volusia county, floridafris.nc.gov/fris_hardfiles/fl/fis/12127cv000c.pdfvolusia county, florida and...

VOLUSIA COUNTY, FLORIDA AND INCORPORATED AREAS Community Name Community Number

DAYTONA BEACH, CITY OF 125099

DAYTONA BEACH SHORES, CITY OF 125100

DeBARY, CITY OF 120672

DELAND, CITY OF 120307

DELTONA, CITY OF 120677

EDGEWATER, CITY OF 120308

FLAGLER BEACH, CITY OF 120087

HOLLY HILL, CITY OF 125112

LAKE HELEN, CITY OF 120674

NEW SMYRNA BEACH, CITY OF 125132

OAK HILL, CITY OF 120624

ORANGE CITY, CITY OF 120633

ORMOND BEACH, CITY OF 125136

PIERSON, TOWN OF 120675

PONCE INLET, TOWN OF 120312

PORT ORANGE, CITY OF 120313

SOUTH DAYTONA, CITY OF 120314

VOLUSIA COUNTY 125155

(UNINCORPORATED AREAS)

REVISED:

February 19, 2014

Federal Emergency Management Agency FLOOD INSURANCE STUDY NUMBER

12127CV000C

VOLUSIA COUNTY

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.

The Federal Emergency Management Agency (FEMA) may revise and republish part or all of this FIS report 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 Map Repository to obtain the most current FIS components.

This FIS report was revised on February 19, 2003, September 29, 2011 and February 19, 2014. Users should refer to Section 10.0, Revisions Description, for further information. Section 10.0 is intended to present the most up-to-date information for specific portions of this FIS report. Therefore, users of this report should be aware that the information presented in Section 10.0 supersedes information in Sections 1.0 through 9.0 of this FIS report. Initial Countywide FIS Effective Date: April 15, 2002

Revised FIS Dates: February 19, 2003 September 29, 2011 February 19, 2014

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TABLE OF CONTENTS Page

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 9

3.0 ENGINEERING METHODS 10

3.1 Riverine Hydrologic Analyses 10

3.2 Riverine Hydraulic Analyses 15

3.3 Coastal Hydrologic Analyses 19

3.4 Coastal Hydraulic Analyses 20

3.5 Vertical Datum 30

4.0 FLOODPLAIN MANAGEMENT APPLICATIONS 30

4.1 Floodplain Boundaries 30

4.2 Floodways 31

5.0 INSURANCE APPLICATIONS 40

6.0 FLOOD INSURANCE RATE MAP 41

7.0 OTHER STUDIES 46

8.0 LOCATION OF DATA 46

9.0 BIBLIOGRAPHY AND REFERENCES 46

10.0 REVISION DESCRIPTIONS 51

10.1 First Revision (Revised February 19, 2003) 51

10.2 Second Revision (Revised September 29, 2011 52

a. Acknowledgments 52

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TABLE OF CONTENTS – continued

b. Coordination 52

c. Scope 52

d. Hydrologic and Hydraulic Analyses 52

e. Floodplain Boundaries 53

f. Floodways 53

g. Bibliography and References 53

10.3 Third Revision (Revised February 19, 2014) 53

a. Acknowledgments 53

b. Coordination 54

c. Scope 54

d. Hydrologic and Hydraulic Analyses 56

e. Floodplain Boundaries 60

f. Floodways 60

g. Bibliography and References 64

FIGURES Figure 1 - Transect Location Map 22 Figure 2 - Transect Schematic 29 Figure 3 - Floodway Schematic 40

TABLES Table 1 - Flooding Sources Studied by Detailed Methods 5 Table 2 - Initial Countywide Scope 5-6 Table 3 - Summary of Discharges 12-14 Table 4 - Summary of Stillwater Elevations 15 Table 5 - Manning’s “n” Values 18 Table 6 - Summary of Coastal Stillwater Elevations 20 Table 7 - Transect Descriptions 23-28 Table 8 - Transect Data 29 Table 9 - Floodway Data 33-39 Table 10 - Community Map History 42-45 Table 11 - First Revision Summary of Stillwater Elevations 51-52 Table 12 - Third Revision Detailed Study Scope 54-55 Table 13 - Incorporated LOMRs 55-56

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TABLES – continued Table 14 - Revised Summary of Discharges 57-58 Table 15 – Third Revision Summary of Stillwater Elevations 58 Table 16 - Revised Hydraulic Model Boundary Conditions 59 Table 17 - Revised Manning’s “n” Values 59 Table 18 - Revised Floodway Data 61-63

EXHIBITS Exhibit 1 - Flood Profiles

B-19 Canal Panels 01P-03P B-19 Canal Tributary No. 1 Panel 04P B-19 Canal Tributary No. 2 Panel 05P B-19 Canal Tributary No. 7 Panel 06P B-27 Canal North Panel 07P B-27 Canal South Panel 08P Bulow Creek Panel 09P Canal Between Panel 10P E Canal Panel 11P Eleventh Street Canal Panel 12P Eleventh Street Canal Tributary No. 2 Panel 13P Groover Branch Panels 14P-15P Halifax Canal Panels 16P-17P Laurel Creek Panels 18P-19P LPGA Canal Panel 20P Little Tomoka River Panels 21P-22P Misner Branch Panels 23P-24P Nova Canal North Reach 1 Panels 25P Nova Canal North Reach 2 Panels 26P-27P Nova Canal South Reach 1 Panels 28P-29P Nova Canal South Reach 2 Panels 30P St. Johns River Panels 31P-34P Shooting Range Canal/Eleventh Street

Canal Tributary No. 2/Eleventh Street Canal Tributary No. 2A Panels 35P-37P

South Canal Panel 38P Spruce Creek Panels 39P-40P Spruce Creek Tributary No. 1 Panel 41P Spruce Creek Tributary No. 2 Panel 42P Spruce Creek Tributary A Panel 43P Thompson Creek Panels 44P Tomoka River Panels 45P-48P Wally Hoffmeyer Canal Panel 49P

Exhibit 2 - Flood Insurance Rate Map Index Flood Insurance Rate Map

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FLOOD INSURANCE STUDY VOLUSIA COUNTY, FLORIDA AND INCORPORATED AREAS

1.0 INTRODUCTION

1.1 Purpose of Study

This Flood Insurance Study (FIS) revises and supersedes the FIS reports and Flood Insurance Rate Maps (FIRMs) in the geographic area of Volusia County, Florida, including: the Cities of Daytona Beach, Daytona Beach Shores, DeBary, Deland, Deltona, Edgewater, Flagler Beach, Holly Hill, Lake Helen, New Smyrna Beach, Oak Hill, Orange City, Ormond Beach, Port Orange, and South Daytona; the Towns of Pierson and Ponce Inlet; and the unincorporated areas of Volusia County (hereinafter referred to collectively as Volusia County), and 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 Volusia 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. Please note that the City of Flagler Beach is geographically located in Volusia and Flagler Counties. For this FIS only the portions of the City of Flagler Beach within Volusia County are included. The portions of the City of Flagler Beach that are geographically located within Flagler County are included in the Flagler County FIS. 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 the unincorporated areas of, and incorporated communities within Volusia County into a countywide FIS. Information on the authority and acknowledgments for all of the incorporated communities within, and the unincorporated areas of, Volusia County, as compiled from their previously printed FIS reports, is shown below.

Daytona Beach, City of: the hydrologic and hydraulic analyses for the FIS report dated June 4, 1990, were obtained from the June 4, 1990, FIS for the unincorporated areas of Volusia County and the study titled Tomoka River and B-19 Canal 100-

year Flood Results for the City of Daytona

Beach (References 1 and 2).

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Daytona Beach Shores, City of: the coastal analyses were conducted for the Wave Height Analysis dated March 16, 1982.

DeBary, City of: the hydrologic and hydraulic analyses for the FIS report dated February 2, 1996, were obtained from the June 4, 1990, FIS for the unincorporated areas of Volusia County (Reference 1).

Edgewater, City of: the hydrologic and hydraulic analyses for the FIS report dated June 4, 1990, were performed for FEMA and completed in August 1978. Additional coastal analyses were performed by FEMA to provide sufficient information for delineation of the floodplain boundaries for the City of Edgewater.

New Smyrna Beach, City of: the coastal analyses were conducted for the Wave Height Analysis dated March 16, 1982.

Oak Hill, City of: the hydrologic and hydraulic analyses for the FIS report dated June 4, 1990, were obtained from the June 4, 1990, FIS for the unincorporated areas of Volusia County (Reference 1).

Ormond Beach, City of: the hydrologic and hydraulic analyses for the FIS report dated June 4, 1990, were obtained from the June 4, 1990, FIS for the unincorporated areas of Volusia County and the study titled Tomoka River Flood Plain

Management Study - Tributaries to the Tomoka

River (References 1 and 3).

Ponce Inlet, Town of: the coastal analyses were conducted for the Wave Height Analysis dated March 16, 1982.

Port Orange, City of: the hydrologic and hydraulic analyses for the FIS report dated June 4, 1990, were obtained from the June 4, 1990, FIS for the unincorporated areas of Volusia County and the study titled Tomoka River and B-19 Canal 100-

year Flood Results for the City of Daytona

Beach (References 1 and 2).

South Daytona, City of: the hydrologic and hydraulic analyses for the FIS report dated June 4, 1990, were obtained from the June 4, 1990, FIS for the unincorporated areas of Volusia County (Reference 1). Additional coastal analyses were performed by FEMA to provide sufficient

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information for delineation of the flood elevation boundaries for the City of South Daytona.

Vol Volusia County (unincorporated areas): the hydrologic and hydraulic analyses for the

FIS report dated June 4, 1990, for the Tomoka River from its mouth to Eleventh Street, Spruce Creek, Spruce Creek Tributaries Nos. 1 and 2, and Bulow Creek, prepared by Gee & Jenson Engineers-Architects-Planners, Inc., for FEMA, under Contract No. EMW-C-0951; the Tomoka River, from Eleventh Street to Interstate 4, was obtained from a report by Camp Dresser & McKee, Inc. (CDM); St. Johns River, were taken from the Lake and Seminole Counties FIS reports; Bulow Creek, were taken from the Flagler County FIS; Spruce Creek Tributary A, obtained from a report submitted by Zev Cohen & Associates, Inc.; Shooting Range Canal, Eleventh Street Canal Tributaries No. 2 and 2A, were taken from a Soil Conservation Service (SCS, now Natural Resources Conservation Service [NRCS]) report; and B-19 Canal Tributaries Nos. 1 and 2, were performed by the SCS (References 2, 4, 5, 6, 7, 3, and 8).

The authority and acknowledgments for the Cities of Deland, Deltona, Holly Hill, Lake Helen, Orange City, and the Town of Pierson are not included because there were no previously printed FIS reports for those communities.

For the April 15, 2002, countywide FIS, the hydrologic and hydraulic analyses were prepared by Taylor Engineering, Inc., for FEMA, under Contract No. EMW-95-C-4761. Daniel W. Cory, Surveyor, Inc., and Morgan & Eklund, Inc., performed riverine and beach/nearshore surveying, respectively, under contract to Taylor Engineering, Inc. That work was completed in August 1996.

Planimetric base map files were provided in digital format by the County of Volusia Information Technology Group, Geographic Information Services, 123 West Indiana Avenue, Deland, Florida 32720. These files were compiled at a scale of 1:4,800 from orthophotos. The coordinate system used for the production of the FIRM is Universal Transverse Mercator (UTM), North American Datum of 1927 (NAD27), Clarke 1866 spheroid.

1.3 Coordination

The initial Consultation Coordination Officer (CCO) meeting was held on September 16, 1994, and attended by representatives of FEMA, Volusia County; several municipalities; local consulting engineering companies; and Taylor Engineering, Inc. Numerous other contacts for coordination and data acquisition were made with appropriate agencies and groups throughout the course of the study, including the following:

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Applied Technology and Management, Inc. McKim and Creed, Inc. Dyer, Riddle & Associates, Inc. Marshall, Provost & Associates Camp Dresser & McKee, Inc. Cities of Daytona Beach, Ormond Beach, New Smyrna Beach, and Port Orange U.S. Army Corps of Engineers (USACE), Jacksonville District USACE Waterways Experiment Station Dewberry & Davis Volusia County Council, Department of Planning and Zoning, Department of Public Works, and Geographic Information Services Florida Department of Environmental Protection (FDEP), and

Department of Transportation (FDOT) National Ocean Service National Weather Service St. Johns River Water Management District (SJRWMD) The News-Journal U.S. Department of Agriculture, NRCS U.S. Environmental Protection Agency USGS, Tallahassee, Jacksonville, and Orlando Subdistricts An inventory of available data pertinent to the countywide FIS was collected from local, county, regional, and state agencies and firms, as well as from the general public. Five field reconnaissances were performed: June 30, July 12-14, July 27, August 4, and August 12, 1995. A meeting was held on September 6, 1995, and on March 6, 1996, and attended by representatives of Taylor Engineering, Inc., and FEMA to discuss study progress, methods, and preliminary results. On April 9, 1996, Taylor Engineering, Inc. met with SJRWMD staff to discuss available information and District rainfall studies pertinent to the countywide FIS (References 9 and 10). The District‘s rainfall depths have been used in countywide stormwater studies in lieu of NOAA TP-40 rainfall depths (Reference 11). The results of that meeting and pertinent District rainfall reports and data were forwarded to FEMA for evaluation. Based on technical review, FEMA selected the NOAA rainfall depths for use in this FIS.

The results of the study were reviewed at the final CCO meeting held on August 4, 1999, and attended by representatives of FEMA, the State, the communities, and the study contractor. All problems raised at that meeting have been addressed.

2.0 AREA STUDIED

2.1 Scope of Study

This FIS covers the geographic area of Volusia 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) where applicable.

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TABLE 1 – FLOODING SOURCES STUDIED BY DETAILED METHODS

Atlantic Ocean Halifax River B-19 Canal Little Tomoka River B-19 Canal Tributary No. 1 Misner Branch B-19 Canal Tributary No.2 Mosquito Lagoon B-19 Canal Tributary No.7 St. Johns River Bulow Creek Shooting Range Canal Canal Between South Canal Crescent Lake Spruce Creek Indian River North Spruce Creek Tributary No. 1 Intracoastal Waterway Spruce Creek Tributary No. 2 E Canal Spruce Creek Tributary A Eleventh Street Canal Thompson Creek Eleventh Street Canal Tributary No.2 Tomoka River Eleventh Street Canal Tributary No. 2A Wally Hoffmeyer Canal Groover Branch

As part of the April 15, 2002, countywide FIS, new or revised detailed analyses were included for the flooding sources shown in Table 2, “Initial Countywide Scope”.

TABLE 2 – INITIAL COUNTYWIDE SCOPE

FLOODING SOURCE NAME LIMITS OF NEW OR REVISED DETAILED STUDY Atlantic Ocean For its entire coastline within Volusia County.

Eleventh Street Canal From the confluence with the Tomoka River to a point approximately 2,800 feet upstream of Clyde Morris Boulevard North.

Eleventh Street Canal Tributary No. 2 From the confluence with the Eleventh Street Canal to confluence of Eleventh Street Canal Tributary No. 2A.

Halifax River From a point approximately 100 feet southwest of the intersection of John Anderson Drive and Highbridge Road to the intersection of Ocean Drive and Peninsula Avenue North.

Indian River North From a point approximately 1,500 feet east of the intersection of Conrad Drive and Redland Drive to a point approximately 1,500 feet southwest of the intersection of South Street and State Route AlA.

Mosquito Lagoon For the entire shoreline within Volusia County.

B-19 Canal From a point approximately 1 mile downstream of Taylor Road to a point approximately 110 feet upstream of Belville Road.

B-19 Canal Tributary No. 7 From the confluence with B-19 Canal to a point approximately 150 feet upstream of Bellville Road.

Groover Branch From the confluence with the Tomoka River to a point approximately 85 feet upstream of Tymber Creek Road North.

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TABLE 2 – INITIAL COUNTYWIDE SCOPE (continued)

FLOODING SOURCE NAME LIMITS OF NEW OR REVISED DETAILED STUDY Little Tomoka River From the confluence with the Tomoka River to a point

approximately 100 feet upstream of State Route 40.

