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Home My WebLink About20190573 Ver 2_Flood Study Smithfield WTP 20190103_20200316 FLOOD STUDY for BUFFALO CREEK WATER TREATMENT PLANT EXPANSION TOWN OF SMITHFIELD, NC PREPARED BY: 905 Jones Franklin Road Raleigh, NC 27606 Engineering Firm License No. C-890 January 3, 2019 Flood Study on Buffalo Creek for WTP Expansion Background The Town of Smithfield Water Treatment Plant is located at 515 North 2nd Street. The Town proposes to expand the WTP which is located in the floodplain of the Neuse River and Buffalo Creek. Both streams are located within FEMA Detailed Study areas. None of the expansion is proposed within the existing floodways of either stream. Based on our discussions with the North Carolina Floodplain Mapping Program, if the project does not cause any encroachments in the floodway/non-encroachment area, there is no requirement to model the impacts unless the local ordinance requires it (higher standard). We have reviewed the Town's Unified Development Ordinance and there does not appear to be any language more restrictive than FEMA's. The purpose of this report is to assess the WTP expansion in order to minimize impacts to upstream property owners due to the presence of existing insurable structures in the Buffalo Creek floodplain upstream of the WTP. The WTP pond expansion is proposed along the existing flow path and parallel to the Neuse River. The pond expansion will not block any additional flow area; therefore, the Neuse River was not modeled in this study. Data Research and Field Observations The Wooten Company (TWC) provided survey data including site topographic contours and proposed WTP expansion plans. A map is included that shows the site topographic contours and proposed WTP expansion along with FEMA cross section locations. Sungate Design Group, P.A. (Sungate) obtained the Effective Detailed Study HEC-RAS model from The North Carolina Floodplain Mapping Program (NCFMP). According to the Flood Insurance Study, the regulatory base flood elevation on Buffalo Creek is controlled by backwater from the Neuse River to River Station 12343. The reach boundary condition in the effective model is set to normal depth (0.001 ft/ft). Due to the significant difference in drainage areas and corresponding times of concentration between the Neuse River and Buffalo Creek, it is possible to experience a 1% annual chance event (100-year) on Buffalo Creek before flood elevations on the Neuse reach peak levels. Therefore, backwater from the Neuse will not be considered in order to evaluate the localized impacts from the WTP expansion. Sungate completed a site visit on June 15, 2018 to verify existing site conditions and Manning’s roughness coefficients. Manning’s roughness coefficients used in the Effective Model appear to match the existing site conditions. Buffalo Creek - Effective Model The NCFMP Effective HEC-RAS model was obtained from NCFMP. The model was created using HEC-RAS version 4.0.0 and contained two plans titled “Multiple Run” and “Floodway Run”. The “Floodway Run” contained the 100-year and Floodway runs. The “Multiple Run” contained the 10, 50, and 500-year events. Both plans will be evaluated for impacts. When rounded to the nearest 0.1 foot, the effective model matches the published Flood Insurance Study (FIS) data. No negative surcharges or positive surcharges greater than 1.00 feet were present in the model. Buffalo Creek - Duplicate Effective Model HEC-RAS version 4.1.0 was used to run the Duplicate Effective model. The Model ran without errors. The Duplicate Effective 1% annual chance water surface elevations and “with floodway” elevations matched the Effective model within reasonable tolerance at all sections within the project area with a maximum decrease of 0.01 foot occurring at several River Stations. No negative surcharges or positive surcharges greater than 1.00 feet were present in the model. Based on this information, HEC-RAS version 4.1 will be used for the Duplicate Effective model and all subsequent models. The Duplicate Effective Model appears to match the existing site conditions and no additional cross sections were necessary. Therefore, a Corrected Effective Model was not created. Buffalo Creek - Revised Model The Duplicate Effective model was used to create the Revised Model. River Stations 1398, 1807, and 2457 were revised to include the proposed