WALTON COUNTY, FLORIDA AND INCORPORATED AREAS

COMMUNITY COMMUNITY NAME NUMBER DE FUNIAK SPRINGS, CITY OF 120318 FREEPORT, CITY OF 120319 PAXTON, TOWN OF 120423 WALTON COUNTY (UNINCORPORATED AREAS) 120317

REVISED SEPTEMBER 29, 2010

Federal Emergency Management Agency FLOOD INSURANCE STUDY NUMBER

12131CV000A

NOTICE TO FLOOD INSURANCE

STUDY USERS

Communities participating in the National Flood Insurance Program have established repositories of flood hazard data for floodplain management and flood insurance purposes. This Flood Insurance Study (FIS) may not contain all data available within the repository. It is advisable to contact the community repository for any additional data. Part or all of this FIS may be revised and republished at any time. In addition, part of this FIS may be revised by the Letter of Map Revision process, which does not involve republication or redistribution of the FIS. It is, therefore, the responsibility of the user to consult with community officials and to check the community repository to obtain the most current FIS components. Initial Countywide FIS Effective Date: March 7, 2000

Revised Countywide FIS Date(s): September 29, 2010

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TABLE OF CONTENTS

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1.0 INTRODUCTION ...............................................................................................................1 1.1 Purpose of Study ..................................................................................................... 1 1.2 Authority and Acknowledgments ............................................................................1 1.3 Coordination ...........................................................................................................3

2.0 AREA STUDIED ................................................................................................................ 4

2.1 Scope of Study ........................................................................................................4 2.2 Community Description .......................................................................................... 7 2.3 Principal Flood Problems ........................................................................................ 8 2.4 Flood Protection Measures ................................................................................... 15

3.0 ENGINEERING METHODS ...........................................................................................15

3.1 Riverine Hydrologic Analyses ..............................................................................15 3.2 Riverine Hydraulic Analyses ................................................................................ 25 3.3 Coastal Hydrologic Analyses ................................................................................30 3.4 Coastal Hydraulic Analyses ..................................................................................34 3.5 Vertical Datum ...................................................................................................... 40

4.0 FLOODPLAIN MANAGEMENT APPLICATIONS ....................................................... 41

4.1 Floodplain Boundaries .......................................................................................... 41 4.2 Floodways ............................................................................................................. 42

5.0 INSURANCE APPLICATION ......................................................................................... 56 6.0 FLOOD INSURANCE RATE MAP ................................................................................ 58 7.0 OTHER STUDIES ............................................................................................................ 58 8.0 LOCATION OF DATA ....................................................................................................58 9.0 BIBLIOGRAPHY AND REFERENCES .........................................................................60

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TABLE OF CONTENTS (continued)

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FIGURES Figure 1 - Transect Location Map ..................................................................................................36 Figure 2 - Transect Schematic ........................................................................................................39 Figure 3 - Floodway Schematic......................................................................................................56

TABLES Table 1 - Flooding Sources Studied By Detailed Methods .............................................................4 Table 2 - Letters of Map Revisions ................................................................................................5 Table 3 - Scope of Revision ...........................................................................................................6 Table 4 - Historical Tide Gage Water Level Records For Florida Panhandle Region..................10 Table 5 - Summary of Discharges .................................................................................................19 Table 6 - Summary of Ponding Elevations ...................................................................................29 Table 7 - Parameter Values For Surge Elevations ........................................................................32 Table 8 - Summary of Still Water Elevations ...............................................................................33 Table 9 - Transect Descriptions ....................................................................................................37 Table 10 - Transect Data .................................................................................................................40 Table 11- Floodway Data ...............................................................................................................44 Table 12 - Community Map History ...............................................................................................59

EXHIBITS Exhibit 1 – Flood Profiles

Alaqua Creek Panels 01P-02P Bay Branch Panels 03P-04P Bear Creek Tributary 1 Panels 05P-06P Bear Creek Tributary 2 Panel 07P Bear Creek Tributary 3 Panel 08P Black Creek Panel 09P Bruce Creek Panels 10P-16P Camp Creek Panel 17P Choctawhatchee River Panels 18P-22P Draper Lake Unnamed Tributary Panel 23P Draper Lake Unnamed Tributary – Tributary No. 1 Panel 24P Fourmile Creek North Tributary Panels 25P-26P

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TABLE OF CONTENTS (continued)

Exhibit 1 – Flood Profiles (continued)

Fourmile Creek North Tributary 1 Panel 27P Fourmile Creek North Tributary 2 Panel 28P Fourmile Creek North Tributary 3 Panel 29P Fourmile Creek North Tributary 4 Panel 30P Fourmile Creek North Tributary 5 Panel 31P Fourmile Creek North Tributary 6 Panel 32P Fourmile Creek South Tributary Panel 33P Gum Creek Panels 34P-35P Lafayette Creek Panels 36P-43P Mill Creek Panels 44P-47P Mill Creek Unnamed Tributary Panels 48P-49P Pate Branch Panel 50P Shoal River Panels 51P-56P

Exhibit 2 – Flood Insurance Rate Maps

Flood Insurance Rate Map Index Flood Insurance Rate Map

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FLOOD INSURANCE STUDY WALTON COUNTY, FLORIDA AND INCORPORATED AREAS

1.0 INTRODUCTION 1.1 Purpose of Study

This countywide Flood Insurance Study (FIS) investigates the existence and severity of flood hazards in, or revises and updates previous FISs/Flood Insurance Rate Maps (FIRMs) for the geographic area of Walton County, Florida, including the Cities of De Funiak Springs and Freeport, the Town of Paxton, and the unincorporated areas of Walton County (hereinafter referred to collectively as Walton County). This FIS aids in the administration of the National Flood Insurance Act of 1968 and the Flood Disaster Protection Act of 1973. This study has developed flood risk data for various areas of the county that will be used to establish actuarial flood insurance rates. This information will also be used by Walton County to update existing floodplain regulations as part of the Regular Phase of the National Flood Insurance Program (NFIP), and by local and regional planners to further promote sound land use and floodplain development. Minimum floodplain management requirements for participation in the NFIP are set forth in the Code of Federal Regulations at 44 CFR, 60.3. 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 FIS are the National Flood Insurance Act of 1968 and the Flood Disaster Protection Act of 1973. This FIS was prepared to include unincorporated areas and incorporated communities within Walton County in a countywide FIS. The authority and acknowledgements for each jurisdiction included in this countywide FIS, as compiled from their previously printed FIS reports, are shown below: Freeport, City of For the FIS dated April 30, 1986, the hydrologic and

hydraulic analyses were obtained from the FIS for the unincorporated areas of Walton County (Reference 1).

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Walton County (Unincorporated Areas) For the FIS dated August 19, 1997, the updated

hydraulic analyses for the Gulf of Mexico were prepared by Dewberry & Davis under contract to FEMA. That work was completed in December 1995. For the FIS dated April 30, 1986, the hydrologic and hydraulic analyses for Alaqua Creek and the hydrologic analysis for the Choctawhatchee River were performed by Stottler Stagg & Associates. The hydraulic data for the Choctawhatchee River were also obtained from Stottler Stagg & Associates. The storm surge elevations for Choctawhatchee Bay and the Gulf of Mexico were obtained from GKY & Associates, Inc. That work was performed for the Federal Emergency Management Agency (FEMA) under Contract No. EM W-C-0969. The hydraulic analyses for Choctawhatchee Bay and the Gulf of Mexico were performed by FEMA. Choctawhatchee Bay and the Gulf of Mexico were performed by FEMA. That work was completed in October 1984.

The authority and acknowledgements for the City of De Funiak Springs and the Town of Paxton are not available because no FIS reports were published for those communities. For the March 7, 2000 revision, the hydrologic and hydraulic analyses for the coastal flood studies of the Florida Panhandle were performed by Woodward-Clyde Consultants for FEMA under Contract No. EMW-95-C-4678/TO043. The coastal 1-percent annual chance stillwater elevations and analyses were revised by Dewberry & Davis, under subcontract to Woodward-Clyde. This work was completed in April 1998. For this revision, additional hydrologic and hydraulic analyses were prepared for FEMA by URS Corporation under contract with the Northwest Florida Water Management District (NWFWMD), a FEMA Cooperating Technical Partner (CTP). The digital base map files were derived from the Florida Department of Revenue aerials produced at a scale of 1:200 from photography dated April 27, 2007. The coordinate system used for the production of the digital FIRMs is State Plane in the Florida HARN North projection zone, referenced to the North American Datum of 1983.

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1.3 Coordination

Consultation Coordination Officer's (CCO) meetings may be held for each jurisdiction in this countywide FIS. An initial CCO meeting is held typically with representatives of FEMA, the community, and the study contractor to explain the nature and purpose of a FIS, and to identify the streams to be studied by detailed methods. A final CCO meeting is held typically with representatives of FEMA, the community, and the study contractor to review the results of the study. On June 10, 1985, the results of the City of Freeport FIS were reviewed and accepted at a final CCO meeting attended by representatives of the community and FEMA. For the April 30, 1986, Walton County, Florida (Unincorporated Areas) FIS, the study was initialized August 8, 1979, in a letter sent to Mr. Bob Anderson (Chairman, Walton County Commission) from Stottler Stagg & Associates. On June 10, 1985, the results of the study were reviewed and accepted at a final CCO meeting attended by representatives of Stottler Stagg & Associates, FEMA, and the county. For the August 19, 1997, Walton County, Florida (Unincorporated Areas) FIS, the county was notified by FEMA in a May 26, 1995, letter that the FIS would be revised using the Dewberry & Davis analyses. For the March 7, 2000 countywide FIS, Walton County was notified by FEMA in a letter dated July 11, 1997, that the existing coastal base flood elevations and FIS would be revised based upon the analyses and investigations performed by Woodward-Clyde Consultants, the study contractor, and their sub-contractor Dewberry & Davis. An intermediate coastal data submission, meeting notification, and transmittal with draft coastal hazard assessment work maps were sent to the county by FEMA on July 15, 1998. Although representatives from FEMA, Woodward-Clyde, and Dewberry & Davis were in the region to conduct meetings from August 24 to 27, 1998, there was no intermediate meeting held with representatives from Walton County. The purpose of the meeting was to inform the county on the progress of the study and to review the draft work maps depicting the revised coastal flood hazard assessments. A final CCO meeting was held on February 8, 1999, and was attended by representatives of FEMA, Walton County, and the City of Freeport. For this revision, an initial CCO (Scoping) meeting was held on November 15, 2005 and was attended by representatives of the study contractors, the communities, the NWFWMD and FEMA. A final CCO meeting was held on May 8, 2008. This meeting was attended by representatives of the study contractors, the communities, the NWFWMD and FEMA.

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2.0 AREA STUDIED 2.1 Scope of Study

This FIS covers the geographic area of Walton County, Florida. All or portions of the flooding sources listed in Table 1 – “Flooding Sources Studied By Detailed Methods,” were studied by detailed methods. Limits of detailed study are indicated on the Flood Profiles (Exhibit 1) and on the FIRM (Exhibit 2).

TABLE 1 - FLOODING SOURCES STUDIED BY DETAILED METHODS

Alaqua Creek Fourmile Creek North Tributary 2 Bay Branch Fourmile Creek North Tributary 3 Bear Creek Fourmile Creek North Tributary 4 Bear Creek Tributary 1 Fourmile Creek North Tributary 5 Bear Creek Tributary 2 Fourmile Creek North Tributary 6 Bear Creek Tributary 3 Fourmile Creek South Tributary Black Creek Gulf of Mexico Bruce Creek Gum Creek Camp Creek Lafayette Creek Choctawhatchee Bay La Grange Bayou Tributary 1 Choctawhatchee River Mill Creek Draper Lake Unnamed Tributary Mill Creek Unnamed Tributary Draper Lake Unnamed Tributary – Tributary No. 1

Pate Branch Ponding Area No. 1

Fourmile Creek North Tributary Ponding Area No. 2 Fourmile Creek North Tributary 1 Shoal River

For the March 7, 2000 countywide FIS, updated coastal hydrologic and hydraulic analyses were performed for the Gulf of Mexico, and Choctawhatchee Bay, west of U.S. Route 331. Limits of the revised coastal analysis are outlined in Section 3.3, “Coastal Hydrologic Analyses.” In addition, Alaqua Creek experienced backwater changes due to the revised coastal analyses.

This revised countywide FIS incorporates five Walton County Letters of Map Revision (LOMRs). Table 2 – “Letters of Map Revision,” is a summary of the LOMRs incorporated into this revised countywide FIS. For this revision, new or revised hydrologic and hydraulic analyses were included for the flooding sources shown in Table 3 – “Scope of Revision.”

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TABLE 2 – LETTERS OF MAP REVISION

Case No. Project Identifier Flooding Source(s) Effective Date 03-04-493P Gulf Hills

Campground Draper Lake Unnamed Tributuary Draper Lake Unnamed Tributary – Tributary No. 1 Ponding Area No. 1 Ponding Area No. 2

April 5, 2004

04-04-299P Noble Dunes

Subdivision Unnamed Ponding Area October 10, 2004

06-04-BC49P Hammock Bay

North Fourmile Creek North Tributary Fourmile Creek North Tributary 1 Fourmile Creek North Tributary 2 Fourmile Creek North Tributary 3 Fourmile Creek North Tributary 4 Fourmile Creek North Tributary 5 Fourmile Creek North Tributary 6 Fourmile Creek South Tributary

December 20, 2006

07-04-0470P Hammock Bay

South Bear Creek Bear Creek Tributary 1 Bear Creek Tributary 2 Bear Creek Tributary 3 Bear Creek Tributary 2.1 LaGrange Bayou Tributary 1 Unnamed Flooding to Bear Creek Tributary 1

March 30, 2007

07-04-3565X Hammock Bay

South Bear Creek Tributary 1 Bear Creek Tributary 3

April 30, 2007

08-04-3897P Grand Dunes

Condominium – 219 Scenic Gulf Drive

Gulf of Mexico March 20, 2009

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TABLE 3 - SCOPE OF REVISION Stream Limits of New or Revised Detailed Study

Bay Branch From its confluence with Bruce Creek to a point

approximately 1.65 miles upstream to its intersection with an unnamed tributary located 945 feet west of U.S. Highway 331.

Black Creek From its intersection with County Highway 3280 to a point approximately 0.17 mile upstream of the confluence of Camp Creek.

Bruce Creek From approximately 1,000 feet downstream of the confluence of Mill Creek to a point approximately 7.45 miles upstream.

Camp Creek

From its confluence with Black Creek to a point approximately 1.0 mile upstream to its confluence with Pate Branch.

Gum Creek From the Shoal River confluence to a point approximately 2.4 miles upstream.

Lafayette Creek From the intersection of State Road 20 upstream to its confluence with an unnamed tributary located 3,300 feet upstream of J.W. Hollington Road.

Mill Creek From its confluence with Bruce Creek upstream approximately 3.46 miles to its intersection with Edgewood Circle.

Mill Creek Unnamed Tributary From its confluence with Mill Creek upstream approximately 0.9 mile to its intersection with Edgewood Circle.

Pate Branch From its confluence with Camp Creek upstream 0.8 miles to its confluence with Turnpike Branch.

Shoal River From the Okaloosa / Walton County line upstream approximately 14.5 miles to its confluence with Gum Creek.

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The areas studied by detailed methods were selected with priority given to all known flood hazard areas and areas of projected development and proposed construction. The scope and methods of study were proposed to and agreed upon by FEMA, the NWFWMD and Walton County. Numerous flooding sources in the county were studied by approximate methods. Approximate analyses were used to study those areas having a low development potential or minimal flood hazards. The scope and methods of study were proposed to and agreed upon by FEMA and Walton County.

2.2 Community Description

Walton County is located on the Gulf of Mexico, approximately in the middle of the Florida Panhandle. Walton County is bordered by Okaloosa County to the west, Covington and Geneva Counties, Alabama to the north, Bay, Holmes, and Washington Counties to the east, and the Gulf of Mexico to the south. The county had a 2008 population of 53,837 (Reference 4). The topography of Walton County varies with slopes ranging from flat, along the Gulf Coast, to moderate in the north half of the county. Terrain along the Gulf of Mexico is high enough to form a barrier against many of the hurricane inland penetration surges. The inland areas are generally rolling, with large areas of forest. Poor drainage in some of the areas allows for the detention of surface water that has produced extensive areas of swamp. The terrain of Walton County rises to an elevation of 345 feet North American Vertical Datum 1988 (NAVD), the highest elevation in Florida, at a location near the Alabama border. Soils of Walton County consist of poorly drained sands with muck along the Gulf Coast, excessively drained sands in the central region and well drained sand and loams in the northern part of the county. The climate of Walton County is subtropical, with a moderating influence from the Gulf of Mexico. The average daily normal temperature varies from 55 degrees Fahrenheit (°F) in January to 82̊ F in August. The annual precipitation is 57.6 inches.

Choctawhatchee Bay is a prominent feature in the county. It is approximately 6 miles wide and extends for approximately 18 miles across the southern portion of the county. It is transversed by the Intracoastal Waterway, which has a dredged channel to the east. The Choctawhatchee River flows into the eastern end of the bay over a wide, swampy flood plain. The river has a large basin that begins in Alabama and is subject to severe rainfall flooding. The Alaqua Creek drainage is contained completely within Walton County. The headwaters are located mid-county near De Funiak Springs, Florida and are primarily south of the I-10 corridor. The system flows south and discharges into Choctawhatchee Bay via Alaqua Bayou. The Bruce Creek / Mill Creek drainages are contained completely

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within Walton County. The headwater areas are located mid-county near De Funiak Springs, Florida beginning just north of the I-10 corridor. Mill Creek joins Bruce Creek, which flows east until its confluence with the Choctawhatchee River along the Washington County boundary. Pate Branch and Camp Creek are part of the Black Creek drainage, which is contained completely within Walton County. Pate Branch begins east of the City of Freeport, Florida located in the southeast quadrant of Walton County and flows south into Camp Creek. Camp Creek flows southward and joins Black Creek just east of County Highway 3280. The Lafayette Creek drainage is contained completely within the southeast quadrant of Walton County. This system, which is situated between the Black Creek and Bruce Creek drainages, initially flows to the west and then turns south at the eastern flank of the City of Freeport, Florida. Lafayette Creek empties into Fourmile Creek, which drains into Choctawhatchee Bay via LaGrange Bayou. The Shoal River is the largest internally drained system in the County, draining the majority of the area in the northwest quadrant. Within Walton County, the Shoal River drainage is located north of the I-10 corridor with the headwaters area situated west of State Road 83. The system flows in a westerly direction beyond the Walton / Okaloosa County boundary before turning south at Crestview, Florida to join the Yellow River.

