MINGO COUNTY, WEST VIRGINIA AND INCORPORATED AREAS

Transcription

1 MINGO COUNTY, WEST VIRGINIA AND INCORPORATED AREAS COMMUNITY NAME COMMUNITY NUMBER DELBARTON, TOWN OF GILBERT, TOWN OF KERMIT, TOWN OF MATEWAN, TOWN OF MINGO COUNTY, (UNINCORPORATED AREAS) WILLIAMSON, CITY OF Please note: this Preliminary FIS report only includes revised updates related to Tug Fork; the unrevised FIS report components will appear in the final FIS report. PRELIMINARY: August 8, 2014 MINGO COUNTY Federal Emergency Management Agency Flood Insurance Study Number 54059CV000B

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) may not contain all data available within the Community Map Repository. Please contact the Community Map 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 FIS Effective Date: October 2, 2012 Revised FIS Dates: ATTENTION: On Flood Insurance Rate Map (FIRM) panels 54059C0216F, 54059C0217F, and 54059C0331F, the Tug Fork levees have not been demonstrated by the City of Williamson and the Town of Matewan or the levee owners to meet the requirements of Section of the National Flood Insurance Program (NFIP) regulations in the Code of Federal Regulations (CFR) at 44 CFR as it relates to the levee s capacity to provide 1-percent-annual-chance flood protection. The subject areas are identified on the FIRM panels (with notes and bounding lines) and in the FIS report as potential areas of flood hazard data changes based on further review. FEMA has updated the levee analysis and mapping procedures for non-accredited levees. Until such time as FEMA is able to initiate a new flood risk project to apply the new procedures, the flood hazard information on the aforementioned FIRM panels that are affected by the Tug Fork levees are being added as a snapshot of the prior effective information presented on the FIRMs and FIS report dated October 2, As indicated above, it is expected that affected flood hazard data within the subject area could be significantly revised. This may result in floodplain boundary changes, 1-percent-annualchance flood elevation changes, and/or changes to flood hazard zone designations. The effective FIRM panels (and the FIS report) will again be revised at a later date to update the flood hazard information associated with the Tug Fork levees when FEMA is able to initiate and complete a new flood risk project to apply the new levee analysis and mapping procedures. Please note: this Preliminary FIS report only includes revised updates related to Tug Fork; the unrevised FIS report components will appear in the final FIS report.

3 TABLE OF CONTENTS Page 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 APPLICATION FLOOD INSURANCE RATE MAP OTHER STUDIES LOCATION OF DATA BIBLIOGRAPHY AND REFERENCES 57

4 TABLE OF CONTENTS - continued Page FIGURES Figure 1 - Frequency-Discharge, Drainage Area Curves: Stafford Branch 18 Figure 2 Floodway Schematic 25 TABLES Table 1 Initial and Final CCO Meetings 4 Table 2 Flooding Sources Studied by Detailed Methods 7 Table 3 Flooding Sources Studied by Approximate Methods 8 Table 4 Summary of Discharges Table 5 Manning s n Values 20 Table 6 Original Sources of Topographic Data 23 Table 7 Updated Sources of Topographic Data 23 Table 8 Floodway Data Table 9 Community Map History 56 Exhibit 1 Flood Profiles Buffalo Creek Gilbert Creek Guyandotte River Horsepen Creek Laurel Fork Marrowbone Creek Mate Creek Moses Fork Pigeon Creek Rockhouse Fork Stafford Branch Trace Fork Tug Fork West Fork Twelvepole Creek Exhibit 2 Flood Insurance Rate Map Index Flood Insurance Rate Map EXHIBITS Panel 01P Panels 02P-06P Panels 07P-09P Panels 10P-13P Panels 14P-17P Panels 18P-19P Panels 20P-25P Panels 26P-27P Panels 28P-41P Panels 42P-44P Panels 45P-46P Panels 47P-49P Panels 50P-63P Panels 64P-66P ii

5 1.0 INTRODUCTION FLOOD INSURANCE STUDY MINGO COUNTY, WEST VIRGINIA AND INCORPORATED AREAS 1.1 Purpose of Study This Flood Insurance Study (FIS) revises and updates previous FISs/Flood Insurance Rate Maps (FIRMs) for the geographic area of Mingo County, West Virginia, including: Towns of Delbarton, Gilbert, Kermit, Matewan, City of Williamson; and the unincorporated areas of Mingo County (hereinafter referred to collectively as Mingo County). This FIS aids in the administration of the National Flood Insurance Act of 1968 and the Flood Disaster Protection Act of This information will allow Mingo County to continue participation in the regular program of flood insurance by the Federal Emergency Management Agency (FEMA) with the most current data. Local and regional planners will use this study in their efforts to promote sound floodplain management. In some states or communities, floodplain management criteria or regulations may exist that are more restrictive or comprehensive than those on which these federally supported studies are based. These criteria take precedence over the minimum federal criteria for purposes of regulating development in the floodplain, as set forth in 44 CFR, In such cases, however, it shall be understood that the state (or other jurisdictional agency) shall be able to explain these requirements and criteria. Please also note that FEMA has identified one or more levees in the City of Williamson and the Town of Matewan that have not been demonstrated by the communities or levee owners to meet the requirements of 44 CFR Section of the NFIP regulations (44CFR65.10) as it relates to the levee s capacity to provide 1-percent-annual-chance flood protection. As such, there are temporary actions are being taken until such time as FEMA is able to initiate a new flood risk project to apply the new levee analysis and mapping procedures. Please refer to the Notice to Flood Insurance Study Users page at the front of this FIS report for more information. 1.2 Authority and Acknowledgements The source of authority for this Flood Insurance Study is the National Flood Insurance Act of 1968 and the Flood Disaster Protection Act of The October 2, 2012, FIS was prepared to incorporate the incorporated communities within Mingo County in a countywide format. Information on the authority and acknowledgments for each jurisdiction included in this countywide FIS, as compiled from their previously printed FIS reports, is shown below. 1