pond expansion. Manning’s n value locations were adjusted to correspond with the expanded pond berm as this area will be maintained and mowed. No other revisions were made to the model. No negative surcharges or positive surcharges greater than 1.00 feet were present in the model. Results The proposed fill from the pond expansion impacts the 1% annual chance (100-year) floodplain at only RS 2457. The fill at RS 1398 and 1807 is located outside the Buffalo Creek 0.2% annual chance (500-year) floodplain when backwater from the Neuse is not considered. The proposed pond expansion has minimal impacts to the 1% annual chance flood elevations along Buffalo Creek with maximum increases of 0.04 feet occurring at RS 3130, 3796, 4645, 4732, and 4769. Increases in the 1% annual chance flood elevations continue to RS 11691 and the model ties to 0.00 feet at RS 11991. (See attached comparison table.) Based on available contour mapping and aerial photography, there do not appear to be any insurable structures upstream of the WTP that would be impacted by the increases to the 1% annual chance flood elevations. It appears the insurable structures in this area are located in the floodplain due to backwater from the Neuse River (elevation 126.7 in the 100-year). APPROX 7.50 MG STORAGE PP AV WV WV MMKR PAVEMENTEXISTING EXISTINGWOOD BRIDGE HYD DIRECTIONAL BORE - SEE PROFILE EX 14" (P-57) 6" FM SVMVMONMVMONAV AV 9' CLF WITH BARB WIRE MMKR S D D WV WV 8 CLF7' CLFBUFFALO CREEK INV. 106.66 INV. 106.55 24" DIP EX 6" DIP ? 7' CLF W/ BWDIRECTIONAL B ORE - SEE PR OFILE EMN EIR EIR EIR EIREIP EIP EIP EIR EIR COUNTY OF JOHNSTONN/F PROTECT EXISTING 12" FM ABANDON/REMOVE EXISTING 6" FM3C06 TOWN OF SMITHFIELD N/F S ABANDON/REMOVE EXISTING 10" FM 115115110105105110115 1051101151151101 15105115115 1151201 1 5 115120115 115115120 125 115 120 125 120 125 1 1 5 120125 115 105110115125120125115110 115120 125 125 1201251251201151 2 0 1151 15 110 110 110 1 10 110110 110 110 110 110 110 110 110 115 110 110 115 120 125 115 110 110 110 110 120115110 110 110 110 110115 12 0 120 120120 12512 5 125 125 125 130 130 125 120 120125 13 0 130 130 125 13012 0 115 125 130120110110110110110115 120 110 125 110 115 120115 110110 115115 120115 120 120 1101151051101051151151 1511 0 105110105115110110 115 110 115 110115110 110 115 115 110 115 110 110 1151 1 0 110 110 130120125115110 135130 135140140 135 140135 145130135 1401 3 5 14013 5 140 130 135 130130 130 135 140 1401 4 5 145WE 123.7' v v vv vv vvv vvvv vvvvvvvv S S S S S S S DOCUMENT NOT CONSIDERED FINAL UNLESS ALL SIGNATURES COMPLETED 12/27/2018SmithfieldWWTP_Hyd_PSH_Workmap.dgnjharvey8/17/99DOCUMENT NOT CONSIDERED FINAL UNLESS ALL SIGNATURES COMPLETED 204 322 828 1398 1807 2457 2986 3130 3796464547324769497856506185NAD 83SMITHFIELD WATER TREATMENT PLANT JOHNSTON COUNTY 0 200'100'200' SCALE: 1"=400' 400'NEUSE RIVERBUFFALO CREEK DUPLICATE EFFECTIVE FLOODWAY DUPLICATE EFFECTIVE 100yr. FLOOD FRINGE DUPLICATE EFFECTIVE 500yr. FLOOD FRINGE SUNGATE DESIGN GROUP, P.A. ENG FIRM LICENSE NO. C-890 TEL (919) 859-2243 RALEIGH, NORTH CAROLINA 27606 905 JONES FRANKLIN ROAD MAPPING SECTION DATA FROM FEMA FLOODPLAIN FLOODWAY, FLOOD FRINGE AND CROSS COMPANY. PROPOSED DESIGN PROVIDED BY THE WOOTEN TOPOGRAPHY, EXISTING CONDITIONS AND Northing: = 647,075, Easting = 2,191,195Northing: = 647,075, Easting = 2,197,299Northing: = 642,358, Easting = 2,191,195Page 1 of 2Northing: = 642,358, Easting = 2,197,299This is an official copy of a portion of the above referenced flood map. This map incorporates changes or amendments which may have been made subsequent to the date on the title block. For the latest product information about National Flood InsuranceProgram flood maps check the FEMA Flood Map Store at www.msc.fema.gov.Panel(s):1694CONTAINS:COMMUNITYCIDTOWN OFSMITHFIELD370140Notice to User: The Map Number(s) shownbelow should be used when placing maporders; the Community Number(s) shownabove should be used on insuranceapplications for the subject community.SELECTED PANELS:MAP NUMBEREFFECTIVE DATE3720169400J12/2/2005 FEMA: National Flood Insurance ProgramPage 2 of 2Panel(s):1694CONTAINS:COMMUNITYCIDTOWN OF SMITHFIELD370140Notice to User: The Map Number(s) shown below should be used when placing maporders; the Community Number(s) shown above should be used on insuranceapplications for the subject community.SELECTED PANELS:MAP NUMBEREFFECTIVE DATE3720169400J12/2/2005NOTES