Rapid population growth, along with the attraction of the beaches, has resulted in some development in areas that would be adversely affected by a hurricane storm tide. Development in stream floodplains, however, is fairly light.

The City of De Funiak Springs is located in the central portion of the county and serves as the county seat. The 2008 population was 5,012 (Reference 4). The City of Freeport is located just north of the northern shoreline of Choctawatchee Bay, approximately 7 miles south of the City of De Funiak Springs. The 2008 population was 1,768 (Reference 4). The Town of Paxton is located on the northern border of Walton County, at the Alabama state line, approximately 25 miles northwest of the City of De Funiak Springs. The 2008 population was 809 (Reference 4).

2.3 Principal Flood Problems

Flood problems in the county can be attributed to both riverine flooding and tidal surge. Riverine flooding occurs as a result of both naturally occurring storm patterns and severe precipitation due to hurricanes. Some of the worst floods to occur in northwestern Florida were the result of high intensity rainfall during hurricanes. The time of concentration of runoff for large basin rivers in northwestern Florida may be several days. Consequently, peak flows do not typically coincide with hurricane tides at the coast. Smaller streams,

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however, have a shorter time of concentration and floodflow occurring concurrently with the storm surge is more likely. This greatly increases the likelihood of inundation of low-lying areas along the coast. Maximum precipitation volumes typically occur in the eastern portion of cyclonic type storm systems. As the storm passes inland, its intensity decreases, but heavy rainfall continues. It is not uncommon in northwestern Florida, for total precipitation to be as high as 24 inches for a hurricane related storm (Reference 5). Normal rainfall patterns are greatest during two distinct periods: 1) during summer, due to afternoon and evening thunderstorms, and 2) during the late winter and early spring, due to frontal systems. The Choctawatchee River, a major river in the county, accounts for much of the flooding in the area. The Choctawatchee River is characterized by wide, flat flood plains varying from several thousand feet to several miles wide. The flat slopes and wide, heavily vegetated flood plains enhance the flood problems by preventing the rapid drainage floodwaters. At flood stage inundation occurs over large areas, flooding forest and farm land, fishing resorts, and other businesses built on the floodplain. Major floods to date include the 1929 flood and the 1975 flood. The 1929 flood was the largest flood ever recorded. At the gaging station near Bruce, Florida, the Choctawhatchee River reached an elevation of 28.94 feet mean sea level (msl), 7.46 feet higher than the next largest flood. The 1975 flood was the second largest flood recorded; it reached an elevation of 21.48 feet msl. The recurrence interval of this 1975 flood is once every 19 years while the 1929 flood interval would be less than once in 500 years. Alaqua Creek, though not as large as the Choctawhatchee River, experiences flooding from both extensive rainfall and high storm surges. Even though no severe flooding problems have been recorded, Alaqua Creek poses a threat to the area’s residential housing and also to future development along the stream. The coastal areas of Walton County are subject to flooding from tidal surges associated with hurricanes both along the Gulf of Mexico and inside Choctawhatchee Bay. Generally, the terrain inland along Choctawatchee Bay rises fairly rapidly and flooding from surges is restricted to only short distances inland of the bay shoreline. Walton County has experienced flooding from several hurricanes since 1870. Reports of high water marks for the hurricanes of 1936 were 8.1 feet NAVD at Fort Walton Beach, Okaloosa County, and from 6.7 to 7.7 feet NAVD at Destin, in Okaloosa County. This compares with the GKY 1-percent annual chance surge prediction of 1.7 to 6.7 feet NAVD. The prediction does not incorporate the effects of wind driven waves or the tidal influences of the heavenly bodies. In October

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1995, Hurricane Opal produced high storm surge tides in Walton County. Hurricane Opal highwater marks along the Gulf of Mexico shoreline of Walton County were from 7.7 to 24.7 feet NAVD and in Choctawhatchee Bay from 5.7 to 6.7 feet NAVD. Present conclusions about recurrence coastal flood elevations rely heavily on historical evidence from the continuous tidal records identified in Table 4. For the March 7, 2000 countywide FIS, in order to evaluate existing FIS coastal flood frequencies and revised 1-percent annual chance stillwater elevations, historical tide gauge water level records for the Florida Panhandle region were used. These water level records are shown in Table 4 – “Historical Tide Gage Water Level Records for Florida Panhandle Region.” Brief notes on the history and damages caused by hurricanes are abstracted from reports by the U.S. Army Corps of Engineers (USACE) (References 6 and 7). Additional information on hurricane history and damages, particularly for recent storms, comes from papers published in the Monthly Weather Review. The following pages list the significant storms affecting the panhandle in this century. Damage figures are those determined for values at the time of the storm, and no attempt has been made to adjust these figures to present day values.

TABLE 4 - HISTORICAL TIDE GAGE WATER LEVEL RECORDS FOR FLORIDA

PANHANDLE REGION

Agency And Gauge I.D. Site Name Latitude Longitude

Mean Tide Range (Feet)

Period of

Record NOS 8728690 Apalachicola 29° 43.6’N 84° 58.9’W 1.11 1967-95 USACE 02359665

Panama City 30° 09’22" N 85° 38’12" W 1.33 1935-95

NOS 8729108 Panama City 30° 09. I’ N 85° 40.0'W 1.24 1975-95 NOS 8729210 Panama City

Beach ~ 30.2° N ~ 85.8° W 1.25 1989-94

USACE 02366990

Destin / East Pass 30° 23’20" N 86° 30’04" W 0.58 1957-94

NOS 8729681 Navarre Beach 30° 22.6’N 86° 51.9'W 0.74 1978-89 NOS 8729840 Pensacola 30° 24.2’N 87° 12.8’W 1.19 1923-95 USACE 02376083

Gulf Beach 30° 18’50" N 87° 25’40" W 0.83 1940-95

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1915 (August 31 – September 6) This storm made landfall near Port St. Joe, Florida with the heaviest damage occurring to the east near Apalachicola, Florida. Damage was estimated to cost $40,000. Tide levels of 7.8 feet mean sea level (msl) were recorded at Carrabelle, Florida. 1917 (September 2l – September 29) This storm made landfall near Fort Walton Beach, Florida with damages estimated at $270,000. Tide levels of 7.8 msl were recorded at Fort Barrancas, Florida. 1924 (September 13 – September 19) Crossing the shoreline near Port St. Joe, this storm caused damage estimated at $275,000. Winds of 80 miles per hour (mph) were recorded at Panama City. 1929 (September 21 – October 4) The center of this storm entered the coast near Panama City. Damage from the storm was estimated at $500,000. 1936 (July 27 – August 1) The center of this storm passed over Fort Walton Beach and Valparaiso, Florida. Damage was estimated at $150,000. Tide levels of 7 to 8 feet msl were recorded at Destin, Florida. A high water mark of 8.4 feet msl was reported at Fort Walton Beach. 1950 Hurricane Baker (August 20 – September 1) The center of this storm entered the coast between Pensacola, Florida, and Mobile, Alabama, with damage estimated at $550,000. Tide levels recorded during the passage of this storm include: 4.5 feet msl at Pensacola and Carrabelle; 5 feet msl at Panama City; and, 6.8 feet msl at Apalachicola. 1953 Hurricane Florence (September 23 – September 28) This storm made landfall between Panama City and Fort Walton Beach with damage estimated at $150,000.

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1956 Hurricane Flossy (September 21 – September 30) This major hurricane caused extensive damage along the Louisiana, Mississippi, and Alabama coasts. Total damage was estimated at $25 million. Tide levels of 5.5 msl were recorded at Fort Walton Beach. Tides at Destin were estimated at 6 to 7 feet msl. 1972 Hurricane Agnes (June 14 – June 22) This storm hit the shoreline near Panama City. Tide levels of 8 to 9 feet msl were recorded at several points from St. George Island to Panacea, Florida. 1975 Hurricane Eloise (September 13 – September 24) Making landfall approximately 40 miles west of Panama City, this storm produced highwater marks, ranging from 10 to 18 feet msl, between Destin and Port St. Joe. Damage to shorefront residential structure was extensive. Over $1.08 billion of damage to residential and commercial property was claimed as a result of this storm. 1979 Hurricane Frederic (August 29 – September 14) Making landfall west of Mobile Bay, in Alabama, this storm resulted in damage to shorelines, residential and commercial structures, along Mississippi, Alabama, as well as Escambia County, Florida shorelines. Dauphin Island, Alabama, sustained extensive damage, resulting from wind and the tidal surge from the Gulf of Mexico. Over $3.5 billion in damage to residential and commercial property were claimed as a result of this storm. 1985 Hurricane Elena (August 29 – September 2) Crossing the shoreline, near Gulfport, Mississippi, this storm resulted in damages to residential and commercial property in portions of Louisiana, Mississippi, Alabama and portions of the western panhandle of Florida. Due to the storm track running parallel to the Florida shoreline, significant damage to shorefront structures was sustained between Apalachicola and Pensacola Beach. Nearly $1.4 billion in damage to residential and commercial property was claimed as a result of this storm (Reference 8). 1985 Hurricane Kate (November 15 – November 23) The second hurricane of 1985 to affect the Florida panhandle was a Category 2 hurricane that made landfall near the Port St. Joe. With sustained winds approaching 100 miles an hour, this storm resulted in damaged to shoreline residential and commercial structures. Storm related damage was reported along eastern portions of the Florida panhandle, as well as in the City of Tallahassee, Florida and northward.

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Over $300 million in damage to residential and commercial property were claimed as a result of this storm (Reference 8). 1994 Tropical Storm Alberto (June 30 – July 7) This storm, although never reaching hurricane intensity, made landfall near Pensacola Beach with only minor beach and structural damage being reported. This slow moving storm stalled over portions of Alabama and Georgia resulting in extensive flooding, due to excessive rainfall, over portions of the Florida panhandle, as well as portions of Alabama and Georgia. Storm related damage exceeded $500 million (Reference 8). 1995 Hurricane Erin (July 31 – August 6) This storm made its second Florida landfall, as a weak Category 2 storm, near Fort Walton Beach, on August 3. Moderate beach erosion was sustained between Navarre Beach and Pensacola Beach. Storm surges varied from 3 feet, in Pensacola Beach to 7 feet, in Navarre Beach. Damage to residential and commercial structures, resulting from hurricane force winds, affected over 2000 structures within portions of the Cities of Pensacola and Mary Esther, as well as Pensacola Beach and Navarre Beach. Storm-related damages to residential and commercial property, within the State of Florida, approached $350 million (Reference 9). 1995 Hurricane Opal (September 27 – October 5) After briefly reaching Category 4 intensity in the Gulf of Mexico, Hurricane Opal made landfall as a Category 3 hurricane, near Pensacola Beach, on October 4. Hurricane force winds were reported between Pensacola Beach and Cape San Blas, with sustained winds exceeding 100 miles an hour, in an area between the Cities of Destin and Panama City Beach. Beaches and dune systems, already weakened by Hurricane Erin, sustained extensive erosion and wash over as a result of the storm. Storm surges varied, depending on location, between 5 and 18 feet. Breaking waves in some areas added approximately 10 feet to the reported storm surge. High water marks above mean sea level, varied from 10 feet in Pensacola Beach, to 18 feet in Panama City Beach, to over 25 feet in Walton County. Beach and dune erosion, as well as damage to commercial and residential structures, was reported to be extensive for shoreline areas of the Gulf of Mexico, as well as portions of shoreline areas of Pensacola Bay, Santa Rosa Sound, and Choctawhatchee Bay. Storm related damages to residential and commercial property exceeded $3 billion (References 10, 11, and 12).

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2004 Hurricane Ivan (September 2 – September 24) Hurricane Ivan made landfall as a Category 3 hurricane with sustained winds exceeding 91 mph near the southern Alabama-western Florida Panhandle border, on September 16th. Ivan became a tropical depression on September 17th over northeast Alabama, yet still strong enough to cause flash floods and tornado damage across most of the southeastern United States. Rainfall totals generally ranged from 3 to 7 inches in Florida. A television station in Pensacola, Florida reported that rainfall exceeded 15 inches. Widespread flooding occurred as a result of the severe rainfall from Hurricane Ivan, which fell on already saturated ground caused by Tropical Storm Bonnie and Hurricane Frances in August and early September. The coastline from Destin, Florida in the panhandle to Mobile Bay, Alabama reported storm surges of 10 to 15 feet. The coastline from Destin east to St. Marks in the Florida Big Bend region had storm surges of 6 to 9 feet. Ivan caused severe damage to the coastal and inland areas of the Florida panhandle. Ivan was the most destructive hurricane to hit Baldwin, Escambia, and Santa Rosa Counties in more than 100 years. The American Insurance Services Group estimates that the insured losses in the United States are over $7 billion, with over $4 billion in Florida alone. The damages of insured and uninsured are over $14 billion. 2005 Hurricane Dennis (July 4 – July 13)

Hurricane Dennis (Dennis) was an unusually strong July major hurricane that left a trail of destruction from the Caribbean Sea to the northern coast of the Gulf of Mexico. Dennis entered the Gulf of Mexico on July 9 as a Category 1 hurricane and intensified over the next 30 hours to Category 3 strength. Dennis made landfall on Santa Rosa Island, Florida, between Navarre Beach and Gulf Breeze, on July 10 as a Category 2 hurricane. The system continued north-northwestward after landfall, with the center moving across the western Florida Panhandle into southwestern Alabama before it weakened into a tropical storm on July 11. Dennis brought hurricane conditions to portions of the western Florida Panhandle and southwestern Alabama. An instrumented tower located at Navarre, Florida measured 1-min average winds of 86 knots and a gust to 105 knots. While hurricane-force winds associated with Dennis covered only a small area, the hurricane had a large cyclonic envelope with tropical storm-force winds extending well to the east of the center over southern Florida and the Florida Panhandle. Dennis produced a storm surge of 6 to 7 feet above normal tide levels on Santa Rosa Island near where the center made landfall. This surge overwashed Santa Rosa Island near and west of Navarre Beach. A storm surge of 6 to 9 feet above normal tide levels occurred in Apalachee Bay, Florida, which inundated parts of the town of St. Marks and other nearby areas. A storm surge of 4 to 6 feet occurred elsewhere in the Florida Panhandle. Dennis is known to have caused nine tornadoes in Florida and one in Georgia, and to have produced widespread heavy rainfall especially along the western Florida Panhandle and Alabama. A

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station located northeast of the City of Tallahassee, Florida reported a storm total rainfall of 6.95 inches and a station 10 miles northwest of Camden, Alabama, reported a storm total rainfall of 12.80 inches. Dennis is reported to have caused 3 deaths in the United States, and the American Insurance Services Group estimates that the insured and uninsured damages were $2.23 billion (Reference 13).

2.4 Flood Protection Measures

There are no flood protection measures or floodplain management activities on the streams of Walton County. A few individuals have built private bulkheads, and some of the new homes are being constructed with the first floor above the 1-percent annual chance base flood elevation.