6 Delbarton, Town of: Gilbert, Town of: Kermit, Town of: Matewan, Town of: The hydrologic and hydraulic analyses for the 1985 FIS report represent a revision of original analyses done by Burgess & Niple, Limited, for the Federal Emergency Management Agency (FEMA), under Contract No. H The updated version was prepared by the U.S. Army Corps of Engineers (USACE), Huntington District, under Inter-Agency Agreement No. IAA-H-9-79, Project Order No. 42. The updated study was completed in September The hydrologic and hydraulic analyses for the 1985 FIS report represent a revision of the original analyses done by Burgess & Niple, Limited, for FEMA, under Contract No. H The updated version was prepared by the USACE, Huntington District, under Inter- Agency Agreement No. IAA-H-9-79, Project Order No. 42. The updated study was completed in September The hydrologic and hydraulic analyses for the 1985 FIS report represent a revision of original analyses done by USACE, Huntington District, for FEMA, under Inter-Agency Agreement No. IAA-H-19-74, Project Order No. 17. This study was completed in October The updated version was prepared by the USACE, Huntington District, under Inter-Agency Agreement No. IAA-H-9-79, Project Order No. 42. The updated study was completed in September The hydrologic and hydraulic analyses for the October 3, 1983, FIS report and the April 3, 1984 FIRM (hereinafter referred to as the 1984 FIS) were prepared by USACE, Huntington District, West Virginia, for FEMA during the study for the unincorporated areas of Mingo County. That work was completed in September For the 1999 FIS report revision, the hydraulic analyses for the Tug Fork and Mate Creek were prepared by the USACE, Huntington District, West Virginia. This work was completed in 1995 and 1997, respectively. 2

7 Mingo County (Unincorporated Areas): The hydrologic and hydraulic analyses for the 1984 FIS report represent a revision of the original analyses performed by the Huntington District of USACE for FEMA. The updated version was also prepared by the Huntington District of USACE for the FEMA, under Interagency Agreement No. IAA-H-9-79, Project Order No. 42. This work was completed in September Williamson, City of: The hydrologic and hydraulic analyses for the 1984 FIS report represent two revisions of the original analyses performed by the Huntington District of USACE for FEMA. In the January 18, 1974, revision, the hydrologic and hydraulic analyses were prepared by the USACE for FEMA, under Inter-Agency Agreement No. IAA-H-9-79, Project Order No. 42. This work was completed in August For the 1992 FIS report revision, hydrologic and hydraulic analyses were performed to reflect the addition of flood protection measures constructed along the Tug Fork. This work was completed in September For the October 2, 2012, revision, the conversion to the Digital Flood Insurance Rate Map (DFIRM) is based upon updated orthophotography, and the transition from the National Geodetic Vertical Datum of 1929 (NGVD29) to the North American Vertical Datum of 1988 (NAVD88). This work was prepared by the USACE, Huntington District, for FEMA, under Inter-Agency Agreement No. HSFE03-04-X The work for this revision was completed in December In addition, for the October 2, 2012, revision, new model-backed approximate studies were performed throughout Mingo County, effectively replacing all previously effective Zone A floodplains. This work was prepared by AMEC Earth and Environmental under an Indefinite Delivery / Indefinite Quantity (IDIQ) Agreement with FEMA, and was completed in May For this latest revision, the model-backed Zone A cross sections with water surface elevations were added to the GIS Database. For this revision, new detailed study of the Tug Fork and the backwater reaches of its tributaries was performed throughout Mingo County, effectively replacing all previously effective floodplains. This work was prepared in coordination between the Kentucky Department of Water (KDOW), FEMA Regions III and IV, and Risk Assessment, Mapping, and Planning Partners (RAMPP), under CTP Agreement Nos. EMA-2010-CA and EMA-2011-CA This work was completed in April

8 For the October 2, 2012, FIS and for this revision, base map information shown on the FIRM panels was created by the West Virginia Statewide Addressing and Mapping Board (SAMB). Imagery was captured at a scale of 1" = 2,400' in the Spring of 2003 for the purpose of producing natural color digital orthophotos at a 2-foot pixel resolution. The projection used in the preparation of this map is Universal Transverse Mercator (UTM) zone 17, North American Datum of 1983 (NAD 83), GRS80 spheroid. 1.3 Coordination Consultation Coordination Officer s (CCO) meetings may be held for each jurisdiction in this countywide FIS. An initial CCO meeting is held typically with representatives of FEMA, the community, and the study contractor to explain the nature and purpose of a FIS and to identify the steams to be studied by detailed methods. A final CCO meeting is held typically with representatives of FEMA, the community, and the study contractor to review the results of the study. The dates of the initial and final CCO meetings held for Mingo County are shown in Table 1, Initial and Final CCO Meetings. TABLE 1 INITIAL AND FINAL CCO MEETINGS Community Initial CCO Date Intermediate CCO Date Final CCO Date Delbarton, Town of June 11, 1975 September 24, 1975 January 28, 1976 Gilbert, Town of June 11, 1975 October 8, 1975 January 28, 1976 Kermit, Town of November 19, 1974 * August 18, 1976 Matewan, Town of * * March 15, 1983 Mingo County January 10, 1979 * January 4, 1984 (Unincorporated Areas) Williamson, City of April 30, 1980 * March 16, 1983 *Data not available For the October 2, 2012, revision, the final CCO meeting was held on June 14, 2011, with representatives of FEMA, the study contractor, and representatives from the communities. For this revision, a Discovery meeting was held on June 13, 2012, with representatives of FEMA, the study contractor, the Kentucky Division of Water, the U.S. Army Corps of Engineers (USACE) Huntington District, the U.S. Senate, the West Virginia Office of Emergency Services, the West Virginia Department of Transportation, the Virginia Department of Conservation, and representatives from the communities. A final CCO meeting was held on, with representatives of FEMA, the study contractor, the Kentucky Division of Water, the U.S. Army Corps of Engineers (USACE) Huntington District, and representatives from the communities. All problems raised at that meeting have been addressed in this study. 4