Misner Branch From the confluence with the Tomoka River to a point approximately 50 feet upstream of Hand Avenue.

Shooting Range Canal/Eleventh Street Canal Tributary No. 2/Eleventh Street Canal Tributary No. 2

From the confluence with the Tomoka River to Clyde Morris North / From Clyde Morris Boulevard North to confluence of Eleventh Street Canal Tributary No. 2 / From to a point approximately 2,600 feet upstream of the confluence with Eleventh Street Canal Tributary No. 2. Confluence.

Thompson Creek From a point approximately 475 feet downstream of U.S. Highway 1 to just downstream of Division Road.

Tomoka River From a point approximately 3.3 miles downstream of U.S. Highway 1 to a point approximately 0.96 mile upstream of U.S. Route 92.

In addition, detailed analyses of Crescent Lake have been incorporated for the April 15, 2002, countywide FIS. 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 April 15, 2002, countywide FIS reflects annexations by the Cities of Daytona Beach, Daytona Beach Shores, DeBary, Deland, Deltona, Edgewater, Holly Hill, New Smyrna Beach, Oak Hill, Orange City, Ormond Beach, Port Orange, and South Daytona and the Town of Ponce Inlet.

For the purpose of the April 15, 2002, FIS, and all future FISs, the stream once known as Tributary No. 7 will now be known as B-19 Canal Tributary No.7.

For the April 15, 2002, FIS, a Letter of Map Revision (LOMR) dated July 21, 1992, in the City of Ormond Beach, and a letter dated January 31, 1991, for the unincorporated areas of Volusia County, both for the Little Tomoka River were incorporated into the FIRM. A Letter of Map Amendment dated February 19, 1992, for a 492-acre parcel of undeveloped land within the unincorporated areas of Volusia County was incorporated into the FIRM.

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 Volusia County.

2.2 Community Description

Volusia County is located in the central portion of the Florida east coast and is

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bordered by Flagler County to the north, Putnam County to the northwest, Lake County to the west, Seminole County to the southwest, Brevard County to the southeast, and the Atlantic Ocean to the east. The land area of Volusia County comprises approximately 1,210 square miles with 50 miles of Atlantic Ocean shoreline. Along the eastern side of the county, the Halifax River and Indian River North/Mosquito Lagoon form long, narrow estuaries which separate the county‘s mainland from its barrier island. Ponce DeLeon Inlet, located near the middle of the coastline, serves as the county‘s only inlet through the barrier island and the major passage through which Atlantic Ocean tides and hurricane surges propagate into the estuaries.

Although the City of Deland, located in the western central portion of the county, serves as the county seat, the county‘s eastern incorporated areas support most of the county‘s population and the highest concentration of residential and commercial land use. The U.S. Census Bureau reports a Volusia County population of 443,343 in 2000. Several major transportation routes serve the county, including Interstates 4 and 95; U.S. Routes 1, 17, and 92; State Routes AlA, 40, and 44; the Intracoastal Waterway; and the Florida East Coast Railway.

Volusia County has a subtropical climate, with long, warm, and humid summers and short, mild winters. The average annual precipitation is approximately 48 inches. Over half of this rainfall occurs during the hurricane season. Based on 1923-1984 data, the seasonal distribution of rainfall ranges from a high of 29.4 inches (June-October) to a low of 10.5 inches (December-March).

The terrain of Volusia County varies considerably. In the western portion of the county, rolling forested hills and moderately steep slopes with numerous small lakes characterize the terrain. Elevations in these areas generally range from approximately 9 to 99 feet North American Vertical Datum of 1988 (NAVD88) (Reference 12). In the central and eastern portions of the county, low lying, mildly sloping terrain with extensive swamps generally characterize the land. Much of this terrain is covered with somewhat impermeable, poorly-drained soil formations with a consistently high water table that varies from 6 feet to less than one foot from the surface. The predominant soils associated with this flat terrain include Myakka-Smyrna-Immokalee, Daytona-Paola-Astatula, Palm Beach-Paola-Canaveral, Hydraquents-Turnbull, and Pomona-Wauchula. The predominant hydrologic soil groups are A/D, B/D, and D (References 13, 14, 15, 16, 17, 18, and 19). Elevations in these areas generally range from -1 to 34 feet NAVD88 (Reference 12).

The St. Johns River, the largest stream in the county, is the state‘s largest wholly contained river with a drainage area of 9,430 square miles and length of approximately 285 miles. Otherwise, most of the major streams are located in the eastern portion of the county. Of these, the two largest are the Tomoka River and Spruce Creek. The Tomoka River drains approximately 159 square miles of the northeastern and central eastern portions of the county, including much of the coastal Cities of Ormond Beach and Daytona Beach. The Tomoka River flows south to north draining several significant tributaries and empties into the Halifax River through the Tomoka Basin where it is subject to coastal surge flooding. Spruce Creek flows south to north, then west to east, and empties into the Halifax River through Strickland Bay, where it is also subject to coastal surge flooding. Spruce Creek drains approximately 91 square miles of the southeastern portion of the county, including Spruce Creek Swamp and significant tributaries such as Turnbull Creek and B-19 Canal. The

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floodplains of these rivers are characterized by low, heavily vegetated swamping areas that extend several hundred feet across in some areas.

2.3 Principal Flood Problems

Flooding in Volusia County results from tidal surges associated with hurricanes, northeasters, and tropical storm activity and from overflow of streams and swamps associated with rainfall runoff. Major rainfall events occur from hurricanes, tropical storms, and thundershowers associated with frontal systems. Some of the worst floods to occur in the area recently were the result of high intensity rainfall during hurricanes or tropical storms such as Gordon and Faye in 1994 and 2008. Having a relatively short time of concentration, the smaller streams tend to reach peak flood flow concurrently with elevated tailwater conditions associated with the coastal storm surge. This greatly increases the likelihood of inundation of low lying areas along the coast observed on several occasions. Areas along the Halifax River, Indian River North, and Mosquito Lagoon are particularly vulnerable to this flooding.

In the eastern portion of the county, most of the flood-prone areas feature relatively impermeable soil, a high water table, and flat terrain. These characteristics contribute significantly to flooding problems. Furthermore, the flat slopes and heavily vegetated floodplains promote backwater effects and aggravate the flood problems by preventing the rapid drainage of floodwaters. However, the vast extent of some floodplains, particularly those of the Tomoka River, serve to mitigate some of the flooding and lower peak discharges by providing overbank storage of floodwaters.

The USGS, NOAA, and the Florida Department of Transportation have installed discharge and stage gages at several locations throughout the county. Limited periods of record and availability of data reduce the usefulness of many county gages for evaluation of major historical flooding. However, USGS stream gages for the Tomoka River and B-19 Canal provide some significant historical flood data. Locations and periods of record for those gages considered in this FIS are listed below.

TR11 Tomoka River at Eleventh Street (1964-present) TR92 Tomoka River at U.S. Highway 92 (1982-1985) B19WR B-19 Canal at Willow Run (1982-1991) B19415 B-19 Canal at State Route 415 (1982-1991)

Storm events and relevant data recorded at these stream gages are shown in the following tabulation.

Date Gage Elevation

(feet NAVD) Daily Mean

Discharge (cfs) September 11, 1964 TRII 11.6 2,170

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October 19, 1968 TRII 11.8 2,100 October 8, 1969 TRII 10.7 1,200 June 5, 1976 TRII 11.4 1,750 November 17, 1994 TRII 10.4 1,050 December 11, 1983 TR92 20.9 * September 27, 1984 TR92 21.2 * December 12, 1983 B19415 * 170 January 22, 1989 B19415 17.3 210 October 10, 1989 B19415 17.8 267 August 15, 1991 B19415 17.7 253 June 21, 1991 B19WR 21.0 190

*Data not available Major flooding events recorded by the Tomoka River gage to date include the 1964, 1968, and 1976 storms. Of these, the 1964 (associated with Hurricane Dora) and 1968 storms were the largest and similar in magnitude. At the Eleventh Street gaging station near Holly Hill, the Tomoka River reached elevations of 11.6 and 11.8 feet NAVD, respectively. For this location, the return period of these storms is approximately five years (based on the discharge-frequency analysis results of this FIS). No other Tomoka River gage records were found for these storms.

In B-19 Canal, the largest storm recorded by the gage at State Route 415 occurred in 1989. This storm produced a peak daily-averaged flow rate of 267 cfs and a stage of 17.8 feet NAVD. For this location, the return period for the 1989 storm is approximately five years.

Floods caused by Crescent Lake can occur in unpredictable cycles. It is possible for the cumulative effect of slightly above-normal rainfall for several consecutive years to cause greater floods than those caused by one year of exceedingly high rainfall. However, a combination of high lake levels; high ground-water levels; and exceedingly high rainfall, which are associated either with several consecutive summer thunderstorms or with a hurricane, can produce extreme flooding. Any unusual combination of meteorologic and hydrologic conditions can produce a rise in the level of Crescent Lake and can result in inundation of the areas adjacent to its normal shoreline (Reference 20).

The coastal areas of Volusia County are subject to flooding from tidal surges associated with hurricanes and northeasters. Observed/recorded high water marks from coastal hurricane surge flooding include those from Hurricane Dora on September 9, 1964. The surge elevation at Ponce De Leon Inlet exceeded 5.9 feet NAVD. At the Seabreeze Bridge on the Halifax River, the surge reached 3.9 feet NAVD (Reference 21).

2.4 Flood Protection Measures

Other than small oceanfront seawalls and numerous, small, man-made canals, no major flood protection structures are known to exist within Volusia County. However, floodplain management measures within the county are extensive. Flooding problems led county and municipal officials to initiate and adopt a series of comprehensive stormwater management plans. Completed in 1995, these plans identified and prioritized flooding problems and developed structural and nonstructural solutions to mitigate flooding while planning for future growth. Structural improvements include

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subdivision swales, berms, and pumping; additional culverts, detention ponds, channel improvements, and weirs. Nonstructural improvements include ordinances which restrict floodplain development. Although the recommended structural improvements have begun, they are not expected to significantly impact this FIS. Available data and results from these stormwater management plans were evaluated and incorporated into this FIS.

3.0 ENGINEERING METHODS

For the flooding sources studied by detailed methods in Volusia 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 1-percent-annual-chance flood in any 50-year period is approximately 40 percent (4 in 10); for any 90-year period, the risk increases to approximately 60 percent (6 in 10). The analyses reported herein reflect flooding potentials based on conditions existing in Volusia County 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 and peak elevation-frequency relationships for each flooding source studied in detail affecting Volusia County.

Precountywide Analyses

For B-19 Canal, Tomoka River, Canal Between, Eleventh Street Canal, and Wally Hoffmeyer Canal in the City of Daytona Beach, the runoff block of the EPA Stormwater Management Model (SWMM), as modified by Camp Dresser & McKee, Inc., was used to generate runoff hydrographs and to perform simplified lake/channel/conduit routing (References 22 and 23). Detailed information on the hydrologic parameters is contained in the study Tomoka River and B-19 Canal 100-

year Flood Results for the City of Daytona Beach (Reference 2). The drainage areas were obtained from this model. The EXTRAN model performs hydraulic routing in the downstream reaches of the watershed (Reference 24). Discharges were obtained from the EXTRAN model.

For the St. Johns River in the City of DeBary and the unincorporated areas of Volusia County, the flood profiles were taken from the Lake and Seminole Counties FISs (References 4 and 5). The 10-, 1-, and 0.2-percent annual chance flood profiles in the FISs were determined from an analysis of gage records on the St. Johns River, which also involved stream routings to correlate past storm events at the stream gage locations. Peak discharge data are therefore unavailable for the St. Johns River.

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For E Canal and South Canal in the City of Edgewater, peak discharge-frequency relationships for floods of the selected recurrence intervals were estimated from a regional flood-frequency analysis based on the gage records of three stations, with lengths of record of 25 years, 15 years, and 12 years. The gaging stations are located at the mouth of South Canal, at the mouth of E Canal, and at Fern Palm Drive on E Canal. The regional flood-frequency analysis provides two curves; the first expresses the flood discharge-time relation, showing variation of peak discharge expressed as a ratio to the mean annual flood, with recurrence interval. The second relates the mean annual flood to drainage area (Reference 25). Thus, by delineating drainage areas of South Canal and E Canal, peak discharges for the selected recurrence intervals could be estimated.

For Eleventh Street Canal Tributary Nos. 2 and 2A, and Shooting Range Canal in the City of Ormond Beach; and B-19 Canal Tributary Nos. 1 and 2, and Spruce Creek in the City of Port Orange and the unincorporated areas of Volusia County, regionalized regression equations, developed by the USGS, in cooperation with the FDOT, were used for deriving peak discharge-frequency relationships (Reference 26). These equations were slightly modified to represent the extensive swamp areas within the drainage basins of the streams by adjusting the lake storage term of the equation so that the computed peak discharges of the selected recurrence intervals agree closely with the peak discharges resulting from the log-Pearson Type III analysis for the streamflow records. The procedures outlined in U.S. Water Resources Council Bulletin No. 17B were used in applying the distributions to the observed streamflow records (Reference 27).

The hydrologic analysis for Spruce Creek Tributary 1, Spruce Creek Tributary 2, Spruce Creek Tributary A, and Bulow Creek are not available.

April 15, 2002, Countywide Analyses

The USACE HEC-l computer program was used to estimate the discharge-frequency relationships for streams studied in detail except for the Eleventh Street Canal, Eleventh Street Canal Tributary No.2, Eleventh Street Canal Tributary No. 2A, and Shooting Range Canal (References 28, 29, 30, and 31). Those streams used SWMM 4.3. Except for the Tomoka River, the limited history of stream gage records for these streams precluded effective statistical analysis. The gage on Tomoka River, located at Eleventh Street near Holly Hill, provided 31 years of data.

Although statistical analyses of these data proved useful for comparison/verification purposes, HEC-l was considered more appropriate for the basin as a whole, which includes four ungaged, detailed study streams. For the Tomoka River, USGS published discharge-frequency relationships, computed by a weighted combination of USGS regression equations and log-Pearson Type III statistical analysis, were compared to the HEC-l discharges with favorable results. For all other streams, USGS regional regression equations were used for comparison purposes. These results also compared reasonably well with the HEC-l results (Reference 26).

HEC-l modeling incorporated the SCS unit hydrograph and kinematic wave routing methods. Parameters supplied to the model of each stream included subbasin runoff curve numbers, lag times, stream cross sections, and Manning’s “n” roughness factors. Curve numbers were calculated using the SCS curve number method (Reference 32) based on FDOT aerial photographs at a scale of 1:25,000 (Reference

12

33), GIS soils and land use coverages (Reference 34), and available, calibrated hydrologic model studies (References 13 and 17). Lag times were calculated using the empirical SCS curve number formula (Reference 35).

The HEC-l models of Tomoka River and B-19 Canal were calibrated and verified using storm discharge data provided by the Tallahassee Subdistrict of the USGS and corresponding hourly rainfall data obtained from the National Weather Service. USGS gages/locations used for calibration were Tomoka River near Holly Hill (Eleventh Street), B-19 Canal at State Route 414, and B-19 Canal at Willow Run. For calibration, an observed storm was simulated with HEC-l and model parameters, including curve numbers, lag times, and initial abstractions, were adjusted until reasonable fits between observed and predicted peak flows were obtained. For verification, a second storm was simulated to establish the accuracy of the calibrated model parameters. Based on the final calibration results, model parameters in downstream, ungaged basins were adjusted similarly to the calibrated parameters for each stream. For Tomoka River, these downstream basins included the detail study stream basins for Groover Branch, Little Tomoka River, Thompson/Strickland Creek, and Misner Branch.

Following successful calibration, the HEC-l models were used to estimate peak discharges for the selected recurrence intervals throughout each stream study reach except for the Eleventh Street Canal, Eleventh Street Canal Tributary No.2, Eleventh Street Canal Tributary No. 2A, and Shooting Range Canal. For those flooding sources, the SWMM 4.3 model was used to estimate 1-percent-annual peak discharge. For these storm events, total storm rainfall amounts were based on the TP-40 rainfall frequency atlas for a 24-hour storm duration (Reference 11). The temporal rainfall distribution used in the models was the SCS Type II Florida modified distribution (Reference 36).