3.0 ENGINEERING METHODS

For the flooding sources studied in detail in the county, standard hydrologic and hydraulic study methods were used to determine the flood hazard data 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 which equals or exceeds the 100-year flood (1-percent chance of annual exceedence) in any 50-year period is approximately 40 percent (4 in 10), and, for any 90-year period, the risk increases to approximately 60 percent (6 in 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 Riverine Hydrologic Analyses

Hydrologic analyses were carried out to establish the peak discharge-frequency relationships for each riverine flooding source studied in detail affecting the county. These hydrologic studies were conducted to provide the necessary streamflow data used to determine flood elevations and associated floodplain and floodway boundaries within these flood sources. March 7, 2000 Countywide FIS Analyses Peak discharge estimates of the 10-, 2-, 1-, and 0.2-percent annual chance events were obtained from a log-Pearson Type III distribution analysis of peak flow data obtained at 20 nearby USGS gaging stations in accordance with the guidelines set

16

forth in U.S. Water Resources Council (WRC) Bulletin No. 17A (Reference 14). Gage records range from 10 to 47 years of length and have an average length of record of 15 years (Reference 15). Two methods were used to determine the discharges used for the Choctawhatchee River. For gaged sites with 10 years or more of record, historical data were fitted to a log-Pearson Type III distribution to obtain the desired discharge-frequency relationship. For this analysis, the methods established in WRC Bulletin No. 17A (Reference 14) were followed utilizing data provided by the Tallahassee Subdistrict of the USGS. For ungaged sites, regional analyses were performed using the procedures in USGS Water Supply Paper (WSP) 1674, “Magnitude and Frequency of Floods in the United States” (Reference 16). To determine the accuracy of the data and curves in WSP No. 1674, various frequency flows at gaged sites were estimated by regional analysis and compared to the log-Pearson Type III distributions obtained from the data at the gages. The log-Pearson Type III distributions were consistently steeper that the regionally determined distributions and always provided the better fit to the actual measured data. Variations in the estimated flows by the two methods often exceeded 100 percent, particularly at the higher recurrence intervals. To minimize the disparity between the regionally determined and log-Pearson Type III flows, it was necessary to modify the regional curves on a hydrologic subunit basis to reflect more accurately flood frequency conditions. The regional analysis methodology of WSP No. 1674 was developed utilizing a log-normal distribution for data through 1961. The initial modifications to the regional analysis were to include all data through the 1977 Water Year and to reconstruct the regional curves in WSP No. 1674 using log-Pearson Type III distributions rather than log-normal distributions. This was done by replotting the Mean Annual Flow (Qm) vs. Drainage Area relationship, taking Qm from the log-Pearson Type III curves at each gage. The ratio of Peak Flow (QP/Qm) vs. Recurrence Interval was also replotted using log-Pearson Type III values. By incorporating skew into the regional analysis, the regionally determined distributions were made similar to the log-Pearson Type III distributions at the gages. The differences in the estimated flows at the gages by the two methods were also smaller, reflecting the fact that the flows were determined by similar distributions and that the regional analysis included an additional 16 years of record at many stations. To further reduce the discrepancies in flows and to bring the regionally determined flows within the expected sampling error at the gages an adjustment factor was applied to the Mean Annual Flow used in the regional analysis. This adjustment was determined in the following manner. For each gaged site in a hydrologic region, flows from the 10-, 2-, 1-, and 0.2-percent annual chance floods determined by a log-Pearson Type III analysis were divided by the regional QP/Qm ratios to give values that represent what Qm should have been for the regional analysis to

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duplicate exactly the log-Pearson Type Ill estimated values at a gage. The six values so obtained were averaged to give a single value Qm', for the station. Plotting Qm' against Qm yielded three straight lines, each representing an individual hydrologically-similar region. The slope of these curves provided a single adjustment factor for each region, applicable to Qm determined from the Qm vs. Drainage Area relationship. This procedure required only one initial correction for streams in a `hydrologic subunit and yielded regionally determined flows that approximate those determined by a log-Pearson Type III analysis. Over the range of annual chance probabilities of interest to this study, the regionally estimated flows fall within the 50-percent confidence interval defined by the confidence limits, applicable to the log-Pearson Type III distributions at the gages. Revised Countywide FIS Analyses For this revised FIS, three methods were employed to estimate streamflows for those systems studied in detail. The availability of historic streamflow data from gages and individual drainage basin characteristics were used to assess and determine the particular hydrologic methodology used for each flood source. Streamflow estimates were developed for the 10-, 2-, 1- and 0.2-percent annual chance events for each of the systems studied in detail. The streamflow estimate results from the individual study areas were compared to the results of a regional assessment, based on a network of gages in the four-county region, to insure consistency. The Shoal River/ Gum Creek Study Area is located on a gaged stream, therefore methodologies for gaged streams were employed to estimate the peak discharge-frequency relationships for this riverine flooding source. The Bruce Creek / Mill Creek, Lafayette Creek and Pate Branch / Camp Creek / Black Creek Study Areas are located on streams either without gages, with limited gage record or not within reasonable proximity to a gage, therefore methodologies for ungaged streams were employed to estimate the peak discharge-frequency relationships for there riverine flooding sources. The Shoal River / Gum Creek Study Area is located in the northwest quadrant of Walton County north of the I-10 corridor. The Shoal River study reach consists of a segment of the Shoal River from the Okaloosa / Walton County line upstream to it confluence with Gum Creek, approximately 14.47 miles in length. The Gum Creek study reach consists of a segment of Gum Creek from its confluence with Shoal River upstream to its confluence with Narrows Creek, approximately 2.41 miles in length. The channel and floodplain areas throughout the basin are primarily forested, with an average channel slope of the combined study reaches of 3.15 feet per mile. The Shoal River Basin has a contributing drainage area of 147 square miles at the Okaloosa County line. This basin can be characterized as rural with upland areas consisting predominantly of cleared pastureland and other agricultural operations with the remaining areas primarily consisting of longleaf evergreen forest

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vegetation. Land use in the basin is predominantly agricultural with only minimal low density urbanization along the US-90 corridor. The overall subbasin area upstream of the Okaloosa County line contains about 0.2-percent lake area. A flood frequency analysis was conducted to estimate streamflows in the in the Shoal River/ Gum Creek Study Area. The USGS gage, Shoal River near Mossy Head, Florida (02368500) was used in this assessment. The Mossy Head gage, which is located on the Shoal River at County Highway 1087, has a drainage area of 123 square miles and data for a 31 year period of record. The methodologies used in this analysis are documented in Bulletin #17B, Guidelines For Determining Flood Flow Frequency, March 1982. Streamflow estimates at other locations within the study reaches were conducted in accordance with methodologies and equations presented in detail in United States Geologic Survey (USGS), Water Resources Investigations 82-4012, Technique For Estimating Magnitude and Frequency of Floods On Natural-Flow Streams In Florida, 1982. A summary of the peak discharge-drainage area relationships for locations within these study reaches is shown in Table 5 – “Summary of Discharges.” The Lafayette Creek Study Area is located in the southeast quadrant of Walton County. The study reach comprises a segment of the creek beginning just upstream of State Road 20 near the eastern flank of the City of Freeport, Florida and going upstream 8.72 miles to its confluence with an un-named tributary located upstream of J.W. Hollington Road. The Lafayette Creek basin has a contributing drainage area of about 36 square miles at the downstream end of the study reach. Overall basin slopes are mild, typical of other Florida panhandle areas adjacent to the Gulf of Mexico. The channel slope within the study reach is about 10 feet per mile and the basin consists of less than 1-percent lakes. The channel and floodplain areas throughout the basin are primarily forested, and upland areas are predominantly cleared pastureland and other agricultural operations with a minor amount of longleaf evergreen forest vegetation. Land use in the basin is predominantly agricultural with only minimal low density urbanization in the City of Freeport along the SR-20 and SR-83 corridors. Adequate stream gage records are not available for the Lafayette Creek study reach. As such, streamflows were estimated at several locations within the study reach using USGS Regional Regression Equations for a series of flood frequencies. The methodologies and equations used in this assessment are presented in detail in United States Geologic Survey (USGS), Water Resources Investigations 82-4012, Technique For Estimating Magnitude and Frequency of Floods On Natural-Flow Streams In Florida, 1982. Data required for this analysis including basin area, channel slope and lake area, were generated with GIS techniques utilizing the 10 meter DEM. (National Elevation Dataset, Horizontal datum: NAD 83, Vertical datum: NAVD 88, 1999). A summary of the peak discharge-drainage area relationships for locations within these study reaches is shown in Table 5 – “Summary of Discharges.”

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TABLE 5 – SUMMARY OF DISCHARGES

Flooding Source and Location

Drainage Area

(Sq. Miles)

Peak Discharges (cfs) 10-

Percent 2-

Percent 1-

Percent 0.2-

Percent ALAQUA CREEK

At mouth 124 6,690 11,305 13,700 20,560 BAY BRANCH

At confluence with Bruce Creek

4.5

1,082

1,428

1,579

1,908

BEAR CREEK TRIBUTARY 1 Approximately 175 feet downstream of the confluence with Bear Creek Tributary 2

1.542 ∗

* 1,000 *

Approximately 50 feet downstream of the confluence with Bear Creek Tributary 3

0.459 * * 596 *

At Unnamed Road 0.184 * * 308 * Approximately 140 feet upstream of Unnamed Road 0.160 * * 272 *

BEAR CREEK TRIBUTARY 2 Just downstream unnamed tributary 1.024 * * 644 *

Approximately 300 feet upstream of Unnamed Road 0.588 * * 371 *

BEAR CREEK TRIBUTARY 3 At Unnamed Road 0.211 * * 253 * Approximately 1,000 feet upstream of Unnamed Road 0.184 * * 233 *

BLACK CREEK At County Highway 3280 42 5,000 10,500 14,000 23,000

BRUCE CREEK At confluence with Bay Branch

12.9

2,846

3,808

4,227

5,144

At West Indian Creek Ranch Road

23.1

4,953

6,595

7,308

8,872

At confluence with Mill Creek

35.4

7,202

9,656

10,721

13,057

CAMP CREEK At confluence with Black Creek

12.8

3,273

4,244

4,821

5,854

∗ Data not available.

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Flooding Source and Location

Drainage Area

(Sq. Miles)

Peak Discharges (cfs) 10-

Percent 2-

Percent 1-

Percent 0.2-

Percent CHOCTAWHATCHEE RIVER

Just upstream of mouth 4,384 64,800 106,000 127,000 187,000 DRAPER LAKE UNNAMED TRIBUTARY

Just upstream of State Highway 30A 0.48 ∗ * 136 *

Approximately 1,200 feet upstream of State Highway 30A

0.12 * * 113 *

DRAPER LAKE UNNAMED TRIBUTARY – TRIBUTARY NO. 1

Approximately 390 feet upstream of the confluence with Draper Lake Unnamed Tributary

0.27 * * 114 *

FOURMILE CREEK NORTH TRIBUTARY

Above Fourmile Creek North Tributary 1 confluence 1.19 * * 714 *

Above Fourmile Creek North Tributary 4 confluence 0.70 * * 323 *

Above Fourmile Creek North Tributary 6 confluence 0.36 * * 156 *

FOURMILE CREEK NORTH TRIBUTARY 1

At mouth 0.34 * * 328 * Above Fourmile Creek North Tributary 2 confluence 0.15 * * 118 *

FOURMILE CREEK NORTH TRIBUTARY 2

At mouth 0.08 * * 119 * FOURMILE CREEK NORTH TRIBUTARY 3

At mouth 0.13 * * 120 * FOURMILE CREEK NORTH TRIBUTARY 4

At mouth 0.23 * * 183 *

∗ Data not available.

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Flooding Source and Location

Drainage Area

(Sq. Miles)

Peak Discharges (cfs) 10-

Percent 2-

Percent 1-

Percent 0.2-

Percent FOURMILE CREEK NORTH TRIBUTARY 5

At mouth 0.20 * * 119 * FOURMILE CREEK NORTH TRIBUTARY 6

At mouth 0.26 * * 140 * FOURMILE CREEK SOUTH TRIBUTARY

At mouth 0.47 * * 463 * Approximately 3,500 feet upstream of mouth 0.19 * * 177 *

GUM CREEK At confluence with Shoal River

40.7

3,107

5,790

7,149

11,023

LAFAYETTE CREEK At J.W. Hollington Road 6.2 746 1,382 1,701 2,580 At State Road 20 36.2 2,530 4,520 5,500 8,230

MILL CREEK At confluence with Bruce Creek

6.7

1,566

2,175

2,441

3,028

MILL CREEK UNNAMED TRIBUTARY

At confluence with Mill Creek

0.7

156

220

249

312

PATE BRANCH At Camp Creek 7.36 1,970 2,502 2,892 3,504

SHOAL RIVER At confluence with Gum Creek

87.6

6,112

11,399

14,176

22,207

At County Road 1087 123 8,140 14,988 18,633 29,141 At Okaloosa County line 147.1 9,038 16,890 21,085 33,3337

* Data not available.

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The Bruce Creek / Mill Creek Study Area is located 7.5 miles upstream of the nearest USGS gage. The Pate Branch / Camp Creek Study Area contains a USGS gage on Pate Branch. The disparity in subbasin area and other characteristics, makes the use of a flood frequency analysis based on gage data inadequate to develop discharge-frequency relationships for these riverine flooding sources. Therefore, rainfall-runoff models were developed to estimate streamflows for the purpose of developing discharge-frequency relationships for these riverine flooding sources. The Black Creek basin does not have a gage data available, therefore a discharge-frequency relationship for this riverine flooding source was developed from a regional assessment based on a network of gages in the four-county region. The Bruce Creek / Mill Creek Study Area is located mid-county, southeast of De Funiak Springs, Florida and is comprised of Bruce Creek, Bay Branch, Mill Creek and an unnamed tributary to Mill Creek. Mill Creek joins Bruce Creek at the downstream terminus of the study area. The Bruce Creek study reach consists of a segment of Bruce Creek from its confluence with Mill Creek upstream approximately 7.45 miles to a location just north of Ingram Road. Bay Branch is tributary to Bruce Creek. The Bay Branch study reach consists of a segment of Bay Branch from its confluence with Bruce Creek upstream 1.65 miles to its intersection with an un-named tributary located 945 feet west of US Highway 331. The Mill Creek study reach extends from its confluence with Bruce Creek to approximately 3.46 miles upstream near the intersection with Edgewood Circle. The Mill Creek unnamed tributary study reach extends from its confluence with Mill Creek to approximately 0.9 miles upstream near the intersection with Edgewood Circle. The channel and floodplain areas throughout the Bruce Creek / Mill Creek Study Area are primarily forested, with an average channel slopes ranging from 7 to 18 feet per mile in the Bruce Creek system and 25 to 59 feet per mile in the Mill Creek system. The Bruce Creek / Mill Creek basin can be characterized as rural with upland areas consisting of longleaf evergreen forest vegetation and areas cleared for pastureland and other agricultural operations. Land use in the basins is predominantly agricultural with only minimal low density urbanization along the US-331 corridor. The Bruce Creek subbasin is 35.5 square miles at the Mill Creek confluence with about 1.9-percent lake area. The Mill Creek subbasin is 6.7 square miles at the Bruce Creek confluence with about 0.5-percent lake area. The Pate Branch / Camp Creek / Black Creek Study Area is located in the southeast quadrant of Walton County and consists of Pate Branch study reach from its confluence with Turnpike branch southward to its confluence with Camp Creek a distance of approximately 0.8 miles; Camp Creek study reach from its confluence with Pate Branch southward to its confluence with Black Creek a distance of approximately 1.1 miles; and Black Creek study reach from its confluence with Camp Creek westward to the bridge at County Highway 3280 a distance of approximately 0.12 miles. The channel and floodplain areas throughout the Study Area are primarily forested, with an average channel slope of 10 feet per mile in the

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Pate Branch / Camp Creek study reach and 0.5 feet per mile in the Black Creek study reach. The Pate Branch / Camp Creek / Black Creek basin can be characterized as rural with upland areas consisting of longleaf evergreen forest vegetation and minor areas cleared for pastureland and other agricultural operations in the Pate Branch/ Camp Creek subbasin. Land use in the basin is predominantly upland forest, minor agricultural use and only minimal low density urbanization along Phillips Drive in the Pate Branch / Camp Creek subbasin and along the SR-20 and County Road 3280 corridors. The Black Creek basin is 42 square miles at the intersection of SR-20, and the Pate Branch/ Camp Creek subbasin is 12.8 square miles at its confluence with Black Creek. The Pate Branch / Camp Creek subbasin has about 0.1-percent lake area. The lake area for Black Creek basin was not determined for this study. Rainfall-runoff computer based models of the Bruce Creek / Mill Creek Study Area and the Pate Branch / Camp Creek study reaches were developed to estimate streamflows for the purpose of developing discharge-frequency relationships for these riverine flooding sources. The Army Corps of Engineers HEC-HMS computer model was used for this assessment The HEC-HMS model utilized the process of convolution in order to compute the design storm hydrograph from the calculated runoff amounts and the specified dimensionless unit hydrograph. Channel routing is performed using the Muskingum-Cunge method. The model framework and other data required for these analyses were generated with GIS techniques utilizing the 10 meter DEM. (National Elevation Dataset, Horizontal datum: NAD 83, Vertical datum: NAVD 88, 1999), as well as land survey data collected as part of this project for selected cross-sections within the study reaches. These data were used to determine drainage sub-basins and routing reaches with a level of discretization suitable to account for hydrologic features within the watershed such as lakes, reservoirs and tributary areas. A GIS based analysis using the sub-basin boundaries, soils and land use data referenced above and tables relating soil type to HSG and land use to runoff curve numbers, was conducted to estimate weighted curve numbers for each sub-basin. The DEM, land use and cover type data were used to estimate sub-basin time of concentration using standard segmental flow methods documented in detail in NRCS TR-55. Reach information for stream channel routing was developed form the DEM and surveyed cross-section data within the study reaches. The spatial aspects such as length and slope of the routing reaches were developed from the DEM. The cross-sectional configuration for each reach was taken from land survey data. The land survey cross-sections were conceptualized to 8-point sections as required in the HEC-HMS model

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To account for the effect of these storage areas on timing and peak discharge, a number of detention areas were incorporated into the model network. There is no available data on storage characteristics of the lakes or reservoirs and no available physical data on the control structures serving these facilities. Required model input data was based on available information and first hand knowledge of the study area acquired from site reconnaissance. Storage ratings were developed from map measurement of the illustrated lake surface area and assumed depth based on topography. Precipitation depth and duration data were developed from Florida Department of Transportation (FDOT) guidelines for the 10-, 2- and 1-percent annual chance events. The precipitation depth for the 0.2-percent annual chance event was estimated from an extrapolation of a log plot of the series. The duration for all frequencies was assumed to 72 hours, which is consistent with standard design storm analysis required by regulatory agencies throughout central and north Florida. All design storm frequencies were temporally distributed using the FDOT 72-hour rainfall distribution, which is consistent with standard design storm analysis required by regulatory agencies throughout central and north Florida. For this study, excess precipitation was translated to the basin outlet using the NRCS Unit Hydrograph methodology implemented through HEC-HMS. The unit hydrograph peak factor may have a significant impact on estimated peak rates of discharge from a particular sub-basin, and no single peak factor is specified for design storm modeling in the region. The overall importance of the peak factor is minimized with increased discretization of sub-basin areas to represent storage and other hydrologic features within the basin. Based on methods outlined in the FDOT drainage manual, a unit hydrograph peak factor of 323 was selected for use in this study. Additionally, the model network was discretized to a relatively high level of detail so as to minimize the impact of slight inaccuracies in the peak factor estimate. A summary of the peak discharge-drainage area relationships for all of the streams studied by detailed methods is shown Table 5 – “Summary of Discharges.”

Discharge for the streams studied by approximate methods were obtained from regional equations taken from a USGS publication (Reference 17).

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3.2 Riverine Hydraulic Analyses

Analyses of the hydraulic characteristics of flooding from the sources studied were carried out to provide estimates of the elevations of floods of the selected recurrence intervals. Users should be aware that flood elevations shown on the FIRM represent rounded 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. For construction and/or floodplain management purposes, users are encouraged to use the flood elevation data presented in this FIS in conjunction with the data shown on the FIRM.

