CLEVELAND COUNTY, OKLAHOMA AND INCORPORATED AREAS VOLUME 1 OF 3

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1 CLEVELAND COUNTY, OKLAHOMA AND INCORPORATED S VOLUME 1 OF 3 PRELIMINARY SEPTEMBER 30, 2011 Community Name Community Number CLEVELAND COUNTY, UNINCORPORATED S LEXINGTON, CITY OF MOORE, CITY OF NOBLE, CITY OF NORMAN, CITY OF OKLAHOMA CITY, CITY OF PURCELL, CITY OF SLAUGHTERVILLE, TOWN OF REVISED: Cleveland County Federal Emergency Management Agency FLOOD INSURANCE STUDY NUMBER 40027CV001B

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 may not contain all data available within the repository. It is advisable to contact the community repository for any additional data. Part or all of this Flood Insurance Study may be revised and republished at any time. In addition, part of this Flood Insurance Study may be revised by the Letter of Map Revision process, which does not involve republication or redistribution of the Flood Insurance Study. It is, therefore, the responsibility of the user to consult with community officials and to check the community repository to obtain the most current Flood Insurance Study components. A listing of the Community Map Repositories can be found on the Index Map. Initial Countywide FIS Effective Date: March 17, 1997 Revised Countywide FIS Dates: January 20, to add Base Flood Elevations, to change Special Flood Hazard Areas, to change zone designations, and to add roads and road names. September 26, to update corporate limits, to change Base Flood Elevations and Special Flood Hazard Areas, to update map format, to add roads and road names, to incorporate previously issued Letters of Map Revision. - to change Base Flood Elevations and Special Flood Hazard Areas, to add roads and road names, to incorporate previously issued Letters of Map Revision.

3 TABLE OF CONTENTS VOLUME INTRODUCTION PURPOSE OF STUDY AUTHORITY AND ACKNOWLEDGMENTS COORDINATION 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 S INSURANCE APPLICATION FLOOD INSURANCE RATE MAP OTHER STUDIES LOCATION OF DATA BIBLIOGRAPHY AND REFERENCES FIGURES FIGURE 1. - SCHEMATIC TABLES TABLE 1. - FLOOD INSURANCE STUDY CONTRACTORS FOR INCORPORATED COMMUNITIES...2 TABLE 2. - STREAMS STUDIED BY DETAILED METHODS TABLE 3. LETTERS OF MAP CHANGE TABLE 4. - SUMMARY OF DISCHARGES TABLE 5. SUMMARY OF ELEVATIONS 30 TABLE 6. - MANNING S n VALUES...35 TABLE 7. - DATA TABLE 8. - COMMUNITY MAP HISTORY i

4 TABLE OF CONTENTS VOLUME 2 Exhibit 1 - Flood Profiles Belle Creek Panel 01P Bishop Creek Panels 02P-09P Bishop Creek Tributary A Panels 10P-11P Bishop Creek Tributary B Panels 12P-13P Bishop Creek Tributary C Panel 14P Brookhaven Creek Panels 15P-18P Brookhaven Creek Tributary A Panel 19P Brookhaven Creek Tributary B Panel 20P Canadian River Panels 21P-29P Canadian River Left Bank Overflow Near Norman (Ten Mile Flat Creek) Panel 30P Canadian River Tributary 1 Panels 31P-35P Canadian River Tributary 2 Panels 36P-39P Chouteau Creek (North of Lexington) Panels 40P-44P Cow Creek Panels 45P-47P Cow Creek Tributary 1 Panels 48P-50P Cow Creek Tributary 2 Panels 51P-54P Cow Creek Tributary 2 North Branch Panels 55P-57P Cow Creek Tributary 2 West Branch Panel 58P Cow Creek Tributary 3 Panels 59P-60P Dave Blue Creek Panels 61P-62P Dave Blue Creek North Panel 63P Dripping Springs Creek Panels 64P-65P East Rock Creek Panel 66P VOLUME 3 Exhibit 1 - Flood Profiles (Continued) Hog Creek Panels 67P-70P Hog Creek Tributary 1 Panels 71P-72P Hog Creek Tributary 2 Panels 73P-74P Hog Creek East Branch Panel 75P Hog Creek West Branch Panels 76P-78P Hog Creek West Branch Tributary 1 Panel 79P Hog Creek West Branch Tributary 2 Panels 80P-82P Imhoff Creek Panels 83P-87P Kelley Creek Panels 88P-90P Lightning Creek Panel 91P Little River Panels 92P-97P Merkle Creek Panels 98P-100P Merkle Creek Overflow Panel 101P ii

5 TABLE OF CONTENTS VOLUME 3 Continued North Fork River Panels 102P-104P Northmoor Creek Panels 105P-106P Rock Creek Panels 107P-109P Stream A Panel 110P Stream B Panels 111P-112P Stream C Panels 113P-114P Stream D Panels 115P-118P Stream E Panels 119P-121P Tributary 0 of Canadian River Tributary 1 Panels 122P-125P Tributary 1 of Canadian River Tributary 1 Panels 126P-127P Tributary 1 of Tributary 1 of Canadian River Tributary 1 Panel 128P Tributary 2 of Canadian River Tributary 1 Panels 129P-130P Tributary 3 of Canadian River Tributary 1 Panels 131P-132P Tributary 4 of Canadian River Tributary 1 Panel 133P Tributary to Stream D Panel 134P Unnamed Tributary to Cow Creek Tributary 2 North Branch Panel 135P Unnamed Tributary to Little River Panels 136P-137P Unnamed Tributary to Stream E Panel 138P Unnamed Tributary to Tributary 3 of Canadian River Tributary 1 Panel 139P Exhibit 2 - Flood Insurance Rate Map Index Flood Insurance Rate Map iii

6 FLOOD INSURANCE STUDY LAHOMA, AND INCORPORATED S 1.0 INTRODUCTION 1.1 PURPOSE OF STUDY This Flood Insurance Study (FIS) revises and updates previous FIS reports and/or Flood Insurance Rate Maps (FIRMs) (References 1 through 6) in the geographic area of Cleveland County, Oklahoma, including the Cities of Lexington, Moore, Noble, Norman, Purcell, and Oklahoma City and the Town of Slaughterville, and the unincorporated areas of Cleveland County (hereinafter referred to collectively as Cleveland County), and aids in the administration of the National Flood Insurance Act of 1968 and the Flood Disaster Protection Act of This study has developed flood risk data for various areas of the community that will be used to establish actuarial flood insurance rates and to assist the community in its efforts to promote sound floodplain management. Minimum floodplain management requirements for participation in the National Flood Insurance Program (NFIP) are set forth in the Code of Federal Regulations at 44 CFR, Please note that the City of Oklahoma City is geographically located in Cleveland, Canadian, Oklahoma, and Pottawatomie Counties. Please note that the City of Purcell is geographically located in Cleveland and McClain Counties. In some states or communities, floodplain management criteria or regulations may exist that are more restrictive or comprehensive than the minimum Federal requirements. In such cases, the more restrictive criteria take precedence and the State (or other jurisdictional agency) will be able to explain them. 1.2 AUTHORITY AND ACKNOWLEDGMENTS The sources of authority for this Flood Insurance Study are the National Flood Insurance Act of 1968 and the Flood Disaster Protection Act of The Flood Hazard Boundary Maps for Cleveland County, Oklahoma and the FIRM for the Town of Slaughterville, Oklahoma were published on June 11, 1982 (and revised June 1, 1989), and April 15, 1992, respectively (References 6 and 7). The hydrologic and hydraulic analyses for the initial study for the City of Lexington were performed by the Natural Resource Conservation Service (NRCS) formerly known as the Soil Conservation Service (SCS), for the Federal Emergency Management Agency (FEMA) formerly known as the Federal Insurance Administration (FIA), under Contract No. IAA- H This study was completed in June 1979 (see Table 1). The hydrologic and hydraulic analyses for the initial study for the City of Moore were prepared by Benham-Blair & Associates, Inc., for FEMA, under Contract No. H This work was completed in June The updated hydraulic analysis for the North Fork River was prepared by Phillips, Stong, and Coon, under agreement with FEMA. The updated work was completed in August The approximate study performed on Stream E was also revised on the basis of data submitted in a Letter of Map Amendment (LOMA) request by Dodson-Roberts Surveying. 1

7 The November 9, 1987, hydrologic and hydraulic analyses for the North Fork River were prepared by the firm of Clarke-Irwin. This work was completed on December 2, The hydrologic and hydraulic analyses in this revision for Stream D and Tributary to Stream D were prepared by John Doyle Engineering Co. Table 1. Flood Insurance Study Contractors for Incorporated Communities Contract or Interagency Community Name Study Contractor Agreement Number Completion Date Lexington, City of NRCS (SCS) IAA-H June 1979 Moore, City of Benham-Blair & Associates, Inc. H-4642 June 1979 Noble, City of NRCS (SCS) IAA-H-17-78, Project Order No. 8 November 1979 Norman, City of USACE IAA-H-16-75, Project Order No. 9 June 1977 Slaughterville, Town of USACE IAA-EMW-95-E-4759, Project No. 4 September 1997 The hydrologic and hydraulic analyses for the reach of Little River upstream of Olympic Street extended, and for Kelley Creek and Northmoor Creek were performed by the U.S. Army Corps of Engineers (USACE), Tulsa District, and presented in a report entitled "Moore, Oklahoma, Special Flood Hazard Area," dated December The hydrologic and hydraulic analyses for the initial study for the City of Noble were performed by the U.S. Department of Agriculture (USDA), NRCS, for FEMA, under Interagency Agreement No. IAA-H-17-78, Project Order No. 8. This study was completed in November Approximate flood boundaries for the City of Noble were determined in January 1976, by Michael Baker Jr., Inc., under contract to FEMA. The hydrologic and hydraulic analyses for the initial study for the City of Norman were performed by the USACE, Tulsa District, for FEMA, under Interagency Agreement No. IAA-H-16-75, Project Order No. 19, and IAA-H-07-76, Project Order No. 1. This work, which was completed in June 1977, covered all significant flooding sources in the City of Norman. The FIRM for the Town of Slaughterville was created from the FIRM.for Cleveland County. Revised hydrologic and hydraulic analyses were performed along Chouteau and Dripping Springs Creeks affecting the Town of Slaughterville and the unincorporated areas of Cleveland County. This restudy was performed by the U.S. Army Corps of Engineers (USACE), Tulsa District, under Interagency Agreement No. EMW-95-E-4759, Project 2