A summary of the drainage area-peak discharge relationships for all streams studied by detailed methods is shown in Table 3, “Summary of Discharges”.

TABLE 3 – SUMMARY OF DISCHARGES

FLOODING SOURCE AND LOCATION

DRAINAGE AREA

(sq. miles)

PEAK DISCHARGES (cfs) 10-Percent-

Annual-Chance

2-Percent-Annual-Chance


0.2-Percent-Annual-Chance

B-19 CANAL At mouth At Willow Run Boulevard At Pelican Bay Drive

10.44 6.86 1.72

623 457 262

912 676 393

1,089 843 477

1,338 1,102 604

B-19 CANAL TRIBUTARY NO. 1

At Interstate 95

0.92

112

210

261

428 B-19 CANAL TRIBUTARY NO. 2

At mouth

0.25

45

86

108


At Bellville Road

0.40

*

*

148

*

13

TABLE 3 – SUMMARY OF DISCHARGES (continued)


DRAINAGE AREA

(sq. miles)


Annual-Chance




BULOW CREEK At Washington Avenue

28.30

1,282

2,258

2,744

4,067

CANAL BETWEEN At mouth

0.49

*

*

154

*

E CANAL At mouth At Fern Palm Drive

3.87 2.66

192 132

236 162

256 176

280 192

ELEVENTH STREET CANAL

At mouth

4.20

*

*

1,070

* ELEVENTH STREET CANAL TRIBUTARY NO. 2

At confluence with Eleventh Street Canal

0.76

*

*

678

* ELEVENTH STREET CANAL TRIBUTARY NO. 2A

Just upstream of Daytona Beach corporate limits

0.28

*

*

678

*

GROOVER BRANCH At Tymber Run Road At Airport Road At Tymber Creek

17.09 16.72 16.34

1,774 1,720 1,650

2,483 2,409 2,316

2,961 2,869 2,759

3,744 3,618 3,482

LITTLE TOMOKA RIVER At Tymber Creek Road

North At Breakway Trail At State Route 40

21.16 18.14 8.78

3,205 2,844 1.508

4,417 3,907 2,066

5,222 4,613 2,438

6,552 5,776 3,046

MISNER BRANCH At mouth At Main Trail Road At State Route 40 At Falls Way Boulevard

2.68 2.49 2.21 1.61

562 501 473 415

775 704 666 573

923 841 796 677

1,177 1,071 1,011 847

SHOOTING RANGE CANAL At Interstate 95

0.50

100.4

188.2

232.7

361.9

SOUTH CANAL At mouth

4.43

372

429

439

491

SPRUCE CREEK At Interstate 95 Just upstream of Fly-In

Road At unnamed road

72.71 52.28 43.05

1,843 1,365 1,101

2,667 1,976 1,594

3,039 2,253 1,820

3,889 2,906 2,366

SPRUCE CREEK TRIBUTARY NO. 2

At confluence with Spruce Creek

8.49

626

919

1,047

1,326

14

TABLE 3 – SUMMARY OF DISCHARGES (continued)


DRAINAGE AREA

(sq. miles)


Annual-Chance




SPRUCE CREEK TRIBUTARY A

At confluence with Spruce Creek

* * * 8,600 *

THOMPSON CREEK At U.S. Highway 1 At FEC railroad At State Route 4 At Tomoka Avenue

0.44 0.28 0.14 0.10

208 144 112 86

291 205 150 118

345 242 175 139

431 297 213 172

TOMOKA RIVER At Old Dixie Highway At U.S. Highway 1 At Interstate Route 95 At State Route 40 At Eleventh Street At U.S. Route 92

145.10 136.60 127.30 88.10 74.70 6.10

5,470 7,489 8,393 4,521 3,520 928

7,396 10,380 11,622 6,206 4,786 1,268

8,914 12,366 13,784 7,332 5,628 1,494

11,522 15,670 17,385 9,185 7,015 1,866

WALLY HOFFMEYER CANAL

At mouth

2.29

*

*

833

* *Data not available

For Crescent Lake, lake level records for 12 lakes in Alachua, Clay, and Marion Counties, which are adjacent to Putnam County, were used to define maximum lake volume-frequency relationships for each site. Seven of these lake-level records had data for more than 20 years, and the maximum length of record is 35 years. Of the 12 records, the shortest is 14 years. The drainage areas for these lakes ranged form 0.19 square mile to 319 square miles, and the surface areas of these lakes ranged from 0.015 square mile (9.6 acres) to 20.6 square miles (more than 13,000 acres). The range of change in lake level was from less than two feet to more than 30 feet. These lakes were also vastly different in outflow characteristics from completely closed (no outflow at any flood frequency) to outflow at all flood frequencies.

Flood-frequency curves were defined for each of the 12 lake-level records. These curves were developed in terms of lake volume measured above a defined base. Volumes were adjusted for outflow, as applicable, and the base level was defined as the mean lake stage. After all annual data (based on year beginning on June 1 and ending on May 31) were adjusted; analyses were carried out to determine the best technique for fitting flood-frequency curves to the lake-volume data. A log-Pearson Type III distribution, using the average skew coefficient as outlined in U.S. Water Resources Council Bulletin 17A, was found to be an acceptable technique for fitting flood-frequency curves to lake-volume data (Reference 37).

Values of the selected recurrence intervals were obtained for each of the 12 lakes from this log-Pearson Type III distribution. A regression analysis of frequency data versus drainage area for the 12 lakes was used to define a regional relationship for each recurrence interval. The analysis showed that drainage basin size explained

15

nearly all of the variation in the lake volumes. Regression analysis was also used to define a regional relationship between the mean lake stage and grassline elevation along the lakes shores of the 12 lakes. The analysis showed that the elevation of the grassline along the shoreline explained nearly all of the variation in mean lake stage.

The Stillwater elevations for the 10-, 2-, 1-, 0.2-percent-annual-chance floods for the Atlantic Ocean coastline subject to tidal surge and Crescent Lake have been determined and are summarized in Table 4, “Summary of Stillwater Elevations”. The analyses reported herein reflect the Stillwater elevations of the Atlantic Ocean due to tidal and wind setup effects and include the contributions from wave action effects.

TABLE 4 – SUMMARY OF STILLWATER ELEVATIONS ELEVATION (feet NAVD)






CRESCENT LAKE 4.1 5.6 6.2 7.5

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 Flood Insurance Rate Map (FIRM) represent rounded whole-foot elevations and may not exactly reflect the elevations shown on the Flood Profiles or in the Floodway Data table in the FIS report. Flood elevations shown on the FIRM are primarily intended for flood insurance rating purposes. For construction and/or floodplain management purposes, users are cautioned to us the flood elevation data presented in this FIS report in conjunction with the data shown on the FIRM.

Except where noted, cross section were obtained form field surveys. All bridges, dams, and culverts were field surveyed to obtain elevation data and structural geometry. Cross sections were located at close intervals upstream and downstream of bridge and culverts to compute the significant backwater effects of these structures.

Locations of selected cross sections used in the hydraulic analyses are shown on the Flood Profiles (Exhibit 1). For stream segments for which a floodway was computed (Section 4.2), selected cross-section locations are also shown on the FIRM (Exhibit 2).

The hydraulic analyses for this FIS were based on unobstructed flow. The flood elevations shown on the profiles are thus considered valid only if hydraulic structures remain unobstructed, operate properly, and do not fail.

All elevations are referenced to the North American Vertical Datum of 1988 (NAVD88). Elevation reference marks (ERMs) used in this study, and their descriptions, are shown on the FIRM. ERMs shown on the FIRM represent those used during the preparation of this and previous FISs. The elevations associated with each ERM were obtained and/or developed during FIS production to establish vertical control for determination of flood elevations and floodplain boundaries shown on the FIRM. Users should be aware that these ERM elevations may have changed since the publication of this FIS. To obtain up-to-date elevation information on National Geodetic Survey (NGS) ERMs shown on this map, please contact the Information

16

Services Branch of the NGS at (301) 713-3242, or visit their website at www.ngs.noaa.gov. Map users should seek verification of non-NGS ERM monument elevations when using these elevations for construction or floodplain management purposes.

Precountywide Analyses

For the St. Johns River in the City of DeBary and unincorporated areas of Volusia County, cross sections were obtained from field surveys (Reference 38). In some cases, topographic maps were used to extend surveyed cross sections (References 39, 40, and 41). Water-surface elevations of floods of the selected recurrence intervals were computed using the USACE HEC-2 step-backwater computer program (Reference 42).

For Canal Between, Eleventh Street Canal, and Wally Hoffmeyer Canal in the City of Daytona Beach, hydraulic data were obtained from the city‘s drainage facility inventory, survey, and field identification. The EXTRAN computer model was used to calculate water-surface profiles (Reference 24). The EXTRAN model received hydrograph input at specific nodal locations by disk file transfer from the RUNOFF hydrologic model (Reference 23).

For E Canal and South Canal in the City of Edgewater, hydraulic analyses were performed based on a combination of methods using the hydraulic characteristics of the canals and accounting for storage in the upstream terrace areas. Water-surface profiles for South Canal inland from the Indian River, along the northern corporate limits of the city and for E Canal from the Indian River north to the east side of FEC railroad were developed using the USGS step-backwater computer program (Reference 43). Computations of water-surface elevations above culverts were done manually or using the USGS computer program for automatic computations of stage-discharge relations at culverts (Reference 44). It was assumed that maximum tidal elevations and maximum freshwater flood elevations will not occur simultaneously. When the tide is highest, flow in the streams will be upstream, not toward the coast. Downstream flow will occur during the freshwater flood peak. Certain culverts or series of culverts in the streams restrict flood flows in both directions, resulting in appreciably higher water-surface elevations upstream (with respect to flow direction) of the culverts than downstream. These culverts, under Magnolia Street and U.S. Highway 1 on South Canal, and under FEC railroad on E Canal, form the boundaries between areas where tidal and freshwater floods predominate under all but the most severe (SOD-year) flooding conditions.

Shallow freshwater flooding, partly due to the culverts and partly due to the nature of the areas, makes storage an important consideration in the wide, flat terrace areas upstream of the control culverts. Shallow flooding in the terrace areas is created by inadequate drainage. To account for storage, stage-discharge ratings upstream of the control culverts in each of the two canals were developed from step-backwater results. These ratings, together with stage-volume curves constructed from cross section properties and input hydrographs developed from regional streamflow records, provided input to a reservoir-routing computer program developed by the USGS (Reference 45). The program simulated storage of excess rainfall in the terrace areas above the control culverts, thereby reducing peak discharge and maximum freshwater flood elevation in those areas. Thus, the stream profiles reflect the superposition of tidal flood elevations on the downstream sections of the step-backwater profiles and

http://www.ngs.noaa.gov/

17

the superposition of storage-adjusted freshwater flood elevations at the upstream ends of the backwater profiles.

Starting water-surface elevations were taken from the analysis of the Indian River performed for the previously published City of New Smyrna Beach FIS (Reference 46).

For Eleventh Street Canal Tributary Nos. 2 and 2A, and Shooting Range Canal in the City of Ormond Beach and the unincorporated areas of Volusia County, water surface elevations were developed using the WSP-2 water-surface profile computer model (Reference 47). Cross sections were obtained from field surveys (Reference 38).

For Spruce Creek in the City of Port Orange, water-surface elevations were developed using the USACE HEC-2 water-surface profile computer model (Reference 48). Water-surface elevations for B-19 Canal Tributaries Nos. 1 and 2 in the City of Port Orange and the unincorporated areas of Volusia County were developed using the WSP-2 water-surface profile computer model (Reference 47).

For Bulow Creek, Spruce Creek, and Spruce Creek Tributary Nos. 1 and 2 in the unincorporated areas of Volusia County, various hydraulic methods were used. Water-surface elevations for floods of the selected recurrence intervals were developed using the USACE HEC-2 water-surface profile computer model (Reference 48). Cross sections for the backwater analyses were obtained from field surveys; in some cases, topographic maps were used to extend surveyed cross sections (References 38, 39, 40, and 41). Cross sections for Bulow Creek were developed from topographic data furnished by Bellemead Corporation, the Volusia County Engineering Department, and the topographic maps (References 49 and 39). The slope/area method was used to set the HEC-2 starting water-surface elevations for Bulow Creek, and Spruce Creek and its tributaries. The 1-percent-annual-chance flooding elevation for Spruce Creek Tributary A was determined by standard step-backwater procedures (Reference 7). The 10-percent-annual-chance flooding elevation was determined by approximate methods.

Roughness factors (Manning’s “n”) used in the hydraulic computations were chosen on the basis of field observations and aerial photographs of the streams and floodplain areas. Roughness values for all streams are shown in Table 5, “Manning’s ‘n’ Values”.

April 15, 2002, Countywide Analyses

Water-surface elevations of floods of the selected recurrence intervals were computed through use of the USACE HEC-2 water-surface profile computer program (References 42 and 50). Starting water-surface elevations for the Tomoka River tributaries were specified as the mean annual Tomoka River flood elevations at the confluence of the tributaries. For the Tomoka River, Mean High Water in Tomoka Basin, provided by the FDEP, was used for the starting water-surface elevation (Reference 51). For B-19 Canal, the slope/area method was used to establish starting water-surface elevations based on stream invert elevations near the beginning of the stream study reach. Disparity in drainage basin areas precluded the use of the coincident Peak method to establish starting elevations on tributaries to main streams. For the Eleventh Street Canal, Eleventh Street Canal TributaryNo.2, Eleventh Street Canal Tributary No. 2A, and Shooting Range Canal, SWMM 4.3 was used for the

18

starting water-surface elevations (Reference 31). All tributaries (Groover Branch, Little Tomoka River, Misner Branch, Thompson Creek, and B-19 Canal) had drainage areas less than 20-percent of their receiving stream (the Tomoka River and Spruce Creek).

Cross sections were obtained from field surveys supplemented with the 1:2,400 scale aerial photographs covering most of the study area and USGS topographic maps (References 39, 40, and 41). Surveys were tied into U.S. Coast and Geodetic Survey and FDOT benchmarks. Cross section and bridge data for Wilmette Road over Thompson Creek were taken from the City of Ormond Beach bridge plans (Reference 52). Based on field surveys, cross section and bridge data for Dimmers and Linville Roads over Groover Branch were provided by CDM.

Roughness factors (Manning’s “n”) were chosen based on field observations, aerial photos, photographs of the stream and floodplain areas, and published text and photographs with recommended roughness values (References 33, 53, and 54). The channel and overbank “n” values for all streams studied by detailed methods are shown in Table 5, “Manning’s “n” Values”.

TABLE 5 – MANNING’S “n” VALUES

Stream Channel “n” Overbank “n” B-19 Canal 0.025-0.04 0.12-0.20 B-19 Canal Tributary No. 1 0.035-0.06 0.045-0.12 B-19 Canal Tributary No. 2 0.035-0.06 0.045-0.12 B-19 Canal Tributary No. 7 0.03-0.04 0.12-0.20 Bulow Creek 0.03 0.08-0.15 Canal Between 0.035-0.06 0.045-0.15 E Canal 0.012-0.045 0.055 Eleventh Street Canal 0.035-0.06 0.045-0.15 Eleventh Street Canal Tributary No. 2 0.035-0.06 0.045-0.12 Eleventh Street Canal Tributary No. 2A 0.035-0.06 0.045-0.12 Groover Branch 0.035-0.04 0.15-0.20 Little Tomoka River 0.035-0.04 0.15-0.20 Misner Branch 0.035-0.04 0.15-0.20 St. Johns River 0.040-0.06 0.035-0.06 Shooting Range Canal 0.035-0.06 0.045-0.12 South Canal 0.012-0.045 0.055 Spruce Creek 0.035-0.06 0.045-0.12 Spruce Creek Tributary No. 1 0.04-0.06 0.08-0.15 Spruce Creek Tributary No. 2 0.04-0.06 0.08-0.15 Spruce Creek Tributary A 0.04-0.06 0.08-0.15 Thompson Creek 0.04 0.2 Tomoka River 0.035-0.04 0.15-0.20 Wally Hoffmeyer Canal 0.035-0.06 0.045-0.15

19

3.3 Coastal Hydrologic Analyses

For the April 15, 2002, revision, the hydrological parameters of the storm surge modeling were found to be adequate given the period of record and activity of tropical cyclones (hurricanes and tropical storms) affecting the study area. Therefore, the 1-Percent Annual Chance stillwater elevations for the Atlantic Ocean, Halifax River, Indian River North, and Mosquito Lagoon were not revised. Wave setup has been previously determined to be a significant contributor to the total stillwater flood levels along the Atlantic Ocean open ocean coastline. However, for this revision, the 1-Percent Annual Chance stillwater elevations for the open areas along the Atlantic Ocean were not modified to include the effects of wave setup. This is based upon an evaluation of the historical flood high-water elevations and tide gage records which indicated that wave setup was not appropriate for inclusion in the open ocean stillwater elevations.