March 7, 2000 Countywide Analyses

Physical data for cross-sections, dams, and culverts utilized for the backwater analysis of streams studied in detail, were obtained by field survey. The surveys were tied into USGS benchmarks so that all elevations were referenced to the NGVD. Locations of selected cross sections used in the hydraulic analyses are shown on the Flood Profiles. Roughness coefficients (Manning’s "n") were estimated by field inspection. Roughness values for the main channels ranged from 0.035 to 0.04, and flood plain values ranged from 0.1 to 0.18, for all streams studied in detail. Water-surface elevations of floods of the selected recurrence intervals were computed through use of the USACE HEC-2 step-backwater computer program (Reference 18). Starting water-surface elevations for main streams were calculated using the slope-area method. Computed water-surface elevations were used to construct profiles for floods of the selected recurrence intervals. The acceptability of the hydraulic input data was checked using engineering judgment and by comparing computed results with historical data recorded at the gaging stations, where such stations existed. A review of the HEC-2 computations on the Choctawhatchee River revealed that the estimated 1-perccent annual chance flood widths did not extend across the obvious floodplain at many of the cross sections. A close inspection of the survey data indicated that, in these cases, the survey had ended on islands in the floodplain. Although upon inspection, it appeared that the survey had not been exceeded, it did leave larger portions of the floodplain out of' the backwater calculations. As a result, the floodway calculations were invalid. Because of' this, approximated methods were used to estimate the 1-perccent annual chance flood elevations on the Choctawhatchee River. The method used involved friction calculations to determine elevations at the cross sections in question as well as interpolation between cross sections that appeared to have acceptable HEC-2 model results.

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Revised Countywide Analyses For this revised FIS, descriptions of the areas studied in detail are presented below. These detailed studies were used to estimate flood elevations for the selected annual chance of exceedance intervals. Steady-state flow modeling was conducted using the Army Corps of Engineers HEC-RAS River Analysis System one-dimensional steady-flow model (v-3.1.3, May 2005). The flood routing analyses produced information on flood stage (elevation) at each cross-section along the river reach, from which baseflood and floodway mapping was developed. The Shoal River / Gum Creek Study Area includes the Shoal River and Gum Creek study reaches. The Shoal River study reach consists of a segment of the Shoal River from the Okaloosa/ Walton County line upstream to it confluence with Gum Creek, approximately 14.47 miles in length. The channel and floodplain areas throughout this reach are primarily forested, with an average channel slope of 2.99 feet per mile. The channel has a sandy bottom with generally heavily vegetated banks, some local obstructions and minor to appreciable meander. The overbank areas are heavy vegetated with trees and underbrush causing a high degree of roughness. This reach has three bridge crossings. The Gum Creek study reach consists of a segment of Gum Creek from its confluence with Shoal River upstream to its confluence with Narrows Creek, approximately 2.41 miles in length. Vegetation and characteristics of the channel and floodplain areas is similar to Shoal River, however the channel slope in this reach is 4.2 feet per mile. This reach has no bridge crossings. The Lafayette Creek study reach comprises a segment of the creek beginning just upstream of State Road 20 near the eastern flank of the City of Freeport, Florida and going upstream 8.72 miles to its confluence with an un-named tributary located upstream of J.W. Hollington Road.. The channel and floodplain areas throughout the study reach are primarily forested with an average channel slope of about 10 feet per mile. The channel, which has a sandy bottom in the upper reach and sand and muck bottom in the lower reach, is characterized by heavily vegetated banks, some local obstructions and minor to appreciable meander. The overbank areas are heavy vegetated with trees and underbrush causing a high degree of roughness. This reach has three bridge crossings. The Bruce Creek / Mill Creek Study Area is comprised four study reaches including Bruce Creek, Bay Branch, Mill Creek and an unnamed tributary to Mill Creek. The Bruce Creek study reach consists of a segment of Bruce Creek from its confluence with Mill Creek upstream approximately 7.45 miles to a location just north of Ingram Road. Bay Branch is tributary to Bruce Creek. The Bay Branch study reach consists of a segment of Bay Branch from its confluence with Bruce Creek upstream 1.65 miles to its intersection with an un-named tributary located 945 feet west of US Highway 331. The channel and floodplain areas throughout the Bruce Creek and Bay Branch study reaches are primarily forested, with some of the floodplain areas in the upper reach of Bruce Creek being cleared pasture land and lakes. The Bruce

27

Creek channel has an average slope of 7 feet per mile and the Bay Branch channel has an average slope of 18 feet per mile. The channel in each of these reaches has a sandy bottom and is characterized by heavily vegetated banks, some local obstructions and minor meander. The overbank areas are heavy vegetated with trees and underbrush causing a high degree of roughness. The Bruce Creek study reach has two bridge crossings and Bay Branch has one culvert crossing. The Mill Creek study reach extends from its confluence with Bruce Creek to approximately 3.46 miles upstream near the intersection with Edgewood Circle. The Mill Creek Unnamed Tributary study reach extends from its confluence with Mill Creek to approximately 0.9 miles upstream near the intersection with Edgewood Circle. The channel and floodplain areas throughout the Mill Creek and Mill Creek Unnamed Tributary study reaches are primarily forested, with some of the floodplain areas in the upper reach of each system being cleared pastureland. The Mill Creek study reach has an average channel slope 25 feet per mile and the Mill Creek Unnamed Tributary reach has an average channel slope of 59 feet per mile. The channel in each of these reaches has a sandy bottom and is characterized by heavily vegetated banks, some local obstructions and minor meander. The overbank areas are heavy vegetated with trees and underbrush causing a high degree of roughness. Each of the study reaches has a single culvert crossing at its upstream terminus. The Pate Branch / Camp Creek / Black Creek Study Area is comprised of three study reaches described as follows: the Pate Branch study reach from its confluence with Turnpike branch southward to its confluence with Camp Creek a distance of approximately 0.8 miles; the Camp Creek study reach from its confluence with Pate Branch southward to its confluence with Black Creek a distance of approximately 1.1 miles; and the Black Creek study reach from its confluence with Camp Creek westward to the bridge at County Highway 3280 a distance of approximately 0.12 miles. The channel and floodplain areas of Pate Branch are forested, with an average channel slope of 16.5 feet per mile. The channel has a sandy bottom with generally heavily vegetated banks, some local obstructions and minor meander. The overbank areas are heavy vegetated with trees and underbrush causing a high degree of roughness. This reach has no bridge crossings. The channel and floodplain areas of Camp Creek are primarily forested with some minor urbanized area on the right overbank, and with an average slope of -5.3 feet per mile. The channel has a sandy bottom with generally heavily vegetated banks, some local obstructions and minor meander. The overbank areas are heavy vegetated with trees and underbrush causing a high degree of roughness. This reach has no bridge crossings. The channel of the Black Creek study reach consists of relatively wide open water with forested banks, and floodplain areas of are primarily forested. The average channel slope in this reach is 0.5 feet per mile. The channel has a sandy bottom with generally heavily vegetated banks, negligible obstructions and no meander. The overbank areas are

28

heavy vegetated with trees and underbrush causing a high degree of roughness. This reach has one bridge crossing.

HEC-RAS models were developed to estimate flood elevations for the 10-, 2-, 1- and 0.2-percent annual chance events for each of the systems studied in detail. The models were developed to account for natural channel geometry and to consider all structures such as bridges, culverts, embankments and levees, and channel modifications, which potentially impact flood levels. Model development is described in the in the follow discussion. The layout of geometric and spatial aspects of the RAS models were developed utilizing GIS based geo-referenced information including a digital elevation model (DEM) of Walton County developed from 2m LIDAR data, 2007 ortho-aerial photography, land survey data for riverine cross-sections and bridges, FDOT bridge plans (SR-83), transportation and stream networks, USGS 7.5 minute quadrangles and field reconnaissance. All of the above referenced elements were initially assembled into a single GIS based work project with a common projection system described above. All points from land survey locations were displayed forming the basic model framework. The location and alignment of additional cross-sections per G&S and HEC-RAS guidelines were selected using the DEM. Channel and overbank distances were then measured from the final layout to define the spatial aspects of the model framework The channel profile for each study reach was developed using survey data to provide known invert elevations and distance between cross-sections from GIS based spatial data as described above. The channel invert elevation for each added cross-section (from LiDAR) were estimated by assuming a uniform slope exist between surveyed cross-sections and estimates were made by linear interpolation between known survey points. Channel cross-sections were obtained primarily from field surveys with supplemental cross-sections being developed utilizing GIS based geo-referenced information including the Walton County DEM (2m LIDAR data), 2007 ortho-aerial photography, USGS 7.5 minute quadrangles and field reconnaissance. Bridge model input was developed primarily from land survey data, which included a top-of-road profile, structural components, abutments, and an upstream cross-section located just upstream of the toe of slope. Bridge model input for the SR-83 Bridge in the Lafayette Creek study reach was developed form bridge plans provided by the FDOT. All field survey was established with horizontal control in Florida North Zone (903) State Plane coordinates, and vertical control in NAVD 1988 datum.

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Channel and floodplain roughness coefficients (Manning’s “n”) were estimated based upon the methodology documented in USGS Water Supply Paper 2339. A combination of field observation, surveyor photographs, and aerial photography was used to establish the parameters used in the methodology. All of the areas studied as part of this revision have channels composed of sandy material and generally have bare bottoms. The channels have a relatively high roughness factor due to overhanging vegetation that persists year round. Similarly, the overbank areas are quite rough due to surface irregularities and heavy vegetation. Roughness values for the main channels ranged from 0.026 to 0.058, and overbank values ranged from 0.094 to 0.268 for all streams studied in detail in this revised countywide analysis. The starting water-surface elevations for the HEC-RAS models were determined using either normal depth or known water surface elevations for areas that were a continuation of the previous FIS. Floodways were determined for the streams in this study using method 4 in HEC-RAS initially, then method 1 to refine the floodway and fix the encroachment stations. All surcharge values are between 0.0 and 1.0, and the floodway contains the channel and is within the 1-percent floodplain at all cross sections.

The hydraulic analyses for the riverine studies are based on the effects of 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. Flood profiles (Exhibit 1) were drawn showing the computed water-surface elevations for floods of the selected annual chance of exceedance intervals. This revised countywide FIS also incorporates the results of several LOMRs. Where applicable, flood profiles (Exhibit 1) were drawn showing the computed water-surface elevations for floods of the selected annual chance of exceedance intervals. Table 6 – “Summary of Ponding Elevations” list ponding elevations for flooding sources studied as part of the LOMRs.

TABLE 6 – SUMMARY OF PONDING ELEVATIONS

Elevation (feet NAVD) Flooding Source and Location

10- Percent

2- Percent

1- Percent

0.2- Percent

Ponding Area 1 * * 26.7 * Ponding Area 2 * * 27.7 *

* Data not available.

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3.3 Coastal Hydrologic Analyses

Hydrologic analyses were carried out to establish the peak elevation-frequency relationships for floods of' the selected recurrence intervals for each flooding source studied in detail affecting the county. Establishing appropriate relationships has been an iterative process, and the following material describes successive stages of analyses reaching present conclusions. Users of the FIRM should also be aware that coastal flood elevations are provided in the Summary of Coastal Stillwater Elevations table in this report. If the elevation on the FIRM is higher than the elevation in this table, a wave height, wave runup, and/or wave setup component likely exists, in which case, the higher elevation should be used for construction and/or floodplain management purposes. Precountywide Analyses Inundations from the Gulf of Mexico and Choctawhatchee Bay caused by passage of storms (storm surge) previously had been determined by the joint probability method (Reference 19). The storm populations were described by probability distributions of 5 parameters that influence surge heights. These were central pressure depression (which measures the intensity of the storm), radius to maximum winds, forward speed of the storm, shoreline crossing point, and crossing angle. These characteristics were described statistically based on an analysis of observed storms in the vicinity of Walton County. Primary sources of data for this were obtained from two U.S. Department of Commerce, National Oceanic and Atmospheric Administration (NOAA) reports (References 20 and 21). A summary of the parameters used for the area is presented in Table 7 – “Parameter Values for Surge Elevations.” For areas subject to flooding directly from the Gulf of Mexico and Choctawhatchee Bay, the FEMA standard surge model was used to simulate the coastal surge generated by any chosen storm (that is, any combination of the 5 storm parameters defined in Table 7). By performing such simulations for a large number of storms, each of known total probability, the frequency distribution of surge height can be established as a function of coastal location. These distributions incorporate the large-scale surge behavior, but do not include an analysis of the added effects associated with much finer scale wave phenomena, such as wave height or runup. As the final step in the calculations, the astronomic tide for the region were statistically combined with the computed storm surge to yield recurrence intervals of total water level (Reference 22). The FEMA storm surge model was utilized to simulate the hydrodynamic behavior of the surge generated by the various synthetic storms. This model utilizes a grid pattern approximating the geographical features of the study area and adjoining areas. Surges were computed utilizing grids of 5 statute miles and 1 statute mile, depending on the resolution required.

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Underwater depths and land heights for the model grid system were obtained from topographic mapping at a scale of 1:24,000 with a contour interval of 5 feet (References 23 and 24).

March 7, 2000 Countywide FIS Analyses The original surge model study was recognized to provide unrealistic flood elevations in view of severe impacts within Walton County from Hurricane Frederic in 1979 (Reference 24). Flooding assessments were then revised to reflect upward adjustments to coastal stillwater elevations. However, experience with Hurricane Opal in 1995 and further review of the available historical record demonstrated the need to reexamine conclusions about coastal flood elevations for Walton County. Most recent investigations reviewed available reports and extensive historical data. including storm surge and wave effects along the Florida Panhandle coast from Hurricane Opal on October 4, 1995 (Reference 10). Existing data and studies include the report on Opal's basic meteorology by the National Hurricane Center, a hindcast for Gulf of Mexico wave action by the Coastal Engineering Research Center, and a National Oceanographic and Atmospheric Administration simulation of coastal storm surge using the numerical SLOSH model. Other primary data were comprised of long-term and Opal-related measurements of wave characteristics at offshore sites (over 25 total years of wave records) by the National Data Buoy Center; historical tide gauge data for water levels at coastal sites (over 275 total years of tide records) by the National Ocean Service and USACE (Table 1); post-Opal coastal dune erosion assessments recorded by the Florida Department of Environmental Protection (FDEP); and post-Opal high water mark surveys and coastal inundation mapping performed by FEMA and the USACE, Mobile District. From those investigations, wave setup was determined to significantly contribute to the total stillwater flood levels along the Gulf of Mexico coastline. The amount of wave setup was calculated using the methodology outlined in the USACE publication Shore Protection Manual (Reference 25).

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Central Pressure Depression (Millibars) 15.2 24.2 33.2 38.2 49.2 60.2 75.2 79.2

Assigned Probabilities 0.32 0.27 0.06 0.11 0.09 0.08 0.05 0.02

Storm Radius To Maximum Winds (Nautical Miles) 12 24 36

Probability 0.23 0.50 0.27

Forward Speed (Knots) 7 13 19

Probabilities: Entering 0.46 0.36 0.18

Direction Of Storm Path

(Degrees From True North)

13

8

ENTERING 167

196

225

Probability 0.2

5 0.23 0.27 0.25

Frequency Of Storm Occurrence (Storm/Nautical Mile/Year) 0.002213

TAB

LE 7

FEDERAL EMERGENCY MANAGEMENT AGENCY

WALTON COUNTY, FL AND INCORPORATED AREAS

PARAMETER VALUES FOR SURGE ELEVATIONS

33

The storm-surge elevations for the 10-, 2-, 1- and 0.2-percent annual chance floods determined for the Gulf of Mexico. and Choctawhatchee Bay are shown in Table 8 – “Summary of Stillwater Elevations.” Although most of the stillwater elevations in Table 8 were adjusted for this revision, stillwater elevations at the following locations remain unchanged from those determined by the storm surge modeling of the precountywide coastal flood studies:

• Shoreline of Choctawhatchee Bay, east of the U.S. Route 331 causeway

from Tucker Bayou to Jolly Bay and along the Intracoastal Waterway.

The analyses reported herein reflect the stillwater elevations due to tidal and wind setup effects and include further contributions from wave action. Wave setup effects are reflected only in the open coast 1-percent annual chance elevations, as noted in Table 8 – “Summary of Stillwater Elevations.”

Revised coastal hydrologic analyses were not performed for this update to the countywide FIS.

TABLE 8 – SUMMARY OF STILL WATER ELEVATIONS

Flooding Source and Location

ELEVATION (feet NAVD) 10-

Percent 2-

Percent 1-

Percent 0.2-

Percent GULF OF MEXICO

Entire open coast shoreline within Walton County and incorporated areas

3.7 6.5 10.21 10.5

Coastal area behind primary frontal dune from Morrison Lake to Powell Lake 3.7 6.5 7.7 10.5

CHOCTAWHATCHEE BAY

Entire shoreline west of U.S. Route 331 causeway

* * 6.7 *

Along shoreline from Tucker Bayou to Jolly Bay along west side of U.S. Route 331 Causeway

2.9 5.5 6.5 8.2

Along Intercoastal waterway

3.1 3.3

* *

6.9 7.2

* *

1 Includes wave setup of 2.5 feet. *Data not available.

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3.4 Coastal Hydraulic Analyses

Hydraulic analyses, considering storm characteristics and the shoreline and bathymetric characteristics of the flooding source studied, were carried out to provide estimates of the elevations of floods of the selected recurrence intervals along each of the shorelines. Precountywide Analyses The methodology for analyzing the effects of wave heights associated with coastal storm surge flooding is described in a report prepared by the National Academy of Sciences (Reference 26). This method is based on the following major concepts. First, depth-limited waves in shallow water reach a maximum breaking height that is equal to 0.78 times the stillwater depth. The wave crest is 70 percent of the total wave height above the stillwater level. The second major concept is that wave height may be diminished by dissipation of energy due to the presence of obstruction, such as sand dunes, dikes and seawalls, buildings, and vegetation. The amount of energy dissipation is a function of the physical characteristics of the obstruction and is determined by procedures prescribed in Reference 26 by the National Academy of Sciences. The third major concept is that wave height can be regenerated in open fetch areas due to the transfer of wind energy to the water. This added energy is related to fetch length and depth.