TO USERSThis is an official FIRMette of a portion of the effective panels listed in the Title Block shownon Page 1. The information represented on this FIRMette was extracted from the effectivedigital flood hazard data available at http://fris.nc.gov/fris.Base flood elevation data, floodway, nonencroachment widths, information on certain areasno in the Special Flood Hazard Areas protected by flood control structures, and otherpertinent data are available in the Flood Insurance Study (FIS) available athttp://fris.nc.gov/fris. Users should be aware that flood elevations shown on this FIRMetterepresent elevations rounded to one tenth of a foot (0.1') and should be utilized inconjunction with data available in the FIS.NOTES TO USERSBase map information and geospatial data used to develop this FIRMette were obtained fromvarious organizations, including the participating local community(ies), state and federalagencies, and/or other sources. The primary base for this FIRM is aerial imagery acquired bythe State in 2010. Information and geospatial data supplied by the local community(ies) thatmet FEMA base map specifications were considered the preferred source for development ofthe base map.See geospatial metadata for the associated digital FIRMette for additional information aboutbase map preparation. Base map features shown on this FIRMette, such as corporate limits,are based on the most up-to-date data available at the time of publication. Changes in thecorporate limits may have occurred since this map was published. Map users should consultthe appropriate community official or website to verify current conditions of jurisdictionalboundaries and base map features. This map may contain roads that were not considered inthe hydraulic analysis of streams where no new hydraulic model was created during theproduction of this statewide format FIRM.Flood elevations on this map are referenced to either or both the North American VerticalDatum of 1988 (NAVD 88) or National Geodetic Datum of 1929 (NGVD 29), and are labeledaccordingly. These flood elevations must be compared to structure and ground elevationsreferenced to the same vertical datum. To obtain current elevation, description, and/or locationinformation for bench marks shown on this map, or for information regarding conversionbetween NGVD 29 and NAVD 88, please contact the Information Services Branch of theNational Geodetic Survey at (301) 713-3242, or visit its website at http://www.ngs.noaa.gov/.MORE INFORMATIONLetters of Map Amendment (LOMA)1-877-336-2627http://msc.fema.gov/Letters of Map Revision (LOMR)919-715-5711www.ncfloodmaps.comFlood Insurance AvailabilityNorth Carolina Division of EmergencyManagement (NCDEM)919-715-5711http://www.nccrimecontrol.org/nfipNational Flood Insurance Program (NFIP)1-877-638-6620http://www.fema.gov/business/nfipQuestions about this FIRMette1-877-336-2627http://fema.govLEGENDLEGENDMAP REVISIONSThere are no map revisions for the selected area. FLOOD INSURANCE STUDY FEDERAL EMERGENCY MANAGEMENT AGENCY A Report of Flood Hazards in JOHNSTON COUNTY, NORTH CAROLINA AND INCORPORATED AREAS Community Name Community Number JOHNSTON COUNTY 370138 TOWN OF BENSON 370504 TOWN OF CLAYTON 370139 TOWN OF FOUR OAKS 370502 TOWN OF KENLY 370501 TOWN OF MICRO 370500 TOWN OF PINE LEVEL 370505 TOWN OF PRINCETON 370485 TOWN OF SELMA 370499 TOWN OF SMITHFIELD 370140 TOWN OF WILSON'S MILLS 370262 EFFECTIVE: 12/2/2005 REVISED: 1/5/2007 Federal Emergency Management Agency State of North Carolina Flood Insurance Study Number 37101CV000 www.fema.gov and www.ncfloodmaps.com County. N/A - Not Applicable Table 7, “Levees” is not applicable in Johnston County. 4.5 Scope of Study For this map maintenance revision, a scoping meeting was held in Johnston County to present the results of initial research to the county and communities within the county and to discuss their floodplain mapping needs. The county and communities were asked to provide input on proposed study priorities and analysis methods. These meetings resulted in the identification of flooding sources having a floodplain mapping need. Map Maintenance Plans were developed based on the results of the scoping meetings and were both mailed to each jurisdiction within Johnston County and posted to the State’s website at www.ncfloodmaps.com. Draft basin plans were developed based on the results of the initial scoping meetings. Final scoping meetings were held by the State and FEMA to provide counties and communities an overview of the draft basin plans, including the proposed scope and schedule for the project, and to provide an opportunity for additional county and community input. After the final scoping meeting was held, the Final Basin Plans were produced. This FIS covers the geographic area of Johnston County, , and all jurisdictions therein. 