9 2.0 AREA STUDIED 2.1 Scope of Study This FIS covers the geographic area of Mingo County, West Virginia. The areas studied by detailed methods were selected with priority given to all known flood hazard areas and areas of projected development and proposed construction. For this revision, the Tug Fork in the Tug Fork watershed (HUC-8: ) was studied. All or portions of the flooding sources listed in Table 2, Flooding Sources Studied by Detailed Methods, were studied by detailed methods in this revision and/or in previously printed FIS reports. Limits of detailed study are indicated on the Flood Profiles (Exhibit 1) and on the FIRM (Exhibit 2).. TABLE 2 FLOODING SOURCES STUDIED BY DETAILED METHODS Buffalo Creek Gilbert Creek Guyandotte River Horsepen Creek Laurel Creek Marrowbone Creek Mate Creek Moses Fork Pigeon Creek Rockhouse Fork Stafford Branch Trace Fork Tug Fork West Fork Twelvepole Creek The following flooding sources and their tributaries listed in Table 3, Flooding Sources Studied by Approximate Methods. 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 and Mingo County. No Letter of Map Revisions were incorporated into this new revision. 2.2 Community Description Mingo County is located in the southwestern portion of West Virginia. It is bordered by Wayne County, Lincoln County, and Logan County to the north, Logan County to the northeast, Wyoming County and McDowell County to the southeast, and Buchanan County, Virginia, and Pike County and Martin County, Kentucky, to the southwest. The total land area contained within Mingo County is 423 square miles. Mingo County was formed from Logan County in The partition resulted from the development of the western part of Logan County following the construction of the Norfolk and Western Railway along the Tug Fork, and the difficulty of communication with the county seat, the Town of Logan, due to poor roads and the rugged terrain. In 2010, the population of Mingo County and incorporated areas was 26,839, as compared to 28,253 in 2000, a decrease of 5%. The population in the incorporated areas of the county increased from 3,104 persons in 2000 to 5,114 persons in The population in the unincorporated areas of Mingo County was 21,725 in 2010, as compared to 25,149 in 2000, a decrease of 14% (U.S. Census Bureau, 2012). The coal mining industry is one of the primary economic activities in Mingo County. Mingo County is the third-largest producer of coal in West Virginia. Annual coal production in 2003 was 12,278,215 tons. Of this total, 6,376,457 tons were produced 5

10 through underground mining methods, while 5,901,758 tons were produced utilizing surface mining methods. The mining industry in Mingo County directly employed 1,260 people in 2003 (West Virginia Coal Association, 2004). TABLE 3 FLOODING SOURCES STUDIED BY APPROXIMATE METHODS BUBBY BRANCH MILLER CREEK BEECH CREEK MILLSTONE BRANCH BEECH FORK MARE BRANCH BIG BRANCH MARROWBONE CREEK BIG MUNCY BRANCH MESSENGER BRANCH BIG PIGEONROOST BRANCH MITCHELL BRANCH BIG SANG KILL MATE CREEK BEN CREEK NEDS BRANCH BREEDEN CREEK NEELY BRANCH BROWNING FORK PEG FORK CANEBRAKE BRANCH PIGEON CREEK CONLEY BRANCH PIGEONROOST CREEK MILLSEAT BRANCH OPENMOUTH BRANCH CANY FORK UPPER BURNING CREEK MIDDLE FORK ELK CREEK PARSLEY BIG BRANCH DAN BRANCH PRETTY BRANCH DINGESS TRACE BRANCH ROCKHOUSE BRANCH DONALDSON BRANCH ROCKHOUSE FORK DANS BRANCH ROAD BRANCH DAVIS BRANCH RIFFE CREEK HOGGER RUN RIGHT FORK BROWNING FORK HARRYS BRANCH RIGHT FORK GILBERT CREEK HORSEPEN CREEK RIGHT FORK LAUREL FORK JACKS FORK RIGHT FORK TRACE FORK JENNIE CREEK RIGHT HAND FORK BEECH CREEK LICK CREEK RUTHERFORD BRANCH LICK FORK SCISSORSVILLE BRANCH OLDFIELD BRANCH SUGARTREE CREEK LEFT FORK BEN CREEK SHARKEY BRANCH LEFT FORK GILBERT CREEK SKILLET CREEK LEFT FORK ELK CREEK SIMS FORK LEFT FORK ALUM CREEK SPICE CREEK LEFT FORK MILLER CREEK SPRUCE FORK LEFT FORK MARROWBONE CREEK SPRING BRANCH LEFT FORK RIFFE BRANCH RIGHTHAND FORK LEFT FORK SPRUCE FORK EAST FORK TWELVEPOLE CREEK LEFT FORK SPRING FORK SOUTH FORK BUFFALO CREEK LEFT HAND LEFT FORK BEN CREEK STONECOAL BRANCH LEFT RIGHT FORK TRACE FORK STRAIGHT FORK ALUM CREEK SYCAMORE CREEK LAUREL BRANCH THACKER CREEK LAUREL FORK TOMS BRANCH LEATHERWOOD CREEK OTEN FORK LITTLE HUFF CREEK TRACE FORK MAUCHLINVILLE BRANCH TURKEY CREEK MIDDLE FORK SPRUCE FORK WHITE OAK BRANCH MILL FORK WEST FORK TWELVEPOLE CREEK 6