March 12, 2000 Countywide FIS Analysis For this revision, the FIS includes a technical wave height analysis using the revised and previously determined 1-percent annual chance flood elevations as described in Section 3.3 above. The analysis was performed as specified in FEMA’s Guidelines and Specifications for Wave Elevation Determination and V Zone Mapping (Reference 27). This revision updates the previous FIS on the basis of the post-hurricane Opal investigations and FEMA's updated delineations of “coastal high hazard area” and “primary frontal dunes,” field investigations, and development of topography and aerial photography. As of 1989, FFMA defines a “coastal high hazard area” as an area of special flood hazards extending from offshore to the inland limit of a primary frontal dune along an open coast and any other area subject to high velocity wave action (i.e., wave heights greater than or equal to 3 feet) from storms or seismic sources. The “primary frontal dune” is defined as a continuous mound or ridge of sand with relatively steep seaward and landward slopes immediately landward and adjacent to the beach and subject to erosion and overtopping from high tides and waves during major coastal storms, such as hurricanes. The inland limit of the primary frontal dune occurs at the point which there is a distinct change from a relatively steep slope to a relatively mild slope. In the August 19, 1997, revision, coastal high hazard areas (V Zone) were redelineated to include inland limits of the primary frontal dune along the Gulf

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of Mexico shoreline within Walton County. In addition, the effects of wave height, wave setup, runup, and beach erosion were determined by detailed methods to verify that the location of the primary frontal dune meets the minimum criteria in locating the inland limit of the coastal high hazard area. Some dunes in Walton County were found to be sufficient enough in size to sustain wave attack, while others were subjected to failure due to wave attacks, erosion and overtopping. Therefore, using standard erosion analysis procedures as outlined in the Guidelines and Specifications for Wave Elevation Determination and V Zone Mapping, dune erosion and retreat were used in developing the eroded profiles (Reference 27). Data used to develop the transects were compiled from various sources, including topographic maps, and FDEP aerial photography and surveys. Wave heights were computed along transects (cross section lines) that were located along coastal and inland bay areas of Walton County, as illustrated in Figure 1 – “Transect Location Map.” The transects were located with consideration given to existing transect locations and to the physical and cultural characteristics of the land so that they would closely represent conditions in the locality. Transects were spaced close together in areas of complex topography and dense development. In areas having more uniform characteristics, they were spaced at larger intervals. It was necessary to locate transects in areas where unique flooding existed and in areas where computed wave heights varied significantly between adjacent transects. The wave height transects for this revision were located along the barrier coastline of the Gulf of Mexico, from the western-most county limits with Okaloosa County to the easternmost limits with Walton County, and along Choctawhatchee Bay, from the Okaloosa County line to the mouth of the Choctawhatchee River. For the barrier islands, the FEMA erosion treatment (540 square foot method) was performed to adjust the wave transect profiles to an eroded condition before conducting the wave height or wave runup analyses using the FEMA wave height analysis models (WHAFIS 3.0 and RUNUP 2.0). For each coastal transect without overtopping by the 1-percent annual chance stillwater elevation, wave runup analyses were conducted using the FEMA wave runup model (RUNUP 2.0). Each transect was taken perpendicular to the shoreline and extended inland to a point where wave action ceased. Along each transect, wave heights, runup depths, and elevations were computed considering the combined effects of changes in ground elevation, vegetation, beach slope, and physical features. The stillwater elevations for the 1-percent annual chance flood were used as the starting elevations for these computations. Wave heights and runup depths were calculated to the nearest 0.1-foot, and wave elevations were determined at whole-foot increments along the transects. The location of the 3-foot breaking wave and the runup depth for determining the terminus of the V Zone (area with velocity wave action) was computed at each transect.

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TABLE 9 – TRANSECT DESCRIPTIONS

Transect Location

Elevation (feet NAVD)

1-Percent Stillwater

Maximum 1-Percent

Wave Crest1

1 At shoreline of Gulf of Mexico, in the unincorporated areas of Walton County, approximately 2.4 miles east of the Okaloosa / Walton County line, extending north approximately 160 feet

10.22 15.8

2 At shoreline of Gulf of Mexico, in the unincorporated areas of Walton County, south of Morris Lake, extending approximately 400 feet into dune line

7.7 15.8

Beginning approximately 400 feet Inland of Gulf of Mexico shoreline, extending inland across Morris Lake

7.7 7.7

3 At shoreline of Gulf of Mexico, in the unincorporated areas of Walton County, approximately 700 feet southeast of intersection of County Route 30-A and Hilltop Street, extending approximately 200 feet into dune line

10.22 15.8

4 At shoreline of Gulf of Mexico, Walton County, approximately 1,200 feet southeast of intersection of County Route 30-A and Blue Mountain Road

10.22 15.8

5 At shoreline of Gulf of Mexico, in the unincorporated areas of Walton County, approximately 1,200 feet southwest of intersection of Hotz Avenue and Garfield Drive

10.22 15.8

Beginning approximately 550 feet inland of Gulf of Mexico shoreline.

7.7 7.7

6 At shoreline of Gulf of Mexico in the unincorporated areas of Walton County, approximately 1,000 feet southeast of intersection of Western Lake shoreline and Boat Ramp Road

10.22 15.8

7 At shoreline of Gulf of Mexico in the unincorporated areas of Walton County, approximately 600 feet southeast of Camp Creek Lake shoreline

10.22 15.8

1 Because of map scale limitations, the maximum wave elevation may not be shown on the FIRM. 2 Includes wave setup of 2.5 feet.

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Transect Location

Elevation (feet NAVD)

1-Percent Stillwater

Maximum 1-Percent

Wave Crest1

8 At shoreline of Gulf of Mexico, in unincorporated areas of Walton County, approximately 3,000 feet southwest of intersection of U.S. Route 98 and County Route 30-A

10.22 15.8

9 At shoreline of Choctawhatchee Bay, in unincorporated areas of Walton County, approximately 3,500 feet north of Wheeler Point

6.5 9.7

10 At shoreline of Choctawhatchee Bay, in unincorporated areas of Walton County, approximately 3,500 feet north of Wheeler Point

6.7 10.1

11 At shoreline of Choctawhatchee Bay, in unincorporated areas of Walton County, approximately 2,300 feet east of Motes Point

6.7 10.1

12 At shoreline of Choctawhatchee Bay, in unincorporated areas of Walton County, at Motes Point

6.7 10.0

13 At shoreline of Choctawhatchee Bay, in unincorporated areas of Walton County, approximately 2,700 feet east of Piney Point

6.7 10.2

14 At shoreline of Choctawhatchee Bay, in unincorporated areas of Walton County, approximately 1 mile east of Basin Bayou

6.7 10.2

15 At shoreline of Choctawhatchee Bay, in unincorporated areas of Walton County, at Hammock Point

6.7 10.1

1 = Because of map scale limitations, the maximum wave elevation may not be shown on the FIRM. 2 = Includes wave setup of 2.5 feet.

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FIGURE 2 – TRANSECT SCHEMATIC

Table 10 – “Transect Data,” lists the flood hazard zone and base flood elevations for each transect, along with the 1-percent annual chance starting stillwater elevation for the respective flooding source. After analyzing wave heights along each transect. wave elevations were interpolated between transects. Various source data were used in the interpolation. including topographic maps, FDEP aerial photography, surveys and engineering judgment (References 28 and 29). Controlling features affecting the elevations were identified and considered in relation to their positions at a particular transect and their variations between transects.

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TABLE 10 – TRANSECT DATA

Flooding Source

Stillwater Elevation (feet NAVD 88)

Zone

Base Flood Elevation

(feet NAVD 88)1 10-

Percent 2-

Percent 1-

Percent 0.2-

Percent GULF OF MEXICO Transects 1-8

3.7

6.5

10.22

10.5

VE AE

13-16 11-13

3.7 6.5 7.7 9.7 VE AE

10-12 8-10

CHOCTAWATCHEE BAY Transect 9

2.9

5.5

6.5

8.2

AE AE

9-10 7-9

Transects 10-15 * * 6.7 * VE AE

9-12 7-9

1 Because of map scale limitations, base flood elevations shown on the FIRM represent average

elevations for the zone depicted. 2 Includes wave setup of 2.5 feet. * Data not available.

Revised Countywide FIS Analyses

For this update to the FIS, there were no new coastal flood studies completed for Walton County and incorporated areas; however, the vertical datum has been converted from NGVD 29 to NAVD 88. For Walton County and incorporated areas, the datum conversion factor from NGVD 29 to NAVD 88 is -0.31 feet.

3.5 Vertical Datum

All FIS’ and FIRMs are referenced to a specific vertical datum. The vertical datum provides a starting point against which flood, ground, and structure elevations can be referenced and compared. Until recently, the standard vertical datum in use for newly created or revised FIS’ and FIRMs was the National Geodetic Vertical Datum of 1929 (NGVD 29). With the finalization of the North American Vertical Datum of 1988 (NAVD 88), many FIS reports and FIRMs are being prepared using NAVD 88 as the referenced vertical datum. All flood elevations shown in this FIS report and on the FIRM are referenced to NAVD 88. Structure and ground elevations in the community must, therefore, be referenced to NAVD 88. It is important to note that adjacent communities may be referenced to NGVD 29. This may result in differences in base flood elevations across the corporate limits between the communities. Prior versions of the FIS report and FIRM were referenced to NGVD 29. When a datum conversion is effected for an FIS report and FIRM, the Flood Profiles

41

and BFEs reflect the new datum values. To compare structure and ground elevations to 1-percent annual chance flood elevations shown in the FIS and on the FIRM, the subject structure and ground elevations must be referenced to the new datum values. As noted above, the elevations shown in the FIS report and on the FIRM for Walton County and incorporated areas are referenced to NAVD 88. Ground, structure, and flood elevations may be compared and/or referenced to NGVD 29 using a standard conversion factor. The conversion factor from NGVD 29 to NAVD 88 is -0.31 feet. The BFEs shown on the FIRM represent whole-foot rounded values. For example a BFE of 102.4 will appear as 102 on the FIRM and 102.6 will appear as 103. Therefore, users that wish to convert the elevations in this FIS to NGVD 29 should apply the stated conversion factor(s) to elevations shown on the Flood Profiles and supporting data tables in the FIS report, which are shown at a minimum to the nearest 0.1 foot. For more information on NAVD 88, see Converting the National Flood Insurance Program to the North American Vertical Datum of 1988, FEMA Publication FIA20/June 1992, or contact the Vertical Network Branch, National Geodetic Survey, Coast and Geodetic Survey, National Oceanic and Atmospheric Administration, Rockville, Maryland 20910 (Internet address http://www.ngs.noaagov).

4.0 FLOODPLAIN MANAGEMENT APPLICATIONS

The NFIP encourages State and local governments to adopt sound floodplain management programs. To assist in this endeavor, each FIS provides 1-percent floodplain data, which may include a combination of the following: 10-, 2-, 1- and 0.2-percent flood elevations; delineations of the 1-percent and 0.2-percent floodplains; and 1-percent floodway. This information is presented on the FIRM and in many components of the FIS, including Flood Profiles, Floodway Data tables, and Summary of Stillwater Elevation tables. Users should reference the data presented in the FIS as well as additional information that may be available at the local community map repository before making flood elevation and/or floodplain boundary determinations. 4.1 Floodplain Boundaries

To provide a national standard without regional discrimination, the 1-percent annual chance flood has been adopted by FEMA as the base flood for floodplain management purposes. The 0.2-percent annual chance flood is employed to indicate additional areas of flood risk in the county. For each stream studied in detail, the 1- and 0.2-percent floodplain boundaries have been delineated using the flood elevations determined at each cross section. For the streams studied in the initial countywide FIS, floodplain boundaries were delineated using the previously printed FIS’ for the incorporated communities and unincorporated

42

areas of Walton County. For the streams studied in detail for this revision, between cross sections, the boundaries were interpolated using a digital elevation model of Walton County developed from 0.7-meter LiDAR data (Reference 30). For each coastal flooding source studied in detail, the 1- and 0.2-percent annual chance floodplain boundaries have been delineated using the flood elevations determined at each transect. Between transects, the boundaries were interpolated using topographic maps at a scale of 1:1,200 and 1:24,000 with contour intervals of 5 and 2 feet, respectively (References 23, 28, and 31). For the flooding sources studied by approximate methods, only the 1-percent annual chance floodplain boundaries were delineated using the Type 15 FIS, Maps of Flood Prone Areas at a scale of 1:24000 and contour intervals of 10 and 5 feet, and a normal depth analysis (References 23 and 31). 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 floodplain boundary corresponds to the boundary of areas of moderate flood hazards. In cases where the 1- and 0.2-percent annual chance floodplain boundaries are close together, only the 1-percent annual chance floodplain boundary has been shown. Small areas within the floodplain boundaries may lie above the flood elevations but cannot be shown due to limitations of the map scale and/or lack of detailed topographic data. For the streams studied by approximate methods, only the 1-percent annual chance floodplain boundaries are shown on the FIRM (Exhibit 2). Areas studied by approximate methods (Zone A) were updated using National Wetlands Inventory (NWI) data, land use and cover, as well as hydrography features (Reference 32).

4.2 Floodways

Encroachment on floodplains, such as structures and fill, reduces flood-carrying capacity, increases flood heights and velocities, and increases flood hazards in areas beyond the encroachment itself. One aspect of floodplain management involves balancing the economic gain from floodplain development against the resulting increase in flood hazard. For purposes of the NFIP, a floodway is used as a tool to assist local communities in this aspect of floodplain management. Under this concept, the area of the 1-percent annual chance floodplain is divided into a floodway and a floodway fringe. The floodway is the channel of a stream, plus any adjacent floodplain areas, that must be kept free of encroachment so that the 1-percent annual chance flood can be carried without substantial increases in flood

43

heights. Minimum Federal standards limit such increases to 1.0-foot, provided that hazardous velocities are not produced. The floodway in this study is presented to local agencies as a minimum standard that can be adopted directly or that can be used as a basis for additional floodway studies. The floodway presented in this study was 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, and are shown in Table 11 – “Floodway Data.” The computed floodway is shown on the FIRM (Exhibit 2). In cases where the floodway and 1-percent annual chance floodplain boundaries are either close together or collinear, only the floodway boundary is shown. No floodway was computed for the Choctawhatchee River, within the limits of Walton County, due to insufficient cross section data. In addition, floodways were not computed for Bear Creek Tributary 1, Bear Creek Tributary 2, Bear Creek Tributary 3, Draper Lake Unnamed Tributary, Draper Lake Unnamed Tributary – Tributary No. 1, Fourmile Creek North Tributary, Fourmile Creek North Tributary 1, Fourmile Creek North Tributary 2, Fourmile Creek North Tributary 3, Fourmile Creek North Tributary 4, Fourmile Creek North Tributary 5, Fourmile Creek North Tributary 6, and Fourmile Creek South Tributary. 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 by 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 3 – “Floodway Schematic.”

CROSS SECTION DISTANCE1 WIDTH (FEET)

SECTION AREA

(SQUARE FEET)

MEAN VELOCITY (FEET PER SECOND)

REGULATORY WITHOUT

FLOODWAY2WITH

FLOODWAY INCREASE

Alaqua Creek

A 450 1,487 7,672 1.8 6.7 1.9 2.9 1.0

B 1,450 1,050 5,095 2.7 6.7 2.5 3.5 1.0

C 2,350 1,183 5,740 2.4 6.7 3.1 4.1 1.0

D 3,950 628 5,168 2.7 6.7 3.6 4.6 1.0

E 5,150 1,339 8,036 1.7 6.7 3.9 4.9 1.0

F 6,650 734 4,808 2.8 6.7 4.1 5.1 1.0

G 8,650 1,171 7,806 1.8 6.7 5.0 6.0 1.0

H 11,140 1,426 10,398 1.3 6.7 6.3 7.3 1.0

I 12,140 1,327 8,938 1.5 6.7 6.6 7.6 1.0

1Feet above mouth2Elevations computed without consideration of storm surge effects from Choctawhatchee Bay

FLOODING SOURCE FLOODWAY BASE FLOOD WATER SURFACE ELEVATION (FEET NAVD 88)

FEDERAL EMERGENCY MANAGEMENT AGENCY WALTON COUNTY, FL

AND INCORPORATED AREAS

FLOODWAY DATA

ALAQUA CREEK

TABLE 11

CROSS SECTION DISTANCE1 WIDTH (FEET)

SECTION AREA

(SQUARE FEET)

MEAN VELOCITY (FEET PER SECOND)

REGULATORY WITHOUT

FLOODWAY WITH FLOODWAY INCREASE

Bay Branch

A 2,340 137 380 4.3 108.3 108.3 109.3 1.0

B 4,858 170 372 3.5 114.3 114.3 115.0 0.7C 7,879 149 149 1.6 121.6 121.6 121.7 0.1D 8,747 507 584 0.3 124.5 124.5 124.5 0

1Feet above confluence with Bruce Creek

FLOODING SOURCE FLOODWAY BASE FLOOD WATER SURFACE ELEVATION (FEET NAVD 88)

FEDERAL EMERGENCY MANAGEMENT AGENCY WALTON COUNTY, FL

AND INCORPORATED AREAS

FLOODWAY DATA

BAY BRANCH

TABLE 11

CROSS SECTION DISTANCE1 WIDTH (FEET)

SECTION AREA (SQUARE FEET)

MEAN VELOCITY (FEET PER SECOND)

REGULATORY WITHOUT

FLOODWAYWITH

FLOODWAY INCREASE

Black Creek

A 0 293 4,079 3.7 6.9 6.9 7.8 0.9

B 1,570 228 3,678 3.8 7.1 7.1 8.0 0.9

1Feet above County Highway 3280

FLOODING SOURCE FLOODWAY BASE FLOOD WATER SURFACE ELEVATION (FEET NAVD 88)

FEDERAL EMERGENCY MANAGEMENT AGENCY WALTON COUNTY, FL

AND INCORPORATED AREAS

FLOODWAY DATA

BLACK CREEK

TABLE 11

CROSS SECTION DISTANCE1 WIDTH (FEET)

SECTION AREA

(SQUARE FEET)