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. Limits of detailed study are indicated on the Flood Profiles and/or Water-surface elevation rasters and/or the FIRM. Table 8, “Flooding Sources Studied by Detailed Methods”, lists all flooding sources within the county that were studied by detailed methods for this FIS and previous FISs. Table 6 - Non-Levee Flood Protection Measures Flooding Source Structure Name Type of Measure Location Description of Measure Falls Lake NP OTHER / MISC STRUCTURE In the mid 1980s, the US Army Corps of Engineers constructed Falls Lake,a multipurpose reservoir on the Neuse River,25 miles upstream of Johnston Co.This project reduces the 1% annual chance frequency flood at the Town of Smithfield by apprx. 3.5 ft. Reservoir Table 8 - Flooding Sources Studied by Detailed Methods: Revised or Newly Studied Source Riverine Sources Affected Communties From To Black Creek The confluence with Neuse River Approximately 230 feet upstream of NC Highway 210 Johnston County Town Of Four Oaks Town Of Smithfield Buffalo Creek The confluence with Neuse River Approximately 300 feet upstream of U.S. Highway 301 Town Of Smithfield Buffalo Creek (Basin 9, Stream 1)The confluence with Little River Approximately 720 feet upstream of NC Highway 42 Johnston County Buffalo Creek West The confluence with Middle Creek The Johnston/Wake County boundary Johnston County Hannah Creek The confluence with Mill Creek (South)Approximately 1,800 feet upstream of Interstate 95 Johnston County Little Creek The confluence with Swift Creek The confluence with Swift Creek Johnston County Town Of Clayton Little Creek Tributary The confluence with Little Creek Approximately 770 feet upstream of U.S. Highway 70 Town Of Clayton Little Poplar Creek The confluence with Poplar Creek Approximately 260 feet upstream of U.S. Highway 70 Johnston County Town Of Smithfield Town Of Wilson's Mills Little River At confluence with Neuse River Approximately 1.0 mile upstream of the Wayne/Johnston County Boundary Johnston County Little River The Johnston/Wayne County boundary Approximately 1,600 feet upstream of State Highway 42 Johnston County Town Of Kenly Town Of Micro Town Of Princeton Little River The Wake/Johnston County Boundary Approximately 300 feet upstream of confluence of Perry Creek (Basin 10, Stream 19) Johnston County Flood Insurance Study Report: JOHNSTON COUNTY, NORTH CAROLINA AND INCORPORATED AREAS Effective Date: December 2, 2005 Page 9 of 90 Table 13 - Summary of Discharges Flooding Source Discharges (cfs) Location Drainage Area (square miles) 10% Annual Chance 2% Annual Chance 1% Annual Chance 1% Annual Future Annual Chance 0.2% Annual Chance Approximately 0.6 mile upstream of the confluence with Black Creek 2.62 **806 ** Approximately 0.1 mile downstream of Plainview Church Road 2.41 **770 ** Approximately 0.1 mile upstream of Plainview Church Road 2.18 **728 ** Approximately 0.3 mile upstream of Plainview Church Road 1.30 **542 ** Buffalo Creek At mouth 5.08 1174 1974 2274 *3147 Approximately 0.25 mile upstream of Buffalo Road 4.57 1119 1888 2174 *3008 Above Buffalo Road 4.13 1057 1792 2066 *2862 Approximately 0.8 mile downstream of Brightleaf Boulevard 3.56 1003 1703 1960 *2707 Approximately 0.5 mile downstream of Brightleaf Boulevard 3.28 970 1649 1897 *2617 Approximately 0.8 mile above Buffalo Road 3.08 947 1610 1851 *2552 Approximately 900 feet downstream of confluence of Buffalo Creek Overflow 2.82 947 1610 1851 *2552 At Railroad 1.69 558 1024 1198 *1722 Just upstream of Brightleaf Boulevard 1.63 527 976 1146 *1658 Just upstream of Ava Gardner Avenue 1.23 439 831 980 *1429 Just downstream of U.S. 70 Bypass 1.18 432 818 963 *1403 Buffalo Creek (Basin 9, Stream 1) At mouth 57.98 3772 5969 6942 *9296 At NC 39 50.39 3803 5985 6930 *9245 At NC 96 45.14 3829 5999 6922 *9207 At NC 42 41.60 3845 6006 6913 *9175 Approximately 1,040 feet downstream of Jordan-Narron Road 38.06 3704 5785 6656 *8834 Approximately 350 feet downstream of