11 Mingo County possesses outstanding rail freight connection with all parts of the country. The double-tracked Norfolk-to-Portsmouth main line of the Norfolk-Southern Railway follows the Tug Fork. The length of the line within the county is 45 miles. Branches have been extended to serve a number of coal mines in West Virginia and Kentucky. Mingo County is traversed by U.S. Route 52 which links Williamson, the county seat, with Huntington to the north and Bluefield to the southeast. U.S. Route 119 links the county with Charleston to the northeast and Pikeville, Kentucky, to the southwest. There is a small airport at Williamson, but the nearest airports providing commercial services are located at Huntington, Charleston, Beckley, and Bluefield. The Tug Fork is the principal stream in the county. From its source in Tazewell County, Virginia, it flows northwest through McDowell County to the county boundary with McDowell-Mingo Counties. The stream then becomes the Mingo County, West Virginia-Buchanan County, Virginia, boundary until it reaches the Kentucky-West Virginia state line where it separates into Mingo County on the north to Pike and Martin Counties, Kentucky to the south. The main tributary of the Tug Fork in Mingo County is Pigeon Creek, which has a drainage area of 142 square miles. Other significant tributaries to the Tug Fork are Buffalo Creek, Marrowbone Creek, and Mate Creek, with drainage areas of 7.05 square miles, 22.6 square miles, and 16 square miles, respectively. Laurel Fork, Rockhouse Fork, and Trace Fork are the major tributaries to Pigeon Creek. The drainage areas of these streams are 16.2 square miles, 32.9 square miles, and 20.8 square miles, respectively. West Fork of Twelvepole Creek rises at the Mingo County-Logan County line 4 miles southeast of Dingess and flows northwest. The drainage area of the stream within Mingo County is 29.7 square miles. Moses Fork, a tributary of West Fork of Twelvepole Creek, has a drainage area of 1.53 square miles. The Guyandotte River forms at the confluence of Devils Fork, Stonecoal Creek and Winding Gulf near the small community of Amigo in Raleigh County, West Virginia, and flows northward to the Ohio River at the City of Huntington. The river and two of its tributaries, Gilbert Creek and Horsepen Creek, drain the easternmost portion of Mingo County. For the portion that flows through Mingo County, the Guyandotte River watershed is rugged and mountainous. The drainage areas of Gilbert Creek and Horsepen Creek are 31.1 square miles and 15.3 square miles, respectively. Elevations within Mingo County range from 585 feet at the confluence of Marrowbone Creek to 2,450 feet 0.75 mile east of Calico. Local relief ranges from approximately 500 feet along the Wayne County boundary to approximately 1,200 feet in the southeastern portion of the county. Except for a limited area in the north drained by the Guyandotte River, the county is included in the Tug Fork and Twelvepole Creek drainage basins. 7

12 The mountains to the southeast of Mingo County were formed by a folding of the rock formations which also created minor folds such as the Warfield Anticline. The Guyandotte River in Logan County and the Tug Fork in Mingo County cut across the Warfield Anticline. The valleys are V-shaped and steep-sloped, and while these streams are generally placid, heavy rainfall events can quickly create the potential for lifethreatening flooding conditions. The hillsides are broken by narrow flat benches of shale and coal not readily seen from the valleys. Mingo County lies in the area immediately northwest of the Appalachian Mountains where minor folds are in contrast with the major fold to the southeast. The Pottsville Rocks of Logan County and Mingo County contain no unusually hard formations. They are composed largely of sandstone members of medium hardness, separated by thin beds of shale. There has been no ponding of the streams and waterfalls, and no extensive rapids have been developed. These conditions make possible the building of railroad tracks with easy grades to the heads of the streams. The climate of Mingo County is classified as continental, characterized by large, annual, daily, and day-to-day ranges of temperature. Weather changes occur every few days from the passing of cold or warm fronts and associated centers of high and low pressure. Records for the state show minimum temperatures in the highlands of -30 degrees Fahrenheit (F) and maximum temperatures in the lowlands exceeding 100 degrees F. The mean annual temperature at Williamson is 56.3 degrees F, while the mean annual precipitation is 43.9 inches. The minimum temperature in Williamson was -18 degrees F in 1985 and the maximum temperature was 107 degrees F in Principal Flood Problems The towns and villages of Mingo County are comparatively small and are mostly located along the Tug Fork, the Guyandotte River, West Fork Twelvepole Creek, and their tributaries. The periodic overflow of these streams is the principal flood problem within the county. The history of flooding along the rivers and streams in the county indicates that flooding can occur during any season of the year. Large frontal storms or decaying tropical storms produce the worst flooding along the larger streams. Thunderstorms occur over small areas and produce severe local floods without affecting adjacent areas. The mountainous topography of the basin is conducive to the rapid concentration of runoff, resulting in quick rises of the streams (flash flooding). Floods are usually of short duration, seldom remaining above the flood stage for more than 24 hours. Since records became available, major floods have occurred along the Tug Fork in Mingo County, including those in 1862, 1875, 1899, 1901, 1908, 1913, 1918, 1929, 1937, 1939, 1955, 1957, 1963, 1977, 2004, 2009, and The April 1977 flood, which is the flood of record for the county, crested at feet at the Williamson gage. Flood stage at Williamson is 27 feet. The April 1977 flood exceeded this stage by 25.5 feet and overtopped the flood-wall by approximately 8.5 feet. Damage estimates for the flood totaled almost $200 million in the Tug Fork basin (USACE, 1977). 8