Inundation from the Atlantic Ocean caused by passage of storms (storm surge) was determined by the joint probability method (Reference 55). The storm populations were described by probability distributions of five 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 Volusia County. Primary sources of data for this were Tropical Cyclones of the North Atlantic Ocean, 18711977 (Reference 56), Some Climatological Characteristics of Hurricanes and Tropical Storms, Gulf and East Coasts of the United States (Reference 57), and Meteorological Criteria for Standard Project Hurricanes and Probable Maximum Hurricane Windfields, Gulf and East Coasts of the United States (Reference 58).

For areas subject to flooding directly from the Atlantic Ocean, the FEMA standard storm surge model was used to simulate the coastal surge generated by any chosen storm (that is, any combination of the five storm parameters defined previously). 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 no 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 is then statistically combined with the computed storm surge to yield recurrence intervals of total water level (Reference 59). A reanalysis of the hurricane storm surge for the Atlantic Ocean was performed by FEMA using the storm surge model SURGE (Reference 60). The reanalysis of the hurricane storm surge for the Atlantic Ocean was performed by FEMA using the storm surge model SURGE (Reference 60). The reanalysis was performed to model two breach locations near Ponce de Leon Inlet. The 1984 Thanksgiving Day northeaster, which caused high flooding in and around Ponce de Leon Inlet, was also modeled by FEMA using SURGE. These reanalyzes showed significant increases in Stillwater elevations near Ponce de Leon Inlet over the elevations shown in the previous Flood Insurance Study Supplement for Volusia County (Reference 61).

The Stillwater elevations for the 10-, 2-, 1-, 0.2-percent-annual-chance floods for the Atlantic Ocean coastline subject to tidal surge have been determined and are summarized in Table 6, “Summary of Coastal Stillwater Elevations”. The analyses

20

reported herein reflect the Stillwater elevations of the Atlantic Ocean due to tidal and wind setup effects and include the contributions from wave action effects.

TABLE 6 – SUMMARY OF COASTAL STILLWATER ELEVATIONS ELEVATION (feet NAVD)


10-Percent Annual-Chance



0.2-Percent Annual-Chance

ATLANTIC OCEAN Entire open coast shoreline within Volusia County

4.6

6.1

6.9

9.7

HALIFAX RIVER/INTRACOASTAL WATERWAY

From northern county boundary to the north side of State Route 40 in Ormond Beach

0.6

2.1

2.9

5.7

HALIFAX RIVER/INTRACOASTAL WATERWAY (continued)

From the south side of State Route 40 to just south of the Daytona Beach northern corporate limits

1.6

3.1

3.9

6.7

From just south of the Daytona Beach northern corporate limits to Dunlawton Boulevard

2.6 4.1 4.9 7.7

INDIAN RIVER NORTH INTRACOASTAL WATERWAY

From Dunlawton Boulevard in Port Orange to just north of the New Smyrna Beach southern corporate limits

3.6 5.1 4.9 8.7

INDIAN RIVER NORTH/MOSQUITO LAGOON From the New Smyrna Beach southern corporate limits to the southern county

2.6 4.1 5.9 7.7

3.4 Coastal Hydraulic Analyses

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 shown 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.

For the April 15, 2002, revision, investigations were conducted to update the coastal hazard assessments and wave elevation determinations using standard FEMA methodologies. The analysis was performed as specified in FEMA’S Guidelines and Specifications for Wave Elevation Determination and V Zone Mapping (References 62 and 63). This revision updates the existing FIS on the basis of the revised wave elevation determinations, FEMA’s updated definitions of “coastal hazard areas” and “primary Frontal dune”, field investigations, and more detailed topography and aerial photography (References 39, 62, 63, 64, 65, 66, and 67).

As described in section 3.3, the Stillwater surge elevations were not revised as part of the April 15, 2002, countywide FIS. Based on the previously published Stillwater elevations, the coastal flood hazard analyses included wave hindcasting, beach erosion, wave runup, wave height, and flood hazard mapping along the entire Volusia County coastline.

The coastal flooding analyses require transects defining the physical features of the

21

offshore bathymetry and floodable onshore topography representative of the Volusia County coastline. Thus, 49 representative transects (generally about one mile apart) were selected to represent spatial changes in topography, development, vegetation, and other physical characteristics that affect erosion, wave height, and wave runup. Transect locations, illustrated in Figure 1, “Transect Location Map”, were selected based on field inspection and aerial photographs of the county’s coastal region (References 33 and 64). Transects, generally perpendicular to the shoreline, terminated on the barrier island at the point where the surge elevation intersected the eroded profile and continued in the inland bays of Halifax River, Indian River North, and Mosquito Lagoon. Transects were obtained from field surveys of beach and offshore profiles, supplemented with 1:1,200 scale aerial photographs with contour intervals of 2 feet and the 1:24,000 scale USGS topographic maps with contour intervals of 5 feet (References 64 and 39). Surveys were positioned at and tied into FDEP reference monuments.

Using the previously published FISs stillwater elevations, beach erosion was computed along each transect to determine the vertical and horizontal limits of the eroded escarpment corresponding to the 1-percent-annual-chance flood event. As detailed in FEMA‘s Guidelines and Specifications for Wave Elevation Determination and V Zone Mapping, transects with frontal dune reservoirs exceeding 540 square feet are considered to experience dune retreat while those with reservoirs less than 540 square feet are considered to experience dune removal (References 62 and 63). Erosion at seawalls and revetments was calculated using methods detailed in the USACE Shore Protection Manual (Reference 65). At selected locations, eroded profiles and volumes were computed using the State of Florida‘s dune erosion model (Reference 65). The results compared favorably with those estimated with FEMA‘s methodology.

Based on the eroded profiles and the previously published FISs stillwater elevations, the wave envelope was computed for each transect. The wave envelope represents the maximum vertical and landward limit of wave activity and includes the wave crest and wave runup elevations. The wave model WHAFIS provided the maximum expected wave crest elevation along each transect (Reference 67). This methodology accounted for fetch length, submerged bathymetry, and type and extent of land cover along each transect. Density, tides and physical dimension of rigid and flexible vegetation, buildings, and other structures (e.g., height, stem diameters, horizontal spacing, etc.) were considered based on aerial photographs and field inspection.

23

FEMA‘s RUNUP model, based on wave runup methodology, then provided the maximum vertical limit of wave activity at the landward terminus of each transect (Reference 67). Representative deep water wave height and period combinations accompanying 1-percent-annual-chance flooding events were obtained from available USACE wave hindcast data. The hindcast wave climate for the nearest location was examined statistically in terms of extreme value theory to determine representative wave height-period combinations. The runup model was applied with wave heights ranging from the significant wave height to the wave height with an exceedance probability of 95 percent and corresponding wave periods to estimate maximum runup along each eroded transect.

Table 7, “Transect Descriptions”, includes a description of each transect location, 1-percent-annual chance stillwater elevation, and maximum 1-percent-annual-chance wave crest elevation.

TABLE 7 – TRANSECT DESCRIPTIONS

TRANSECT LOCATION

ELEVATION (feet NAVD) Atlantic Ocean


Stillwater

Maximum 1-Percent-

Annual-Chance Wave Crest

1

At a point approximately 1,700 feet north of Highbridge Road at FDEP reference monument R-6 from the Atlantic coastline westward across the Halifax River / Intracoastal Waterway floodplain to Mound Grove

7.0 11.0

2

At a point approximately 1.2 miles south of Highbridge Road at FDEP reference monument R-12 from the Atlantic coastline westward across the Halifax River/Intracoastal Waterway floodplain

7.0 11.0

3

Between Sea Oats Terrace and Sea Bridge Drive at FDEP reference monument R-18 from the Atlantic coastline westward across the Halifax River/Intracoastal Waterway floodplain and the northern edge of the Tomoka Basin

7.0 11.0

5

Between Sunrise Avenue and Ocean Breeze Circle at FDEP reference monument R-30 from the Atlantic coastline westward across the Halifax River / Intracoastal Waterway floodplain

7.0 11.0

6

Between Aqua Vista Drive and Sandra Drive at FDEP reference monument R-34 from the Atlantic coastline westward across the Halifax River / Intracoastal Waterway floodplain

7.0 11.0

7

Between Holland Road and Town and Country Lane at FDEP reference monument R-36 from the Atlantic coastline westward across the Halifax River / Intracoastal Waterway floodplain

6.91 10.91

8

Between Sandy Beach Drive and Neptune Park Drive at FDEP reference monument R-40 from the Atlantic coastline westward across the Halifax River / Intracoastal Waterway floodplain

6.91 10.91

24

TABLE 7 – TRANSECT DESCRIPTIONS (continued)

TRANSECT LOCATION



Stillwater

Maximum 1-Percent-

Annual-Chance Wave Crest

9

Between Sunny Shore and Brooks Drive at FDEP reference monument R-42 from the Atlantic coastline westward across the Halifax River / Intracoastal Waterway floodplain

7.0 11.0

10

Between Amsden Road and Neptune Avenue at FDEP reference monument R-48 from the Atlantic coastline westward across the Halifax River / Intracoastal Waterway floodplain

7.0 11.0

11

Between Osceola Avenue and Seminole Avenue at FDEP reference monument R-55 from the Atlantic coastline westward across the Halifax River / Intracoastal Waterway floodplain

7.0 11.0

12

Between Byron Ellinor Drive and Rockefeller Drive at FDEP reference monument R-57 from the Atlantic coastline westward across the Halifax River / Intracoastal Waterway floodplain

7.0 11.0

13

Between Cardinal Drive and Wren Road at FDEP reference monument R-60 from the Atlantic coastline westward across the Halifax River / Intracoastal Waterway floodplain

7.0 11.0

14

Between Boylston Avenue and Williams Avenue at FDEP reference monument T-66 from the Atlantic coastline westward across the Halifax River / Intracoastal Waterway floodplain

7.0 11.0

15

Between Driftwood Avenue and University Boulevard at FDEP reference monument R-72 from the Atlantic coastline westward across the Halifax River / Intracoastal Waterway floodplain

7.0 11.0

16

Between University Boulevard and Jessamine Boulevard at FDEP reference monument R-73 from the Atlantic coastline westward across the Halifax River / Intracoastal Waterway floodplain

7.0 11.0

17

Between Oakridge Boulevard and Butler Boulevard at FDEP reference monument R-79 from the Atlantic coastline westward across the Halifax River / Intracoastal Waterway floodplain

7.0 11.0

18

Between Main Street and Harvey Avenue at FDEP reference monument R-84 from the Atlantic coastline westward across the Halifax River / Intracoastal Waterway floodplain

7.0 11.0

25


TRANSECT LOCATION



Stillwater

Maximum 1-Percent-Annual-

Chance Wave Crest

19

Between U.S. Route 92 and Vermont Avenue at FDEP reference monument R-86 from the Atlantic coastline westward across the Halifax River / Intracoastal Waterway floodplain

7.0 11.0

20

At a point approximately 600 feet southeast of the intersection of Silver Beach Avenue and Atlantic Avenue North at FDEP reference monument R-90 from the Atlantic coastline westward across the Halifax River / Intracoastal Waterway floodplain

7.0 11.0

21

Between Browning Avenue and Moore Avenue at FDEP reference monument R-96 from the Atlantic coastline westward across the Halifax River / Intracoastal Waterway floodplain

7.0 11.0

22

Between Dundee Road and Sea Spray Street at FDEP reference monument T-103 from the Atlantic coastline westward across the Halifax River / Intracoastal Waterway floodplain

7.0 11.0

23

Between Beachcomber Street and Florida Shores Boulevard at FDEP reference monument R-105 from the Atlantic coastline westward across the Halifax River / Intracoastal Waterway floodplain

7.0 11.0

24

Between Thames Avenue and Gay Gayle Terrace at FDEP reference monument R-108 from the Atlantic coastline westward across the Halifax River / Intracoastal Waterway floodplain

7.0 11.0

25

Between Van Avenue and Atares Avenue at FDEP reference monument T-113 from the Atlantic coastline westward across the Halifax River / Intracoastal Waterway floodplain

7.0 11.0

26

Between Dahlia Avenue and Phillis Avenue at FDEP reference monument R-120 from the Atlantic coastline westward across the Halifax River / Intracoastal Waterway floodplain

7.0 11.0

27

Between Toronita Avenue and Sea Gull Street at FDEP reference monument R-126 from the Atlantic coastline westward across the Halifax River / Intracoastal Waterway floodplain

7.0 11.0

26


TRANSECT LOCATION



Stillwater


Chance Wave Crest

28

Between Seahaven Drive and Ashley Court at FDEP reference monument R-132 from the Atlantic coastline westward across the Halifax River / Intracoastal Waterway floodplain

7.0 11.0

29

Between Pompano Drive and Loggerhead Court at FDEP reference monument R-138 from the Atlantic coastline westward across the Halifax River / Intracoastal Waterway floodplain

7.0 11.0

30

Between Jennifer Circle and Inlet Point Boulevard at FDEP reference monument R-144 from the Atlantic coastline westward across the Halifax River / Intracoastal Waterway floodplain

7.0 11.0

31

At a point approximately 0.74 mile north of the intersection of Peninsula Avenue North and Ocean Drive at FDEP reference monument R-150 from the Atlantic coastline westward across the Indian River / Intracoastal Waterway floodplain

7.0 11.0

32

Between Cortez Street and Tide Street at FDEP reference monument R-156 from the Atlantic coastline westward across the Indian River / Intracoastal Waterway floodplain

7.0 11.0

33

Between Florida Avenue and Flagler Avenue at FDEP reference monument R-162 from the Atlantic coastline westward across the Indian River / Intracoastal Waterway floodplain

7.0 11.0

34

Between 3rd Avenue East and 4th Avenue East at FDEP reference monument R-166 from the Atlantic coastline westward across the Indian River / Intracoastal Waterway floodplain

7.0 11.0

35

Between 14th Avenue East and 15th Avenue East at FDEP reference monument R-170 from the Atlantic coastline westward across the Indian River / Intracoastal Waterway floodplain

7.0 11.0

36

Between 22nd Avenue East and 23rd Avenue East at FDEP reference monument R-173 from the Atlantic coastline westward across the Indian River / Intracoastal Waterway floodplain

7.0 11.0

27


TRANSECT LOCATION



Stillwater


Chance Wave Crest

37

Between 27nd Avenue East and 30th Avenue at FDEP reference monument R-175 from the Atlantic coastline westward across the Indian River / Intracoastal Waterway floodplain

7.0 11.0

38

Between Sun Village Court and Bay Breeze Bay at FDEP reference monument R-180 from the Atlantic coastline westward across the Indian River / Intracoastal Waterway floodplain

7.0 11.0

39

At a point approximately 500 feet south of Watts Drive at FDEP reference monument R-185 from the Atlantic coastline westward across the Indian River / Intracoastal Waterway floodplain

7.0 11.0

40

At a point approximately 2,000 feet south of Bottle Island Road at FDEP reference monument R-189A from the Atlantic coastline westward across the Indian River / Intracoastal Waterway floodplain

7.0 11.0

41

Between Croaker Avenue and Drum Avenue at FDEP reference monument R-195 from the Atlantic coastline westward across the Indian River / Intracoastal Waterway floodplain

7.0 11.0

42

Between Haddock Avenue and Halibut Avenue at FDEP reference monument R-201 from the Atlantic coastline westward across the Indian River / Intracoastal Waterway floodplain

7.0 11.0

43

Between Sheepshead Avenue and Snook Avenue at FDEP reference monument R-205 from the Atlantic coastline westward across the Indian River/Intracoastal Waterway floodplain

7.0 11.0

44

At a point approximately 2,400 feet south of Trout Avenue at FDEP reference monument R-210 from the Atlantic coastline westward across the Indian River / Intracoastal Waterway floodplain

7.0 11.0

45

At a point approximately 1.55 miles south of Trout Avenue at FDEP reference monument R-216 from the Atlantic coastline westward across the Indian River / Intracoastal Waterway floodplain

7.0 11.0

28


TRANSECT LOCATION



Stillwater


Chance Wave Crest

46

Just east of the intersection of State Route A1A and Eldora Road at FDEP reference monument R-221 from the Atlantic coastline westward across the Indian River / Intracoastal Waterway floodplain

7.0 11.0

47

At a point approximately 2,700 feet south of South Street at FDEP reference monument R-226 from the Atlantic coastline westward across the Indian River / Intracoastal Waterway floodplain

7.0 11.0

48

At a point approximately 1.27 miles south of South Street at FDEP reference monument R-230 from the Atlantic coastline westward across the Indian River / Intracoastal Waterway floodplain

7.0 11.0

49

At a point approximately 1.9 miles south of South Street at FDEP reference monument R-234 from the Atlantic coastline westward across the Indian River/Intracoastal Waterway floodplain

7.0 11.0

As of 1989, FEMA 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 or nearly 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. The inland limit of the primary frontal dune occurs at the point where there is a distinct change form a relatively steep slope to a relatively mild slope.