Jordan Narron Road 38.00 **7240 ** Approximately 0.4 mile upstream of Jordan Narron Road 37.02 **7120 ** Approximately 0.5 mile upstream of Jordan Narron Road 36.54 **7060 ** Approximately 1.0 mile upstream of Jordan Narron Road 34.04 **6760 ** Approximately 2.0 mile upstream of Jordan Narron Road 33.07 **6630 ** Approximately 2,320 feet downstream of Covered Bridge Road 32.50 3410 5334 6137 *8154 Approximately 390 feet downstream of Covered Bridge Road 32.10 **6510 ** Approximately 0.7 mile upstream of Covered Bridge Road 31.11 **6390 ** Approximately 1.0 mile downstream of Wendell Road 28.82 **6090 ** Approximately 4,500 feet downstream of Wendell Road 28.80 3166 4962 5713 *7600 Approximately 0.9 mile downstream of Wendell Road 26.14 **5730 ** Approximately 600 feet downstream of Lake Wendell Road 25.60 2941 4618 5322 *7089 Approximately 0.2 mile upstream of Wendell Road 23.30 **5330 ** Approximately 0.4 mile upstream of Lake Wendell Road 23.11 **5300 ** Approximately 1.1 mile upstream of Lake Wendell Road 22.12 **5160 ** NP 22.10 2690 4235 4884 *6516 Approximately 1.2 mile upstream of Lake Wendell Road 21.21 **5030 ** Approximately 0.3 mile upstream of Stotts Mill Road 20.22 **4880 ** NP 20.21 2544 4012 4629 *6182 Buffalo Creek Overflow Just above confluence with Buffalo Creek 1.69 332 440 468 *570 Buffalo Creek West Flood Insurance Study Report: JOHNSTON COUNTY, NORTH CAROLINA AND INCORPORATED AREAS Effective Date: December 2, 2005 Page 16 of 90 Table 22 - Floodway Data Floodway Source Floodway Water Surface Elevation Cross Section Distance (Feet Above Mouth) Width (Feet)Section Area (Square Feet) Mean Velocity (Feet Per Second) Regulatory 1% Annual Chance Future Water-Surface Elevation Without Floodway With Floodway Increase 1131 113,138 743.0 2831.0 1.2 173.9 *173.9 174.8 0.9 1138 113,788 500.0 2276.0 1.5 174.7 *174.7 175.6 0.9 1146 114,592 815.0 3245.0 1.0 175.5 *175.5 176.5 1.0 1151 115,077 509.0 2095.0 1.6 176.1 *176.1 177.0 0.9 1157 115,745 478.0 2433.0 1.4 176.9 *176.9 177.9 1.0 1166 116,606 566.0 2541.0 1.3 177.9 *177.9 178.9 1.0 1174 117,447 635.0 3348.0 1.0 178.6 *178.6 179.6 1.0 1187 118,683 699.0 3379.0 1.0 179.3 *179.3 180.3 1.0 1199 119,895 695.0 2867.0 1.2 180.3 *180.3 181.3 1.0 1208 120,840 700.0 2718.0 1.2 181.2 *181.2 182.1 0.9 1217 121,672 720.0 2949.0 1.1 181.9 *181.9 182.9 1.0 1228 122,797 540.0 1999.0 1.7 183.0 *183.0 183.9 0.9 1235 123,463 505.0 2135.0 1.5 183.9 *183.9 184.8 0.9 1244 124,428 680.0 2978.0 1.1 184.7 *184.7 185.7 1.0 1257 125,723 448.0 1771.0 1.9 185.6 *185.6 186.6 1.0 1276 127,586 680.0 3569.0 0.9 188.2 *188.2 189.1 0.9 1280 128,036 773.0 3904.0 0.8 188.4 *188.4 189.3 0.9 1286 128,623 800.0 3354.0 1.0 188.6 *188.6 189.5 0.9 1290 129,036 509.0 2330.0 1.1 188.9 *188.9 189.9 1.0 1295 129,497 603.0 2486.0 1.0 189.1 *189.1 190.1 1.0 1300 129,959 466.0 1859.0 1.3 189.5 *189.5 190.4 0.9 1307 130,686 530.0 1575.0 1.6 190.1 *190.1 191.1 1.0 1310 131,036 522.0 1756.0 1.4 190.7 *190.7 191.6 0.9 1315 131,536 299.0 1081.0 2.3 191.4 *191.4 192.4 1.0 1320 132,036 343.0 1496.0 1.7 192.2 *192.2 193.2 1.0 Buffalo Creek 008 828 350.0 2013.0 1.1 126.52 *117.32 118.32 1.0 014 1,398 537.0 3293.0 0.7 126.62 *117.52 118.52 1.0 018 1,807 296.0 1566.0 1.5 126.62 *117.62 118.52 0.9 025 2,457 304.0 2201.0 1.0 126.62 *117.92 118.92 1.0 038 3,796 222.0 2533.0 0.9 126.71 *119.0 119.5 0.5 057 5,650 302.0 2862.0 0.8 126.71 *124.4 124.8 0.4 062 6,185 265.0 3224.0 0.7 126.71 *124.4 124.8 0.4 067 6,746 240.0 2771.0 0.8 126.71 *124.4 124.8 0.4 071 7,068 200.0 2459.0 0.9 126.71 *124.4 124.9 0.5 074 7,449 136.0 1537.0 1.4 126.71 *124.4 124.9 0.5 078 7,804 218.0 2494.0 0.9 126.71 *124.4 125.0 0.6 082 8,232 237.0 2411.0 0.9 126.71 *124.5 125.0 0.5 086 8,630 255.0 2489.0 0.8 126.71 *124.5 125.1 0.6 093 9,287 275.0 2641.0 0.8 126.71 *124.5 125.1 0.6 097 9,676 285.0 2329.0 0.9 126.71 *124.6 125.2 0.6 101 10,072 235.0 1689.0 1.2 126.71 *124.6 125.2 0.6 103 10,333 257.0 1927.0 1.0 126.71 *124.6 125.3 0.7 106 10,646 245.0 1622.0 1.2 126.71 *124.6 125.4 0.8 Flood Insurance Study Report: JOHNSTON COUNTY, NORTH CAROLINA AND INCORPORATED AREAS Effective Date: December 2, 2005 Page 4 of 37 Table 22 - Floodway Data Floodway Source Floodway Water Surface Elevation Cross Section Distance (Feet Above Mouth) Width (Feet)Section Area (Square Feet) Mean Velocity (Feet Per Second) Regulatory 1% Annual Chance Future Water-Surface Elevation Without Floodway With