8 Order No. 4, Amendment No. 1, and completed in September This study was also revised to incorporate the determination of a Letter of Map Revision (LOMR) dated May 15, 1997, along Imhoff Creek. The revised maps went effective on January 20, Under Contract No. EMT-2002-CO-0048 for the Federal Emergency Management Agency (FEMA), Watershed VI Alliance combined communities within Cleveland County, as well as the unincorporated areas, into a countywide Flood Insurance Study, as compiled from previously published Flood Insurance Study report narratives. Watershed VI Alliance also completed hydrologic and hydraulic analyses on several riverine streams and incorporated a study from Clour Engineering on Dave Blue Creek North. The revised maps went effective on September 26, The hydrologic and hydraulic analyses for this revision of Dave Blue Creek, Little River, Stream A, Stream E, Tributary 3 of Canadian River Tributary 1, Unnamed Tributary to Cow Creek Tributary 2 North Branch, and Unnamed Tributary to Little River were performed by Risk Assessment, Mapping, and Planning Partners (RAMPP), for FEMA under Contract No. HSFEHQ-09-D-0369, Task Order HSFE06-09-J Base map information was provided in digital format by the Geo Information Systems department of the University of Oklahoma and by the City of Norman, GIS Division. The coordinate system used for the production of this FIRM is Oklahoma State Plane South zone (FIPSZONE 3502) and North American Datum of 1983 (NAD 83) GRS80 spheroid horizontal datum. 1.3 COORDINATION The results of the September 26, 2008, countywide revision were reviewed at the final Consultation and Coordination Officer s (CCO) meeting held on December 7, 2006, and attended by representatives of FEMA; the Oklahoma Water Resources Board; the Cities of Lexington, Moore, Noble, Norman, and Oklahoma City; the Town of Slaughterville; Cleveland County; and the study contractor. All problems raised at that meeting have been addressed in this study. The history of the Flood Insurance Studies coordination activities for the individual communities before this countywide are presented below. City of Lexington The initial CCO meeting was held in December 1977 and attended by representatives of FEMA, the NRCS, and the Town of Lexington. During the meeting, streams requiring detailed study were identified. Results of the hydraulic analyses were coordinated with the U.S. Geological Survey (USGS) published reports and the draft Norman Flood Insurance Study prepared by the USACE. On January 7, 1980, the results of the study were reviewed at the final meeting attended by representatives of FEMA, the NRCS, and community officials. The study was acceptable to the community. 3

9 City of Moore On March 15, 1978, the nature and purpose of the study were explained, corporate boundaries were delineated, and streams requiring detailed and approximate study were identified at an initial CCO meeting attended by representatives of FEMA, the City of Moore, and Benham-Blair & Affiliates, Inc. (the original study contractor). An announcement was placed in the local newspaper at the beginning of the study stating its objectives and designating a city official that should be contacted for those having information pertinent to the study. On January 7, 1980, the results of the study were reviewed at a final CCO meeting held with representatives of FEMA, the city, and the study contractor. City of Noble Streams requiring detailed study were identified at a meeting attended by representatives of the study contractor, FEMA, and representatives of the City of Noble in December Results of the hydrologic analyses were coordinated with the USGS published reports and the draft Norman Flood Insurance Study prepared by the USACE. On August 12, 1980, the results of the study were reviewed at the final meeting attended by representatives of the study contractor, FEMA, and community officials. The study was acceptable to the community. City of Norman A search for pertinent information was made at all levels of local, state, and Federal government. Public officials and local interests were informed about the study and its intended purposes at a meeting held in the City of Norman on December 19, Attendees included representatives from the City of Norman, the USDA, NRCS, and the USACE, Tulsa District. Streams to be studied in detail and by approximate methods were selected. On August 5, 1975, FEMA conducted an initial coordination meeting with city, state, and Federal officials and the local public to provide a complete understanding of the scope of work and to solicit and encourage community input into the study. Periodically, City of Norman officials were briefed about the progress of the report. A final coordination meeting was held in Norman on September 8, 1977, to present the results of the study. City officials were previously furnished draft copies of the Flood Insurance Study report. The initial CCO meeting for this countywide revision was held with representatives of FEMA, the communities, and the study contractors on October 27, 2009 to identify the streams to be studied by detailed methods. 2.0 STUDIED 2.1 SCOPE OF STUDY This Flood Insurance Study covers the geographic area of Cleveland County, Oklahoma, including the incorporated communities listed in section

10 Streams studied by detailed methods are provided in Table 2. The stream study types are identified as being either Detail or Redelineation. Detail streams are those streams that were newly studied within the County. The Redelineation streams are those streams previously studied and had elevations and flood boundaries adjusted to conform to the new maps datum and topographic data. 2.2 COMMUNITY DESCRIPTION Cleveland County is located in Central Oklahoma. It has a land area of approximately 529 square miles. The Canadian River flows southeast, forming the west boundary of the county. The City of Oklahoma City, which is part of one of the largest metropolitan areas in the nation, lies in the north. Cleveland County is bordered by Oklahoma County in the north, Pottawatomie County in the east, McClain County in the south and west, and Canadian County in the northwest. The City of Norman is the county seat. Beginning as a tent city in April 1889, Cleveland County has grown to a population of 255,755 in 2010, which includes the population in the incorporated cities (Reference 8). Local enterprises and economic contributors include agriculture, light industry, the University of Oklahoma, Tinker Air Force Base, and Central State Hospital. Cleveland County is located among gently rolling hills. Native vegetation consists of prairie grasses, scrub oak and scattered hard-wood trees. The topography varies from semi-arid, flat upland to gently rolling. The County is served by U.S. Highways 9, 37, 39, 59, 62, and 77, and Interstate Highways 35 and 44. Air service is provided by Oklahoma City's airport. At present, Oklahoma City, the City of Norman, and the City of Noble are experiencing rapid growth. In the City of Norman, the present development trend within the city's corporate limits is generally to the west, in the Brookhaven Creek watershed. The majority of development in the watersheds of Imhoff, Merkle, Brookhaven, and Rock Creeks is residential and limited commercial. Floodplain areas along the streams are typically open grass and farmland, except along the riparian areas where tree and brush concentrations vary from scattered to dense. Floodplains along smaller streams are narrow and generally densely wooded. Land use along the larger streams is principally agricultural, while land use along the floodplains of the smaller streams in the western parts of the county is commercial or residential. 5

11 Stream Study Type Table 2. Streams Studied by Detailed Methods Reach Length, (miles) Study Area Belle Creek Redelineation 1.4 From Cemetery Road upstream to a point located approximately 1,900 feet upstream of Maguire Road Bishop Creek Redelineation 6.9 From its confluence with the Canadian River upstream to Carter Avenue Bishop Creek Tributary A Redelineation 1.9 From its confluence with Bishop Creek upstream to a point located approximately 600 feet upstream of Sinclair Drive Bishop Creek Tributary B Redelineation 0.7 From its confluence with Bishop Creek upstream to Acres Street Bishop Creek Tributary C Redelineation 0.8 From its confluence with Bishop Creek upstream to a point located approximately 470 feet upstream of Brooks Street Brookhaven Creek Redelineation 3.9 From its confluence with the Canadian River upstream to Rock Creek Road Brookhaven Creek Tributary A Redelineation 0.4 From its confluence with Brookhaven Creek upstream to Rock Creek Road Brookhaven Creek Tributary B Redelineation 0.2 From the mouth to approximately 920 feet upstream Canadian River Redelineation 38.2 From approximately 16,350 feet downstream of U.S. Highway 77 upstream to the Canadian River Left Bank Overflow near Norman Redelineation 4.0 Cleveland County, Oklahoma, county boundary From railroad bridge upstream to Tecumseh Road Canadian River Tributary 1 Redelineation 5.7 From its confluence with Canadian River upstream to a point located approximately 225 feet upstream of SW 104th Street Canadian River Tributary 2 Redelineation 4.7 From its confluence with Canadian River upstream to a point located approximately 6,924 feet upstream of 119th Street Chouteau Creek Redelineation 6.7 From its confluence with Canadian River upstream to Cemetery Road Cow Creek Redelineation 6.5 From its confluence with Canadian River upstream to a point located approximately 1,100 feet upstream of an earth dam Cow Creek Tributary 1 Redelineation 2.3 From its confluence with Cow Creek upstream to a point located approximately 150 feet upstream of SW 104th Street Cow Creek Tributary 2 Redelineation 4.1 From its confluence with Cow Creek to the Cleveland County, Oklahoma, county boundary Cow Creek Tributary 2 North From its confluence with Cow Creek Tributary 2 upstream to a point located Redelineation 3.0 Branch approximately 7,700 feet upstream of Rockwell Avenue Cow Creek Tributary 2 West From its confluence with Cow Creek Tributary 2 upstream to a point located Redelineation 0.9 Branch approximately 1,300 feet upstream of SW 104th Street 6

12 Table 2. Streams Studied by Detailed Methods (continued) Stream Study Type Reach Length, (miles) Study Area Cow Creek Tributary 3 Redelineation 2.0 From its confluence with Cow Creek upstream to a point located approximately 2,750 feet upstream of Dirt Road Dave Blue Creek Redelineation 0.9 From its confluence with Still Creek upstream to a point located approximately 450 feet downstream of North Main Street Dave Blue Creek Detail 1.2 From a point located approximately 450 feet downstream of North Main Street upstream to a point approximately 0.4 mile upstream of Post Oak Road Dave Blue Creek North Detail 0.8 From approximately 50 feet downstream of State Highway 9 to a point located approximately 4,125 feet upstream of State Highway 9 Dripping Springs Creek Redelineation 4.4 From its confluence with Chouteau Creek upstream to a point located approximately 3,750 feet upstream of Maguire Road East Rock Creek Detail 1.0 From a point located approximately 500 feet downstream of 36th Avenue NE upstream to a point located approximately 350 feet upstream of Private Drive Hog Creek Redelineation 4.3 From SE 149th Street upstream to the Cleveland County, Oklahoma, county boundary Hog Creek Tributary 1 Redelineation 1.5 From its confluence with Hog Creek upstream to a point located approximately 5,450 feet upstream of Choctaw Road Hog Creek Tributary 2 Redelineation 1.8 From a point located approximately 1,700 feet downstream of earthfill dam upstream to a point located approximately 1,600 feet upstream of SE 104th Street Hog Creek East Branch Redelineation 0.6 From its confluence with Hog Creek upstream to the Cleveland County, Oklahoma, county boundary Hog Creek West From its confluence with Hog Creek upstream to SE 89th Street Redelineation 1.8 Branch Hog Creek West From the mouth to approximately 960 feet upstream Redelineation 0.2 Branch Tributary 1 Hog Creek West From its confluence with Hog Creek West Branch upstream to a point located approximately Redelineation 1.2 Branch Tributary 2 4,850 feet upstream of Hiwassee Road Imhoff Creek Redelineation 3.7 From its confluence with the Canadian River upstream to the Atchison, Topeka, and Santa Fe Railway Kelley Creek Redelineation 0.7 From its confluence with Little River upstream to a point located approximately 675 feet upstream of North Markwell Avenue Lightning Creek Redelineation 0.7 From Cleveland County, Oklahoma, county boundary upstream to a point located approximately 100 feet upstream of Walker Avenue Little River Detail 8.0 From a point located approximately 600 feet downstream of 12th Avenue NE upstream to a point located approximately 4,500 feet downstream of Southwest 34th Street 7