Figure 2, “Transect Schematic”, represents a sample transect illustrating the relationship between Stillwater elevation, eroded ground elevation profile, wave envelope, and the locations of the A/V zone boundary.

29

FIGURE 2 – TRANSECT SCHEMATIC

Table 8, “Transect Data”, includes the flooding source, 10-, 2-, 1- and 0.2-percent-annual-chance Stillwater elevations, zone designation, and base flood elevation.

TABLE 8 – TRANSECT DATA

FLOODING SOURCE

ELEVATION (feet NAVD)

ZONE

BASE FLOOD ELEVATION (feet NAVD)1





ATLANTIC OCEAN Transects 1-4 4.6 6.1 6.9 9.7 VE 10,11 Transects 5, 6 4.6 6.1 6.9 9.7 VE 9-11 Transects 7, 8 4.6 6.1 6.9 9.7 VE 10,11 Transects 9-12 4.6 6.1 6.9 9.7 VE 9-11 Transects 13 4.6 6.1 6.9 9.7 VE 10,11 Transects14 4.6 6.1 6.9 9.7 VE 11,12 Transects 15-20 4.6 6.1 6.9 9.7 VE 9-11 Transects 21-23 4.6 6.1 6.9 9.7 VE 10,11 Transects 24 4.6 6.1 6.9 9.7 VE 9-11 Transects 25-39 4.6 6.1 6.9 9.7 VE 9-11 Transects 40 4.6 6.1 6.9 9.7 VE 10,11 Transects 41 4.6 6.1 6.9 9.7 VE 9-11 Transects 42 4.6 6.1 6.9 9.7 VE 9-11 AO Depth 1 foot Transect 43 4.6 6.1 6.9 9.7 VE 9-11 Transects 44-49 4.6 6.1 6.9 9.7 VE 9-11 HALIFAX RIVER/INDIAN RIVER/INTRACOASTAL WATERWAY Transects 1 0.6 2.1 2.9 5.7 AE 3,4 Transects 2-10 0.6 2.1 2.9 5.7 AE 3-5 Transects 11-16 1.6 3.1 3.9 6.7 AE 4-6 Transects 17 1.6 3.1 3.9 6.7 AE 5,6 Transects 18-20 2.6 4.1 4.9 7.7 AE 5-7 Transects 21-25 2.6 4.1 4.9 7.7 AE 5-7 Transects 26, 27 3.6 5.1 5.9 8.7 AE 6-8 Transects 28 3.6 5.1 5.9 8.7 AE 6-8 Transects 29-37 3.6 5.1 5.9 8.7 AE 6-8

30

Transects 38, 39 2.6 4.1 4.9 7.7 AE 5,6 Transects 40 2.6 4.1 4.9 7.7 AE 5-7 Transects 41-49 2.6 4.1 4.9 7.7 AE 5-7 1Because of map scale limitations, the maximum wave elevation may not be shown on the FIRM.

3.5 Vertical Datum

All FIS reports and FIRMs are referenced to a specific vertical datum. The vertical datum provides a starting point against which flood, ground, and structure elevations can be referenced and compared. Until recently, the standard vertical datum in use for newly created or revised FIS reports and FIRMs was the National Geodetic Vertical Datum of 1929 (NGVD29). With the finalization of the North American Vertical Datum of 1988 (NAVD88), many FIS reports and FIRMs are being prepared using NAVD88 as the referenced vertical datum.

All flood elevations shown in this FIS report and on the FIRM are referenced to NAVD88. Structure and ground elevations in the community must, therefore, be referenced to NAVD88. The datum shift value in Volusia County to convert from NGVD29 to NAVD88 is -1.09 feet.

For more information on NAVD88, see the FEMA publication entitled Converting the

National Flood Insurance Program to the North American Vertical Datum of 1988 (FEMA, 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.noaa.gov).

Temporary vertical monuments are often established during the preparation of a flood hazard analysis for the purpose of establishing local vertical control. Although these monuments are not shown on the FIRM, they may be found in the Technical Support Data Notebook associated with the FIS report and FIRM for this community. Interested individuals may contact FEMA to access these data.

4.0 FLOODPLAIN MANAGEMENT APPLICATIONS

The NFIP encourages State and local governments to adopt sound floodplain management programs. Therefore, each FIS provides 1-percent-annual-chance flood elevations and delineations of the 1- and 0.2-percent-annual-chance floodplain boundaries 1-percent-annual-chance floodway to assist communities in developing floodplain management measures. This information is presented on the FIRM and in many components of the FIS, including Flood Profiles, Floodway Data Table, and Summary of Stillwater Elevation Table. 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 l-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 community. For each stream studied by detailed methods, the

http://www.ngs.noaa.gov/

31

1- and 0.2-percent-annual-chance floodplain boundaries have been delineated using the flood elevations determined at each cross section.

For the pre-countywide study, the boundaries between cross sections were interpolated using topographic maps at a scale of scale of 1:12,000 with a contour interval of 2 feet; and at a scale of 1:24,000 with a contour interval of 5 feet (References 68 and 39). For flooding sources studied by approximate methods, floodplain boundaries were taken from the previously published unincorporated areas of Volusia County FIS (Reference 1).

For the April 15, 2002, countywide FIS, floodplain boundaries between cross sections were interpolated using digitized topographic maps. For most study reaches, 1:2,400 scale photogrammetric maps with contour intervals of 1 foot were digitized for mapping purposes (References 40 and 41). These study reaches included the Tomoka River, Misner Branch, Thompson Creek, B-19 Canal, and a portion of the Little Tomoka River. For Groover Branch and the upstream portion of the Little Tomoka River, 1:24,000 scale USGS topographic maps with a contour interval of 5 feet were used (Reference 39). For mapping these streams, 1 foot contour interval maps were generated from the 5 foot contour maps using digital terrain modeling. For streams studied by approximate/limited detail methods, boundaries were delineated/digitized on 1:2,400 scale photogrammetric maps with a contour interval of 1 foot and the 1:24,000 scale USGS topographic maps using computed flood elevations determined from Volusia County stormwater management studies (References 12, 13, 14, 15, 39, 40, 41, 69, and 70).

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, AE, V, and VE); and the 0.2-percent-annual-chance floodplain boundary corresponds to the boundary of areas of moderate flood hazards. In cases where the 1- and 0.2-percent-annual-chance floodplain boundaries are close together, only the 1-percent-annual-chance floodplain boundary has been shown. Small areas within the floodplain boundaries may lie above the flood elevations but cannot be shown due to limitations of the map scale and/or lack of detailed topographic data.

For the streams studied by approximate methods, only the 1-percent-annual-chance floodplain boundary is shown on the FIRM (Exhibit 2).

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 heights. Minimum Federal standards limit such increases to 1.0 foot, provided that hazardous velocities are not produced. The floodways in this study are presented to local agencies as

32

minimum standards that can be adopted directly or that can be used as a basis for additional floodway studies.

The floodway presented in this FIS report and on the FIRM 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 have been tabulated for selected cross sections (Table 9). In cases where the floodway and 1-percent-annual-chance floodplain boundaries are either close together or collinear, only the floodway boundary has been shown.

Portions of the Tomoka River floodway encroach on the corporate limits of the Cities of Daytona Beach and Ormond Beach. Portions of the Groover Branch, Misner Branch, the Little Tomoka River, and Thompson Creek floodways encroach on the corporate limits of the City of Ormond Beach. The B-19 Canal floodway lies within the corporate limits of the Cities of Port Orange and Daytona Beach. The study reaches of Groover Branch, Misner Branch, Little Tomoka River, and Thompson Creek are affected by the backwater of their receiving water body, the Tomoka River. Two study reaches are affected by tidal backwater. These study reaches correspond to Tomoka River (affected by Tomoka Bay/Halifax River) and B-19 Canal (affected by Spruce Creek).

Near the mouths of streams studied in detail, floodway computations are made without regard to flood elevations on the receiving water body. Therefore, “Without Floodway” elevations presented in Table 9 for certain downstream cross sections of B-19 Canal, Bulow Creek, Groover Branch, Little Tomoka River, Misner Branch, Spruce Creek, Spruce Creek Tributary No.1, Spruce Creek Tributary No.2, and Tomoka River are lower than the regulatory flood elevations in that area, which must take into account the 1-percent-annual-chance flooding due to backwater from other sources.

There were no floodways calculated for Canal Between, B-19 Canal Tributary No.1, B-19 Canal Tributary No.2, E Canal, Eleventh Street Canal, Eleventh Street Canal Tributary No.2, Eleventh Street Canal Tributary No. 2A, Shooting Range Canal, South Canal, Spruce Creek Tributary A, St. Johns River, and Wally Hoffmeyer Canal.

For Thompson Creek, floodway encroachments within the 1-percent-annual-chance floodplain boundary will create surcharges which overtop the drainage divide, major highways, and evacuation routes. Therefore, Thompson Creek floodways were set at the 1-percent-annual-chance floodplain boundary.

Floodways were not determined for stream reaches studied with approximate or limited detail methods.

CROSS SECTION DISTANCE1 WIDTH (FEET)

SECTION AREA

(SQUARE FEET)

MEAN VELOCITY (FEET PER SECOND)

REGULATORY (FEET NAVD)

WITHOUT FLOODWAY

(FEET NAVD)

WITH FLOODWAY

(FEET NAVD)

INCREASE (FEET)

B-19 CanalA 380 52 323 3.4 3.9 3.32 4.3 1.0B 1,634 93 442 2.3 4.8 4.8 5.3 0.5C 3,243 27 95 10.8 6.9 6.9 6.9 0.0D 5,797 25 94 11.0 14.0 14.0 14.0 0.0E 8,479 39 246 4.0 18.6 18.6 18.6 0.0F 9,234 36 188 5.3 20.4 20.4 20.4 0.0G 10,718 40 219 3.7 23.3 23.3 23.3 0.0H 13,313 52 403 2.1 25.9 25.9 25.9 0.0I 13,412 37 251 3.1 26.1 26.1 26.3 0.2J 16,852 47 317 2.5 27.2 27.2 27.4 0.2K 19,214 47 328 2.4 27.4 27.4 27.7 0.3L 21,558 44 313 2.5 27.9 27.9 28.3 0.4M 23,554 200 963 0.8 28.1 28.1 28.7 0.6N 26,548 109 482 1.0 28.2 28.2 29.1 0.9O 29,678 38 456 1.0 28.3 28.3 29.3 1.0P 33,079 42 290 0.3 28.7 28.7 29.7 1.0

¹Feet above mouth2Elevation computed without consideration of backwater effects from Spruce Creek

FLOODING SOURCE FLOODWAY BASE FLOOD WATER SURFACE ELEVATION

FEDERAL EMERGENCY MANAGEMENT AGENCY VOLUSIA COUNTY, FL

AND INCORPORATED AREAS

FLOODWAY DATA

B-19 CANAL

TABLE 8TABLE 8TABLE 8TABLE 8TABLE 8TABLE 8TABLE 8TABLE 8TABLE 8TABLE 8TABLE 8TABLE 8TABLE 8TABLE 8TABLE 8

TA

BL

E 9


SECTION AREA

(SQUARE FEET)



WITHOUT FLOODWAY

(FEET NAVD)

WITH FLOODWAY

(FEET NAVD)

INCREASE (FEET)

B-19 Canal Tributary No. 7

A 1,004 46 359 0.4 28.6 28.6 29.6 1.0

Bulow CreekA 10,830 328 1,449 1.9 2.92 2.53 3.4 0.9B 12,000 600 2,637 1.0 2.92 2.83 3.8 1.0C 16,702 538 3,181 0.9 4.9 4.9 5.8 0.9D 21,649 834 4,835 0.5 5.2 5.2 6.2 1.0

Groover BranchA 650 385 2,547 1.2 8.9 5.54 6.5 1.0B 1,735 77 541 5.5 8.9 7.04 8.0 1.0C 3,071 77 698 4.2 9.0 9.0 10.0 1.0D 3,510 122 802 3.7 9.8 9.8 10.7 0.9E 4,562 176 1,534 1.8 12.3 12.3 13.1 0.8F 5,858 109 1,081 2.7 16.7 16.7 17.3 0.6G 7,207 51 583 4.7 18.8 18.8 19.8 1.0

¹Feet above mouth2Coastal flooding elevation; extracted from FIRM3Elevation computed without consideration of storm surge from Halifax River/Intracoastal Waterway4Elevation computed without consideration of backwater effects from Tomoka River




FLOODWAY DATA

B-19 CANAL TRIBUTARY NO. 7 - BULOW CREEK - GROOVER BRANCH


TA

BL

E 9


SECTION AREA

(SQUARE FEET)



WITHOUT FLOODWAY

(FEET NAVD)

WITH FLOODWAY

(FEET NAVD)

INCREASE (FEET)

Little Tomoka RiverA 800 406 2,670 2.0 9.1 5.42 6.4 1.0B 1,851 55 820 6.4 9.9 9.9 10.8 0.9C 3,998 484 5,196 1.0 12.1 12.1 13.1 1.0D 5,686 316 3,297 1.5 13.7 13.7 14.7 1.0E 6,577 87 930 5.0 14.5 14.5 15.5 1.0F 7,706 411 3,879 1.2 16.1 16.1 17.1 1.0G 8,757 237 2,206 2.1 17.1 17.1 18.0 0.9H 10,664 138 1188 3.6 20.3 20.3 20.9 0.6I 13,866 432 2,717 0.9 25.6 25.6 26.6 1.0J 15,062 115 718 3.4 28.2 28.2 28.6 0.4

Misner BranchA 275 49 349 2.6 7.3 4.12 5.1 1.0B 2,161 265 1,311 0.6 7.3 4.92 5.8 0.9C 4,578 29 227 3.5 7.3 6.12 7.0 0.9D 6,436 37 248 2.7 7.5 7.5 8.5 1.0E 8,705 16 147 4.6 12.6 12.6 13.6 1.0F 10,856 16 131 0.7 13.6 13.6 14.5 0.9

¹Feet above mouth2Elevation computed without consideration of backwater effects from Tomoka River




FLOODWAY DATA

LITTLE TOMOKA RIVER - MISNER BRANCH


TA

BL

E 9


SECTION AREA

(SQUARE FEET)



WITHOUT FLOODWAY

(FEET NAVD)

WITH FLOODWAY

(FEET NAVD)

INCREASE (FEET)