Floodway Increase 109 10,921 234.0 1376.0 1.4 126.71 *124.7 125.4 0.7 112 11,230 175.0 734.0 2.7 126.71 *124.9 125.6 0.7 117 11,691 110.0 660.0 2.9 126.71 *125.5 126.3 0.8 120 11,991 125.0 718.0 2.6 126.71 *125.8 126.7 0.9 123 12,343 147.0 807.0 2.4 126.71 *126.3 127.2 0.9 127 12,671 87.0 620.0 3.1 126.9 *126.9 127.8 0.9 130 13,000 132.0 679.0 2.8 127.9 *127.9 128.8 0.9 134 13,388 122.0 642.0 2.9 129.2 *129.2 130.2 1.0 137 13,713 86.0 378.0 4.9 130.6 *130.6 131.5 0.9 139 13,945 32.0 235.0 7.9 132.1 *132.1 132.9 0.8 142 14,195 32.0 247.0 7.5 133.8 *133.8 134.4 0.6 148 14,814 210.0 1383.0 1.3 136.9 *136.9 137.8 0.9 Buffalo Creek (Basin 9, Stream 1) 005 494 1006.0 9563.0 0.7 151.91 *146.0 147.0 1.0 014 1,427 1291.0 12151.0 0.6 151.91 *146.2 147.2 1.0 025 2,500 1341.0 11179.0 0.6 151.91 *146.3 147.3 1.0 036 3,562 1415.0 11171.0 0.6 151.91 *146.5 147.5 1.0 044 4,373 764.0 4927.0 1.4 151.91 *146.7 147.7 1.0 065 6,538 767.0 7160.0 1.0 151.91 *150.5 151.3 0.8 079 7,878 1149.0 8906.0 0.8 151.91 *150.8 151.7 0.9 088 8,757 1290.0 8700.0 0.8 151.91 *151.0 151.9 0.9 096 9,607 890.0 5195.0 1.3 151.91 *151.4 152.3 0.9 117 11,703 690.0 6667.0 1.0 155.8 *155.8 156.3 0.5 123 12,309 800.0 6630.0 1.1 155.9 *155.9 156.4 0.5 132 13,166 890.0 7106.0 1.0 155.9 *155.9 156.5 0.6 138 13,836 1050.0 7430.0 0.9 156.0 *156.0 156.6 0.6 147 14,716 1201.0 8630.0 0.8 156.2 *156.2 157.0 0.8 156 15,616 960.0 5872.0 1.2 156.5 *156.5 157.4 0.9 181 18,109 871.0 4402.0 1.6 158.7 *158.7 159.7 1.0 193 19,275 1329.0 6357.0 1.1 159.7 *159.7 160.6 0.9 204 20,395 1160.0 5080.0 1.4 160.3 *160.3 161.3 1.0 216 21,579 1450.0 4767.0 1.5 161.8 *161.8 162.8 1.0 233 23,295 1023.0 5743.0 1.2 163.6 *163.6 164.7 1.1 240 23,960 1040.0 4368.0 1.6 164.6 *164.6 165.6 1.0 254 25,386 1100.0 6263.0 1.1 166.1 *166.1 166.9 0.8 273 27,315 709.0 5479.0 1.3 170.1 *170.1 170.4 0.3 285 28,538 929.0 6555.0 1.1 170.4 *170.4 171.0 0.6 295 29,489 1206.0 8080.0 0.9 170.7 *170.7 171.5 0.8 307 30,732 1241.0 6604.0 1.1 171.2 *171.2 172.1 0.9 321 32,059 1270.0 7297.0 1.0 171.8 *171.8 172.8 1.0 331 33,138 1336.0 6648.0 1.0 172.3 *172.3 173.3 1.0 339 33,931 1283.0 6086.0 1.1 172.9 *172.9 173.9 1.0 352 35,151 1145.0 4899.0 1.4 174.3 *174.3 175.2 0.9 365 36,469 855.0 4392.0 1.6 176.0 *176.0 177.0 1.0 Flood Insurance Study Report: JOHNSTON COUNTY, NORTH CAROLINA AND INCORPORATED AREAS Effective Date: December 2, 2005 Page 5 of 37 3800 4000 4200 4400 4600 4800 5000 5200 5400 5600 100 110 120 130 140 150 Buffalo Creek Detailed Study Plan: 1) REV 2) DUP EFF FW Buffalo Creek 2.0 Station (ft)Elevation (ft)Legend WS 100-FW - DUP EFF FW WS 100-FW - REV WS 100-year - REV WS 100-year - DUP EFF FW Ground - DUP EFF FW Ineff - DUP EFF FW Bank Sta - DUP EFF FW Encroachment - DUP EFF FW Ground - REV Ineff - REV Bank Sta - REV Encroachment - REV 4000 4200 4400 4600 4800 5000 5200 5400 5600 100 110 120 130 140 150 Buffalo Creek Detailed Study Plan: 1) REV 2) DUP EFF FW Buffalo Creek 3.0 (Expanded Pond) Station (ft)Elevation (ft)Legend WS 100-FW - DUP EFF FW WS 100-FW - REV WS 100-year - REV WS 100-year - DUP EFF FW Ground - DUP EFF FW Bank Sta - DUP EFF FW Encroachment - DUP EFF FW Ground - REV Bank Sta - REV Encroachment - REV 4400 4600 4800 5000 5200 5400 5600 5800 105 110 115 120 125 130 135 140 145 Buffalo Creek Detailed Study Plan: 1) DUP EFF FW 2) REV Buffalo Creek 4.0 Station (ft)Elevation (ft)Legend WS 100-FW - REV WS 100-FW - DUP EFF FW WS 100-year - REV WS 100-year - DUP EFF FW Ground - REV Bank Sta - REV Encroachment - REV Ground - DUP EFF FW Bank Sta - DUP EFF FW Encroachment - DUP EFF FW River Sta Plan W.S. Elev W.S. Elev Project Impact 100 yr.100 yr 100-yr Elevation w/FW Revised-Duplicate (ft)(ft)(ft) 14814 Floodway Run 136.86 137.77 14814 DUP EFF FW 136.85 137.77 14814 REV 136.85 137.77 0.00 14596 Floodway Run 136.47 137.42 14596 DUP EFF FW 136.47 137.42 14596 REV 136.47 137.42 0.00 14511 Culvert 14419 Floodway Run 134.78 135.59 14419 DUP EFF FW 134.78 135.59 14419 REV 134.78 135.59 0.00 14195 Floodway Run 133.82 134.37 14195 DUP EFF FW 133.82 134.37 14195 REV 133.82 134.37 0.00 13945 Floodway Run 132.06 132.91 13945 DUP EFF FW 132.06 132.91 13945 REV 132.06 132.91 0.00 13713 Floodway Run 130.62 131.5 13713 DUP EFF FW 130.62 131.5 13713 REV 130.62 131.5 0.00 13388 Floodway Run 129.18 130.16 13388 DUP EFF FW 129.18 130.16 13388 REV 129.18 130.16 0.00 13000 Floodway Run 127.87 128.84 13000 DUP EFF FW 127.87 128.84 13000 REV 