13 Table 2. Streams Studied by Detailed Methods (continued) Stream Study Type Reach Length, (miles) Study Area Little River Redelineation 5.6 From a point located approximately 4,500 feet downstream of Southwest 34th Street upstream to a point located just upstream of Nail Parkway Merkle Creek Redelineation 3.1 From a point located just downstream of Interstate 35 upstream to West Robinson Street North Fork River Redelineation 6.9 From a point approximately 4,900 feet downstream of South Sunnylane Road upstream to a point approximately 500 feet upstream of Northeast 23rd Street Northmoor Creek Redelineation 1.3 From its confluence with Little River upstream to a point located approximately 1,700 feet upstream of Northeast 27th Street Rock Creek Redelineation 2.4 From the limit of backwater from Little River approximately 1,270 feet above mouth upstream to a point located approximately 2,450 feet upstream of East Rock Creek Road Stream A Detail 1.1 From its confluence with North Fork River upstream to a point located approximately 400 feet upstream of Sooner Drive Stream B Detail 1.4 From its confluence with North Fork River upstream to a point located approximately 1,800 feet upstream of Southeast 19th Street Stream C Redelineation 3.0 From its confluence with North Fork River upstream to a point located approximately 4,720 feet upstream of Northeast 12th Street Stream D Redelineation 3.7 From its confluence with North Fork River upstream to Northwest 3rd Street Stream E Redelineation 0.9 From a point located approximately 9,600 feet upstream of its confluence with Little River upstream to a point located approximately 2,200 feet upstream of the confluence of Unnamed Tributary to Stream E Stream E Detail 1.5 From a point located approximately 2,200 feet upstream of the confluence of Unnamed Tributary Tributary 0 of Canadian River Tributary 1 Tributary 1 of Canadian River Tributary 1 Tributary 2 of Canadian River Tributary 1 Tributary 3 of Canadian River Tributary 1 Detail 4.3 Redelineation 1.7 Redelineation 2.3 Redelineation 0.9 to Stream E upstream to a point located approximately 900 feet upstream of Penn Lane. From its confluence with Canadian River Tributary 1 to a point located approximately 700 feet upstream of North Nottingham Way From its confluence with Canadian River Tributary 1 to a point located approximately 9,000 feet upstream of its confluence with Canadian River Tributary 1 From its confluence with Canadian River Tributary 1 to a point located approximately 4,850 feet upstream of South Western Avenue From its confluence with Canadian River Tributary 1 upstream to a point approximately 800 feet downstream of Southwest 119th Street 8

14 Table 2. Streams Studied by Detailed Methods (continued) Stream Tributary 3 of Canadian River Tributary 1 Tributary 4 of Canadian River Tributary 1 Study Type Reach Length, (miles) Detail 1.0 Redelineation 1.1 Tributary to Stream D Redelineation 0.2 Unnamed Tributary to Cow Creek Tributary 2 North Branch Unnamed Tributary to Little River Unnamed Tributary to Stream E Detail 0.8 Detail 1.9 Redelineation 0.3 Study Area From a point approximately 800 feet downstream of Southwest 119th Street upstream to a point approximately 350 feet upstream of Southwest 107th Street From its confluence with Canadian River Tributary 1 to a point located approximately 5,550 feet upstream of its confluence with Canadian River Tributary 1 From its confluence with Stream D upstream to a point located approximately 975 feet upstream of its confluence with Stream D From its confluence with Cow Creek Tributary 2 North Branch to a point located approximately 4,000 feet upstream of the confluence of Cow Creek Tributary 2 North Branch From its confluence with Little River upstream to a point approximately 300 feet upstream of Southwest 34 th Street From its confluence with Stream E upstream to a point located approximately 1,400 feet upstream of its confluence with Stream E 9

15 This revision also incorporates Letters of Map Change (LOMCs) issued by FEMA for updated areas within the revised panels between September 2008 and July 2011, including all or portions of the Letters of Map Revision (LOMRs) shown below in Table 3: Letters of Map Change. Table 3. Letters of Map Change Flooding Source Case Number Project Identifier Effective Date North Fork River \ Stream C P Rock Creek Estates Reissuance LOMR 03/19/2009 Unnamed Tributary to Tributary 3 of Canadian River Tributary P Greenbriar Pointe, Section 1 (Reissuance of LOMR P) 07/27/2009 Canadian River Tributary 1 / Tributary 3 of Canadian River Tributary P Vintage Farms Addition, Section 3 01/22/2010 North Fork River P Seiter Farms Addition (Reissuance of LOMR P) 02/02/2010 Bishop Creek / Bishop Creek Tributary C Tributary 3 of Canadian River Tributary 1 North Fork River \ Stream A Tributary 1of Canadian River Tributary P Bishop Creek (Reissuance of LOMR P) 02/05/ P Kingsbrook Floodplain Revision 07/28/ P Joshua s Landing 4/25/ P Cascata Lakes 7/28/2011 Brookhaven Creek Tributary A P Heritage Fine Homes Property The climate in Central Oklahoma is subhumid. The average annual temperature is about 61 F, with ranges of 37 F in January to 83 F in July. Annual average precipitation of the region is 33 inches, which occurs during the growing season. Snowfall is about 10 inches (Reference 9). The Canadian River originates near the Colorado-New Mexico border, about 110 miles west of the Oklahoma panhandle, and flows eastward to its 10

16 confluence with Eufaula Lake in eastern Oklahoma. The total drainage area of the basin is about 47,705 square miles. Willow Creek and East and West Willow Creeks flow south-southeast and drain into the Canadian River. The drainage pattern in the study area is dominated by the Canadian River. Chouteau Creek, affecting the City of Lexington, originates 2.5 miles north of City of Lexington and flows south through the center of town, entering the Canadian River at a location 3 miles south of town. The original Chouteau Creek was diverted into the Canadian River 2.5 miles north of Lexington and does not affect the flooding in town except for floods exceeding the 1-percent-annual-chance flood event. Chouteau Creek has a very flat drainage basin with low velocities insufficient to remove sediments from channels creating drainage problems. The drainage basin is primarily cropland on moderately permeable soils. Still Creek lies just west of Noble in the floodplain of Canadian River. During the study, the creek was found to be a part of the Canadian River during flood stage and is not a separate flooding source. Dave Blue Creek flows west in the northwest part of town with a length of 1.8 miles and a drainage area of 2.1 square miles. The flow comes from newly developing areas. Belle Creek flows south just east of U.S. Highway 77 with a length of 2.6 miles and a drainage area of 2.3 square miles. The flow into Belle Creek is from existing and new developments, with streets and houses increasing the amount of flooding. Dripping Springs Creek flows south in the far eastern part of the corporate limits with a length of 2.7 miles and a drainage area of 3.8 square miles at the corporate boundary. The flow into Dripping Springs Creek is from rolling hills and native pastures, with few housing developments. Typical creeks have moderately steep slopes with well-defined drainage patterns that are lined with trees and shrubs. Bishop Creek, Imhoff Creek, Merkle Creek, and Brookhaven Creek, in the areas of the City of Norman, are subject to extensive development. In recent years, channel improvements had been done to these creeks to improve drainage and modify the floodways. The North Fork River is located in the eastern portion of the City of Moore and flows generally south to the confluence with the Little River. The topography of the North Fork River basin is moderately rolling. Within the corporate limits, the river has a drainage area of approximately 15 square miles, with an average basin slope of approximately 28 feet per mile. The majority of the development in the basin within the City of Moore consists of medium-density residential and light- and medium-density commercial areas. The remainder of the basin is mainly open pasture and rangeland. The majority of the soils found in the basin upland areas are the Kirkland silt loam and the Renfrow silt loam, which generally drain slowly. Lowlands are occupied by the Yahola silt loam and the Vernon clay loam. The Yahola silt loam is moderately well drained and found in the 11

17 floodplains, while the Vernon clay loam is slowly drained and found adjacent to the streams. Stream A is located in the southeastern portion of the City of Moore and flows south to its confluence with the North Fork River. The majority of the area near the stream is undeveloped, with only light-density residential development sparsely located on rangeland and pasture. The total drainage area is 1.4 square miles, and the basin slope averages 55 feet per mile. Stream B, located in the southeastern portion of the City of Moore, is also a tributary of the North Fork River and flows south. Most of the land near the stream is rangeland and pasture, with a few scattered light residential areas. Stream B has a total drainage area of 1.4 square miles and an average slope of 50 feet per mile. Stream C is located in the east-central portion of the city and flows south to its confluence with the North Fork River. The drainage basin of the stream consists mostly of open rangeland and pasture, with a few single-family residences. Stream C has a drainage area of 3.3 square miles and an average basin slope of 31 feet per mile. Stream D flows southeast to its confluence with the North Fork River. The upper portion of the stream basin contains several medium- and high-density residential developments, while the lower portion is mainly undeveloped rangeland and pasture. The drainage area of Stream D is 2.4 square miles and the average basin slope is 32 feet per mile. The Little River is located in the central portion of the City of Moore and flows south through the city. The topography of the basin is moderately rolling. The soils of the Little River basin are very similar to those found in the North Fork River basin. One additional soil type prevalent in the uplands of the Little River basin is the Bethany silt loam, which is generally very slowly drained. Within the study area, the Little River has a drainage area of 8.7 square miles and an average basin slope of 34.5 feet per mile. The majority of the development within the Little River basin is located north of South 19th Street. The development consists of medium- and light-density commercial areas in the central business district and numerous high- and medium-density residential areas both north and south of the central business district. Most of the development south of South 19th Street is light-commercial along Interstate Highway 35. The remainder of the basin is mainly undeveloped pasture and rangeland. Stream E is located in the southwestern portion of Moore and flows southeast to its confluence with the Little River. The majority of the development in the Stream E basin is located north of South 19th Street and consists mainly of medium- and heavy-density single-family residences and light-density commercial areas along Southwest 4th Street. The remainder of the basin is undeveloped pasture, except for minor commercial development along Interstate Highway 35. The drainage area of Stream E is 3 square miles, and the average basin slope is 24 feet per mile. Kelley Creek and Northmoor Creek flow generally south to the confluence with the Little River, along the west side and the east side of U.S. Highway 77, respectively. 12