MEAN VELOCITY (FEET PER SECOND) REGULATORY

WITHOUT FLOODWAY WITH FLOODWAY INCREASE

Bruce Creek

A 13,098 1233 12,908 2.3 73.0 73.0 73.9 0.9

B 15,773 276 1,689 8.0 74.9 74.9 75.8 0.9C 18,732 802 7,857 3.7 78.1 78.1 79.1 1.0D 23,549 417 3,174 5.2 80.7 80.7 81.7 1.0E 27,022 440 3,235 4.4 84.1 84.1 85.0 0.9F 29,541 359 2,348 6.0 87.5 87.5 88.4 0.9G 30,668 601 3,459 5.3 88.6 88.6 89.6 1.0H 36,003 553 2,718 4.7 95.3 95.3 96.3 1.0I 39,334 386 2,404 4.9 101.2 101.2 102.2 1.0J 43,872 708 3,911 4.5 105.8 105.8 106.8 1.0K 46,804 365 1,290 4.8 108.5 108.5 109.5 1.0L 50,766 591 2,050 3.0 113.8 113.8 114.8 1.0

1Feet above McKinnon Bridge Road

FLOODING SOURCE FLOODWAY BASE FLOOD WATER SURFACE ELEVATION (FEET NAVD 88)

FEDERAL EMERGENCY MANAGEMENT AGENCY WALTON COUNTY, FL

AND INCORPORATED AREAS

FLOODWAY DATA

BRUCE CREEK

TABLE 11

CROSS SECTION DISTANCE1 WIDTH (FEET)

SECTION AREA

(SQUARE FEET)

MEAN VELOCITY (FEET PER SECOND)

REGULATORY WITHOUT

FLOODWAY2WITH

FLOODWAY INCREASE

Camp Creek

A 506 317 2,662 1.7 7.2 5.0 6.0 1.0

B 1,211 99 1,395 3.3 7.2 5.0 6.0 1.0

C 1,951 138 1,936 2.4 7.2 5.3 6.3 1.0

D 2,785 128 1,877 2.5 7.2 5.4 6.4 1.0

E 4,149 102 1,635 2.8 7.2 5.6 6.5 0.9

F 5,388 248 2,529 1.8 7.2 5.8 6.8 1.0

1Feet above confluence with Black Creek

2Elevations computed without consideration of backwater effects from Black Creek

FLOODING SOURCE FLOODWAY BASE FLOOD WATER SURFACE ELEVATION (FEET NAVD 88)

FEDERAL EMERGENCY MANAGEMENT AGENCY WALTON COUNTY, FL

AND INCORPORATED AREAS

FLOODWAY DATA

CAMP CREEK

TABLE 11

CROSS SECTION DISTANCE1 WIDTH (FEET)

SECTION AREA

(SQUARE FEET)

MEAN VELOCITY (FEET PER SECOND)

REGULATORY WITHOUT

FLOODWAYWITH

FLOODWAY INCREASE

Gum Creek

A 385 1,543 18,745 0.8 149.8 149.8 150.8 1.0

B 2,476 999 6,916 1.0 150.4 150.4 151.4 1.0

C 4,303 744 5,319 1.3 152.0 152.0 152.8 0.8

D 7,052 383 2,845 2.5 152.3 152.3 153.1 0.8

E 8,941 771 5,292 1.4 154.9 154.9 155.8 0.9

F 12,696 1,221 4,846 1.5 156.2 156.2 157.0 0.8

1Feet above confluence with Shoal River

FLOODING SOURCE FLOODWAY BASE FLOOD WATER SURFACE ELEVATION (FEET NAVD 88)

FEDERAL EMERGENCY MANAGEMENT AGENCY WALTON COUNTY, FL

AND INCORPORATED AREAS

FLOODWAY DATA

GUM CREEK

TABLE 11

CROSS SECTION DISTANCE1 WIDTH (FEET)

SECTION AREA

(SQUARE FEET)

MEAN VELOCITY (FEET PER SECOND)

REGULATORY WITHOUT

FLOODWAYWITH

FLOODWAY INCREASE

Lafayette Creek

A 5,422 636 5,742 1.0 9.7 9.7 10.5 0.8

B 7,885 750 6,669 0.7 10.5 10.5 11.4 0.9

C 11,094 398 3,282 1.5 12.3 12.3 13.3 1.0

D 14,684 450 4,147 1.1 14.7 14.7 15.7 1.0

E 18,274 529 4,108 1.1 17.0 17.0 18.0 1.0

F 21,773 367 2,632 1.7 19.3 19.3 20.3 1.0

G 23,570 247 1,793 2.5 23.0 23.0 23.5 0.5

H 26,848 420 4,706 0.9 24.2 24.2 25.2 1.0

I 30,340 600 5,049 0.8 25.4 25.4 26.3 0.9

J 32,971 325 2,679 1.5 26.4 26.4 27.3 0.9

K 37,342 235 1,739 1.0 33.5 33.5 34.3 0.8L 40,120 210 1,071 1.6 35.6 35.6 36.5 0.9M 42,793 255 1,288 1.3 39.1 39.1 40.0 0.9N 45,917 131 811 2.1 45.9 45.9 46.7 0.8O 47,506 350 1,120 1.5 50.2 50.2 50.5 0.3P 49,359 97 494 3.4 53.5 53.5 54.0 0.5Q 51,443 585 2,743 0.6 57.9 57.9 58.2 0.3

1Feet above confluence with Fourmile Creek

FLOODING SOURCE FLOODWAY BASE FLOOD WATER SURFACE ELEVATION (FEET NAVD 88)

FEDERAL EMERGENCY MANAGEMENT AGENCY WALTON COUNTY, FL

AND INCORPORATED AREAS

FLOODWAY DATA

LAFAYETTE CREEK

TABLE 11

CROSS SECTION DISTANCE1 WIDTH (FEET)

SECTION AREA (SQUARE FEET)

MEAN VELOCITY (FEET PER SECOND) REGULATORY

WITHOUT FLOODWAY WITH FLOODWAY INCREASE

Mill Creek

A 2,388 208 1258 3.2 74.6 74.6 75.6 1.0

B 5,481 136 559 5.7 83.9 83.9 84.8 0.9C 11,467 141 447 5.4 104.6 104.6 105.6 1.0D 18,205 30 52 1.0 145.7 145.7 145.7 0.0

1Feet above confluence with Bruce Creek

FLOODING SOURCE FLOODWAY BASE FLOOD WATER SURFACE ELEVATION (FEET NAVD 88)

FEDERAL EMERGENCY MANAGEMENT AGENCY WALTON COUNTY, FL

AND INCORPORATED AREAS

FLOODWAY DATA

MILL CREEK

TABLE 11

CROSS SECTION DISTANCE1 WIDTH (FEET)

SECTION AREA

(SQUARE FEET)

MEAN VELOCITY (FEET PER SECOND)

REGULATORY WITHOUT

FLOODWAY WITH FLOODWAY INCREASE

Mill Creek

Unnamed Tributary

A 701 44 49 6.8 129.5 129.5 129.5 0.0B 1,558 33 46 5.7 138.6 138.6 139.1 0.5C 2,399 21 32 4.1 148.3 148.3 148.9 0.6D 3,590 130 42 2.7 161.1 161.1 161.1 0.0E 4,709 19 43 0.9 174.8 174.8 174.8 0.0

1Feet above confluence with Mill Creek

FLOODING SOURCE FLOODWAY BASE FLOOD WATER SURFACE ELEVATION(FEET NAVD 88)

FEDERAL EMERGENCY MANAGEMENT AGENCY WALTON COUNTY, FL

AND INCORPORATED AREAS

FLOODWAY DATA

MILL CREEK UNNAMED TRIBUTARY

TABLE 11

CROSS SECTION DISTANCE1 WIDTH (FEET)

SECTION AREA

(SQUARE FEET)

MEAN VELOCITY (FEET PER SECOND)

REGULATORY WITHOUT

FLOODWAY2WITH

FLOODWAY INCREASE

Pate BranchA 749 375 2,202 1.3 7.2 5.9 6.9 1.0

B 1,316 280 1,853 1.4 7.2 6.0 7.0 1.0

C 2,694 207 1,427 1.9 7.2 6.5 7.5 1.0D 3,549 211 1,517 1.8 7.2 6.9 7.9 1.0E 3,916 201 1,412 1.9 7.2 7.1 8.1 1.0

1Feet above confluence with Camp Creek

2Elevations computed without consideration of backwater effects from Camp Creek

FLOODING SOURCE FLOODWAY BASE FLOOD WATER SURFACE ELEVATION (FEET NAVD 88)

FEDERAL EMERGENCY MANAGEMENT AGENCY WALTON COUNTY, FL

AND INCORPORATED AREAS

FLOODWAY DATA

PATE BRANCH

TABLE 11

CROSS SECTION DISTANCE1 WIDTH (FEET)

SECTION AREA

(SQUARE FEET)

MEAN VELOCITY (FEET PER SECOND)

REGULATORY WITHOUT

FLOODWAY2WITH

FLOODWAY INCREASE

Shoal River

A 169 1,152 14,645 1.4 111.1 111.1 112.0 0.9

B 1,720 1,503 18,691 1.1 111.7 111.7 112.7 1.0

C 4,478 1,802 24,957 0.8 112.5 112.5 113.5 1.0

D 5,689 1,650 19,144 1.1 112.8 112.8 113.8 1.0

E 7,717 1,036 14,412 1.5 113.6 113.6 114.6 1.0

F 9,080 1,388 16,240 1.3 114.3 114.3 115.3 1.0

G 12,343 951 13,668 1.5 116.5 116.5 117.4 0.9

H 15,351 1,921 15,360 1.4 118.5 118.5 119.5 1.0

I 17,293 1,504 15,591 1.2 119.7 119.7 120.7 1.0

J 21,398 1,938 18,303 1.1 122.1 122.1 123.0 0.9

K 24,285 2,911 27,988 0.7 123.1 123.1 124.1 1.0L 25,944 1,743 15,637 1.2 123.7 123.7 124.6 0.9M 28,859 1,293 13,961 1.3 125.6 125.6 126.5 0.9N 31,465 1,358 23,167 0.8 126.7 126.7 127.6 0.9O 33,253 1,042 16,375 1.1 127.1 127.1 128.1 1.0P 36,986 1,506 15,350 1.2 128.5 128.5 129.5 1.0Q 38,718 1,224 18,834 1.0 129.1 129.1 130.1 1.0R 41,478 790 10,321 1.8 131.3 131.3 132.2 0.9S 44,778 1,141 16,323 1.1 132.9 132.9 133.9 1.0T 48,064 1,341 15,087 1.2 134.0 134.0 134.9 0.9U 50,158 860 13,048 1.4 134.6 134.6 135.6 1.0

1Feet above county boundary

FLOODING SOURCE FLOODWAY BASE FLOOD WATER SURFACE ELEVATION (FEET NAVD 88)

FEDERAL EMERGENCY MANAGEMENT AGENCY WALTON COUNTY, FL

AND INCORPORATED AREAS

FLOODWAY DATA

SHOAL RIVER

TABLE 11

CROSS SECTION DISTANCE1 WIDTH (FEET)

SECTION AREA

(SQUARE FEET)

MEAN VELOCITY (FEET PER SECOND)

REGULATORY WITHOUT

FLOODWAYWITH

FLOODWAY INCREASE

Shoal River

V 52,932 876 12,090 1.4 135.9 135.9 136.9 1.0

W 56,367 543 7,642 2.3 138.1 138.1 139.1 1.0

X 59,452 1,180 9,343 1.9 140.6 140.6 141.6 1.0

Y 61,499 649 7,834 2.2 142.6 142.6 143.5 0.9

Z 65,799 1,226 15,610 0.9 145.3 145.3 146.3 1.0

AA 68,763 1,140 13,476 1.1 146.3 146.3 147.3 1.0

AB 71,353 1,226 11,333 1.3 147.5 147.5 148.5 1.0

AC 73,607 1,138 12,245 1.2 148.9 148.9 149.9 1.0

1Feet above county boundary

FLOODING SOURCE FLOODWAY BASE FLOOD WATER SURFACE ELEVATION (FEET NAVD 88)

FEDERAL EMERGENCY MANAGEMENT AGENCY WALTON COUNTY, FL

AND INCORPORATED AREAS

FLOODWAY DATA

SHOAL RIVER

TABLE 11

56

FIGURE 3 – FLOODWAY SCHEMATIC

5.0 INSURANCE APPLICATION

For flood insurance rating purposes, flood insurance zone designations are assigned to a community based on the results of the engineering analyses. The zone areas follow: Zone A Zone A is the flood insurance rate zone that corresponds to the 1-percent annual chance floodplains that are determined in the FIS by approximate methods. Because detailed hydraulic analyses are not performed for such areas, no base flood elevations or depths are shown within this zone. Zone AE Zone AE is the flood insurance rate zone that corresponds to the 1-percent annual chance floodplains that are determined in the FIS by detailed methods. In most instances, whole-foot base flood elevations derived from the detailed hydraulic analyses are shown at selected intervals within this zone.

57

Zone AH Zone AH is the flood insurance rate zone that corresponds to the areas of 1-percent annual chance shallow flooding (usually areas of ponding) where average depths are between 1 and 3 feet. Whole-foot base flood elevations derived from the detailed hydraulic analyses are shown at selected intervals within this zone. Zone AO Zone AO is the flood insurance rate zone that corresponds to the areas of 1-percent annual chance shallow flooding (usually sheet flow on sloping terrain) where average depths are between 1 and 3 feet. Average whole-foot depths derived from the detailed hydraulic analyses are shown within this zone. Zone A99 Zone A99 is the flood insurance rate zone that corresponds to areas of the 1-percent annual chance floodplain that will be protected by a Federal flood protection system where construction has reached specified statutory milestones. No base flood elevations or depths are shown within this zone. Zone V Zone V is the flood insurance rate zone that corresponds to the 1-percent annual chance coastal floodplains that have additional hazards associated with storm waves. Because approximate hydraulic analyses are performed for such areas, no base flood elevations are shown within this zone. Zone VE Zone VE is the flood insurance rate zone that corresponds to the 1-percent annual chance coastal floodplains that have additional hazards associated with storm waves. Whole-foot base flood elevations derived from the detailed hydraulic analyses are shown at selected intervals within this zone. Zone X Zone X is the flood insurance rate zone that corresponds to areas outside the 0.2-percent annual chance floodplain, areas within the 0.2-percent annual chance floodplain, and to areas of 1-percent annual chance flooding where average depths are less than 1-foot, areas of 1-percent annual chance flooding where the contributing drainage area is less than 1 square mile, and areas protected from the 1-percent annual chance flood by levees. No base flood elevations or depths are shown within this zone.

58

Zone D Zone D is the flood insurance rate zone that corresponds to unstudied areas where flood hazards are undetermined, but possible.

6.0 FLOOD INSURANCE RATE MAP

The FIRM is designed for flood insurance and floodplain management applications. For flood insurance applications, the map designates flood insurance rate zones as described in Section 5.0 and, in the 1-percent annual chance floodplains that were studied by detailed methods, shows selected whole-foot base flood elevations or average depths. Insurance agents use the zones and base flood elevations in conjunction with information on structures and their contents to assign premium rates for flood insurance policies.

For floodplain management applications, the map shows by tints, screens, and symbols the 1- and 0.2-percent annual chance floodplains. Floodways and the locations of selected cross sections used in the hydraulic analyses and floodway computations are shown where applicable.

The current FIRM presents flooding information for the entire geographic area of Walton County. Previously, separate Flood Hazard Boundary Maps and/or FIRMs were prepared for each identified flood-prone incorporated community and the unincorporated areas of the county. This countywide FIRM also includes flood hazard information that was presented separately on Flood Boundary and Floodway Maps, where applicable. Historical data relating to the maps prepared for each community, up to and including the March 7, 2000 countywide FIS, area presented in Table 10 – “Community Map History.”

7.0 OTHER STUDIES

FISs have been prepared for areas located adjacent to Walton County including, Okaloosa County and Bay County, Florida (References 33 and 34). Information pertaining to revised and unrevised flood hazards for each jurisdiction within Walton County, Florida has been compiled into this FIS. Therefore, this FIS supersedes all previously printed FIS reports, FIRMs, and FBFMs for all jurisdictions within Walton County, Florida (City of De Funiak Springs, City of Freeport, Town of Paxton, and the unincorporated areas of Walton County).

8.0 LOCATION OF DATA

Information concerning the pertinent data used in the preparation of this study can be obtained by contacting FEMA, Mitigation Division, Koger Center - Rutgers Building, 3003 Chamblee Tucker Road, Atlanta, Georgia 30341.

59

COMMUNITY NAME INITIAL IDENTIFICATION FLOOD HAZARD BOUNDARY MAP REVISIONS DATE

FIRM EFFECTIVE DATE

FIRM REVISIONS DATE

De Funiak Springs, City of

November 22, 1974 January 9, 1976 December 21, 1984 March 7, 2000

Freeport, City of

October 29, 1976 None April 30, 1986 March 7, 2000

Paxton, Town of

March 7, 2000 None March 7, 2000 March 7, 2000

Walton County (Unincorporated Areas)

February 21, 1975 None November 16, 1977 October 1, 1983 April 30, 1986 August 3, 1992 August 19, 1997 March 7, 2000

TAB

LE 12

FEDERAL EMERGENCY MANAGEMENT AGENCY

WALTON COUNTY, FL AND INCORPORATED AREAS

COMMUNITY MAP HISTORY

60

9.0 BIBLIOGRAPHY AND REFERENCES 1. Federal Emergency Management Agency, Flood Insurance Study, Walton County,

Florida (Unincorporated Areas), Washington, D.C., August 19, 1997. 2. Federal Emergency Management Agency, Flood Insurance Rate Map, Town of De

Funiak Springs, Walton County, Florida, Washington, D.C., December 21, 1989. 3. Federal Emergency Management Agency, Flood Insurance Study, City of Freeport,

Walton County, Florida, Washington, D.C., April 30, 1986. 4. U.S. Census Bureau Web Page, http://www.census.gov, January 19, 2010. 5. United States Air Force, Armament Development and Test Center, Hurricane

Effects in the Choctawhatchee Bay Area, Brent F. Waiter and Jack C. Rosenau, April 1971.