13 The second largest flood occurred in March 1963 and crested at 44.5 feet (Williamson gage), approximately 0.9 feet higher than the flood of January The February 1862 and the July 1875 floods crested at approximately 42.2 feet and 43.2 feet, respectively. The discharges associated with the floods of April 1977, March 1963, and January 1957 were 94,000 cubic feet per second (cfs), 46,050 cfs, and 44,750 cfs, respectively. The estimated recurrence intervals for the floods were 555 years, 20 years, and 17 years, respectively. The flood of record in Mingo County along the Guyandotte River and most of its tributaries occurred in March Other major floods occurred in July 1875, January 1918, March 1934, February 1939, February-March 1955, January 1957, January 1974, and April The March 1963 flood crested at feet at the Logan gage and had a discharge of 55,000 cfs (U.S. Department of the Interior, 1980). 2.4 Flood Protection Measures Construction was initiated on R.D. Bailey Lake and Dam in June 1967 and completed in The project is located along the Guyandotte River, which places it in both Mingo County and Wyoming County, approximately 6 miles upstream of Gilbert, West Virginia. The 310-foot high dam project is operated primarily for the reduction of flood damage in the Guyandotte River basin and as a unit in the comprehensive plan for flood control in the Ohio River Valley. Other purposes served are water quality control, recreation, and fish and wildlife (USACE, 1981). Laurel Lake Wildlife Management Area is located on Laurel Fork in the northwestern portion of Mingo County about 17 miles east of Kermit. Established in 1960, Laurel Lake and dam are used for recreation and provide no flood protection. Within the City of Williamson and the Town of Matewan there are one or more levees that have not been demonstrated by the communities or levee owners to meet the requirements of 44 CFR Section of the NFIP regulations as they relates to the levee s capacity to provide 1-percent-annual-chance flood protection. Please refer to the Notice to Flood Insurance Study Users page at the front of this FIS report for more information. In the Town of Matewan, the 2,350-foot long floodwall was built between 1992 and 1997, and includes a pedestrian walkway with access to the Matewan Central Business District (CBD) and two fisherman access platforms. In the City of Williamson, following the flood of January 1957, flood protection was provided on the right bank of the Tug Fork. The flood protection consists of 2,135 feet of concrete wall, a pump station, and 16 gated openings. It is estimated that flood damage totaling $3.7 million was prevented through The April 1977 flood exceeded the January 1957 flood crest by 9 feet. 9

14 The West Williamson system is located within the City of Williamson 1.5 miles downstream of the federally-constructed flood control works located in the main part of the city. Restoration of the West Williamson local system was completed by the USACE in In 1988, the USACE work began on the floodwall intended to protect the Williamson CBD, which was completed in ENGINEERING METHODS For the flooding sources studied in detail in the county, standard hydrologic and hydraulic study methods were used to determine the flood hazard data for this study. Flood events of a magnitude which 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 premium rates. These events, commonly termed the 10-, 50-, 100-, and 500-year floods, have a 10-, 2-, 1-, and 0.2-percent chance, respectively, of being equaled or exceeded during any year. Although the recurrence interval represents the long-term average period between floods of a specific magnitude, rare floods could occur at short intervals or even within the same year. The risk of experiencing a rare flood increases when periods greater than one year are considered. For example, the risk of having a flood which equals or exceeds the 100-year flood (one-percent chance of annual occurrence) in any 50-year period is about 40 percent (four in ten) and, for any 90-year period, the risk increases to about 60 percent (six in ten). The analyses reported here reflect flooding potentials based on conditions existing in the county at the time of completion of this study. Maps and flood elevations will be amended periodically to reflect future changes. Note: within the City of Williamson and the Town of Matewan there are one or more levees that have not been demonstrated by the communities or levee owners to meet the requirements of 44 CFR Section of the NFIP regulations as it relates to the levee s capacity to provide 1- percent-annual-chance flood protection. Please refer to the Notice to Flood Insurance Study Users page at the front of this FIS report for more information. 3.1 Hydrologic Analyses Hydrologic analyses were carried out to establish the peak discharged-frequency relationships for floods of the selected recurrence intervals for each flooding source studied in detail affecting the county. Pre-countywide Analyses For each community within Mingo County that had a previously printed FIS report, the unrevised hydrologic analyses described in those reports have been compiled and are summarized below. In Mingo County and the incorporated areas that had a FIS report, natural dischargefrequency curves were obtained from a USACE study for the Tug Fork valley (USACE, 1977). The curves are based upon a regional analysis developed in accordance with the method outlined by Leo R. Beard s, Statistical Methods in Hydrology (January 1962), and Water Resources Council Bulletin 17B, September 1981 (Beard, 1962; Water Resources Council, 1977). 10