127.87 128.84 0.00 12671 Floodway Run 126.86 127.79 12671 DUP EFF FW 126.86 127.79 12671 REV 126.86 127.79 0.00 12343 Floodway Run 126.30 127.22 12343 DUP EFF FW 126.30 127.22 12343 REV 126.30 127.22 0.00 HEC-RAS River: Buffalo Creek Reach: Main Profile: 100 Yr. River Sta Plan W.S. Elev W.S. Elev Project Impact 100 yr.100 yr 100-yr Elevation w/FW Revised-Duplicate (ft)(ft)(ft) HEC-RAS River: Buffalo Creek Reach: Main Profile: 100 Yr. 11991 Floodway Run 125.84 126.72 11991 DUP EFF FW 125.84 126.72 11991 REV 125.84 126.72 0.00 11691 Floodway Run 125.45 126.28 11691 DUP EFF FW 125.45 126.28 11691 REV 125.46 126.28 0.01 11230 Floodway Run 124.88 125.62 11230 DUP EFF FW 124.88 125.62 11230 REV 124.89 125.62 0.01 10921 Floodway Run 124.72 125.44 10921 DUP EFF FW 124.71 125.44 10921 REV 124.73 125.44 0.02 10646 Floodway Run 124.65 125.35 10646 DUP EFF FW 124.64 125.35 10646 REV 124.66 125.35 0.02 10333 Floodway Run 124.60 125.29 10333 DUP EFF FW 124.59 125.29 10333 REV 124.61 125.29 0.02 10072 Floodway Run 124.57 125.23 10072 DUP EFF FW 124.57 125.23 10072 REV 124.59 125.23 0.02 9676 Floodway Run 124.56 125.18 9676 DUP EFF FW 124.55 125.18 9676 REV 124.57 125.18 0.02 9287 Floodway Run 124.53 125.13 9287 DUP EFF FW 124.53 125.13 9287 REV 124.55 125.13 0.02 8630 Floodway Run 124.5 125.05 8630 DUP EFF FW 124.49 125.05 8630 REV 124.51 125.05 0.02 8232 Floodway Run 124.47 125 River Sta Plan W.S. Elev W.S. Elev Project Impact 100 yr.100 yr 100-yr Elevation w/FW Revised-Duplicate (ft)(ft)(ft) HEC-RAS River: Buffalo Creek Reach: Main Profile: 100 Yr. 8232 DUP EFF FW 124.47 125 8232 REV 124.48 125 0.01 7804 Floodway Run 124.45 124.95 7804 DUP EFF FW 124.44 124.95 7804 REV 124.46 124.95 0.02 7449 Floodway Run 124.43 124.88 7449 DUP EFF FW 124.42 124.88 7449 REV 124.44 124.88 0.02 7068 Floodway Run 124.41 124.85 7068 DUP EFF FW 124.41 124.85 7068 REV 124.43 124.85 0.02 6746 Floodway Run 124.40 124.82 6746 DUP EFF FW 124.40 124.82 6746 REV 124.42 124.82 0.02 6185 Floodway Run 124.39 124.79 6185 DUP EFF FW 124.38 124.78 6185 REV 124.40 124.78 0.02 5650 Floodway Run 124.37 124.75 5650 DUP EFF FW 124.36 124.75 5650 REV 124.38 124.75 0.02 4978 Floodway Run 124.34 124.71 4978 DUP EFF FW 124.34 124.71 4978 REV 124.35 124.71 0.01 4848 Culvert 4769 Floodway Run 119.14 119.66 4769 DUP EFF FW 119.13 119.66 4769 REV 119.17 119.66 0.04 4732 Floodway Run 119.13 119.66 4732 DUP EFF FW 119.12 119.66 4732 REV 119.16 119.66 0.04 4697 Bridge River Sta Plan W.S. Elev W.S. Elev Project Impact 100 yr.100 yr 100-yr Elevation w/FW Revised-Duplicate (ft)(ft)(ft) HEC-RAS River: Buffalo Creek Reach: Main Profile: 100 Yr. 4645 Floodway Run 119.11 119.57 4645 DUP EFF FW 119.10 119.57 4645 REV 119.14 119.57 0.04 3796 Floodway Run 119.02 119.47 3796 DUP EFF FW 119.01 119.47 3796 REV 119.05 119.47 0.04 3130 Floodway Run 118.97 119.35 3130 DUP EFF FW 118.96 119.35 3130 REV 119.00 119.35 0.04 3070 Culvert 2986 Floodway Run 117.99 118.99 2986 DUP EFF FW 117.99 118.99 2986 REV 118.02 118.99 0.03 2457 Floodway Run 117.87 118.85 2457 DUP EFF FW 117.87 118.85 2457 REV 117.87 118.85 0.00 1807 Floodway Run 117.57 118.52 1807 DUP EFF FW 117.57 118.52 1807 REV 117.57 118.52 0.00 1398 Floodway Run 117.48 118.45 1398 DUP EFF FW 117.48 118.45 1398 REV 117.48 118.45 0.00 828 Floodway Run 117.31 118.27 828 DUP EFF FW 117.31 118.27 828 REV 117.31 118.27 0.00 322 Floodway Run 117.00 117.74 322 DUP EFF FW 117.00 117.74 322 REV 117.00 117.74 0.00 268 Bridge 204 Floodway Run 116.30 117.24 River Sta Plan W.S. Elev W.S. Elev Project Impact 100 yr.100 yr 100-yr Elevation w/FW Revised-Duplicate (ft)(ft)(ft) HEC-RAS River: Buffalo Creek Reach: Main Profile: 100 Yr. 204 DUP EFF FW 116.30 117.24 204 REV 116.30 117.24 0.00 Denotes Maximum Increase in 100-year Event River Sta Plan W.S. Elev W.S. Elev W.S. Elev 10 yr.50 yr 500 yr (ft)(ft)(ft) 14814 Floodway Run 134.10 136.61 137.46 14814 DUP EFF FW 134.10 136.61 137.46 14814 REV 134.10 136.61 137.46 14596 Floodway Run 133.37 136.16 137.16 14596 DUP EFF FW 133.37 136.16 137.16 14596 REV 133.37 136.16 137.16 14511 Culvert Culvert Culvert 14419 Floodway Run 132.64 134.27 136.19 14419 DUP EFF FW 132.64 134.27 136.19 14419 REV 132.64 134.27 136.19 14195 Floodway Run 131.78 133.35 135.07 14195 DUP EFF FW 131.78 133.35 135.07 14195 REV 131.78 133.35 135.07 13945 Floodway Run 130.58 131.75 132.82 13945 DUP EFF FW 130.58 131.75 132.82 13945 REV 130.58 131.75 132.82 13713 Floodway