18 2.3 PRINCIPAL FLOOD PROBLEMS Generally, the major storms experienced in the vicinity are produced by heavy rainfall from frontal-type storms that occur in the spring and summer months. Major flooding can be produced by the intense, rainfall-localized thunderstorms. Peak flow data have been recorded for the Canadian River in the Purcell area since July The most severe floods of record occurred on May 4, 1941, and June 23, The recorded peak flows for these two floods were 200,000 cubic feet per second (cfs) and 153,000 cfs, respectively. Their frequency of occurrence is 193 years and 66 years, respectively. Other major historic floods occurred in 1904 and In recent years, no major flooding has occurred on the Canadian River, giving floodplain residents a false sense of security. Historic flooding information on Chouteau Creek was limited. Residents indicated that historic floods of the Canadian River overflowed near the U.S. Highway 77 bridge and flowed south through the eastern part of Lexington. Flooding of the small streams in the City of Noble occurs when high-intensity rainfall occurs on the tributaries causing floods of short duration. Belle Creek flooding is increasing from smaller storms due to heavy undergrowth near stream channels and more runoff water flowing from developed areas. Flooding on the smaller streams in the City of Norman area is usually caused by intense rainfall resulting from local thunderstorms. The amount of flooding is generally increased in the areas where natural and manmade obstructions in the floodplain impede large flows. Manmade obstructions include bridges, culverts, housing and commercial development, and earth fills. As the amount and density of urban development continues to increase, the amount of runoff can also be expected to increase, increasing the flood heights and amount of damage. Limited flood data were available for the City of Moore, since there are no gages on the streams within the study area. The history of flooding within the city was obtained from local newspaper accounts and local residents. Flooding in this part of Oklahoma occurs during the spring and fall and is associated with heavy thunderstorms and tornadoes. A major storm occurred on September 22, According to the local newspaper, 9.5 inches of rain fell in a 24-hour period, with 3.4 inches occurring in a two-hour period. The total rainfall of this storm approximated a 1-percent-annual-chance 24-hour storm; however, the two-hour precipitation is considerably less than the intensity expected in a 1-percent-annual-chance storm, making the assignment of a frequency to this storm very difficult. Other events of a smaller magnitude occurred in May 1957, June 1957, May 1967, and May The following excerpt from The Norman Transcript describes the storm (Reference 10): "Moore was apparently the hardest hit as more than five inches of rain this morning flooded streets and low-lying areas. Moore police and fire department personnel reported at least 25 persons rescued from stranded autos." "Ten more were moved out of their homes in the vicinity of First Street and Irving." 13

19 "...Moore had received only 1.60 inches of rain by 7 A.M. today, but by 9 A.M. the total had risen to five inches." The Moore Monitor had the following account of the storm (Reference 11): "A 9.51-inch rain fell on Moore during a 24-hour period this week, resulting in dozens of stranded motorists and the evacuation of at least one family by the Moore Fire Department."...several houses in the area of 1st Street and Irving were flooded. Moore received only 1.60 inches of rain by 7 A.M. Tuesday, but by 9 A.M. the total had risen to five inches. Almost five more inches fell before 7 A.M. Wednesday." Other events of a smaller magnitude occurred in Moore in May 1957, June 1957, May 1967, and May However, no information was found concerning these storms other than information from residents. Several hydraulic structures along streams in the study area became inundated by backwater effects and consequently are submerged obstructions to flow. Structures with some degree of siltation that would affect flow-carrying capacity are the Southeast 19th Street structure on Stream B and the Southwest 34th Street structure on Stream E. Structures that are considered constrictive are the U.S. Highway 77 and the East Hills Drive structures on the North Fork River, and the Southeast 34th Street structure on Stream A. 2.4 FLOOD PROTECTION MEASURES The Canadian River has three major flood-control structures located upstream from the study area. The Conchas and Ute Reservoirs are located on the upper reaches in the eastern part of New Mexico. Lake Meredith (Sanford Reservoir) is located on the Canadian River in the Texas panhandle. Because of the large amount of intervening drainage area of the Canadian River between the reservoirs and the Norman vicinity, the amount of flood reduction in the study area is minor. Lake Thunderbird, located on the Little River at mile 96.2, has a drainage area of 256 square miles, and its project purpose is for flood control, water supply, recreation, fish, and wildlife. Other pertinent information on Lake Thunderbird includes the following data: Top of dam - 1,071.4 National American Vertical Datum of 1988 (NAVD); Maximum pool - 1,065.1 NAVD 88; top of flood control pool - 1,049.8 NAVD 88; and Top of conservation pool 1,039.4 NAVD 88. Lake Thunderbird will contain the upstream runoff from the 10-, 2-, 1-, and 0.2-percentannual-chance floods. The elevations for these selected recurrence intervals for Lake Thunderbird are shown in Section 3.2 in Table 5, "Summary of Elevations." 14

20 Stanley Draper Lake is located on East Elm Creek, about 3.5 miles above the creek's confluence with the Little River. The primary purpose for Stanley Draper Lake is water supply, and its flood-control storage is insignificant. Portions of Imhoff and Merkle Creeks have been channelized. Flooding will be significantly reduced on Imhoff Creek between Oklahoma Highway 9 and Lindsey Street because of the channel improvement. The majority of the 1- and 0.2-percent-annualchance flood waters will stay within the banks of Imhoff Creek along this portion of the stream. The channelization along Merkle Creek (between Lindsey Street and Interstate Highway 35) will not significantly reduce the flooding on that stream. The City of Norman has adopted zoning ordinances, subdivision regulations, and building permit requirements as part of its program to reduce the losses caused by flooding and to ensure proper land use in the floodplains. Chouteau Creek's major drainage area has been diverted into the Canadian River approximately 2.5 miles north of Lexington. The diversion channel contains adequate capacity for storms in excess of the 1-percent-annual-chance flood event. The flooding in the City of Lexington due to storms up to the 1-percent-annual-chance flood is produced by the intervening area below the Highway 77 Chouteau Creek bridge at the diversion channel. The City of Noble has adopted zoning ordinances to regulate land use near the floodplain. Non-structural measures of flood protection are being considered to aid in the prevention of future flood damage. These measures are in the form of land-use regulations adopted from the Code of Federal Regulations, which controls building within areas that have a high risk of flooding. Accelerated residential growth has occurred in the City of Moore in the last several years. Along with this expansion of the residential area, channel improvements have been made in connection with this construction; however, there are no known planned or existing dams or floodwater-retarding structures on streams in the study area. Lake Thunderbird, located southeast of the City of Moore, regulates flow in the Little River; however, within the study limits, the Little River is unaffected by this reservoir. Cleveland County participates in the regulator phase of the NFIP and, therefore, has adopted a local floodplain ordinance to regulate development as part of its program to reduce flood losses. 3.0 ENGINEERING METHODS For the flooding sources studied by detailed methods in the community, standard hydrologic and hydraulic study methods were used to determine the flood hazard data required for this study. Flood events of a magnitude 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 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 1 year are considered. For example, the risk of having a flood 15

21 which equals or exceeds the 1-percent-annual-chance flood (1 percent chance of annual exceedance) in any 50-year period is approximately 40 percent (4 in 10); for any 90-year period, the risk increases to approximately 60 percent (6 in 10). The analyses reported herein reflect flooding potentials based on conditions existing in the community at the time of completion of this study. Maps and flood elevations will be amended periodically to reflect future changes. 3.1 HYDROLOGIC ANALYSES Hydrologic analyses were carried out to establish peak discharge-frequency relationships for each flooding source studied by detailed methods affecting the community. Discharge-frequency data for the Canadian River were based on a Log-Pearson Type III frequency analysis of long-term gaging station records at the Bridgeport, Newcastle, and Noble, Oklahoma stream gages. The analysis was performed in accordance with guidelines set forth in the Interagency Advisory Committee on Water Data Bulletin 17B (Reference 12). A straight-line extrapolation was then used to determine the 0.2-percent-annual-chance peak flow. The Bridgeport gage was located about 75 miles upstream of Norman, Oklahoma and was operating from October 1944 to September The Newcastle gage was located on the U.S. Highway 62 bridge over the Canadian River, approximately two miles west of Norman; it was in operation from October 1938 to September The Noble gage has been in operation since October Canadian River discharge-frequency data had previously been developed for six Flood Insurance Studies within the general vicinity of Purcell. Those studies produced two conflicting discharge-frequency curves for basically the same reach of river. The 1- percent-annual-chance flood discharge in three of the studies was estimated to be 192,000 cfs, and was estimated to be 169,249 cfs in the three other Flood Insurance Studies. Therefore, an in-depth analysis was conducted for this study to resolve the flowfrequency discrepancies. The final adopted frequency curve uses the maximum annual peak flows recorded at the Bridgeport, Newcastle, Noble, and Purcell stream gages for the period of 1939 through Examinations of the five largest recorded floods at the Bridgeport, Newcastle, and Purcell stream gages were made to determine the relative contributing drainage area for each flood and the relative contributing rainfall producing the estimated hydrographs. Analysis of the estimated hydrographs and the respective rainfall hydrographs at various rainfall stations reveals that the May 1941 flood peak of 200,000 cfs at Newcastle was produced by an extremely broad rainfall event that had much of the rainfall occurring in the upper portion of the basin in New Mexico and the Texas panhandle. Two other major floods occurred at the Newcastle gage in the same water year, These floods occurred in July and September of that year. Both the July 27, 1941, flood peak of 142,000 cfs and the September 25, 1941, flood peak of 150,000 cfs were produced by similar-type rainfall events that had much of the rainfall occurring in the extreme upper portion of the basin, upstream of where present-day Lake Meredith lies. Lake Meredith was constructed by the Bureau of Reclamation in 1965 on the mainstem of the Canadian River in the Texas Panhandle. Based on the preceding information and an estimate of the effective drainage areas involved, it was concluded that the effective peak annual discharge for the May 1941 Newcastle gage recorded flow, had Lake Meredith been in place in that year, would be about 135,000 cfs. This value was 16