15 Twenty U.S. Geological Survey (USGS) stream gaging stations in the surrounding drainage basins were used in the regional analysis. Periods of record ranged from 16 to 60 years and represented drainage areas of 31 to 3,892 square miles (U.S. Department of the Interior, Undated; 1965). A timeline of 60 years was adopted as being representative and was used in computing the estimated frequency for each evaluating center. Flows on the Guyandotte River have been modified by the R.D. Bailey Lake and Dam since 1974 (USACE, 1968; 1965; and May 1975). The nearest downstream gage is located at Man, West Virginia. The zero of the gage is feet, with a drainage area of 762 square miles. The 1-percent-annual-chance flood was reduced 10.3 feet at this location. In the Town of Gilbert, provisional equations developed by the USGS were applied to establish the 10-, 2-, and 1-percent-annual-chance peak flood discharges for Stafford Branch (U.S. Department of the Interior, July 1975). Stafford Branch has no stream flow records, therefore equations were based on a log-pearson Type III analyses of gaging station records with subsequent regression analyses to define the parameters needed for application to ungaged watersheds. The 0.2-percent-annual-chance frequency peak discharges were determined from an extrapolation of the constants used in the USGS equations. Peak discharges for the approximate study area on Stafford Branch were determined by application of the 1-percent-annual-chance frequency equation (U.S. Department of the Interior, July 1975). October 2, 2012 Analyses No new detailed hydrologic analyses were carried out for the October 2, 2012, countywide study. New approximate hydrologic analyses were performed on all previously effective approximate stream reaches as part of this countywide update. For this revision, Tug Fork Analyses Hydrologic analyses were carried out to establish the peak elevation-frequency relationships for floods of the selected recurrence intervals for the Tug Fork. Hydrologic analyses are typically performed at the watershed level and depend on factors such as watershed size and shape; land use and urbanization; natural or manmade storage; a n d various models or methodologies may be applied. A gage analysis was applied to develop the discharges used in the hydraulic analyses for the Tug Fork. Greater detail (including assumptions, analysis, and results) is available in the archived project documentation. Five USGS stream gaging stations in the surrounding drainage basins were used in the regional analysis. The represented drainage area for the Tug Fork is 1,280 square miles, and the five gage records reflect periods ranging from 16 to 94 years. 11

16 A summary of drainage area-peak discharge relationships for the streams studied by detailed methods is show in Table 4, Summary of Discharges. FLOODING SOURCE AND LOCATION TABLE 4 - SUMMARY OF DISCHARGES PEAK DISCHARGES (cfs) DRAINAGE AREA (sq. miles) 10-PERCENT - ANNUAL CHANCE 2-PERCENT - ANNUAL CHANCE 1-PERCENT - ANNUAL CHANCE 0.2-PERCENT - ANNUAL CHANCE BUFFALO CREEK At its confluence with Tug Fork ,050 1,700 2,100 2,900 GILBERT CREEK At its confluence with the Guyandotte River ,300 5,300 6,200 8,500 At a point approximately 85 feet upstream of the confluence of Skillet Creek ,000 4,800 5,600 7,800 At a point approximately 10 feet upstream of the confluence of Horsepen Creek ,275 2,050 2,450 3,400 At a point approximately 170 feet upstream of the confluence of Adams Fork ,500 1,800 2,500 GUYANDOTTE RIVER * At the State Route 80 bridge ,600 15,800 17,600 23,700 At a point approximately 360 feet upstream of the confluence of Cane Brake ,700 12,800 13,800 23,700 At a point approximately 65 feet upstream of the County Route 52/4 bridge 571 7,600 7,700 7,800 23,700 At a point approximately 1,545 feet upstream of the confluence of Little Huff 535 7,500 7,500 7,500 23,700 *All flows routed through the R.D. Bailey Lake and Dam 12

17 FLOODING SOURCE AND LOCATION TABLE 4 - SUMMARY OF DISCHARGES - continued PEAK DISCHARGES (cfs) DRAINAGE AREA (sq. miles) 10-PERCENT - ANNUAL CHANCE 2-PERCENT - ANNUAL CHANCE 1-PERCENT - ANNUAL CHANCE 0.2-PERCENT - ANNUAL CHANCE HORSEPEN CREEK At its confluence with Gilbert Creek ,600 2,250 3,000 4,200 At a point approximately 142 feet upstream of the confluence of Browning Fork ,275 1,500 2,100 At a point approximately 996 feet upstream of the confluence of Smith Branch ,140 1,600 LAUREL FORK At its confluence with Pigeon Creek ,340 5,350 6,300 8,700 At a point approximately 585 feet upstream of the confluence of Right Fork ,450 4,000 4,800 6,700 At a point approximately 390 feet upstream of Laurel Lake Dam ,450 2,400 2,800 3,900 MARROWBONE CREEK At its confluence with Tug Fork ,450 4,000 4,800 6,800 At a point approximately 70 feet upstream of the confluence of Left Fork ,050 3,400 4,000 5,600 At a point approximately 1,915 feet downstream of the confluence of Nelly Branch ,600 2,700 3,200 4,500 MATE CREEK At its confluence with Tug Fork ,960 3,150 3,720 5,200 At a point approximately 900 feet upstream of the confluence of Rutherford Branch ,720 2,850 3,400 4,800 At a point approximately 500 feet upstream of the confluence of Mitchell Branch ,400 2,300 2,700 3,800 13