Spruce CreekA 4,700 908 4,630 0.8 5.92 1.03 2.0 1.0B 5,655 624 3,072 1.2 5.92 1.33 2.2 0.9C 11,275 196 1,792 2.0 5.92 2.23 2.9 0.7D 19,100 299 2,617 1.4 5.92 3.13 3.8 0.7E 24,525 228 2,278 1.5 5.92 3.63 4.2 0.6F 29,050 481 2,855 1.1 5.92 3.9 4.6 0.7G 29,780 496 3,149 1.0 5.92 4.0 4.7 0.7H 33,370 244 1,694 1.8 5.92 4.5 5.5 1.0I 40,145 275 2,086 1.4 5.92 5.3 6.3 1.0J 47,645 545 2,344 1.2 5.92 6.6 7.4 0.8K 49,278 498 2,753 1.1 8.3 8.3 9.0 0.7L 50,903 249 1,181 1.9 9.1 9.1 10.0 0.9M 52,303 373 2,215 1.0 10.1 10.1 11.1 1.0N 53,138 172 924 2.0 10.7 10.7 11.7 1.0O 57,568 113 764 2.4 16.0 16.0 17.0 1.0P 58,568 66 612 3.0 17.1 17.1 18.0 0.9Q 59,283 130 751 2.4 17.7 17.7 18.6 0.9R 62,399 51 570 3.2 21.2 21.2 21.6 0.4

¹Feet above U.S. Highway 12Coastal flooding elevation; extracted from the FIRM3Elevation computed without consideration of backwater effects from Tomoka River




FLOODWAY DATA

SPRUCE CREEK


TA

BL

E 9

CROSS SECTION DISTANCE WIDTH (FEET)

SECTION AREA

(SQUARE FEET)



WITHOUT FLOODWAY

(FEET NAVD)

WITH FLOODWAY

(FEET NAVD)

INCREASE (FEET)

Spruce CreekTributary No. 1

A 5751 111 501 2.4 8.8 6.72 7.7 1.0B 3,1051 52 286 4.2 10.3 10.3 11.2 0.9C 5,0141 101 392 2.1 13.3 13.3 14.3 1.0D 6,6651 47 216 3.9 19.9 19.9 20.2 0.3E 8,4661 174 522 1.6 26.0 26.0 26.5 0.5

Spruce CreekTributary No. 2

A 5901 76 286 3.7 10.4 7.92 8.8 0.9B 2,9541 46 221 4.7 16.7 16.7 17.7 1.0

Thompson CreekA 673 43 257 1.3 4.8 4.8 4.8 0.0B 1,4023 40 312 1.0 4.9 4.9 5.1 0.2C 1,7633 46 242 1.0 4.9 4.9 5.2 0.3D 3,4413 37 217 1.2 4.9 4.9 5.2 0.3E 4,1313 22 85 3.0 4.9 4.9 5.2 0.3F 4,9803 14 110 1.4 5.7 5.7 5.7 0.0G 5,6843 13 98 1.3 5.7 5.7 5.7 0.0H 8,0693 20 154 0.9 5.7 5.8 5.8 0.1

¹Feet above mouth2Elevation computed without consideration of backwater effects form Spruce Creek3Feet above U.S. Highway 1




FLOODWAY DATA

SPRUCE CREEK TRIBUTARY NO. 1 - SPRUCE CREEK TRIBUTARY NO. 2 - THOMPSON CREEK


TA

BL

E 9


SECTION AREA

(SQUARE FEET)



WITHOUT FLOODWAY

(FEET NAVD)

WITH FLOODWAY

(FEET NAVD)

INCREASE (FEET)

Tomoka RiverA 3,345 203 2,174 4.1 2.92 1.83 1.8 0.0B 7,428 272 2,729 3.3 3.4 3.4 3.8 0.4C 14,219 418 4,165 2.1 4.6 4.6 5.5 0.9D 20,034 2,445 15,745 0.7 5.4 5.4 6.4 1.0E 22,925 241 3,677 3.4 5.7 5.7 6.7 1.0F 23,484 249 3,905 3.2 5.9 5.9 6.9 1.0G 25,739 659 7,158 1.7 6.3 6.3 7.3 1.0H 30,663 281 4,786 2.7 7.0 7.0 8.0 1.0I 35,095 756 8,739 1.5 7.5 7.5 8.5 1.0J 38,241 309 4,866 2.8 7.8 7.8 8.7 0.9K 43,152 477 6,335 2.2 8.5 8.5 9.5 1.0L 45,210 542 6,734 2.1 8.9 8.9 9.9 1.0M 46,912 311 4,754 1.3 9.2 9.2 10.2 1.0N 49,810 448 4,298 1.8 9.4 9.4 10.4 1.0O 52,677 774 8,499 0.9 10.4 10.4 11.4 1.0P 54,934 536 6,267 1.0 11.3 11.3 12.3 1.0Q 58,152 522 5,686 1.0 12.6 12.6 13.6 1.0R 60,216 629 6,323 0.9 13.4 13.4 14.4 1.0S 63,130 249 2,026 2.8 14.7 14.7 15.7 1.0T 66,328 534 5,327 1.0 16.5 16.5 17.5 1.0U 69,247 557 5,904 0.8 17.5 17.5 18.5 1.0V 71,744 432 4,063 1.1 18.2 18.2 19.2 1.0W 74,895 394 2,859 1.5 19.9 19.9 20.9 1.0

¹Feet above confluence with Tomoka Basin2Coastal flooding elevation; extracted from the FIRM3Elevation computed without consideration of storm surge effects from Tomoka Basin




FLOODWAY DATA

TOMOKA RIVER


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SECTION AREA

(SQUARE FEET)



WITHOUT FLOODWAY

(FEET NAVD)

WITH FLOODWAY

(FEET NAVD)

INCREASE (FEET)

Tomoka RiverContinued

X 76,734 319 2,812 1.5 21.0 21.0 22.0 1.0Y 80,125 640 4,346 1.0 22.5 22.5 23.5 1.0Z 84,475 191 1,269 1.2 24.0 24.0 24.8 0.8

AA 86,737 399 2,490 0.6 24.1 24.1 24.9 0.8AB 88,161 422 2,336 0.8 24.1 24.1 24.9 0.8AC 89,559 780 3,773 0.2 24.1 24.1 24.9 0.8

¹Feet above confluence with Tomoka Basin




FLOODWAY DATA

TOMOKA RIVER


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The area between the floodway and 1-percent-annual-chance floodplain boundaries is termed the floodway fringe. The floodway fringe encompasses the portion of the floodplain that could be completely obstructed without increasing the water-surface elevation of the 1-percent-annual-chance flood more than 1.0 foot at any point. Typical relationships between the floodway and the floodway fringe and their significance to floodplain development are shown in Figure 3.

FIGURE 3 – FLOODWAY SCHEMATIC

5.0 INSURANCE APPLICATIONS

For flood insurance rating purposes, flood insurance zone designations are assigned to a community based on the results of the engineering analyses. These zones are as follows:

Zone A

Zone A is the flood insurance risk 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 BFEs or base flood depths are shown within this zone.

Zone AE

Zone AE is the flood insurance risk zone that corresponds to the 1-percent-annual-chance floodplains that are determined in the FIS by detailed methods. In most instances, whole-foot BFEs derived from the detailed hydraulic analyses are shown at selected intervals within this zone.

Zone AH

Zone AH is the flood insurance risk zone that corresponds to the 1-percent-annual-chance shallow flooding (usually areas of ponding) where average depths are between 1 and 3 feet.

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Whole-foot BFEs derived from the detailed hydraulic analyses are shown at selected intervals within this zone.

Zone AO

Zone AO is the flood insurance risk zone that corresponds to the 1-percent-annual-chance shallow flooding (usually sheet flow on sloping terrain) where average depths are between 1 and 3 feet. Average whole-foot base flood depths derived from the detailed hydraulic analyses are shown within this zone.

Zone V

Zone V is the flood insurance risk 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 BFEs are shown within this zone.

Zone VE

Zone VE is the flood insurance risk zone that corresponds to the 1-percent-annual-chance coastal floodplains that have additional hazards associated with storm waves. Whole-foot BFEs derived from the detailed hydraulic analyses are shown at selected intervals within this zone.

Zone X

Zone X is the flood insurance risk zone that corresponds to areas outside the 0.2-percent-annual-chance floodplain, areas within the 0.2-percent-annual-chance floodplain, 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 BFEs or base flood depths are shown within this zone.

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 risk 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 BFEs or average depths. Insurance agents use the zones and BFEs 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.

The countywide FIRM presents flooding information fro the entire geographic area of Volusia County. Previously, FIRMs were prepared for each incorporated community and the unincorporated areas of the County identified as flood-prone. This countywide FIRM also includes flood-hazard information that was presented separately on Flood Boundary and Floodway Maps (FHBMs), where applicable. Historical data relating to the maps prepared for each community are presented in Table 10, “Community Map History”.

COMMUNITY NAMEINITIAL

IDENTIFICATION

FLOOD HAZARD BOUNDARY MAP

REVISIONS DATESFIRM EFFECTIVE

DATEFIRM REVISIONS

DATE

Daytona Beach, City of September 8, 1970 None September 7, 1973 July 1, 1974May 27, 1977

September 16, 1982June, 4 1990

Daytona Beach Shores, City of January 29, 1971 None September 7, 1973 July 1, 1974September 26, 1975

May 27, 1977September 16, 1982

DeBary, City of1 November 23, 1973 None November 23, 1973 July 1, 1974July 1, 1977April 4, 1983

October 1, 1983February 2, 1996

Deland, City of July 3, 1995 None July 3, 1995 None

Deltona, City of1 November 23, 1973 None November 23, 1973 July 1, 1974July 1, 1977April 4, 1983

October 1, 1983February 2, 1996

1The land area for this community was previously shown on the FIRM for the unincorporated areas of Volusia County, but was not identified as a separate NFIPcommunity until February 2, 1996. Therefore, the dates for this community were taken from the FIRM for the unincorporated areas of Volusia County.

FEDERAL EMERGENCY MANAGEMENT AGENCY

VOLUSIA COUNTY, FL

AND INCORPORATED AREASCOMMUNITY MAP HISTORY

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IDENTIFICATION



DATEFIRM REVISIONS

DATE

Edgewater, City of August 23, 1974 January 14, 1977 September 3, 1980 June 4, 1990

Flagler Beach, City of1 November 23, 1973 None November 23, 1973 July 1, 1974July 1, 1977April 4, 1983

October 1, 1983June 4, 1990July 2, 1992

February 2, 1996

Holly Hill, City of September 7, 1973 None September 7, 1973 July 1, 1974October 31, 1975

April 22, 1977

Lake Helen, City of April 15, 2002 None April 15, 2002 None

New Smyrna Beach, City of December 7, 1973 None December 7, 1973 July 1, 1974May 27, 1977

December 12, 1979September 16, 1982

October 1, 1983June 16, 1992

Oak Hill, City of June 4, 1990 None June 4, 1990 July 15, 19921The land area for this community was previously shown on the FIRM for the unincorporated areas of Volusia County, but was not identified as a separate NFIPcommunity until February 19, 2014. Therefore, the dates for this community were taken from the FIRM for the unincorporated areas of Volusia County.


VOLUSIA COUNTY, FL


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IDENTIFICATION



DATEFIRM REVISIONS

DATE

Orange City, City of September 2, 1994 None September 2, 1994 None

Ormond Beach, City of November 20, 1970 None September 7, 1973 July 1, 1974May 27, 1977

September 16, 1982June 4, 1990

Pierson, Town of April 15, 2002 None April 15, 2002 None

Ponce Inlet, Town of August 9, 1974 February 13, 1976 October 8, 1976 September 16, 1982October 1, 1983June 16, 1992

Port Orange, City of July 19, 1974 None May 16, 1977 September 5, 1984June 4, 1990

South Daytona, City of June 28, 1974 September 5, 1975 October 8, 1976 June 4, 1990


VOLUSIA COUNTY, FL


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IDENTIFICATION



DATEFIRM REVISIONS

DATE

Volusia County November 23, 1973 None November 23, 1973 July 1, 1974July 1, 1977April 4, 1983

October 1, 1983June 4, 1990July 2, 1992

February 2, 1996


VOLUSIA COUNTY, FL


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7.0 OTHER STUDIES

FISs have been prepared for the unincorporated areas of Brevard, Flagler, Lake, Putnam, and Seminole Counties (References 73, 6, 4, 20, and 5).

Information pertaining to revised and unrevised flood hazards for each jurisdiction within Volusia County has been compiled into this FIS. Therefore, this FIS supersedes the previously printed FIS report and FIRM dated September 29, 2011, for Volusia County and incorporated areas (Reference 72).

8.0 LOCATION OF DATA

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

9.0 BIBLIOGRAPHY AND REFERENCES

1. Federal Emergency Management Agency, Flood Insurance Study, Volusia County, Florida (Unincorporated Areas), Washington, D.C., June 4, 1990, FIS report; February 2, 1996, FIRM.

2. Camp Dresser & McKee, Inc., Tomoka River and B-19 Canal 100-year Flood Results for the City of Daytona Beach, November 1988, revised March 1989.

3. U.S. Department of Agriculture, Soil Conservation Service, Tomoka River Floodplain Management Study - Tributaries to the Tomoka River, 1986.

4. Federal Emergency Management Agency, Flood Insurance Study, Lake County, Florida (Unincorporated Areas), Washington, D.C., April 1, 1982.

5. Federal Emergency Management Agency, Flood Insurance Study, Seminole County, Florida (Unincorporated Areas), Washington, D.C., April 17, 1995.

6. Federal Emergency Management Agency, Flood Insurance Study, Flagler County, Florida (Unincorporated Areas), Washington, D.C., July 15, 1992.

7. Zev Cohen & Associates, Inc., Spruce Creek Fly-In Report, February 1986.

8. U.S. Department of Agriculture, Soil Conservation Service, Tomoka River Flood Plain Management Study (Part II) B-19 Canal, 1986.

9. St. Johns River Water Management District, 24-Hour Rainfall Distributions for Surface Water Basins within the St. Johns River Water Management District, Northeast Florida, Technical Publication SJ 91-3, Palatka, Florida, 1991.

10. St. Johns River Water Management District, Rainfall Analysis for Northeast Florida, Part IV: 24-Hour to 96-Hour Maximum Rainfall for Return Periods 10 Years, 25 Years, and 100 Years, Technical Publication SJ 88-3, Palatka, Florida, 1988.

11. D.M. Hershfield, Rainfall Frequency Atlas of the United States, U.S. Weather Bureau, Technical Paper No. 40, Washington, D.C., 1961.

47

12. U.S. Geological Survey (USGS). Topographic Maps. Scale 1:100,000 metric, contour interval 5 meters. Daytona Beach, FL, 1978; New Smyrna Beach, FL, 1978; Orlando, FL, 1979; Titusville, FL, 1979.

13. Volusia County Tomoka River Watershed Management Plan: Stormwater Control, Conservation, and Aquifer Recharge Program, West Palm Beach, Florida, April 2, 1995 (Final Report).

14. Marshall, Provost & Associates, Noval Canal System Watershed Management Plan: Volusia County Stormwater Control, Conservation, and Aquifer Recharge Program, New Smyrna Beach, Florida, March 1995.

15. Marshall, Provost & Associates, Spruce Creek and Rose Bay OFW Watershed Management Plan: Volusia County Stormwater Control, Conservation, and Aquifer Recharge Program, New Smyrna Beach, Florida. July 1995.

16. Marshall, McCully & Associates, Indian River Lagoon/Mosquito Lagoon Watershed Management Plan: Volusia County Stormwater Control, Conservation, and Aquifer Recharge Program, July 1994.

17. McKim & Creed, B-19 Canal Watershed Management Plan, Ormond Beach, Florida, April 1995.

18. Camp Dresser & McKee, Inc., Volusia County Halifax River Watershed Management Plan: Stormwater Control, Conservation, and Aquifer Recharge Program, West Palm Beach, Florida, July 1994.

19. Applied Technology & Management, Inc., Turnbull Creek Watershed Management Plan, Gainesville, Florida, July 1994.

20. Federal Emergency Management Agency, Flood Insurance Study, Putnam County, Florida (Unincorporated Areas), Washington, D.C. August 16, 1994.

21. Research Planning Institute, Inc. Storm Surge Levels Near Halifax Plantation, Northeast Volusia County, Florida. Columbia, S.C.