22 later used in the frequency analysis. The resulting discharge-frequency curve developed for the Canadian River in this study yields a 1-percent-annual-chance flood discharge of 162,000 cfs. The initial rainfall-runoff model for Chouteau Creek (North of Lexington) was developed using the USACE computer program 723-X6-L2010, Flood Hydrograph Package," HEC-1, PC version dated September 1990 (Reference 13). The total basin was subdivided into five subareas ranging in size from 0.19 to 6.99 square miles. Snyder's unit hydrograph coefficients Tp and Cp, rainfall depths and loss rates, and routing criteria were developed as input for the HEC-1 model. A 15-minute computation interval was used. An initial rainfall loss of 1.0 inch and an average infiltration rate of 0.04 inches per hour were selected for the Chouteau Creek basin, based on previous studies of basins similar in size, topography, and soil characteristics in the general vicinity. The normal-depth storage method of flood routing is used to route flood hydrographs between subareas. Storage-discharge relations were computed from typical channel characteristics for each reach. Point rainfall used to determine the discharge-frequency curve for Chouteau Creek was taken from the U.S. Weather Bureau Technical Paper No. 40, "Rainfall Frequency Atlas of the United States," and the NOAA Technical Memorandum NWS Hydro-35, "Five- to 60-Minute Precipitation Frequency for the Eastern and Central United States" (Reference 14). A restudy of Chouteau Creek from just downstream of Bryant Road upstream to Cemetery Road used the same HEC-1 model as was used for the original study, but divided the basin into nine subbasins to obtain discharge values at specific locations (mainly at the upper and lower reaches of the restudy). Due to a greater number of subbasins, the revised HEC-1 model yielded different discharge values at common points when compared to the original HEC-1 model, even though identical parameters were used. For consistency, discharges from the original HEC-1 model were used where common points between the two models occurred. Snyder's unit-hydrograph coefficients were developed for each subbasin modeled and were based on 0-percent urbanization, as observed during field reconnaissance in February Development of the land in the study area was limited to two-lane roads and scattered housing, so the effects of urbanization were considered 0. Initial loss rates in the revised model were varied to allow the computed discharge values to better match the original computed discharge values. The modified-puls method of routing was used to route flood hydrographs downstream to the next combining point. Chouteau Creek (North of Lexington), Belle Creek, Dripping Springs Creek, North Fork River, and Little River and its tributaries' hydrologic characteristics were evaluated using the USGS-Water Resources Investigations Open File Report (Reference 15), which is a regional method based on regression analysis. The method relates drainage area, channel slope, percent area of storage, and mean annual precipitation to the peak discharge by empirical equations. The Dave Blue Creek hydrologic characteristics were evaluated by unit hydrographs and runoff curve numbers (Reference 16) so that reservoir routing could be accomplished at road fills. For flood flows on the streams in the City of Norman, except the Canadian River, the drainage areas were appropriately subdivided and synthetic unit hydrographs determined for each subarea, using Snyder's method (Reference 17). Rainfall data for the selected floods were obtained from the U.S. Weather Bureau Technical Publication No. 40 (Reference 18), and the estimated rainfall excesses were applied to the unit hydrographs 17

23 to obtain the runoffs. Runoffs from the individual subareas were then routed by the storage-discharge method and combined to determine peak flows at various points along the streams. The unit hydrographs used were adjusted to reflect the effects of development presently existing in the watershed. For streams studied in the City of Moore, discharges were developed for the selected recurrence intervals from the methodology contained in the USGS Water Resources Investigation (Reference 15). This procedure involves the computation of discharges through regression equations developed by the USGS. The peak flow rates are based on drainage area, basin slope, mean annual precipitation, and urbanization. A relationship of drainage area to discharge for the Little River was used to develop flows for Kelley Creek and Northmoor Creek, and the upper reach of Little River upstream of Olympic Street extended (Reference 19). The Imhoff Creek hydrologic characteristics were analyzed using the USACE HEC-1 (Reference 13) program in a study dated August 20, 1996 prepared by Baldischwiler Engineering Company. For the detail study streams Stream B, East Rock Creek, and Tributary 0 of Canadian River Tributary 1, the USACE HEC-HMS model (version 3.0) was used for hydrologic analysis. The HEC-HMS model used the SCS curve number method for infiltration, the SCS Unit hydrograph technique for run-off transformation, and modified Puls method for open channel routing. For Dave Blue Creek North, the USACE HEC-1 model was used for the analysis. The HEC-1 model used the SCS curve number method for infiltration, the SCS Unit hydrograph technique for run-off transformation, and Muskingum method for routing. For Streams A and E which are located in the City of Moore, discharges were determined for the 10-, 2-, 1-, and 0.2-percent-annual-chance flood recurrence intervals using the methodology contained in the USGS Water Resources Investigation This procedure involves the computation of discharges through regression equations developed by the USGS. The peak flow rates are based on drainage area, basin slope, mean annual precipitation, and urbanization. Little River and Unnamed Tributary to Little River were evaluated using the USGS- Water Resources Investigations Open File Report 77-54, which is a regional method based on regression analysis. The method relates drainage area, channel slope, percent are storage, and mean annual precipitation to the peak discharge by empirical equations. Revised Analyses Discharges for detailed studied streams were developed using regression equations contained in the USGS report. Discharges for Dave Blue Creek, Unnamed Tributary of Cow Creek Tributary 2 North Branch and Unnamed Tributary to the Little River were based on the Regional Regression Equations (RRE) developed for rural streams in Oklahoma by the U.S. Geological Survey (USGS, 1997), where as discharges for the Little River and Stream E were based on the Urban Regression Equations developed by the USGS for urbanized watersheds. 18

24 Peak discharge-drainage area relationships for the streams studied by detailed methods are shown in Table 4, Summary of Discharges. 3.2 HYDRAULIC ANALYSES Analyses of the hydraulic characteristics of flooding from the sources studied were carried out to provide estimates of the elevations of floods of the selected recurrence intervals. Users should be aware that flood elevations shown on the Flood Insurance Rate Map (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. Cross sections for the backwater computations for the Canadian River and Chouteau Creek were field surveyed. Field measurements of bridge geometry were made where plans were not available. City of Norman topographic mapping dated 1985 with 2-foot contour intervals and a scale of 1"=200' was used to supplement the surveyed sections where necessary. In addition, 2-foot contour interval topographic mapping at a scale of 1"=200', obtained from the Oklahoma Department of Transportation, was used to model the area around the Highway 44 bridge in more detail. Roughness coefficients (Manning's "n") were based on field investigations and aerial photographs obtained from the Agricultural Stabilization and Conservation Service. The Manning's "n" values used were.020 to.030 for the channels and.030 to.065 for the overbanks on the Canadian River, and.070 for the channel and.040 to.070 for the overbanks on Chouteau Creek. Water-surface profiles for the 10-, 2-, 1-, and 0.2-percent-annual-chance floods were computed using the USACE's computer program, HEC-2, "Water Surface Profiles," PC version 4.6.0, dated February 1991 (Reference 20). The Canadian River was studied by the SCS for the Lexington, Purcell, and Noble, Oklahoma, Flood Insurance Studies in 1979 using the SCS WSP-2 step-backwater computer program (Reference 21). This model covers the area from the lower limit of study to station 80,000 in the new model. A HEC-2 model was developed by the USACE for the Norman Flood Insurance Study in 1977 and later used in the Oklahoma City, Goldsby, and Newcastle Flood Insurance Studies. This model covers the area from station 80,000 to the upper limit of study in the new model. A divided-flow condition was found to exist due to the Atchison, Topeka, and Santa Fe Railway bridge. The flow is divided from section 37,322 to section 49,561 immediately upstream of the bridge. The left overbank track fill is high enough to prevent the flow from overtopping the tracks, forcing the flow through the bridge opening and right overbank where it is channeled along the tracks before reentering the main channel at section 37,322. A separate HEC-2 model was developed to model the flow along the right overbank parallel to the track fill. In this model, split flow cards were used to model the weir flow along the lower end of the tracks where the flow crosses the tracks and reenters the main channel. Because the elevation of the tracks is higher than the computed water-surface elevation in the main channel at cross section 37,322, critical depth controls the starting water-surface elevation of the divided-flow model. 19

25 Flooding Source and Location Table 4. Summary of Discharges Drainage Area Peak Discharges (cubic feet per second) (square miles) 10-percent 2-percent 1-percent 0.2-percent BELLE CREEK At Section A ,188 2,036 2,484 3,591 At U.S. Highway ,558 1,895 2,729 At Section L ,314 1,597 2,298 BISHOP CREEK At State Highway ,373 7,929 9,256 12,183 At Constitution Street ,839 7,128 8,313 10,680 At Confluence with Tributary C ,843 4,134 4,795 6,106 At Confluence of Bishop Creek Tributary B ,178 1,654 1,905 2,428 At Acres Street BISHOP CREEK TRIBUTARY C At Acres Street ,340 1,780 2,010 2,500 At Brooks Street ,340 1,780 2,010 2,500 BROOKHAVEN CREEK At Cross Section B ,970 4,330 4,950 6,600 At 36th Street NW ,180 3,150 3,600 4,700 Just downstream of Robinson Street ,680 2,460 2,860 4,000 Just upstream of Crossroads Boulevard ,0301 1,550 1,820 2,650 Just downstream of confluence with Tributary A ,300 1,520 2,230 Just downstream of confluence with Tributary B BROOKHAVEN CREEK TRIBUTARY A At Pendleton Drive ,285 At Rock Creek Road BROOKHAVEN CREEK TRIBUTARY B Approximately 250 feet upstream of confluence with Brookhaven Creek CANADIAN RIVER At Purcell, Oklahoma 21, , , , ,000 20

26 Table 4. Summary of Discharges (Cont d) Drainage Area Peak Discharges (cubic feet per second) Flooding Source and Location (square miles) 10-percent 2-percent 1-percent 0.2-percent CANADIAN RIVER TRIBUTARY feet upstream of the mouth ,634 4,758 5,969 8,968 At Southwest 149th Street ,085 3,780 4,733 7,098 At Highway ,645 2,984 3,727 5,575 At Pennsylvania Avenue ,094 1,984 2,467 3,672 At Southwest 119th Street ,215 1,792 CANADIAN RIVER TRIBUTARY 2 At Southwest 149th Street ,016 1,813 2,244 3,326 At Southwest 119th Street ,286 1,585 2,339 CHOUTEAU CREEK AT LEXINGTON At Section A ,243 1,512 2,195 At Catalpa Street ,087 1,319 1,910 At Center Street ,042 1,264 1,830 At Section P ,012 1,227 1,776 CHOUTEAU CREEK (NORTH OF LEXINGTON) At confluence with the Canadian River ,120 13,570 15,660 20,180 Upstream of confluence with Dripping Springs Creek ,921 6, , ,361 Upstream of 96th Street ,799 6,948 7,903 9,891 At Cemetery Road ,959 5,535 6,250 7,783 COW CREEK At the mouth ,712 6,763 8,534 12,897 At Southwest 119th Street ,590 2,870 3,579 5,345 At Southwest 104th Street ,795 2,226 3, mile south of Southwest 89th Street ,439 1,782 2,641 COW CREEK TRIBUTARY 1 At the mouth ,560 1,934 2,870 At Southwest 104th Street ,028 1,270 1,877 1Discharges decrease downstream due to storage effects in the floodplain 21