18 TABLE 4 - SUMMARY OF DISCHARGES - continued PEAK DISCHARGES (cfs) DRAINAGE AREA (sq. miles) 10-PERCENT - ANNUAL CHANCE 14 2-PERCENT - ANNUAL CHANCE 1-PERCENT - ANNUAL CHANCE 0.2-PERCENT - ANNUAL CHANCE FLOODING SOURCE AND LOCATION PIGEON CREEK At its confluence with Tug Fork ,000 15,500 18,000 24,600 At a point approximately 140 feet upstream of the confluence of Laurel Fork ,200 11,600 13,900 19,000 At a point approximately 585 feet upstream of the Trace Fork Creek ,500 9,000 10,600 14,900 At a point approximately 865 feet upstream of the confluence of Rockhouse Fork ,500 4,000 4,800 6,700 At a point approximately 405 feet upstream of the confluence of Ferrell Branch ,200 3,700 4,400 6,100 At a point approximately 770 feet upstream of the confluence of Oldfield Branch ,700 2,800 3,300 4,700 At a point approximately 135 feet upstream of the confluence of Little Laurel Branch ,400 2,300 2,750 3,800 ROCKHOUSE FORK At its confluence with Pigeon Creek ,000 3,200 3,750 5,220 At a point approximately 910 feet upstream of the confluence of Curry Branch ,700 2,800 3,300 4,600 At a point approximately 155 feet upstream of the confluence of Big Pigeonroost Branch 9.1 1,240 2,050 2,450 3,450 TRACE FORK At its confluence with Pigeon Creek ,320 3,800 4,550 6,350 WEST FORK OF TWELVEPOLE CREEK At a point approximately 760 feet downstream of the confluence of Shaft Branch 7.5 1,700 2,700 3,000 4,000 At a point approximately 755 feet upstream of the County Route 3/12 bridge ,080 1,450

19 FLOODING SOURCE AND LOCATION DRAINAGE AREA (sq. miles) TABLE 4 - SUMMARY OF DISCHARGES - continued 10- PERCENT ANNUAL CHANCE PEAK DISCHARGES (cfs) PERCENT PERCENT PERCENT ANNUAL ANNUAL ANNUAL CHANCE CHANCE CHANCE 0.2- PERCENT ANNUAL CHANCE TUG FORK At gage at Kermit 1,280 48,900 65,100 78,500 93, ,000 Just upstream of the confluence of Upper Burning Creek 1,189 44,800 59,400 71,400 84, ,000 Just upstream of the confluence of Pigeon Creek 1,040 38,200 50,200 60,000 70,500 97,800 At gage at City of Williamson ,700 44,000 52,400 61,200 84,000 Just upstream of the confluence of Peter Creek ,000 40,200 47,700 55,500 75,500 Just downstream of the West Virginia-Kentucky state border ,300 35,300 41,500 48,100 64,700 The drainage area-peak discharge relationships for Stafford Branch are shown in Figure 1, Frequency-Discharge, Drainage Area Curves. 15

20 3.2 Hydraulic Analyses Analyses of the hydraulic characteristics of the flooding sources studied were carried out to provide estimates of the elevations of floods of the selected recurrence intervals. Users should be aware that base 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 tables 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 in conjunction with the data shown on the FIRM. The hydraulic analyses for this FIS were based on unobstructed flow. The flood elevations shown on the Flood Profiles are thus considered valid only if hydraulic structures remain unobstructed, operate properly, and do not fail. Cross sections for the backwater analyses were compiled by photogrammetric methods to model conveyance of the valleys. All bridges and culverts were field surveyed to obtain elevation data and structural geometry. For streams for which hydraulic analyses were based on cross sections, 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 shown on the Flood Insurance Rate Map (Exhibit 2). Pre-countywide Analyses For each incorporated community within Mingo County that had a previously printed FIS report, the unrevised hydraulic analyses described in those reports have been compiled and are summarized below. In the Town of Delbarton, Pigeon Creek and Rockhouse Fork were studied by detailed methods. In the Town of Gilbert, the Guyandotte River, Gilbert Creek, and Stafford Branch were studied by detailed methods. In the unincorporated areas of Mingo County, Marrowbone Creek, Pigeon Creek, Laurel Fork, Trace Fork, Rockhouse Fork, Buffalo Creek, Mate Creek, the Guyandotte River, Gilbert Creek, Horsepen Creek, West Fork Twelvepole Creek, and Moses Fork were studied by detailed methods. Roughness factors (Manning s n ) used in the hydraulic computations were assigned on the basis of field inspection of the floodplain areas. These computations depend on such factors as type and amount of vegetation, channel configuration, and water depth. Water-surface elevations of floods of the selected recurrence intervals were computed using the USACE-HEC-2 step-backwater computer program (USACE, 1979). Starting water-surface elevations for the streams studied by detailed methods were determined by the slope/area method. 17

21 Flood profiles were drawn showing computed water-surface elevations to an accuracy of 0.5 foot for floods of the selected recurrence intervals. Locations of selected cross sections used in the hydraulic analyses are shown on the Flood Profiles (Exhibit 1). October 2, 2012 Analyses No new detailed hydraulic analyses were carried out for the October 2, 2012, countywide study. New approximate hydraulic analyses were performed as part of the October 2, 2012, countywide study. For this revision, Tug Fork Analyses In the unincorporated areas of Mingo County, the Town of Kermit, and the City of Williamson, the Tug Fork was studied by detailed methods using the USACE s HEC- RAS model, version All hydraulic models are one-dimensional and assume steady flow. In addition, all models assume a completely subcritical water surface profile. HEC-RAS models were developed for the 10-, 4-, 2-, 1-, and 0.2-percent-annual-chance flood events. Roughness factors (Manning s n values) used in the hydraulic computations were assigned on the basis of field inspection of the floodplain areas. These computations depend on such factors as type and amount of vegetation, channel configuration, and water depth. The channel n and overbank n values for the streams studied by detailed methods are shown in Table 5, Manning s n Values. TABLE 5 MANNING S n VALUES Stream Channel n Overbank n Buffalo Creek Gilbert Creek Guyandotte River Horsepen Creek Laurel Fork Marrowbone Creek Mate Creek Moses Fork Pigeon Creek Rockhouse Fork Trace Fork Tug Fork West Fork Twelvepole Creek