6. U.S. Army Corps of Engineers, Mobile District, Report on Hurricane Survey of

Northwest Florida Coast, Mobile, Alabama, December 1964. 7. U.S. Army Corps of Engineers, Mobile District, Floodplain Information - Vicinity

of Pensacola, Escambia, and Santa Rosa Counties, Florida, Mobile, Alabama, June 1972.

8. U.S. Department of Commerce, National Oceanic and Atmospheric

Administration, Tropical Prediction Center, The Deadliest, Costliest and Most Intense United States Hurricanes of this Century (NOAA Technical Memorandum NWS TPC-1), updated June 1997.

9. Edward N. Rappaport, U.S. Department of Commerce, National Oceanic and

Atmospheric Administration, National Hurricane Center, Preliminary Report: Hurricane Erin, 31 July - 6 August,1995, November 1995.

10. Dewberry & Davis, Coastal Flooding Studies of the Florida Panhandle, report

submitted through Woodward-Clyde Federal Services to Federal Emergency Management Agency, September 15, 1997.

11. Max Mayfield, U.S. Department of Commerce. National Oceanic and

Atmospheric Administration, National Hurricane Center. Preliminary Report: Hurricane Opal 27 September - 5 October, 1995. November 1995.

12. Mark E. Leadon, P.E.. Florida Department of Environmental Protection. Bureau of

Beaches and Coastal Systems, Hurricane Opal: Erosional and Structural Impacts to Florida's Gulf Coast, October 1996.

61

13. National Oceanic and Atmospheric Administration (NOAA)/Coastal Service

Center (CSC), Tropical Cyclone Report, Hurricane Dennis, 4 – 13 July 2005, Beven, J., National Hurricane Center, 22 November, 2005. Retrieval date January 23, 2008. http://maps.noaa.gov/hurricane/reports.jsp

14. U.S. Water Resources Council, Bulletin 17A, “Guidelines for Determining Flood

Flow Frequency,” March 1976. 15. U.S. Geological Survey, Water-Data Report FL-75-1., Tallahassee, Florida. June

1976. 16. U.S. Geological Survey, Water Supply Paper No. 1674, Magnitude and

Frequency of Floods in the United States: Part 2B. South Atlantic Slope and Eastern Gulf of Mexico Basin, 1966.

17. U.S. Geological Survey, Water Resources Investigations 82-4012, Technique for

Estimating Magnitude and Frequency of Floods on Natural-Flow Streams in Florida, Tallahassee, Florida, 1982.

18. U.S. Army Corps of Engineers, Hydrologic Engineering Center, HEC-2 Water-

Surface Profiles Generalized Computer Program, Davis. California. November 1976.

19. U.S. Department of Commerce, Environmental Sciences Services

Administration. Technical Memorandum WBTM, Hydro 11, Joint Probability Method of Tide Frequency Analysis Applied to Atlantic City and Long Beach Island. New Jersey. Vance A. Myers. April 1970.

20. U.S. Department of Commerce, National Oceanic, and Atmospheric

Administration, Technical Report NWS-15, Some Climatological Characteristics of Hurricanes and Tropical Storms, Gulf and East Coasts of the United States. Francis P. Ho., Richard W. Schwerdt, and Hugo V. Goodyear, May 1975.

21. U.S. Department of Commerce, National Hurricane Project, Report No. 33,

Meteorological Considerations Pertinent to Standard Project Hurricane, Atlantic and Gulf Coasts of the United States, Howard E. Graham, Dwight E. Nunn, November 1959.

22. Tetra Tech, Inc., Coastal Flooding Storm Surge Model, Parts 1 and 2. prepared

for the Federal Emergency Management Agency, 1981 . 23. U.S. Geological Survey, 7.5 Minute Series Topographic Maps, Scale 1:24000.

Contour Interval 5 feet: Bunker, Florida, 1970, photorevised, 1976; Destin,

62

Florida, 1970, photorevised, 1976; Choctaw Beach, Florida, 1970, photorevised. 1976; Freeport, Florida, 1970. photorevised 1976; Miramar Beach, Florida, 1970, photorevised, 1976; Grayton Beach, Florida, 1970, photorevised, 1976; Point Washington, Florida, 1970, photorevised. 1976; Seminole Hills. Florida, 1943.

24. GKY Associates, Inc., in cooperation with the Federal Emergency Management

Agency, Hurricane Sure Model, Florida Panhandle Communities, December 1982.

25. U.S. Army Corp of Engineers, Coastal Engineering Research Center, Shore

Protection Manual, Vicksburg, Mississippi, 1977. 26. National Academy of Sciences, Methodology for Calculating Wave Actions

Effects Associated with Storm Surges, 1977. 27. Federal Emergency Management Agency, Guidelines & Specifications for Wave

Elevation Determination and V Zone Mapping, Washington, D.C., March 1995. 28. Florida Department of Environmental Protection, Walton County Coastal

Construction Control Line, aerial photographs, October 1995, scale I = 100'. 29. Florida Department of Natural Resources, Aerial Photographs, Walton County,

December 1980.

30. Department of Commerce, National Oceanic and Atmospheric National Ocean Services, Coastal Services Center, 2006 Walton County, Florida LiDAR Mapping, Vector Digital Data, May 06, 2007

31. U.S. Department of the Interior, Geological Survey, 7.5-Minute Series

Topographic Maps, Scale 1:24,000, Contour Interval 5 feet: Bunker, Florida, photorevised 1976; Choctaw Beach, Florida, photorevised 1976, Destin, Florida, 1970, photorevised 1976; Freeport, Florida, photorevised 1976, Grayton Beach, Florida, 1970, photorevised 1976; Miramar Beach, Florida, 1970, photorevised 1976; Point Washington, Florida, 1970, photorevised 1976; Seminole Hills, Florida, 1943. Contour Interval 10 feet: Bruce, Florida, 1944; Darlington, Florida-Alabama, 1973; De Funiak Springs East, Florida, 1973; De Funiak Springs West, Florida; 1973; Dorcas, Florida, 1973; Gaskin, Florida-Alabama, 1973, Liberty, Florida, 1973; Mossy Head, Florida, 1973; New Harmony, Florida, 1973; Niceville, Florida, 1970, photorevised, 1976; Paxton, Florida-Alabama, 1973; Ponce DeLeon, Florida, 1948; Portland, Florida, 1970, photorevised, 1976; Red Bay, Florida 1949; Red Head, Florida, 1945; Rock Hill, Florida, 1970, photorevised, 1976; Spenser Flats, Florida, 1973.

63

32. United States Fish and Wildlife Services, Walton Wetlands, Location and Attribution for Wetland Areas, November 1, 2005.

33. Federal Emergency Management Agency, Flood Insurance Study, Okaloosa

County, Florida Incorporated Areas, December 6, 2002 34. Federal Emergency Management Agency, Flood Insurance Study, Bay County,

Florida and Incorporated Areas, June 2, 2009.

80

85

90 90

95 95

100 100

105 105

110 110

115 115

120 120

125 125

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 6500

ELE

VA

TIO

N IN

FEET

(N

AV

D 8

8)

STREAM DISTANCE IN FEET ABOVE CONFLUENCE WITH BRUCE CREEK

FED

ER

AL

EM

ER

GEN

CY

MA

NA

GEM

EN

T A

GEN

CY

WA

LTO

N C

OU

NT

Y,

F LA

ND

IN

CO

RP

OR

AT

ED

AR

EA

S

FLO

OD

PR

OFIL

ES

BA

Y B

RA

NC

H

03P

A B

CO

NFL

UEN

CE W

ITH

BR

UC

E C

REEK

LEGEND

0.2% ANNUAL CHANCE FLOOD

1% ANNUAL CHANCE FLOOD

2% ANNUAL CHANCE FLOOD

10% ANNUAL CHANCE FLOOD

STREAM BED

CROSS SECTION LOCATION

BACKWATER FROM BRUCE CREEK

10% AND 2% ANNUAL CHANCE FLOOD

PROFILES ARE TOO CLOSE TO THE

1% ANNUAL CHANCE ELEVATION

TO BE SHOWN SEPARATELY

NOTE:

105

110

115 115

120 120

125 125

130 130

135 135

140 140

145 145

150 150

6500 7000 7500 8000 8500 9000 9500 10000 10500 11000 11500 12000 12500 13000

ELE

VA

TIO

N IN

FEET

(N

AV

D 8

8)

STREAM DISTANCE IN FEET ABOVE CONFLUENCE WITH BRUCE CREEK

FED

ER

AL

EM

ER

GEN

CY

MA

NA

GEM

EN

T A

GEN

CY

WA

LTO

N C

OU

NT

Y,

F LA

ND

IN

CO

RP

OR

AT

ED

AR

EA

S

FLO

OD

PR

OFIL

ES

BA

Y B

RA

NC

H

04P

C D

U.S

. H

IGH

WA

Y 3

31

LIM

IT O

F D

ET

AIL

ED

ST

UD

Y

LEGEND

0.2% ANNUAL CHANCE FLOOD

1% ANNUAL CHANCE FLOOD

2% ANNUAL CHANCE FLOOD

10% ANNUAL CHANCE FLOOD

STREAM BED

CROSS SECTION LOCATION

CULVERT

10% AND 2% ANNUAL CHANCE

FLOOD PROFILES ARE TOO CLOSE TO

THE 1% ANNUAL CHANCE ELEVATION

TO BE SHOWN SEPARATELY

NOTE:

-30

-25

-20 -20

-15 -15

-10 -10

-5 -5

0 0

5 5

10 10

15 15

0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600

ELE

VA

TIO

N IN

FEET

(N

AV

D 8

8)

STREAM DISTANCE IN FEET ABOVE COUNTY HIGHWAY 3280

FED

ER

AL

EM

ER

GEN

CY

MA

NA

GEM

EN

T A

GEN

CY

WA

LTO

N C

OU

NT

Y,

F LA

ND

IN

CO

RP

OR

AT

ED

AR

EA

S

FLO

OD

PR

OFIL

ES

BLA

CK

CR

EEK

09P

A B

CO

NFL

UEN

CE O

F C

AM

P C

REEK

LIM

IT O

F D

ET

AIL

ED

ST

UD

Y

LEGEND

0.2% ANNUAL CHANCE FLOOD

1% ANNUAL CHANCE FLOOD

2% ANNUAL CHANCE FLOOD

10% ANNUAL CHANCE FLOOD

STREAM BED

CROSS SECTION LOCATION

CO

UN

TY

HIG

HW

AY

32

80

CONTROLLED BY CHOCTAWATCHEE BAYFLOODING DOWNSTREAM OF THIS POINT

40

45

50 50

55 55

60 60

65 65

70 70

75 75

80 80

85 85

11000 11500 12000 12500 13000 13500 14000 14500 15000 15500 16000 16500 17000 17500

ELE

VA

TIO

N IN

FEET

(N

AV

D 8

8)

STREAM DISTANCE IN FEET ABOVE MCKINNON BRIDGE ROAD

FED

ER

AL

EM

ER

GEN

CY

MA

NA

GEM

EN

T A

GEN

CY

WA

LTO

N C

OU

NT

Y,

F LA

ND

IN

CO

RP

OR

AT

ED

AR

EA

S

FLO

OD

PR

OFIL

ES

BR

UC

E C

REEK

10P

A B

LIM

IT O

F D

ET

AIL

ED

ST

UD

Y

CO

NFL

UEN

CE O

F M

ILL

CR

EEK

RED

HIL

L R

OA

D

LEGEND

0.2% ANNUAL CHANCE FLOOD

1% ANNUAL CHANCE FLOOD

2% ANNUAL CHANCE FLOOD

10% ANNUAL CHANCE FLOOD

STREAM BED

CROSS SECTION LOCATION

45

50

55 55

60 60

65 65

70 70

75 75

80 80

85 85

90 90

17500 18000 18500 19000 19500 20000 20500 21000 21500 22000 22500 23000 23500 24000

ELE

VA

TIO

N IN

FEET

(N

AV

D 8

8)

STREAM DISTANCE IN FEET ABOVE MCKINNON BRIDGE ROAD

FED

ER

AL

EM

ER

GEN

CY

MA

NA

GEM

EN

T A

GEN

CY

WA

LTO

N C

OU

NT

Y,

F LA

ND

IN

CO

RP

OR

AT

ED

AR

EA

S

FLO

OD

PR

OFIL

ES

BR

UC

E C

REEK

11P

C

D

CO

NFL

UEN

CE O

F P

AN

TH

ER

CR

EEK

LEGEND

0.2% ANNUAL CHANCE FLOOD

1% ANNUAL CHANCE FLOOD

2% ANNUAL CHANCE FLOOD

10% ANNUAL CHANCE FLOOD

STREAM BED

CROSS SECTION LOCATION

55

60

65 65

70 70

75 75

80 80

85 85

90 90

95 95

100 100

24000 24500 25000 25500 26000 26500 27000 27500 28000 28500 29000 29500 30000 30500

ELE

VA

TIO

N IN

FEET

(N

AV

D 8

8)

STREAM DISTANCE IN FEET ABOVE MCKINNON BRIDGE ROAD

FED

ER

AL

EM

ER

GEN

CY

MA

NA

GEM

EN

T A

GEN

CY

WA

LTO

N C

OU

NT

Y,

F LA

ND

IN

CO

RP

OR

AT

ED

AR

EA

S

FLO

OD

PR

OFIL

ES

BR

UC

E C

REEK

12P

E

F

WES

T IN

DIA

N C

REEK

RA

NC

H R

OA

D

LEGEND

0.2% ANNUAL CHANCE FLOOD

1% ANNUAL CHANCE FLOOD

2% ANNUAL CHANCE FLOOD

10% ANNUAL CHANCE FLOOD

STREAM BED

CROSS SECTION LOCATION

60

65

70 70

75 75

80 80

85 85

90 90

95 95

100 100

105 105

30500 31000 31500 32000 32500 33000 33500 34000 34500 35000 35500 36000 36500 37000

ELE

VA

TIO

N IN

FEET

(N

AV

D 8

8)

STREAM DISTANCE IN FEET ABOVE MCKINNON BRIDGE ROAD

FED

ER

AL

EM

ER

GEN

CY

MA

NA

GEM

EN

T A

GEN

CY

WA

LTO

N C

OU

NT

Y,

F LA

ND

IN

CO

RP

OR

AT

ED

AR

EA

S

FLO

OD

PR

OFIL

ES

BR

UC

E C

REEK

13P

G

H

LEGEND

0.2% ANNUAL CHANCE FLOOD

1% ANNUAL CHANCE FLOOD

2% ANNUAL CHANCE FLOOD

10% ANNUAL CHANCE FLOOD

STREAM BED

CROSS SECTION LOCATION

70

75

80 80

85 85

90 90

95 95

100 100

105 105

110 110

115 115

37000 37500 38000 38500 39000 39500 40000 40500 41000 41500 42000 42500 43000 43500

ELE

VA

TIO

N IN

FEET

(N

AV

D 8

8)

STREAM DISTANCE IN FEET ABOVE MCKINNON BRIDGE ROAD

FED

ER

AL

EM

ER

GEN

CY

MA

NA

GEM

EN

T A

GEN

CY

WA

LTO

N C

OU

NT

Y,

F LA

ND

IN

CO

RP

OR

AT

ED

AR

EA

S

FLO

OD

PR

OFIL

ES

BR

UC

E C

REEK

14P

I

LEGEND

0.2% ANNUAL CHANCE FLOOD

1% ANNUAL CHANCE FLOOD

2% ANNUAL CHANCE FLOOD

10% ANNUAL CHANCE FLOOD

STREAM BED

CROSS SECTION LOCATION

80

85

90 90

95 95

100 100

105 105

110 110

115 115

120 120

125 125

43500 44000 44500 45000 45500 46000 46500 47000 47500 48000 48500 49000 49500 50000

ELE

VA

TIO

N IN

FEET

(N

AV

D 8

8)

STREAM DISTANCE IN FEET ABOVE MCKINNON BRIDGE ROAD

FED

ER

AL

EM

ER

GEN

CY

MA

NA

GEM

EN

T A

GEN

CY

WA

LTO

N C

OU

NT

Y,

F LA

ND

IN

CO

RP

OR

AT

ED

AR

EA

S

FLO

OD

PR

OFIL

ES

BR

UC

E C

REEK

15P

J K

CO

NFL

UEN

CE O

F B

AY

BR

AN

CH

LEGEND

0.2% ANNUAL CHANCE FLOOD

1% ANNUAL CHANCE FLOOD

2% ANNUAL CHANCE FLOOD

10% ANNUAL CHANCE FLOOD

STREAM BED

CROSS SECTION LOCATION

95

100

105 105

110 110

115 115

120 120

125 125

130 130

135 135

140 140

50000 50500 51000 51500 52000 52500 53000 53500 54000 54500 55000 55500 56000 56500

ELE

VA

TIO

N IN

FEET

(N

AV

D 8

8)

STREAM DISTANCE IN FEET ABOVE MCKINNON BRIDGE ROAD

FED

ER

AL

EM

ER

GEN

CY

MA

NA

GEM

EN

T A

GEN

CY

WA

LTO

N C

OU

NT

Y,

F LA

ND

IN

CO

RP

OR

AT

ED

AR

EA

S

FLO

OD

PR

OFIL

ES

BR

UC

E C

REEK

16P

L

LIM

IT O

F D

ET

AIL

ED

ST

UD

Y

LEGEND

0.2% ANNUAL CHANCE FLOOD

1% ANNUAL CHANCE FLOOD

2% ANNUAL CHANCE FLOOD

10% ANNUAL CHANCE FLOOD

STREAM BED

CROSS SECTION LOCATION

-25

-20

-15 -15

-10 -10

-5 -5

0 0

5 5

10 10

15 15

20 20

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 6500

ELE

VA

TIO

N IN

FEET

(N

AV

D 8

8)