27 Table 4. Summary of Discharges (Cont d) Drainage Area Peak Discharges (cubic feet per second) Flooding Source and Location (square miles) 10-percent 2-percent 1-percent 0.2-percent COW CREEK TRIBUTARY 2 At the mouth ,679 4,885 6,143 9, mile east of Rockwell Avenue ,749 3,169 3,960 5, mile east of Council Road ,546 2,817 3,520 5,266 At the County Line Road ,363 2,505 3,131 4, mile west of County Line Road ,559 1,940 2,890 COW CREEK TRIBUTARY 2 WEST BRANCH At the mouth ,304 1,618 2,402 COW CREEK TRIBUTARY 2 NORTH BRANCH At the mouth ,561 2,856 3,572 5, mile north of Southwest 119th Street ,432 2,628 3,286 4, mile west of Rockwell Avenue ,242 1,539 2,284 COW CREEK TRIBUTARY 3 At the mouth ,063 1,926 2,393 3, mile south of Southwest 89th Street ,455 1,802 2,673 DAVE BLUE CREEK At Section A ,126 1,709 2,020 2,633 At Section E ,395 1,630 2,119 Immediately downstream of Oak Road ,321 DAVE BLUE CREEK NORTH Approximately 200 feet downstream of Highway ,282 1,540 2,066 At stream station 3,000 * ,234 DRIPPING SPRINGS CREEK At confluence with Chouteau Creek ,932 6,940 7,757 9,795 At Banner Road ,453 4,803 5,508 7,073 At Cemetery Road ,624 3,763 4,277 5,335 At Maguire Road ,644 2,027 2,980 At Section I ,041 1,524 *Information not available 22

28 Table 4. Summary of Discharges (Cont d) Drainage Area Peak Discharges (cubic feet per second) Flooding Source and Location (square miles) 10-percent 2-percent 1-percent 0.2-percent EAST ROCK CREEK Approximately 500 feet downstream of Northeast 36th Avenue ,230 3,640 4,280 6,340 Approximately 500 feet upstream of Northeast 36th Avenue ,160 3,520 4,050 6,020 Approximately 5,800 feet downstream of Alameda Street ,476 2,310 2,620 3,830 HOG CREEK At Southeast 149th Street ,493 9,978 12,638 19,171 At Southeast 104th Street ,975 9,093 11,521 17,482 At Southeast 745th Street ,936 5,344 6,725 10,136 At Hawassee Road ,798 3,281 4,108 6,159 At Westminster Road ,630 2,030 3,019 HOG CREEK EAST BRANCH At the mouth ,481 2,690 3,356 5, mile upstream of Southeast 74th Street ,116 2,031 2,527 3,767 HOG CREEK TRIBUTARY 1 At the mouth ,695 2,108 3,139 At Choctaw Road ,081 1,338 1,984 HOG CREEK TRIBUTARY 2 At Indian Meridian Road ,204 2,203 2,747 4,104 At Southeast 104th Street ,786 2,225 3,319 At Triple XXX Road ,146 1,697 HOG CREEK WEST BRANCH At Choctaw Road ,613 4,764 5,988 9,014 At Hiwassee Road ,977 3,596 4,504 6,755 At Anderson Road ,437 2,611 3,257 4,867 At Southeast 74th Street ,019 1,858 2,310 3,441 HOG CREEK WEST BRANCH TRIBUTARY 1 At the mouth ,074 1,328 1,966 HOG CREEK WEST BRANCH TRIBUTARY 2 At the mouth ,351 1,676 2,491 23

29 Flooding Source and Location Table 4. Summary of Discharges (Cont d) Drainage Area Peak Discharges (cubic feet per second) (square miles) 10-percent 2-percent 1-percent 0.2-percent IMHOFF CREEK At confluence with the Canadian River ,540 5,220 6,100 8,600 Approximately 1,500 feet downstream of Lindsey Street ,300 4,840 5,630 7,940 At Boyd Street ,430 3,500 4,050 5,640 At Atchison, Topeka, and Santa Fe Railway ,280 1,820 2,100 2,890 KELLEY CREEK At confluence with the Little River ,150 1,380 1,930 At Northwest 12th Street ,100 At Northwest 22nd Street LIGHTNING CREEK At Southwest 29th Street ,980 7,451 8,019 11, mile upstream of Southwest 44th Street ,244 4,357 5,416 7,053 At Southwest 59th Street ,840 3,731 4,726 6, mile upstream of Southwest 59th Street ,051 2,356 3,189 3,912 At Southwest 74th Street ,243 1,867 2,445 At the Detention Pond above 74th Street ,123 2,300 3,665 5,010 At Western Avenue ,360 2,041 2,378 3,199 LITTLE RIVER Immediately downstream of 12th Ave NE ,488 12,492 15,210 21,003 Immediately upstream of Confluence with North Folk River ,373 9,604 11,641 16,117 Immediately upstream of confluence with Rock Creek ,131 8,932 10,808 14,995 Approximately 1636 feet upstream N Porter Ave ,959 8,494 10,269 14,265 Approximately 2544 feet downstream W Franklin Rd ,540 7,405 8,931 12,435 Approximately 1625 feet upstream W Franklin Rd ,550 7,409 8,935 12,452 Approximately 2002 feet downstream 24th Ave NW ,561 7,382 8,902 12,452 Approximately 1265 feet upstream of W Indian Hill Rd ,307 6,786 8,175 11,435 Downstream of the confluence of Stream E ,590 4,355 5,320 7,680 At a point near the south end of the Moore WWTP ,905 3,115 3,755 5,330 At a point approximately 1,300 feet upstream of South 34th Street ,870 3,030 3,640 5,132 At a point approximately 70 feet downstream of Telephone Road ,619 2,568 3,058 4,254 At a point approximately 1,350 feet upstream of Southwest 17th Street ,577 2,508 2,989 4,161 At a point approximately 910 feet downstream of Southwest 4th Street ,554 2,489 2,971 4,145 At a point approximately 70 feet upstream of Telephone Road ,124 1,808 2,158 3,013 24

30 Flooding Source and Location Table 4. Summary of Discharges (Cont d) Drainage Area Peak Discharges (cubic feet per second) (square miles) 10-percent 2-percent 1-percent 0.2-percent LITTLE RIVER (CONT D) At a point approximately 150 feet upstream of Telephone Road ,036 1,686 2,019 2,835 At a point approximately 80 feet downstream of Broadway ,497 1,794 2,525 At a point approximately 75 feet downstream of North 12th Street ,402 1,681 2,370 At Meadowbrook Avenue ,100 At Cedar Nail Parkway MERKLE CREEK At Interstate Highway ,380 3,370 3,870 5,330 At Main Street ,950 2,710 3,120 4,310 At Robinson Street ,060 1,690 NORTH FORK RIVER At the confluence of Stream A ,610 6,190 7,640 11,165 At a point approximately 1,200 feet upstream of the confluence of Stream ,375 5,780 7,125 10,405 At a point approximately 1,220 feet upstream of the confluence of Stream ,980 5,120 6,305 9,200 At a point approximately 100 feet upstream of the confluence of ,420 4,150 5,100 7,425 Stream D At a point approximately 200 feet upstream of the confluence of ,700 2,830 3,435 4,905 Stream C At a point approximately 1,200 feet upstream of Southeast Fourth Street ,410 2,370 2,875 4,125 At a point approximately 2,165 feet downstream of Northeast 12th Street ,045 1,775 2,160 3,110 At East Hill Drive ,354 1,629 2,308 Downstream of Northeast 22nd Street ,045 1,254 1,770 25

31 Flooding Source and Location Table 4. Summary of Discharges (Cont d) Drainage Area Peak Discharges (cubic feet per second) (square miles) 10-percent 2-percent 1-percent 0.2-percent NORTHMOOR CREEK At Bellaire Drive ,170 1,670 At Northeast 27th Street ,100 ROCK CREEK At confluence with Little River ,310 2,290 3,730 4,800 At Cross Section L ,600 2,180 2,460 3,130 At Rock Creek Road ,290 1,450 1,850 At Cross Section Y ,060 1,190 1,500 STREAM A At its confluence with North Fork River ,959 2,449 3,944 At a point upstream of Southeast 34th Street ,255 1,550 2,280 STREAM B At its confluence with North Fork River ,160 1,890 2,150 3,220 Approximately 100 feet upstream of Southeast 19th Street ,250 1,980 2,260 3,400 STREAM C At its confluence with the North Fork River ,300 2,280 2,810 4,115 At a point downstream of Southeast 4th Street ,120 1,960 2,410 3,530 At a point approximately 2,870 feet upstream of Southeast 4th Street ,060 1,860 2,285 3,340 At a point approximately 1,250 feet downstream of Northeast 12th Street ,725 2,115 3,090 At a point approximately 1,480 feet upstream of Northeast 12th Street ,450 1,775 2,590 26

32 Table 4. Summary of Discharges (Cont d) Drainage Area Peak Discharges (cubic feet per second) Flooding Source and Location (square miles) 10-percent 2-percent 1-percent 0.2-percent STREAM D At its confluence with the North Fork River ,160 1,970 2,395 3,455 At a point approximately 1,215 feet downstream of Bryant Avenue ,155 1,940 2,350 3,360 At a point approximately 1,715 feet upstream of Bryant Avenue ,105 1,855 2,245 3,210 At a point immediately south of Southeast 19th Street ,585 1,910 2,710 At a point approximately 1,360 feet upstream of Southeast 19th Street ,445 1,735 2,438 At a point approximately 4,325 feet upstream of Southeast 19th Street ,300 1,550 2,165 STREAM E At a point approximately 1,275 feet downstream of Southwest 34th Street ,216 2,051 2,493 3,586 At a point approximately 75 feet downstream of Southwest 34th Street ,056 1,780 2,160 3,100 At a point approximately 1,125 feet upstream of Southwest 34th Street ,002 1,689 2,049 2,941 At a point approximately 1,975 feet upstream of Southwest 34th Street ,551 1,872 2,667 At a point approximately 2,985 feet upstream of Southwest 34th Street ,320 1,590 2,263 Immediately upstream of SW 14th Street Immediately downstream of Penn Lane TRIBUTARY 0 OF CANADIAN RIVER TRIBUTARY 1 At Highway ,692 2,097 3,111 Approximately 200 feet upstream of Greenlee Chase* ,430 1,660 2,600 At Southwest 119th Street ,005 1,238 1,825 Approximately 100 feet downstream of Santa Fe Avenue* ,120 1,630 TRIBUTARY 1 OF CANADIAN RIVER TRIBUTARY 1 At Southwest 149 th Street ,446 1,786 2,643 At Highway ,226 1,569 2,327 TRIBUTARY 1 OF TRIBUTARY 1 OF CANADIAN RIVER TRIBUTARY 1 At the confluence with Tributary 1 of Canadian River Tributary *Studied as part of second revision which extended the limit of detailed studies. 27