22 Qualifying bench marks within a given jurisdiction are cataloged by the National Geodetic Survey (NGS) and entered into the National Spatial Reference System (NSRS). First or Second Order Vertical bench marks that have a vertical stability classification of A, B, or C are shown and labeled on the FIRM with their 6-character NSRS Permanent Identifier. Bench marks cataloged by the NGS and entered into the NSRS vary widely in vertical stability classification. NSRS vertical stability classifications are as follows: Stability A: Monuments of the most reliable nature, expected to hold position / elevation well (e.g., mounted in bedrock) Stability B: Monuments which generally hold their position / elevation well (e.g., concrete bridge abutments) Stability C: Monuments which may be affected by surface ground movements (e.g., concrete mounted below frost line) Stability D: Mark of questionable or unknown vertical stability (e.g., concrete monument above frost line, or steel witness post). In addition to NSRS bench marks, the FIRM may also show vertical control monument established by a local jurisdiction; these monuments will be shown on the FIRM with the appropriate designations. Local monuments will only be placed on the FIRM if the community has requested that they be included, and if the monuments meet the aforementioned NSRS inclusion criteria. To obtain current elevation, description, and/or location information for bench marks shown on the FIRM for this jurisdiction, please contact the Information Services Branch of the NGS at (301) , or visit their Web site, It is important to note that temporary vertical monuments are often established during the preparation of a flood hazard analysis for the purposes of establishing local vertical control. Although these monuments are not shown on the digital FIRM, they may be found in the Technical Support Data Notebook associated with this FIS and FIRM. Interested individuals may contact FEMA to access this data 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 FISs and FIRMs was the National Geodetic Vertical Datum of 1929 (NGVD29). With the completion of the North American Vertical Datum of 1988 (NAVD88), many FIS reports and FIRMs are being prepared using NAVD88 as the referenced vertical datum. 19

23 All flood elevations shown in the FIS report and on the FIRM are referenced to NAVD88. Structure and ground elevations in the community must, therefore, be referenced to NAVD88. It is important to note that adjacent communities may be referenced to NGVD29. This may result in differences in base flood elevations across corporate limits between the communities. All flood elevations shown in this FIS report and on the FIRM are referenced to NAVD88. A conversion factor of feet was applied to the NGVD29 elevations in Mingo County to convert to NAVD88. Structure and ground elevations in the county must, therefore, be referenced to NAVD88. It is important to note that adjacent communities and counties may be referenced to NGVD29. This may result in differences in Base Flood Elevations (BFEs) across the community and county boundaries. NGVD 0.70 = NAVD For more information on NAVD88, see Converting the National Flood Insurance Program to the North American Vertical Datum of 1988, FEMA Publication FIA-20/June 1992, or contact the National Geodetic Survey at the following address: NGS, Information Services NOAA, N/NGS12 National Geodetic Survey SSMC-3, # East-West Highway Silver Spring, Maryland (301) 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-, 4-, 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, and Floodway Data 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 Flood Boundaries In order to provide a national standard without regional discrimination, the 1-percentannual-chance flood has been adopted by the FEMA as the base flood for purposes of floodplain management measures. The 0.2-percent-annual-chance flood is employed to indicate additional areas of flood risk in the community. For each stream studied in detail, the boundaries of the 1- and 0.2-percent-annual-chance floods have been delineated using the flood elevations determined at each cross section; between cross sections, the boundaries were interpolated using topographic maps. For information 20

24 regarding the scale and sources of these maps, see Tables 6 and 7, Original Sources of Topographic Data and Updated Sources of Topographic Data. TABLE 6 ORIGINAL SOURCES OF TOPOGRAPHIC DATA LOCATION SCALE CONTOUR INTERVAL (Feet) Town of Delbarton 1:24,000 5 Town of Gilbert 1:2, :24, Town of Kermit 1:2,400 5 Town of Matewan 1:200 5 Mingo County 1:200 5 City of Williamson 1:200 5 TABLE 7 UPDATED SOURCES OF TOPOGRAPHIC DATA LOCATION SCALE CONTOUR INTERVAL (Feet) Town of Kermit 1:600 2 Town of Matewan 1:600 2 Mingo County 1:600 2 City of Williamson 1:600 2 The 1- and 0.2-percent-annual-chance floodplain boundaries are shown on the FIRM. 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 cannot be shown due to limitations of the map scale and/or lack of detailed topographic data. For the October 2, 2012, revision, the conversion to the Digital Flood Insurance Rate Map (DFIRM) and the development of new approximate Zone A floodplains were based upon updated topography provided by the USGS and the West Virginia State Addressing and Mapping Board (WVSAMB) 3 Meter Digital Elevation Models, The October 2, 2012, revision also includes the transition from the National Geodetic Vertical Datum of 1929 (NGVD29) to the North American Vertical Datum of 1988 (NAVD88). For this revision, the development of new detailed floodplains of the Tug Fork were based upon updated topography collected by Photoscience, Inc. using Light Detection and Ranging (LiDAR) data provided by the West Virginia Department of Environmental Protection (WVDEP). Within the City of Williamson and the Town of Matewan there are one or more levees that have not been demonstrated by the communities or levee owners to meet the requirements of 44 CFR Section of the NFIP regulations as it relates to the levee s capacity to provide 1-percent-annual-chance flood protection. As such, the floodplain 21