STREAM DISTANCE IN FEET ABOVE CONFLUENCE WITH BLACK CREEK

FED

ER

AL

EM

ER

GEN

CY

MA

NA

GEM

EN

T A

GEN

CY

WA

LTO

N C

OU

NT

Y,

F LA

ND

IN

CO

RP

OR

AT

ED

AR

EA

S

FLO

OD

PR

OFIL

ES

CA

MP

CR

EEK

17P

A B C D E

F

CO

NFLU

EN

CE W

ITH

BLA

CK

CR

EEK

LEGEND

0.2% ANNUAL CHANCE FLOOD

1% ANNUAL CHANCE FLOOD

2% ANNUAL CHANCE FLOOD

10% ANNUAL CHANCE FLOOD

STREAM BED

CROSS SECTION LOCATION

1% ANNUAL CHANCE BACKWATER FROM BLACK CREEK

LIM

IT O

F D

ET

AIL

ED

ST

UD

Y

115

120

125 125

130 130

135 135

140 140

145 145

150 150

155 155

160 160

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 6500

ELE

VA

TIO

N IN

FEET

(N

AV

D 8

8)

STREAM DISTANCE IN FEET ABOVE CONFLUENCE WITH SHOAL RIVER

FED

ER

AL

EM

ER

GEN

CY

MA

NA

GEM

EN

T A

GEN

CY

WA

LTO

N C

OU

NT

Y,

F LA

ND

IN

CO

RP

OR

AT

ED

AR

EA

S

FLO

OD

PR

OFIL

ES

GU

M C

REEK

34P

A B C

CO

NFL

UEN

CE W

ITH

SH

OA

L R

IVER

LEGEND

0.2% ANNUAL CHANCE FLOOD

1% ANNUAL CHANCE FLOOD

2% ANNUAL CHANCE FLOOD

10% ANNUAL CHANCE FLOOD

STREAM BED

CROSS SECTION LOCATION

120

125

130 130

135 135

140 140

145 145

150 150

155 155

160 160

165 165

6500 7000 7500 8000 8500 9000 9500 10000 10500 11000 11500 12000 12500 13000

ELE

VA

TIO

N IN

FEET

(N

AV

D 8

8)

STREAM DISTANCE IN FEET ABOVE CONFLUENCE WITH SHOAL RIVER

FED

ER

AL

EM

ER

GEN

CY

MA

NA

GEM

EN

T A

GEN

CY

WA

LTO

N C

OU

NT

Y,

F LA

ND

IN

CO

RP

OR

AT

ED

AR

EA

S

FLO

OD

PR

OFIL

ES

GU

M C

REEK

35P

D E

F

LIM

IT O

F D

ET

AIL

ED

ST

UD

Y

LEGEND

0.2% ANNUAL CHANCE FLOOD

1% ANNUAL CHANCE FLOOD

2% ANNUAL CHANCE FLOOD

10% ANNUAL CHANCE FLOOD

STREAM BED

CROSS SECTION LOCATION

-15

-10

-5 -5

0 0

5 5

10 10

15 15

20 20

25 25

30 30

5400 5900 6400 6900 7400 7900 8400 8900 9400 9900 10400 10900 11400 11900

ELE

VA

TIO

N IN

FEET

(N

AV

D 8

8)

STREAM DISTANCE IN FEET ABOVE CONFLUENCE WITH FOURMILE CREEK

FED

ER

AL

EM

ER

GEN

CY

MA

NA

GEM

EN

T A

GEN

CY

WA

LTO

N C

OU

NT

Y,

F LA

ND

IN

CO

RP

OR

AT

ED

AR

EA

S

FLO

OD

PR

OFIL

ES

LAFA

YET

TE C

REEK

36P

A B

C

LEGEND

0.2% ANNUAL CHANCE FLOOD

1% ANNUAL CHANCE FLOOD

2% ANNUAL CHANCE FLOOD

10% ANNUAL CHANCE FLOOD

STREAM BED

CROSS SECTION LOCATION

ST

AT

E H

IGH

WA

Y 2

0 /

LIM

IT O

F S

TU

DY

-10

-5

0 0

5 5

10 10

15 15

20 20

25 25

30 30

35 35

11900 12400 12900 13400 13900 14400 14900 15400 15900 16400 16900 17400 17900 18400

ELEV

ATIO

N IN

FEE

T (N

AVD

88)

STREAM DISTANCE IN FEET ABOVE CONFLUENCE WITH FOURMILE CREEK

FEDE

RAL

EME R

GENC

Y M

A NAG

EMEN

T AG

ENC Y

WA L

TON

COU N

TY, F

LAN

D IN

COR P

ORAT

ED A

R EAS

F LOO

D PR

O FIL

ES

L AFA

Y ETT

E C R

EEK

2237

37P

D

E

LEGEND0.2% ANNUAL CHANCE FLOOD

1% ANNUAL CHANCE FLOOD

2% ANNUAL CHANCE FLOOD

10% ANNUAL CHANCE FLOOD

STREAM BED

CROSS SECTION LOCATION

-5

0

5 5

10 10

15 15

20 20

25 25

30 30

35 35

40 40

18400 18900 19400 19900 20400 20900 21400 21900 22400 22900 23400 23900 24400 24900

ELEV

ATIO

N IN

FEE

T (N

AVD

88)

STREAM DISTANCE IN FEET ABOVE CONFLUENCE WITH FOURMILE CREEK

FEDE

RAL

EME R

GENC

Y M

A NAG

EMEN

T AG

ENC Y

WA L

TON

COU N

TY, F

LAN

D IN

COR P

ORAT

ED A

R EAS

F LOO

D PR

O FIL

ES

L AFA

Y ETT

E C R

EEK

223233

38P

F

G

LEGEND0.2% ANNUAL CHANCE FLOOD

1% ANNUAL CHANCE FLOOD

2% ANNUAL CHANCE FLOOD

10% ANNUAL CHANCE FLOOD

STREAM BED

CROSS SECTION LOCATION

STAT

E HI

GHW

AY 8

3

0

5

10 10

15 15

20 20

25 25

30 30

35 35

40 40

45 45

24900 25400 25900 26400 26900 27400 27900 28400 28900 29400 29900 30400 30900 31400

ELE

VA

TIO

N IN

FEET

(N

AV

D 8

8)

STREAM DISTANCE IN FEET ABOVE CONFLUENCE WITH FOURMILE CREEK

FED

ER

AL

EM

ER

GEN

CY

MA

NA

GEM

EN

T A

GEN

CY

WA

LTO

N C

OU

NT

Y,

F LA

ND

IN

CO

RP

OR

AT

ED

AR

EA

S

FLO

OD

PR

OFIL

ES

LAFA

YET

TE C

REEK

39P

H

I

LEGEND

0.2% ANNUAL CHANCE FLOOD

1% ANNUAL CHANCE FLOOD

2% ANNUAL CHANCE FLOOD

10% ANNUAL CHANCE FLOOD

STREAM BED

CROSS SECTION LOCATION

CO

NFL

UEN

CE O

F M

AG

NO

LIA

CR

EEK

0

5

10 10

15 15

20 20

25 25

30 30

35 35

40 40

45 45

31400 31900 32400 32900 33400 33900 34400 34900 35400 35900 36400 36900 37400 37900

ELEV

ATIO

N IN

FEE

T (N

AVD

88)

STREAM DISTANCE IN FEET ABOVE CONFLUENCE WITH FOURMILE CREEK

FEDE

RAL

EME R

GENC

Y M

A NAG

EMEN

T AG

ENC Y

WA L

TON

COU N

TY, F

LAN

D IN

COR P

ORAT

ED A

R EAS

F LOO

D PR

O FIL

ES

L AFA

Y ETT

E C R

EEK

4

40P

J

K

LEGEND0.2% ANNUAL CHANCE FLOOD

1% ANNUAL CHANCE FLOOD

2% ANNUAL CHANCE FLOOD

10% ANNUAL CHANCE FLOOD

STREAM BED

CROSS SECTION LOCATION

UNNA

MED

ROA

D

10

15

20 20

25 25

30 30

35 35

40 40

45 45

50 50

55 55

37900 38400 38900 39400 39900 40400 40900 41400 41900 42400 42900 43400 43900 44400

ELEV

ATIO

N IN

FEE

T (N

AVD

88)

STREAM DISTANCE IN FEET ABOVE CONFLUENCE WITH FOURMILE CREEK

FEDE

RAL

EME R

GENC

Y M

A NAG

EMEN

T AG

ENC Y

WA L

TON

COU N

TY, F

LAN

D IN

COR P

ORAT

ED A

R EAS

F LOO

D PR

O FIL

ES

L AFA

Y ETT

E C R

EEK

41

41P

L M

WOL

F CR

E EK

LEGEND0.2% ANNUAL CHANCE FLOOD

1% ANNUAL CHANCE FLOOD

2% ANNUAL CHANCE FLOOD

10% ANNUAL CHANCE FLOOD

STREAM BED

CROSS SECTION LOCATION

CONF

LUEN

C E O

F

20

25

30 30

35 35

40 40

45 45

50 50

55 55

60 60

65 65

44400 44900 45400 45900 46400 46900 47400 47900 48400 48900 49400 49900 50400 50900

ELEV

ATIO

N IN

FEE

T (N

AVD

88)

STREAM DISTANCE IN FEET ABOVE CONFLUENCE WITH FOURMILE CREEK

FEDE

RAL

EME R

GENC

Y M

A NAG

EMEN

T AG

ENC Y

WA L

TON

COU N

TY, F

LAN

D IN

COR P

ORAT

ED A

R EAS

F LOO

D PR

O FIL

ES

L AFA

Y ETT

E C R

EEK

2

42P

N O

P

LEGEND0.2% ANNUAL CHANCE FLOOD

1% ANNUAL CHANCE FLOOD

2% ANNUAL CHANCE FLOOD

10% ANNUAL CHANCE FLOOD

STREAM BED

CROSS SECTION LOCATION

J.W

. HO L

LING

TON

ROAD

35

40

45 45

50 50

55 55

60 60

65 65

70 70

75 75

80 80

50900 51400 51900 52400 52900 53400 53900 54400 54900 55400 55900 56400 56900 57400

ELE

VA

TIO

N IN

FEET

(N

AV

D 8

8)

STREAM DISTANCE IN FEET ABOVE CONFLUENCE WITH FOURMILE CREEK

FED

ER

AL

EM

ER

GEN

CY

MA

NA

GEM

EN

T A

GEN

CY

WA

LTO

N C

OU

NT

Y,

F LA

ND

IN

CO

RP

OR

AT

ED

AR

EA

S

FLO

OD

PR

OFIL

ES

LAFA

YET

TE C

REEK

43P

Q

LIM

IT O

F D

ET

AIL

ED

ST

UD

Y

LEGEND

0.2% ANNUAL CHANCE FLOOD

1% ANNUAL CHANCE FLOOD

2% ANNUAL CHANCE FLOOD

10% ANNUAL CHANCE FLOOD

STREAM BED

CROSS SECTION LOCATION

45

50

55 55

60 60

65 65

70 70

75 75

80 80

85 85

90 90

0 400 800 1200 1600 2000 2400 2800 3200 3600 4000 4400 4800 5200

ELE

VA

TIO

N IN

FEET

(N

AV

D 8

8)

STREAM DISTANCE IN FEET ABOVE CONFLUENCE WITH BRUCE CREEK

FED

ER

AL

EM

ER

GEN

CY

MA

NA

GEM

EN

T A

GEN

CY

WA

LTO

N C

OU

NT

Y,

F LA

ND

IN

CO

RP

OR

AT

ED

AR

EA

S

FLO

OD

PR

OFIL

ES

MIL

L C

REEK

44P

A

CO

NFL

UEN

CE W

ITH

BR

UC

E C

REEK

ED

GEW

OO

D C

IRC

LE

LEGEND

0.2% ANNUAL CHANCE FLOOD

1% ANNUAL CHANCE FLOOD

2% ANNUAL CHANCE FLOOD

10% ANNUAL CHANCE FLOOD

STREAM BED

CROSS SECTION LOCATION

BACKWATER EFFECTS FROM BRUCE CREEK

70

75

80 80

85 85

90 90

95 95

100 100

105 105

110 110

115 115

5200 5600 6000 6400 6800 7200 7600 8000 8400 8800 9200 9600 10000 10400

ELEV

ATIO

N IN

FEE

T (N

AVD

88)

STREAM DISTANCE IN FEET ABOVE CONFLUENCE WITH BRUCE CREEK

FEDE

RAL

EME R

GENC

Y M

A NAG

EMEN

T AG

ENC Y

WA L

TON

COU N

TY, F

LAN

D IN

COR P

ORAT

ED A

R EAS

F LOO

D PR

O FIL

ES

MIL

L CR

E EK

4

45P

B

LEGEND0.2% ANNUAL CHANCE FLOOD

1% ANNUAL CHANCE FLOOD

2% ANNUAL CHANCE FLOOD

10% ANNUAL CHANCE FLOOD

STREAM BED

CROSS SECTION LOCATION

90

95

100 100

105 105

110 110

115 115

120 120

125 125

130 130

135 135

10400 10800 11200 11600 12000 12400 12800 13200 13600 14000 14400 14800 15200 15600

ELE

VA

TIO

N IN

FEET

(N

AV

D 8

8)

STREAM DISTANCE IN FEET ABOVE CONFLUENCE WITH BRUCE CREEK

FED

ER

AL

EM

ER

GEN

CY

MA

NA

GEM

EN

T A

GEN

CY

WA

LTO

N C

OU

NT

Y,

F LA

ND

IN

CO

RP

OR

AT

ED

AR

EA

S

FLO

OD

PR

OFIL

ES

MIL

L C

REEK

46P

C

CO

NFL

UEN

CE O

F M

ILL

CR

EEK

UN

NA

MED

TR

IBU

TA

RY

LEGEND

0.2% ANNUAL CHANCE FLOOD

1% ANNUAL CHANCE FLOOD

2% ANNUAL CHANCE FLOOD

10% ANNUAL CHANCE FLOOD

STREAM BED

CROSS SECTION LOCATION

110

115

120 120

125 125

130 130

135 135

140 140

145 145

150 150

155 155

15600 16000 16400 16800 17200 17600 18000 18400 18800 19200 19600 20000 20400 20800

ELEV

ATIO

N IN

FEE

T (N

AVD

88)

STREAM DISTANCE IN FEET ABOVE CONFLUENCE WITH BRUCE CREEK

FEDE

RAL

EME R

GENC

Y M

A NAG

EMEN

T AG

ENC Y

WA L

TON

COU N

TY, F

LAN

D IN

COR P

ORAT

ED A

R EAS

F LOO

D PR

O FIL

ES

MIL

L CR

E EK

4

47P

D

EDGE

WOO

D C I

RCLE

L IM

IT O

F DE

TAIL

E D S

TUD Y

LEGEND0.2% ANNUAL CHANCE FLOOD

1% ANNUAL CHANCE FLOOD

2% ANNUAL CHANCE FLOOD

10% ANNUAL CHANCE FLOOD

STREAM BED

CROSS SECTION LOCATION

CULVERT

110

115

120 120

125 125

130 130

135 135

140 140

145 145

150 150

155 155

0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600

ELEV

ATIO

N IN

FEE

T (N

AVD

88)

STREAM DISTANCE IN FEET ABOVE CONFLUENCE WITH MILL CREEK

FEDE

RAL

EME R

GENC

Y M

A NAG

EMEN

T AG

ENC Y

WA L

TON

COU N

TY, F

LAN

D IN

COR P

ORAT

ED A

R EAS

F LOO

D PR

O FIL

ES

MI L

L CR

E EK

UNNA

ME D

TRI

BUTA

RY

48P

A B

C

CONF

LUEN

C E W

ITH

MIL

L CR

EEK

LEGEND0.2% ANNUAL CHANCE FLOOD

1% ANNUAL CHANCE FLOOD

2% ANNUAL CHANCE FLOOD

10% ANNUAL CHANCE FLOOD

STREAM BED

CROSS SECTION LOCATION

BACKWATER FROM MILL CREEK

140

145

150 150

155 155

160 160

165 165

170 170

175 175

180 180

185 185

2600 2800 3000 3200 3400 3600 3800 4000 4200 4400 4600 4800 5000 5200

ELEV

ATIO

N IN

FEE

T (N

AVD

88)

STREAM DISTANCE IN FEET ABOVE CONFLUENCE WITH MILL CREEK

FEDE

RAL

EME R

GENC

Y M

A NAG

EMEN

T AG

ENC Y

WA L

TON

COU N

TY, F

LAN

D IN

COR P

ORAT

ED A

R EAS

F LOO

D PR

O FIL

ES

MI L

L CR

E EK

UNNA

ME D

TRI

BUTA

RY

4

49P

D

E

EDGE

WOO

D C I

RCLE

L IM

IT O

F DE

TAIL

E D S

TUD Y

LEGEND0.2% ANNUAL CHANCE FLOOD

1% ANNUAL CHANCE FLOOD

2% ANNUAL CHANCE FLOOD

10% ANNUAL CHANCE FLOOD

STREAM BED

CROSS SECTION LOCATION

CULVERT

-25

-20

-15 -15

-10 -10

-5 -5

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10 10

15 15

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(N

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STREAM DISTANCE IN FEET ABOVE CONFLUENCE WITH CAMP CREEK

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0.2% ANNUAL CHANCE FLOOD

1% ANNUAL CHANCE FLOOD

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CROSS SECTION LOCATION

1% ANNUAL CHANCE BACKWATER FROM CAMP CREEK

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105 105

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ELEV

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STREAM DISTANCE IN FEET ABOVE COUNTY BOUNDARY

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ELEV

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STREAM DISTANCE IN FEET ABOVE COUNTY BOUNDARY

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ELEV

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STREAM DISTANCE IN FEET ABOVE COUNTY BOUNDARY

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ELEV

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STREAM DISTANCE IN FEET ABOVE COUNTY BOUNDARY

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ELEV

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STREAM DISTANCE IN FEET ABOVE COUNTY BOUNDARY

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STREAM DISTANCE IN FEET ABOVE COUNTY BOUNDARY

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