33 Table 4. Summary of Discharges (Cont d) Drainage Area Peak Discharges (cubic feet per second) Flooding Source and Location (square miles) 10-percent 2-percent 1-percent 0.2-percent TRIBUTARY 2 OF CANADIAN RIVER TRIBUTARY 1 At Pennsylvania Avenue ,446 1,786 2,643 At Western Avenue ,628 TRIBUTARY 3 OF CANADIAN RIVER TRIBUTARY 1 At Southwest 134th Street ,368 1,692 2,507 Immediately upstream of confluence with unnamed Tributary ,333 1,596 2,253 Approximately 843 feet downstream of SW 107th ST ,250 1,496 2,111 Immediately downstream of SW 111Th ST ,167 1,396 1,971 At Southwest 119th Street ,228 TRIBUTARY 4 OF CANADIAN RIVER TRIBUTARY 1 At Southwest 119th Street ,189 1,471 2,178 UNNAMED TRIBUTARY TO COW CREEK TRIBUTARY 2 NORTH BRANCH Downstream End of the Study Limit ,068 2,151 2,731 4,434 Approximately 1,777 feet downstream of SW 89th ST ,068 2,155 2,739 4,453 Approximately 730 feet downstream of SW 89th ST ,804 2,293 3,733 UNNAMED TRIBUTARY TO LITTLE RIVER Approximately 1,120 feet upstream of Mathis-Fox Lane ,568 1,872 2,594 Approximately 2306 feet downstream of SW 39TH Street ,516 1,810 2,508 Immediately upstream of S. Eastern Ave ,076 1,497 UNNAMED TRIBUTARY TO TRIBUTARY 3 OF CANADIAN RIVER TRIBUTARY 1 Approximately 40 feet downstream of Southwest 119 th Street 0.24 * * 748 * Approximately 560 feet downstream of Southwest 119 th Street 0.39 * * 1,152 * Approximately 1,255 feet downstream of Southwest 119 th Street 0.45 * * 1,341 * *Information not available 28

34 Cross-section information for this model was based on USGS 7.5-minute quadrangle maps with a scale of 1:24,000, with contour intervals of 10 feet, and surveyed information where available. Trial and error was used to balance the water-surface elevation computed at cross section 49,561 for the divided-flow model and the mainchannel model. For example, the total 1-percent-annual-chance flow for the river was 162,000 cfs, and a combination of 122,000 cfs in the main channel and 40,000 cfs in the divided flow was found to give approximately the same elevation at cross section 49,561 for both models. A flow diversion of approximately 18,950 cfs occurs along the western corporate limits of the City of Norman, Oklahoma, in the vicinity of the intersection of Rock Creek Road and 72nd Avenue. Approximately 13,450 cfs of the diversion from the main channel flows in an easterly direction toward Ten-Mile Flat Creek. This flow splits just west of 60th Avenue, with approximately 2,350 cfs flowing in a southwesterly direction toward the Canadian River, and approximately 5,000 cfs and 6,100 cfs flowing toward Ten-Mile Flat Creek through two low spots along a line of high ground near 60th Avenue. Approximately 5,500 cfs of the diversion from the main channel flows in a southerly direction until it combines with the 2,350 cfs flowing from the northeast. Of this combined 7,850 cfs, approximately 6,250 cfs rejoins the Canadian River floodplain approximately 5,000 feet downstream of the diversion from the main channel, and approximately 1,600 cfs flows in a southeasterly direction into Ten-Mile Flat Creek. The 5,500 cfs breakout from the Canadian River was determined by reviewing the flow distribution in the east overbank of Cross Section AB (143,454) of the HEC-2 model for the Canadian River. All other flows and elevations were determined using Manning's equation and rating curves to balance the flows until the water-surface elevations and friction slopes were consistent. The base flood elevations (BFEs) along the path of the split flow vary from 1,132 feet NGVD at the main channel of the Canadian River to approximately 1,126 feet NGVD at Ten-Mile Flat Creek, with certain areas designated as shallow flooding. It was also determined that the elevation at Rock Creek Road along Ten-Mile Flat Creek was 1,126 feet NGVD, and the upstream area will be inundated by the 1-percent-annual-chance flood to a depth of less than 1 foot. Flood profiles were computed for both the left-overbank flow and the main-channel flow using the HEC-2 model. A floodway was then computed for the main-channel flow on the basis of equal conveyance reduction from each side of the floodplain. No previous computer models exist for the reach of Chouteau Creek North of Lexington, and no unusual modeling situations were encountered. Flood profiles were drawn showing the computed water-surface elevations for the 10-, 2-, 1-, and 0.2-percentannual-chance floods. Cross sections for the backwater analyses of the Canadian River, Belle Creek, Dripping Springs Creek, and Dave Blue Creek were obtained by field surveys. All bridges and culverts were field-checked to obtain elevation data and structural geometry. Channel roughness factors (Manning's "n") used in the hydraulic computations were based on field observations of the streams and floodplain areas. Roughness values of the Canadian River ranged from to 0.25, with overbank values ranging from to for all floods. Roughness values on Belle Creek, Dripping Springs Creek, and Dave Blue Creek varied from to in channels, and from to for overbank 29

35 flows. The acceptability of all hydraulic factors was checked by computations that duplicated historic flood profiles. Water-surface elevations of floods were computed by using the SCS step-backwater computer program (Reference 21). Dave Blue Creek required the use of the SCS Reservoir Routing computer program to compute water-surface elevations above the railroad embankment in a flood-storage area. Starting water-surface elevations for all streams studied in detail were obtained using the slope-area method. For Bishop Creek and its tributaries, Imhoff Creek, Merkle Creek, Merkle Creek Overflow, Brookhaven Creek, and Rock Creek, cross sections of the stream channels and immediate overbanks were mainly obtained by field surveys. These sections were extended into the overbank areas using 5-foot contour interval topographic maps (Reference 22) and 10-foot contour interval USGS quadrangle maps (Reference 23). All bridge geometry was field measured. Roughness coefficients (Manning's "n") for the streams studied were based on field reconnaissance, typical photographs of the area, and data obtained from other studies, where available. Manning's coefficients for the channels and overbank areas are in Table 6, Manning s n Values. Water-surface elevations were computed using the USACE HEC-2 step-backwater computer program (Reference 24). Starting water-surface elevations for Main Stem Bishop Creek, Imhoff Creek, Merkle Creek, Merkle Creek Overflow, Brookhaven Creek, and Rock Creek were derived by the slope-area method. The starting elevations for the tributaries to Bishop Creek were based on coincident flooding occurring on Main Stem Bishop Creek. For streams studied by the approximate method, the 1-percent-annualchance flood boundaries were delineated using a combination of available USGS Flood Prone Area Maps (Reference 25), and a normal depth analysis based on flows obtained using the regional frequency relations, as explained in the USGS report entitled "Flood Characteristics for Oklahoma Streams" (Reference 26). Profiles were not prepared for these streams. To determine the water-surface elevations on Lake Thunderbird, flow data from the stream gage at Tecumseh, Oklahoma were used in the analysis. These flows were reduced by a drainage-area ratio to represent the flows at Lake Thunderbird Dam, and volume-duration-frequency curves were developed. The resulting volume was then converted to elevations by using an elevation-capacity table for the lake and by assuming the conservation pool to be at maximum capacity. The frequency-elevation relationships for Lake Thunderbird are shown in the following: Table 5. Summary of Elevations Flooding Source Elevation above NAVD (feet) and Location 10-percent 2-percent 1-percent 0.2-percent Lake Thunderbird 1, , , ,054.5 For North Fork River and its tributaries, Streams A, B, C, and D, Tributary to Stream D, Little River, and Stream E, valley cross sections and roadway sections were obtained 30

36 from field surveys. All bridges and culverts were field surveyed to obtain elevation data and structural geometry. Channel roughness coefficients (Manning's "n") used in the hydraulic computations were assigned during the field reconnaissance and were based on engineering judgment and methodology described in two publications (References 27 and 28). The channel "n" and overbank "n" values for the streams studied by detailed methods are in Table 6, Manning s n Values. Water-surface elevations of floods of the selected recurrence intervals were computed using the USACE HEC-2 step-backwater computer program (Reference 24). The HEC-2 program dated September 1990 was used for the computations of the profiles for Kelley Creek and Northmoor Creek (Reference 20). Flood profiles were drawn showing computed water-surface elevations for floods of the selected recurrence intervals. Starting water-surface elevations for the North Fork River, the Little River, and Stream E were calculated by the slope-area method. Starting water-surface elevations for Streams A, B, C, and D were interpolated from the profiles of the North Fork River. Starting water-surface elevations for Kelley Creek and Northmoor Creek were based on the Little River computed water-surface elevations at the confluence with these creeks. Water-surface elevations were determined using the USACE HEC-2 computer program (Reference 20) for Chouteau Creek and Dripping Springs Creek. Cross sections for the backwater computations were obtained by field survey. The starting water-surface elevations for Chouteau Creek were taken from the original study. Due to coincident flooding of Chouteau and Dripping Springs Creeks in the restudy area, starting watersurface elevations for Dripping Springs Creek were taken from the revised HEC-2 model for Chouteau Creek. Roughness coefficients (Manning's "n" values) for Chouteau Creek ranged from to in the channel and from to in the overbanks. For Dripping Springs Creek, the Manning's "n" value was in the channel and ranged from to in the overbanks. The flood boundaries for the 1- and 0.2-percentannual-chance floods have been delineated using the flood elevations determined at each cross section. Between cross sections, the boundaries were interpolated using topographic maps at a scale of 1:24,000, enlarged to 1:7,200 (Reference 29). Floodways along Chouteau and Dripping Springs Creeks were computed on the basis of equal-conveyance reduction from each side of the floodplain. The water-surface elevations for Imhoff Creek were determined using the USACE HEC- 2 computer program (References 20). A topographic map at a scale of 1:2,400, with a contour interval of 2 feet (Reference 30) was used to delineate the revised floodplain boundaries along Imhoff Creek. Cross-section data for the backwater analyses for Canadian River Tributary 1 and Tributary 4 of Canadian River Tributary 1 were obtained from aerial photography utilizing a stereo plotter to determine point elevations for selected locations. All bridges, dams, and culverts were field surveyed to obtain elevation data and structural geometry. Water-surface elevations for floods of the selected recurrence intervals were originally computed using the USGS step-backwater computer program (Reference 31). The USACE HEC-2 computer program was used to compute the water-surface profiles for all or portions of Canadian River Tributary 1 (Reference 20). Both the USGS step-backwater and the USACE HEC-2 computer programs route selected discharges upstream to 31