Run 129.18 130.29 131.46 13713 DUP EFF FW 129.18 130.29 131.46 13713 REV 129.18 130.29 131.46 13388 Floodway Run 127.93 128.89 129.94 13388 DUP EFF FW 127.93 128.89 129.94 13388 REV 127.93 128.89 129.94 13000 Floodway Run 126.41 127.53 128.68 13000 DUP EFF FW 126.41 127.53 128.68 13000 REV 126.41 127.53 128.68 12671 Floodway Run 125.30 126.44 127.74 12671 DUP EFF FW 125.30 126.44 127.74 12671 REV 125.30 126.44 127.74 12343 Floodway Run 124.69 125.82 127.2 12343 DUP EFF FW 124.69 125.82 127.2 12343 REV 124.69 125.82 127.2 HEC-RAS River: Buffalo Creek Reach: Main Profile: Multiple River Sta Plan W.S. Elev W.S. Elev W.S. Elev 10 yr.50 yr 500 yr (ft)(ft)(ft) HEC-RAS River: Buffalo Creek Reach: Main Profile: Multiple 11991 Floodway Run 124.16 125.29 126.74 11991 DUP EFF FW 124.16 125.29 126.74 11991 REV 124.16 125.29 126.74 11691 Floodway Run 123.72 124.82 126.34 11691 DUP EFF FW 123.72 124.82 126.34 11691 REV 123.72 124.82 126.34 11230 Floodway Run 122.43 123.92 125.82 11230 DUP EFF FW 122.43 123.91 125.82 11230 REV 122.43 123.91 125.82 10921 Floodway Run 121.52 123.6 125.67 10921 DUP EFF FW 121.52 123.59 125.67 10921 REV 121.52 123.59 125.67 10646 Floodway Run 121.01 123.48 125.59 10646 DUP EFF FW 121.01 123.47 125.59 10646 REV 121.01 123.47 125.59 10333 Floodway Run 120.70 123.4 125.54 10333 DUP EFF FW 120.70 123.39 125.54 10333 REV 120.70 123.39 125.54 10072 Floodway Run 120.53 123.36 125.51 10072 DUP EFF FW 120.53 123.35 125.51 10072 REV 120.53 123.35 125.51 9676 Floodway Run 120.41 123.34 125.49 9676 DUP EFF FW 120.41 123.32 125.49 9676 REV 120.41 123.33 125.49 9287 Floodway Run 120.34 123.31 125.46 9287 DUP EFF FW 120.34 123.29 125.46 9287 REV 120.34 123.3 125.46 8630 Floodway Run 120.25 123.26 125.41 8630 DUP EFF FW 120.25 123.24 125.41 8630 REV 120.25 123.25 125.41 8232 Floodway Run 120.19 123.23 125.37 River Sta Plan W.S. Elev W.S. Elev W.S. Elev 10 yr.50 yr 500 yr (ft)(ft)(ft) HEC-RAS River: Buffalo Creek Reach: Main Profile: Multiple 8232 DUP EFF FW 120.19 123.21 125.37 8232 REV 120.19 123.21 125.37 7804 Floodway Run 120.14 123.2 125.34 7804 DUP EFF FW 120.14 123.18 125.34 7804 REV 120.14 123.19 125.34 7449 Floodway Run 120.11 123.17 125.31 7449 DUP EFF FW 120.11 123.16 125.31 7449 REV 120.11 123.16 125.31 7068 Floodway Run 120.08 123.16 125.29 7068 DUP EFF FW 120.08 123.15 125.29 7068 REV 120.09 123.15 125.29 6746 Floodway Run 120.07 123.15 125.28 6746 DUP EFF FW 120.07 123.13 125.28 6746 REV 120.07 123.14 125.28 6185 Floodway Run 120.04 123.13 125.25 6185 DUP EFF FW 120.04 123.11 125.25 6185 REV 120.04 123.12 125.25 5650 Floodway Run 120.02 123.1 125.22 5650 DUP EFF FW 120.02 123.09 125.22 5650 REV 120.02 123.09 125.22 4978 Floodway Run 119.98 123.07 125.18 4978 DUP EFF FW 119.98 123.06 125.19 4978 REV 119.99 123.06 125.18 4848 Culvert Culvert Culvert 4769 Floodway Run 118.41 119.01 119.61 4769 DUP EFF FW 118.42 118.98 119.6 4769 REV 118.42 118.99 119.62 4732 Floodway Run 118.41 119 119.61 4732 DUP EFF FW 118.41 118.98 119.6 4732 REV 118.42 118.98 119.62 4697 Bridge Bridge Bridge River Sta Plan W.S. Elev W.S. Elev W.S. Elev 10 yr.50 yr 500 yr (ft)(ft)(ft) HEC-RAS River: Buffalo Creek Reach: Main Profile: Multiple 4645 Floodway Run 118.39 118.97 119.57 4645 DUP EFF FW 118.40 118.94 119.57 4645 REV 118.40 118.94 119.59 3796 Floodway Run 118.36 118.9 119.43 3796 DUP EFF FW 118.37 118.87 119.43 3796 REV 118.37 118.88 119.45 3130 Floodway Run 118.34 118.85 119.34 3130 DUP EFF FW 118.35 118.83 119.34 3130 REV 118.35 118.83 119.36 3070 Culvert Culvert Culvert 2986 Floodway Run 115.67 117.54 119.12 2986 DUP EFF FW 115.67 117.54 119.12 2986 REV 115.69 117.57 119.16 2457 Floodway Run 115.55 117.43 118.98 2457 DUP EFF FW 115.55 117.43 118.98 2457 REV 115.55 117.43 118.99 1807 Floodway Run 115.14 117.12 118.69 1807 DUP EFF FW 115.14 117.12 118.69 1807 REV 115.14 117.12 118.69 1398 Floodway Run 115.05 117.04 118.59 1398 DUP EFF FW 115.05 117.04 118.59 1398 REV 115.05 117.04 118.59 828 Floodway Run 114.78 116.87 118.41 828 DUP EFF FW 114.78 116.87 118.41 828 REV 114.78 116.87 118.41 322 Floodway Run 114.17 116.56 118.09 322 DUP EFF FW 114.17 116.56 118.09 322 REV 114.17 116.56 118.09 268 Bridge Bridge Bridge 204 Floodway Run 113.88 115.81 117.61 River Sta Plan W.S. Elev W.S. Elev W.S. Elev 10 yr.50 yr 500 yr (ft)(ft)(ft) HEC-RAS River: Buffalo Creek Reach: Main Profile: Multiple 204 DUP EFF FW 113.88 115.81 117.61 204 REV 113.88 115.81 117.61