22. W.C. Huber, et al., Storm Water Management Model User’s Manual Version III, Municipal Environmental Research Center, Office of Research and Development, U.S. Environmental Protection Agency, Cincinnati, Ohio, November 1981, Second Printing May 1982.

23. Camp Dresser & McKee, Inc., Runoff User’s Manual and Documentation, Annandale, Virginia, October 1988.

24. L.A. Roesner, et al., EXTRAN User’s Manual and Program Documentation, Camp Dresser & McKee, Inc., Annandale, Virginia, October 1988.

25. U.S. Department of the Interior, Geological Survey, Water Supply Paper 1543-A, Flood Frequency Analysis, 1960.

26. U.S. Department of the Interior, U.S. Geologic Survey, in cooperation with the Florida Department of Transportation, Water Resources Investigations 82-4012, Technique for Estimating Magnitude and Frequency of Floods on Natural Flow Streams in Florida, 1982.

48

27. U.S. Department of the Interior, Geological Survey, Interagency Advisory Committee on Water Data, Office of Water Data Coordination, Hydrology Subcommittee, Bulletin No. 17B, Guidelines for Determining Flood Flow Frequency, September 1981, revised March 1982.

28. U.S. Army Corps of Engineers, Hydrologic Engineering Center, HEC-l Flood Hydrograph Package, (Version 4.0.1 E), Davis, California, May 1991.

29. U.S. Army Corps of Engineers, Hydrologic Engineering Center, Introduction and Application of Kinematic Wave Routing Techniques Using HEC-l (Training Document No. 10), Davis, California, 1979.

30. U.S. Army Corps of Engineers, Hydrologic Engineering Center, Infiltration and Soil Moisture Redistribution in HEC-l (Technical Paper No. 95), Davis, California, 1984.

31. U.S. Environmental Protection Agency, SWMM Computer Program, Version 4.3, May 1994.

32. U.S. Soil Conservation Service, Urban Hydrology for Small Watersheds (Technical Release No. 55), Littleton, Colorado: Water Resources Publications, 1986.

33. Florida Department of Transportation (FDOT), Aerial photographs, Flagler and Volusia Counties, Tallahassee, Florida, 1992 and 1993.

34. Geographic Information Services, Computer files of selected GIS coverages. Volusia County, Florida, 1991-1995.

35. P.B. Bedient and W.C. Huber, Hydrology and Flood Plain Analysis, New York: Addison-Wesley, 1988.

36. Florida Department of Transportation, Drainage Manual (Volume 2-A), Tallahassee, Florida, 1987.

37. Water Resources Council, Guidelines for Determining Flood Flow Frequency, Bulletin 17A, Washington, D.C., June 1977.

38. Ground and Bathymetric Surveys, obtained by Florida Engineering Associates, Inc., Panama City, Florida, 1984.

39. U.S. Department of the Interior, Geological Survey, 7.5-Minute Series Topographic Maps, Scale 1:24,000, Contour Interval 5 Feet: Flagler Beach West, Florida, 1956, photorevised 1970; Flagler Beach East, Florida, 1956, photorevised 1970; Ormond Beach, Florida, 1956, photorevised 1970; Daytona Beach, Florida, 1952, photorevised 1970; Port Orange, Florida, 1956, photorevised 1970; New Smyrna Beach, Florida, 1956, photorevised 1970; Edgewater, Florida, 1950, photorevised 1970; Aerial, Florida, 1950, photorevised 1970; Oak Hill, Florida, 1949, photorevised 1970; Pardon Island, Florida, 1949, photorevised 1970.

40. Abrams Aerial Survey Corporation, St. Petersburg, Florida, and Lansing, Michigan, Aerial Photography with Contours, Scale 1:2,400, Contour Interval 1 Foot: City of Ormond Beach and City of Daytona Beach, Florida, January 1983.

49

41. Abrams Aerial Survey Corporation, St. Petersburg, Florida, and Lansing, Michigan, Aerial Photography with Contours, Scale 1:2,400, Contour Interval 1 Foot: City of Port Orange, Florida, March 1981.

42. U.S. Army Corps of Engineers, Hydrologic Engineering Center, HEC-2 Water Surface Profiles, Generalized Computer Program, Davis, California, May 1991.

43. U.S. Department of the Interior, Geological Survey, Open-File Report 76-499, Computer Applications for Step-Backwater and Floodway Analyses, 1976.

44. U.S. Department of the Interior, Geological Survey, Computer Program A-526, Automatic Computation of Stage-Discharge Relations at Culverts, Matthai, Stull, and Davidian.

45. U.S. Department of the Interior, Geological Survey, Water Resources Division, Downstream-Upstream Reservoir Routing, M. Jennings, Bay, St. Louis, Mississippi, 1977.

46. Federal Emergency Management Agency, Flood Insurance Study, City of New Smyrna Beach, Volusia County, Florida, Washington, D.C., June 16, 1992.

47. U.S. Department of Agriculture, Soil Conservation Service, Technical Release No. 61, WSP-2 Computer Program, May 1976.

48. U.S. Army Corps of Engineers, Hydrologic Engineering Center, HEC-2 Water Surface Profiles, Generalized Computer Program, Davis, California, November 1976.

49. Bellemead Development Corp., Daytona Beach, Florida, Topographical Maps, Surveyed Section Lines and Aerial Photography, Bulow Creek Area, Volusia County.

50. U.S. Army Corps of Engineers, Hydrologic Engineering Center, HEC-2 Water Surface Profiles: Users Manual, Davis, California, September 1990.

51. Doug Thompson, Florida Department of Environmental Protection, personal communication, November 25, 1996.

52. Upham, Inc. December 16, 1994. Willmeite Ave. Plan/Profile -Station 53+00 to 59+00. Ormond Beach, Florida.

53. U.S. Department of the Interior, Geological Survey, Guide for Selecting Manning’s Roughness Coefficients for Natural Channels and Flood Plains (Water-Supply Paper 2339), Washington, D.C., 1989.

54. Ven Te Chow, Open-Channel Hydraulics, New York: McGraw-Hill, 1959.

55. U.S. Department of Commerce, Environmental Science Services Administration, Technical Memorandum, WBTM, Hydro 11, Joint Probability Method of Tide Frequency Analysis, V.A. Myers, April 1970.

56. U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Weather Service, Tropical Cyclones of the North Atlantic Ocean, 1871-1977, June 1978.

50

57. U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Weather Service, Technical Report NWS-15, Some Climatological Characteristics of Hurricanes and Tropical Storms, Gulf and East Coasts of the United States, F.P. Ho, R.W. Schwerdt and H.V. Goodyear, May 1975.

58. U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Weather Service, Technical Report NWS-23, Meteorological Criteria for Standard Project Hurricanes and Probable Maximum Hurricane Windfields, Gulf and East Coasts of the United States, F.P. Ho, R.W. Schwerdt and R.R. Watkins, 1979.

59. Federal Emergency Management Agency, User‘s Manual for Wave Height Analysis, revised February 1981.

60. Federal Emergency Management Agency, Coastal Flood Storm Surge Model, SURGE, Washington, D.C., 1988.

61. Federal Emergency Management Agency, Flood Insurance Study Supplement - Wave Height Analysis, Volusia County, Unincorporated Areas, Florida, April 1983.

62. Federal Emergency Management Agency, Guidelines and Specifications for Study Contractors, Washington, D.C., January 1995.

63. Federal Emergency Management Agency, Federal Insurance Administration, Guidelines and Specifications for Wave Elevation Determination and V Zone Mapping, Washington, D.C., March 1995.

64. Florida Department of Environmental Protection, Coastal construction control line Aerial Photographs with Contours, 1:1,200 scale, 2 feet contours, State Topographic Office, Florida Department of Transportation, Tallahassee, Florida, August 23, 1978.

65. U.S. Army Corps of Engineers, Coastal Engineering Research Center, Waterways Experiment Station, Shore Protection Manual, Vicksburg, Mississippi, 1984.

66. Federal Emergency Management Agency, Wave Height Analysis for Flood Insurance Studies Computer Program, Version 3.0, September 1988.

67. Federal Emergency Management Agency, RUNUP Computer Program, Version 2.0.

68. City of Daytona Beach, Florida, Aerial Topography with Contours, Scale 1:12,000, Contour Interval 2 feet: Daytona Beach, Florida, January 1983.

69. Camp Dresser & McKee, Inc., Turnbull Creek Watershed Study (Exhibit B): Structure Identification and Floodplain Delineations, Photogramatic survey of Turnbull Creek, Volusia County project #1564-28, West Palm Beach, Florida, July 1987.

70. Camp Dresser & McKee, Inc., Turnbull Creek Watershed for the County of Volusia, West Palm Beach, Florida, 1988.

71. Aeromap, U.S., Inc., Ormond Beach, Florida, Topographic Map of Ormond Beach, Florida, Scale 1:200, Contour Interval 1 Foot: City of Ormond Beach, Florida, 1995.

72. Federal Emergency Management Agency, Flood Insurance Study, Volusia County, Florida and Incorporated Areas, Washington, D.C., April 15, 2002.

51

73. Federal Emergency Management Agency, Flood Insurance Study, Brevard County, Florida and Incorporated Areas, Washington, D.C., Flood Insurance Rate Map, August 18, 1992; Flood Insurance Study, November 19, 1997.

74. Streamline Technologies, Inc., Advanced Interconnected Channel and Pond Routingmodel, v. 3.02, April 2007.

75. St. Johns River Water Management District, Digital Orthophoto Quadrangles, Quads 3909, 3910, 3911, 4009, 4010, 4011; Collected December 2003-January 2004.

76. U.S. Department of the Interior, Geological Survey, 7.5-Minute Series Topographic Maps, Scale 1:24,000, Contour Interval 5 Feet: Lake Ashby, Florida, 1988; Lake Helen, Florida, 1966, photorevised 1980; Orange City, Florida, 1964, photorevised 1980; Osceola, Florida, 1988; Osteen, Florida, 1980; Sanford, Florida, 1988.

77. Doyle G. Abramson, PSM # 6156, Merrick and Company, City of Deltona Survey and Map Report, February 4, 2005, 1 foot Orthophotography Deliverable, Collected February 2004-May 2004.

78. Soil Survey Staff, Natural Resources Conservation Service, United States Department of Agriculture. Soil Survey Geographic (SSURGO) Database for Volusia County, FL. Available online at http://soildatamart.nrcs.usda.gov.

10.0 REVISION DESCRIPTIONS

This section has been added to provide information regarding significant revisions made since the original FIS report and FIRM were printed. Future revisions may be made that do not result in the republishing of the FIS report. All users are advised to contact the Community Map Repository at the address below to obtain the most up-to-date flood hazard data.

Volusia County Office of Growth Management 123 West Indian Avenue

Deland, FL 32720 10.1 First Revision (February 19, 2003)

For this revision, the floodplains for portions of Groover Branch, Halifax River/Intracoastal Waterway, Little Tomoka River, Misner Branch, Thompson Creek, Tomoka River, and Strickland Creek have been redelineated in the City of Ormond Beach, based on new topographic information. In addition, a LOMR dated April 16, 2002, in the City of Ormond Beach, was incorporated into the FIRM. This LOMR reflects revised hydrologic and hydraulic analyses and more up-to-date and detailed topographic information for Ponding Areas 1 through 4. The results of this LOMR are shown in Table 11, “First Revision Summary of Stillwater Elevations”.

TABLE 11 – FIRST REVISION SUMMARY OF STILLWATER ELEVATIONS ELEVATION (feet NAVD)






PONDING AREA 1 * * 22.9 * PONDING AREA 2 * * 22.9 *

http://soildatamart.nrcs.usda.gov/

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TABLE 11 – FIRST REVISION SUMMARY OF STILLWATER ELEVATIONS (cont.) ELEVATION (feet NAVD)






PONDING AREA 3 * * 21.9 * PONDING AREA 4 * * 22.9 * *Data not available

The hydrologic and hydraulic analyses remain unchanged from the April 15, 2002, countywide FIS.

Floodplain boundaries were delineated/digitized on 1:200 scale photogrammetric maps with a contour interval of 1 foot, using computed flood elevations taken from the previously published Volusia County and incorporated areas FIS (References 1 and 2). All affected flooding sources are located in the City of Ormond Beach. These flooding sources included portions of Groover Branch, Halifax River/Intracoastal Waterway, Little Tomoka River, Misner Branch, Thompson Creek, Tomoka River, and Strickland Creek.

10.2 Second Revision (Revised September 29, 2011)

a. Acknowledgments

The hydrologic and hydraulic analyses for this revision were performed by Tetra Tech HAI, for the City of Deltona, under City Purchase Orders 50412, 50576, 6608, 7343, and 7527. This work was completed in April 2007.

b. Coordination

No coordination information is available for this revision.

c. Scope

This revision includes a restudy of Lake Gleason, Lake McGarity, Lake Theresa, and Providence drainage basins.

d. Hydrologic and Hydraulic Analyses

Detailed hydrologic and hydraulic analysis based on updated topographic information were carried out using the Interconnected Channel and Pond Routing (ICPR) model, version 3.02 (Reference 1).

Aerial photographs, USGS topographic maps, survey data, one-foot photogrammetric aerials, and the City of Deltona’s 1999 Stormwater Management Master Plan were used to identify existing drainage systems and to delineate the sub-bassins (References 2, 3, 4, and 5).

Composite run off curve numbers for the sub-basins were determined based on soils and land use data. Soils data were developed from the USDA NRCS Soils Survey of Volusia County, Florida (Reference 6). Land use data was obtained from the St. Johns River Water Management District’s 1995 Land Use map.

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Input data for the ICPR model was obtained from data gathered from a limited ground survey and USGS maps during the preparation of the original model developed as a part of the City of Deltona’s 1999 Stormwater Management Plan (Reference 5). Tetra Tech HAI also used additional input data obtained from one foot photogrammetric aerials and limited field survey (Reference 4).

e. Floodplain Boundaries

For the September 29, 2011 revision, floodplain boundaries for most ponding areas, including lakes and natural and man-made depressions, within the study basins have been revised. Base (1-percent-annual-chance) flood elevations (BFEs) have been established or revised for some of these ponding areas.

f. Floodways

Floodways were not computed for the September 29, 2011 revision.

g. Bibliography and References

1. Streamline Technologies, Inc., Advanced Interconnected Channel and Pond Routingmodel, v. 3.02, April 2007.

2. St. Johns River Water Management District, Digital Orthophoto Quadrangles, Quads 3909, 3910, 3911, 4009, 4010, 4011; Collected December 2003-January 2004.

3. U.S. Department of the Interior, Geological Survey, 7.5-Minute Series Topographic Maps, Scale 1:24,000, Contour Interval 5 Feet: Lake Ashby, Florida, 1988; Lake Helen, Florida, 1966, photorevised 1980; Orange City, Florida, 1964, photorevised 1980; Osceola, Florida, 1988; Osteen, Florida, 1980; Sanford, Florida, 1988.

4. Doyle G. Abramson, PSM # 6156, Merrick and Company, City of Deltona Survey and Map Report, February 4, 2005, 1 foot Orthophotography Deliverable, Collected February 2004-May 2004.

5. City of Deltona, FL, Stormwater Management Plan, 1999.

6. Soil Survey Staff, Natural Resources Conservation Service, United States Department of Agriculture. Soil Survey Geographic (SSURGO) Database for Volusia County, FL. Available online at http://soildatamart.nrcs.usda.gov.

10.3 Third Revision (Revised February 19, 2014)

a. Acknowledgments

The hydrologic and hydraulic analyses for this study were performed by Taylor Engineering, Inc. (a member of BakerAECOM LLC), for the Federal

http://soildatamart.nrcs.usda.gov/

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Emergency Management Agency (FEMA), under Contract No. HSFEHQ-09-D-0368. This work was completed in February 2013.

b. Coordination

The initial Consultation Coordination Officer (CCO) meeting was held on August 10, 2009, and attended by representatives of the study contractor, the Cities of Daytona Beach, DeBary Shores, Deland, Deltona, Edgewater, Holly Hill, Lake Helen, Oak Hill, Orange City, Ormond Beach, Port Orange, Smyrna Beach, and South Daytona and Volusia County.