37 determine the flood elevation from point to point upon the conservation of energy principle. Flood profiles were drawn showing computed water-surface elevations for floods of the selected recurrence intervals. For the study or restudy of Canadian River, Canadian River Tributary 1, Canadian River Tributary 2, Cow Creek, Cow Creek Tributary 1, Cow Creek Tributary 2, Cow Creek Tributary 2 West Branch, Cow Creek Tributary 3, Cow Creek Tributary 2 North Branch, Hog Creek, Hog Creek, East Branch, Hog Creek Tributary 1, Hog Creek Tributary 2, Hog Creek West Branch, Hog Creek West Branch Tributary 1, Hog Creek West Branch Tributary 2, Lightning Creek, Tributary 0 to Canadian River Tributary 1, Tributary 1 of Canadian River, Tributary 1, Tributary 2 of Canadian River Tributary 1, Tributary 3 of Canadian River Tributary 1, and Tributary 4 of Canadian River Tributary 1, topographic mapping at a scale of 1"=200' was used to determine cross section geometry for use in the backwater computer models. The aerial flights in the development of the topographic mapping were conducted in December Bridge geometry was field measured and supplemented with as-built plans where possible. Water-surface profiles for the 10-, 2-, 1-, and 0.2-percent-annual-chance frequency floods were computed using the USACE computer program 723-X6-L202A, "HEC-2 Water Surface Profiles" PC Version dated May 1991 (Reference 20). The slope/area option in the HEC-2 program was used as starting conditions for all flood frequencies. Channel roughness coefficients (Manning's "n") used in the hydraulic computations were assigned during the field reconnaissance and were based on engineering judgment and methodology described in two publications (References 27 and 28). The channel "n" and overbank "n" values for the streams studied by detailed methods are in Table 6, Manning s n Values. Most of the cross sections for East Rock Creek were developed from topographic data with 2 feet contour interval provided by the City of Norman. Most of the cross sections for Stream B and Tributary 0 to Canadian River Tributary 1 were developed from Light Detection and Ranging (LIDAR) data provided by the City of Oklahoma City. LIDAR data was captured in March A few surveyed cross sections were also utilized. Starting water surface elevations for East Rock Creek and Stream B were based on normal depth calculations. Known water surface elevations at tshe previous limit of detailed study were used as starting water surface elevations for Tributary 0 to Canadian River Tributary 1. Channel roughness factors (Manning s n ) used in the hydraulic computations for the above detailed study streams were obtained from field reconnaissance and typical photographs of the areas. Manning s n coefficients for the channel and overbank areas are as shown in Table 6. Revised Analyses For the study of Dave Blue Creek, Little River, Stream A, Stream E, Tributary 3 of Canadian Tributary 1, Unnamed Tributary to Cow Creek Tributary 2 North Branch and Unnamed Tributary to Little River, below-water sections of channels and near overbanks of selected cross sections, bridges, and culverts were field surveyed in detailed to obtain elevation data and structure geometry. For each survey cross sections, the field elevation was blended with overbank topographic data obtained from the 2-foot LiDAR contours provided by Cleveland County. For rest of the cross sections, elevation data were obtained from 2-foot LiDAR contours provided by Cleveland County and a reasonable bathymetric assumption was performed for LiDAR-cut channel cross-sections from surveyed cross-sections channels. All topographic data was referenced to the vertical 32

38 datum of NAVD 88. Since a subcritical flow analysis is performed, downstream boundary conditions are required. The downstream boundary conditions for all the stream reaches were determined using known-water surface elevations from effective FIS report and profiles. Channel roughness factors (Manning's "n") used in the hydraulic computations for all streams studied in this project were chosen on the basis of engineering judgment, aerial photos, and field observations. Water surface elevations for the 10-percent, 2-percent, 1-percent, and 0.2-percent-annual-chance floods were computed using the USACE HEC-RAS Version step-backwater computer program. Water-surface profiles for the 10-, 2-, 1-, and 0.2-percent-annual-chance frequency floods for Dave Blue Creek North, East Rock Creek, Stream B, and Tributary 0 to Canadian River Tributary 1 were computed using the USACE computer program HEC-RAS Version dated May 2003 (Reference 32). Locations of selected cross sections used in the hydraulic analyses are shown on the Flood Profiles (Exhibit 1). For stream segments for which a floodway was computed (Section 4.2), selected cross-section locations are also shown on the FIRM (Exhibit 2). The hydraulic analyses for this study were based on unobstructed flow. The flood elevations shown on the profiles are thus considered valid only if hydraulic structures remain unobstructed, operate properly, and do not fail. All elevations are referenced to the NAVD. Elevation reference marks and the descriptions of the marks used in this study are shown on the maps. All qualifying bench marks within a given jurisdiction that are cataloged by the National Geodetic Survey (NGS) and entered into the National Spatial Reference System (NSRS) as First or Second Order Vertical and 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 abutment) Stability C: Monuments which may be affected by surface ground movements (e.g., concrete monument 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 monuments 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. 33

39 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 at It is important to note that temporary vertical monuments are often established during the preparation of a flood hazard analysis for the purpose of establishing local vertical control. Although these monuments are not shown on the FIRM, they may be found in the Technical Support Data Notebook associated with 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 used for newly created or revised FIS reports and FIRMs was the National Geodetic Vertical Datum of 1929 (NGVD). With the completion of the North American Vertical Datum of 1988 (NAVD), many FIS reports and FIRMs are now prepared using NAVD as the referenced vertical datum. Flood elevations shown in this FIS report and on the FIRM are referenced to the NAVD. These flood elevations must be compared to structure and ground elevations referenced to the same vertical datum. Some of the data used in this revision were taken from the prior effective FIS reports and FIRMs and adjusted to NAVD88. The datum conversion factor from NGVD29 to NAVD88 in Cleveland County is feet. For additional information regarding conversion between the NGVD and NAVD, visit the National Geodetic Survey website at or contact the National Geodetic Survey at the following address: Vertical Network Branch, N/CG13 National Geodetic Survey, NOAA Silver Spring Metro Center East-West Highway Silver Spring, Maryland (301) Temporary vertical monuments are often established during the preparation of a flood hazard analysis for the purpose of establishing local vertical control. Although these monuments are not shown on the FIRM, they may be found in the Technical Support Data Notebook associated with the FIS report and FIRM for this community. Interested individuals may contact FEMA to access these data. To obtain current elevation, description, and/or location information for benchmarks shown on this map, please contact the Information Services Branch of the NGS at (301) , or visit their website at 34

40 Table 6. Manning s n Values Roughness Co-efficient Flooding Source Channel Overbank Bishop Creek Tributary A Bishop Creek Tributary B Bishop Creek Tributary C Brookhaven Creek Canadian River Tributary Canadian River Tributary Cow Creek Cow Creek Tributary Cow Creek Tributary Cow Creek Tributary Dave Blue Creek East Rock Creek Hog Creek Hog Creek East Branch Hog Creek Tributary Hog Creek Tributary Hog Creek West Branch Hog Creek West Branch Tributary Hog Creek West Branch Tributary Imhoff Creek Lightning Creek Little River Main Stem Bishop Creek Merkle Creek Merkle Creek Overflow North Branch of Cow Creek Tributary North Fork River Rock Creek Stream A Stream B Stream C Stream D Stream E Tributary 0 of Canadian River Tributary Tributary 1 of Canadian River Tributary Tributary 2 of Canadian River Tributary Tributary 3 of Canadian River Tributary Tributary 4 of Canadian River Tributary West Branch of Cow Creek Tributary Unnamed Tributary to Cow Creek Tributary 2 North Branch Unnamed Tributary to Little River

41 4.0 FLOODPLAIN MANAGEMENT APPLICATIONS The NFIP encourages State and local governments to adopt sound floodplain management programs. Therefore, each Flood Insurance Study provides 1-percent-annual-chance flood elevations and delineations of the 1- and 0.2-percent-annual-chance floodplain boundaries and 1- percent-annual-chance floodway to assist communities in developing floodplain management measures. 4.1 FLOODPLAIN BOUNDARIES To provide a national standard without regional discrimination, the 1-percent-annualchance (100-year) flood has been adopted by FEMA as the base flood for floodplain management purposes. The 0.2-percent annual chance (500-year) flood is employed to indicate additional areas of flood risk in the community. For each stream studied_ by detailed methods, the 1- and 0.2-percent-annual-chance floodplain boundaries have been delineated using the flood elevations determined at each cross section. Between cross sections, the boundaries were interpolated using topographic maps at a scale of 1:24,000, with contour intervals of 5 and 10 feet (References 22, 23, 25, and 29). USGS 7.5-minute quadrangle maps with contour intervals of 10 feet (Reference 29) were enlarged to a scale of 1" = 600 feet, for use as a base map for the Canadian River and Chouteau Creek studies. In Norman, Zone AE floodplain boundaries have been mapped to topographic information created in (Reference 33). The 1- and 0.2-percent-annual-chance floodplain boundaries are shown on the FIRM (Exhibit 2). On this map, the 1-percent-annual-chance floodplain boundary corresponds to the boundary of the areas of special flood hazards (Zones A and AE); and the 0.2- percent-annual-chance floodplain boundary corresponds to the boundary of areas of moderate flood hazards (Zone X). 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 streams studied by approximate methods, only the 1-percent-annual-chance floodplain boundary is shown on the FIRM. For Stream E, more accurate data obtained from field surveys were available at the most upstream area of approximate study. 4.2 S Encroachment on floodplains, such as structures and fill, reduces flood-carrying capacity, increases flood heights and velocities, and increases flood hazards in areas beyond the encroachment itself. One aspect of floodplain management involves balancing the economic gain from floodplain development against the resulting increase in flood hazard. For purposes of the NFIP, a floodway is used as a tool to assist local communities in this aspect of floodplain management. Under this concept, the area of the 1-percentannual-chance floodplain is divided into a floodway and a floodway fringe. The floodway is the channel of a stream, plus any adjacent floodplain areas, that must be kept free of encroachment so that the 1-percent-annual-chance flood can be carried without substantial increases in flood heights. Minimum Federal standards limit such increases to 1.0 foot, provided that hazardous velocities are not produced. The floodways in this study 36

42 are presented to local agencies as minimum standards that can be adopted directly or that can be used as a basis for additional floodway studies. The floodways presented in this study were computed for certain stream segments on the basis of equal conveyance reduction from each side of the floodplain. Floodway widths were computed at cross sections. Between cross sections, the floodway boundaries were interpolated. The results of the floodway computations are tabulated for selected cross sections (Table 7). In cases where the floodway and 1-percent-annual-chance floodplain boundaries are either close together or collinear, only the floodway boundary is shown. Portions of the floodways for Canadian River, Hog Creek East Branch, Hog Creek West Branch, Lightning Creek extend beyond the county boundary. Floodway computations for the North Fork River were revised as a result of a channelization and the extension of the limit of detailed study. A floodway was not computed for Dave Blue Creek North, Kelley Creek, or Northmoor Creek. Near the mouths of streams studied in detail, floodway computations are made without regard to flood elevations on the receiving water body. Therefore, "Without Floodway" elevations presented in Table 7 for certain downstream cross sections of Choteau Creek, Cow Creek Tributary 2, Imhoff Creek, Stream D are lower than the regulatory flood elevations in that area, which must take into account the 1-percent annual chance flooding due to backwater from other sources. The area between the floodway and 1-percent-annual-chance floodplain boundaries is termed the floodway fringe. The floodway fringe encompasses the portion of the floodplain that could be completely obstructed without increasing the water-surface elevation of the 1-percent-annual-chance flood more than 1.0 foot at any point. Typical relationships between the floodway and the floodway fringe and their significance to floodplain development are shown in Figure 1. Figure 1. Floodway Schematic 37