ABOVE MOUTH 14,500 FLOOD PRUFHIS BEESON BRANCH LEGEND EGO-YEAR FLOOD 100-YEAR FLOOD 50-YEAR FLCOD 10-YEAR FLOOD STREAMBED CROSS SECTION LOCATION DEPARTMENT 0F HOUSING AND URBAN DEVELOPMENT cnIFBFFEIET FIIIIE AL [us KALB 001 IEIP ELEVATION (FEET NGVDI 940 930 920 910 900 500 I000 1500 2000 2500 3000 STREAM DISTANCE IN FEET ABOVE MOUTH 3500 4000 4500 H000 PROFILES BEESON BRANCH TRIBUTARY LEGEND EOOYEARFLOOD IOOYEARFLOOD SOYEARFLOOD IGYEARFLOOD STREAMBED CROSS SECTION LOCATION 5000 DEPARTMENT 0F HOUSING AND URBAN DEVELOPMENT cmf Si} "FEE? FIIIIE," AL [DE KALB CUJ II4I ELEVATION (FEET NGVD) 920 910 900 890 880 870 860 500 1000 1500 2000 2500 3000 3500 STREAM[NSTANCEINFEETABOVEFWOUTH 4000 4500 LEGEND 500YEARFLOOD 100YEARFLOOD SOYEARFLOOD 10YEARFLOOD STREAMBED CROSSSECT1ON LOCATION 5000 5500 6000 :I: CJI I: G17 -1: III-l Z -J Ill Lb (l) (=3 (£5 l: E =~ z I=l ‘I’ (=3 = g —l x l-l- m 1| :=l G17 r- Z LU 2 O- 2-: a “ °§uI 5E2 g§.g III: E3 Q26- EQI-S wgZ: 2: S (=5 55 3 Fir LU I>.E ca I52 “Lu Om +- “' i:: L?’ — 5 Q r- I <1 O. LU Q I5P =22”; $5.5 =25? 2E2; =21 2a s: E ._< .5: EE B >5 =¢E:E=_Eu< 8552. E23“. Ew=z3w>m= 25E: 9,2 025:0: H6 EwsE<¢w= 1GP O 0 2 1 9 9 AQ>UZ Em“: zo;<>m_.m_ 900 LEGEND 500-YEAR FLOOD 100 YEAR FLOOD 50-YEAR FLOOD 10-YEAR FLOOD STREAMBED CROSS SECTION LOCATION 7000 6500 6000 STREAM DISTANCE IN FEET ABOVE MOUTH X < E525: maze; 5.2a 2.52: .592 <=u =d<= u=_ ._< .22; E2 B >5 =Q=~=2=_Eu< M55235 632E Ewsafiwic 72mm: mz< @2630: é 5255mm I7P 0 3 2 .| 9 AQ>O2 Hum“: 20_._.<>m4m 900 LEGEND BOO-YEAR FLOOD 100 YEAR FLOOD ‘SO-YEAR FLOOD IO-YEAR FLOOD STREAMBED 890 CROSS SECTION LOCATION 2500 2000 I000 I500 STREAM DISTANCE II\I FEET ABOVE IVIOUTH 500 ELEVATION (FEET NGVDI 940 930 920 010 9'00 890 880 500 1000 I500 2000 2500 3000 3500 4000 STREAM DISTANCE IN FEET ABOVE MOUTH 4500 LEGEND 500-YEAR FLOOD TOO-YEAR FLOOD 50-YEAR FLOOD IO-YEAR FLOOD STREAIVIBED CROSS SECTION LOCATION 6000 6500 FL000 PRUFILES ALLEN BRANCH DEPARTMENT OF HOUSING AND URBAN DEVELOPMENT CITY AL [DE KALB 00.] 18F =Qz<=m 52 3E2: =23“ I: s; E ._< .m_=><._ EE “S Eu =Q=EEEEu< @2535 “£26m Ewzmfiwio 25E: Qz< wzfizc: i. ~zw§E<$= 19F 0 r0 4 9 E>02 hmr: zo_»<>w.m_ 500-YEAR FLOOD 100 YEAR FLOOD 50-YEAR FLOOD STREAMBED CROSS SECTION LOCATION LEGEND x £5 930 920 910 9000 8500 8000 7000 7500 STREAM DISTANCE IN FEET ABOVE MOUTH 6 500 IlllllfllflfljflijifllfiifllliiflflflilifllflllllHlli