The results of the study were reviewed at the final CCO meeting held on June 9, 2011, and attended by representatives of FEMA, the community, and the study contractor. All problems raised at that meeting have been addressed.

c. Scope

This revision includes a revised detailed analysis of the B-19 Canal and Thompson Creek, as well as new detailed analysis of B-27 Canal (subdivided into reaches for model reporting purposes), LPGA Canal, Laurel Creek, Halifax Canal and Nova Canal (subdivided into reaches for model reporting purposes) as detailed by Table 12, “Third Revision Detailed Study Scope”. The remaining effective base flood elevations were redelineated on updated topography (Reference 3).

TABLE 12 – THIRD REVISION DETAILED STUDY SCOPE FLOODING SOURCE NAME LIMITS OF NEW OR REVISED DETAILED STUDY B-19 Canal From the confluence with Spruce Creek to a point approximately

430 feet upstream of Beville Road. B-27 Canal

B-27 Canal North From the confluence with LPGA Canal to Division Avenue.

B-27 Canal South From the confluence with LPGA Canal to a point approximately 750 feet upstream of Brentwood Drive.

Halifax Canal From the confluence with Nova Canal at a point approximately at the intersection of Nova Road and Canal View Boulevard to a point approximately 260 feet North of Powers Avenue at the upstream termination of Spruce Creek.

Nova Canal Nova North Reach 1 From the confluence with LPGA Canal to a point approximately 20

feet upstream of Alabama Avenue.

Nova North Reach 2 From the confluence with LPGA Canal to a point approximately 900 feet upstream of Orange Avenue.

Nova South Reach 1 From the confluence with Reed Canal to a point approximately 3200 feet upstream of Alabama Avenue.

Nova South Reach 2 From the confluence with Reed Canal to a point approximately 500 feet upstream of Herbert Street.

55

TABLE 12 – THIRD REVISION DETAILED STUDY SCOPE (continued) FLOODING SOURCE NAME LIMITS OF NEW OR REVISED DETAILED STUDY Laurel Creek From the confluence with the Strickland Creek to a point

approximately 330 feet upstream of Laurel Oaks Circle.

LPGA Canal From the confluence with B-27 Canal to the outlet with the Halifax River.

Thompson From a point approximately 580 feet downstream of U.S. Highway 1 to a point approximately 640 feet upstream of Division Avenue.

The revision also includes new approximate analyses for B-21 Canal, Deep Creek, and Cow Creek. In addition, the LOMRs listed in Table 13 were incorporated into the FIRM.

TABLE 13 – INCORPORATED LOMRS CASE NUMBER

EFFECTIVE DATE

SUMMARY OF REVISIONS COMMUNITIES AFFECTED

09-04-784P 10/30/2009 North Lake Talmadge, South Lake Talmadge, Blue Lake, Lake Hammock, Duck Decoy Depression, Jacobs Pond, Lori Pond, and Miller Lake – Developed new Base Flood Elevation (BFEs) with new hydrologic and hydraulic analysis and updated topographic data.

City of Deland, Volusia County

09-04-1747P 07/27/2010 Ponding Areas 5 and 6 – Developed Base Flood Elevations (BFEs) with new hydrologic and hydraulic analysis and new topographic data.

City of Deltona

09-04-2678P 08/26/2009 Twin Lake, Quail Lake, Cinnamon Bay, Tropic Lagoon, Terra Alta Depressional Area, Kings Lake, Lower Lake, DGCC Pond, Upper Lake, Pine Valley Court Pond, Lake Anna Maria, Lake Maud, Lake Olivia, No Name Lake, Lake Susan, Lake Hibiscus, Gem Lake, Lake Marie, Half Moon Lake, Mirror Lake, Lago Linda, Lake of the Woods, Lake Louise, Angeles Lake Bonita Lake, Lake Charles, Woodbound Lake, Bass Lake, Unnamed Lake No. 5, Unnamed Lake No. 6, Turtle Pond, James Pond, Gasline Lake – Revised Zone A ponding areas based on updated topographic data.

City of Debary, City of Deltona, City of Orange City, Volusia County

56

TABLE 13 – INCORPORATED LOMRS (continued)

CASE NUMBER

EFFECTIVE DATE

SUMMARY OF REVISIONS COMMUNITIES AFFECTED

10-04-6547P 12/20/2010 Ponding Areas 5 – 10 – Developed a Base Flood Elevation (BFE) with a new hydrologic analysis and new topographic data.

City of Daytona Beach, Volusia County

d. Hydrologic and Hydraulic Analyses

USACE HEC-HMS computer program computed peak flood discharges for B-19, Laurel Canal, and Thompson Creek (Reference 4). HEC-HMS modeling incorporated the SCS unit hydrograph and kinematic wave routing methods. The model used a SCS Type II Florida modified temporal rainfall distribution. Other parameters included precipitation totals for selected recurrence intervals, subbasin runoff curve numbers, lag times, stream cross sections, and Manning’s “n” roughnes factors. Watershed boundaries and subbasins were delineated using GIS tools and aerial photographs. Rainfall totals were based on Technical Paper 40 (Reference 5). Curve numbers were calculated using the SCS curve number method (Reference 6) based on St. Johns Water Management District (SJWMD) soils and landuse data. Lag times were calculated using SCS Method (Reference 7).

This revision incorporated components of an integrated hydrology and hydraulic study performed by Camp Dresser & Mckee (CDM) on the Nova Canal System which includes the B-27, Halifax, LPGA, and Nova Canals (Reference 8). Using this model as a base, the contractor revised model elements based on field and GIS inspections. The EPA’s SWMM model version 5.0.021 was used to compute peak flood discharges for B-27, Halifax, LPGA and Nova Canals (Reference 9). Model parameters included subbasin area; average width of subbasin, average subbasin slope, percent directly connected impervious area, roughness coefficients for pervious and impervious land uses, initial abstraction and infiltration rates. The Horton soil infiltration equation was used to simulate infiltration into the soil. The SWMM model uses Modified Rational equation to calculate runoff from each subbasin.

The B-21 canal approximate hydrology and hydraulic modeling was based upon the Inter-Connected Pond Routing (ICPR) modeling by Environmental Consulting and Technology, Inc. (Reference 10, 11). This revision uses selected data output in close proximity to the main flooding sources to delineate floodplains.

The Deep Creek and Cow Creek approximate modeling was based upon SWMM modeling performed by CDM (Reference 9, 12). This revision uses selected data output in close proximity to the main flooding sources to delineate floodplains.

Peak drainage-discharge area relationships for the 10-, 2-, 1-, and 0.2-percent-annual-chance floods are shown in Table 14.

57

TABLE 14 – REVISED SUMMARY OF DISCHARGES


DRAINAGE AREA

(sq. miles)


Annual-Chance




B-19 CANAL At mouth At Willow Run Boulevard At Pelican Bay Drive

10.4 6.9 1.7

623 457 262

912 676 393

1,089 843 477

1,338 1,102 604


At Interstate 95

0.9

112

210

261

428


At mouth

0.3

45

86

108


At Bellville Road

0.4

*

*

148

*

B-27 CANAL NORTH At Walker Street At Calle Grande Avenue

1.4 0.4

81

204

102 250

110 297

113 388

B-27 CANAL SOUTH At 10th Street At State Route 430

0.8 0.1

92

333

110 422

120 480

133 573

LAUREL CREEK

At U.S. Highway 1 At Wilmette Avenue At Granada Boulevard At Division Avenue At Hand Avenue

2.4 1.8 1.2 0.5 0.3

331 242 166 143 104

479 348 238 207 146

579 421 287 249 175

747 541 369 319 224

LPGA CANAL At FEC Railroad At Center Avenue

8.8 6.6

448 377

464 405

568 419

631 443

NOVA NORTH REACH 1 At Confluence with LPGA

Canal At 15th Street At. Alabama Avenue

2.0

1.4 0.8

125

68 70

149

89 94

160

108 110

183

137 130

NOVA NORTH REACH 2

At 10th Street At Jersey Avenue At 6th Street At 4th Street

4.6 4.4 3.7 3.3

526 245 219 227

665 269 259 256

715 282 282 279

878 304 311 321

NOVA SOUTH REACH 1

At Confluence with Reed Canal

At Old Big Tree Road At Bellville Road At Bellevue Avenue

5.2

4.2 3.4 2.3

524

856 370 282

574

1028 407 295

593

1305 424 288

657

1696 440 263

58

TABLE 14 – REVISED SUMMARY OF DISCHARGES (continued)


DRAINAGE AREA

(sq. miles)


Annual-Chance




NOVA SOUTH REACH 2

At Confluence with Reed Canal

At Madeline Avenue At Herbert Street

2.2

1.2 0.4

641

249 84

710

249 102

742

249 115

773

249 132

THOMPSON CREEK

At U.S. Highway 1 At Wilmette Avenue At Granada Boulevard At Division Avenue

0.6 0.6 0.3 0.1

232 229 166 66

303 300 231 89

352 350 275 105

427 433 341 129

The LOMRs that were incorporated into this study established Stillwater elevations based on new hydrologic and hydraulic analyses and more up-to-date and detailed topographic information. The results are summarized in Table 15, “Third Revision Summary of Stillwater Elevations”.

TABLE 15 – THIRD REVISION SUMMARY OF STILLWATER ELEVATIONS ELEVATION (feet NAVD)






BLUE LAKE * * 57.0 * DUCK DECOY DEPRESSION * * 57.3 * JACOBS POND * * 63.1 * LAKE HAMMOCK * * 57.3 * LORI POND * * 63.6 * MILLER LAKE * * 57.0 * NORTH LAKE TALMADGE * * 57.0 * SOUTH LAKE TALMADGE * * 57.0 * PONDING AREA 5 (City of Deltona) * * 34.9 * PONDING AREA 6 (City of Deltona) * * 33.9 * PONDING AREA 5 (City of Daytona Beach) * * 25.9 * PONDING AREA 6 (City of Daytona Beach) * * 25.9 * PONDING AREA 7 * * 27.9 * PONDING AREA 8 * * 27.9 * PONDING AREA 9 * * 24.9 * PONDING AREA 10 * * 24.9 * *Data not available

Water-surface elevations of floods of the selected recurrence intervals were computed through use of the USACE HEC-RAS water-surface profile computer program for Thompson Creek, Laurel Creek, and B-19 Canal (Reference 13).

59

TABLE 16 – REVISED HYDRAULIC MODEL BOUNDARY CONDITIONS

Flooding Source Boundary Condition Method B-19 Canal Normal Depth B-27 Canal North NA – Downstream tied to LPGA Canal B-27 Canal South NA – Downstream tied to LPGA Canal Halifax Canal 1-year still-water level = 1.91 feet NAVD88 LPGA Canal 1-year still-water level = 0.91feet NAVD88 Laurel Creek Mean High Water = 0.04 feet NAVD881 Nova Canal NA – Tied into LPGA to the North and Halifax Canal to the South. Thompson Creek Mean High Water = 0.04 feet NAVD881 1data.labins.org – Station 0954

Cross sections were obtained from existing data sources including the effective study’s models and then field verified. Where discrepancies or deficiencies were discovered, field surveys were obtained. All channel data was supplemented with current LiDAR data for overbanks. Field data collection was conducted using Static and Real Time GPS occupations, as well as, conventional survey techniques. Watershed level control was established by static GPS occupation with position and elevation subsequently determined by OPUS (Online Positioning User Service) solution using CORS (Continuously Operating Reference Station) network stations. In areas with multiple watershed level control points, these control points were checked across the control network for vertical consistency and independently checked against National Geodetic Survey (NGS) monuments if available and recoverable.

Roughness factors (Manning’s “n”) were chosen based on field observations, aerial photos, photographs of the stream and floodplain areas, and published text and photographs with recommended roughness values (Reference 11). The channel and overbank “n” values for all streams studied by detailed methods are shown in Table 17, “Revised Manning’s “n” Values”.

TABLE 17 – REVISED MANNING’S “n” VALUES Stream Channel “n” Overbank “n” B-19 Canal 0.025-0.06 0.10-0.20 B-27 Canal North 0.04 0.065-0.07 B-27 Canal South 0.04-0.05 0.065-0.07 Halifax Canal 0.02-0.05 0.045-0.08 Laurel Creek 0.035 0.10 LPGA Canal 0.035-0.05 0.045-0.1 Nova Canal 0.04-0.065 0.045-0.07 Thompson Creek 0.030-0.033 0.10

60

e. Floodplain Boundaries

For this revision, floodplain boundaries between cross sections were interpolated using LiDAR provided by the Volusia County Public Works Department (Reference 3). This data was created as part of the 2006/2007 Volusia County LiDAR DTM Project, dated October 2007. The LiDAR DTM was developed in accordance with the 2006 Volusia LiDAR specifications. The DTM is intended to support 2 foot contours, and the vertical accuracy of ground points in unobscured areas is 0.3-feet RMSE. The DTM was developed to perform preliminary storm water project design and evaluation, perform preliminary roadway alignment analysis, evaluate and assess flood potential, revise FEMA flood maps, review hurricane storm surge models and to generate a DTM to be used for future ortho photography collection efforts.

f. Floodways Floodways were computed for B-19 Canal, Laurel Creek, and Thompson Creek. The results of the floodway computations have been tabulated for selected cross sections in Table 18.


SECTION AREA

(SQUARE FEET)



WITHOUT FLOODWAY

(FEET NAVD)

WITH FLOODWAY

(FEET NAVD)

INCREASE (FEET)

B-19 CanalA 647 74 312 4.1 5.92 2.73 3.0 0.3B 1,874 70 336 3.7 5.92 4.73 5.1 0.4C 3,462 60 335 3.7 9.1 9.1 9.1 0.0D 5,039 30 210 5.7 10.0 10.0 10.1 0.1E 6,137 69 215 5.6 16.9 16.9 16.9 0.0F 7,037 58 308 3.8 17.9 17.9 17.9 0.0G 8,989 79 427 2.7 20.0 20.0 20.0 0.0H 9,769 38 220 5.2 21.1 21.1 21.1 0.0I 12,129 35 214 4.6 24.0 24.0 24.5 0.5J 13,851 58 347 2.5 25.7 25.7 26.1 0.4K 16,064 74 392 1.9 26.9 26.9 27.3 0.4L 17,718 55 313 2.1 27.2 27.2 27.6 0.4M 18,492 44 338 1.8 27.3 27.3 27.7 0.4N 19,487 53 345 1.7 27.4 27.4 27.8 0.4O 22,540 760 1,573 0.4 27.4 27.4 28.3 0.9P 23,930 2,159 6,081 0.1 27.5 27.5 28.4 0.9Q 26,336 742 1,609 0.3 27.5 27.5 28.4 0.9R 28,279 1,273 4,683 0.1 27.6 27.6 28.5 0.9S 31,176 135 506 0.8 27.7 27.7 28.6 0.9T 34,457 176 1,027 0.2 28.8 28.8 29.7 0.9

¹Feet above mouth2Includes combined probability2Elevation computed without consideration of backwater effects from Spruce Creek




REVISED FLOODWAY DATA

B-19 CANAL

TA

BL

E 8

FEET (NGVD)FEET (NAVD)

TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 1

8


SECTION AREA

(SQUARE FEET)



WITHOUT FLOODWAY

(FEET NAVD)

WITH FLOODWAY

(FEET NAVD)

INCREASE (FEET)

Laurel CreekA 163 301 1,049 0.6 5.52 0.03 0.0 0.0B 2,427 69 323 1.8 5.52 1.53 1.5 0.0C 3,417 109 859 0.6 5.5 5.5 6.4 0.9D 5,940 236 1,313 0.3 5.5 5.5 6.5 1.0E 7,751 822 2,966 0.1 5.5 5.5 6.5 1.0F 7,987 777 2,241 0.2 5.6 5.6 6.5 0.9G 10,808 192 539 0.5 6.7 6.7 7.6 0.9H 11,090 55 271 1.0 6.7 6.7 7.6 0.9I 12,474 55 298 0.8 6.7 6.7 7.7 1.0J 13,148 1,349 8,059 0.0 6.7 6.7 7.7 1.0K 13,399 145 523 0.4 6.7 6.7 7.7 1.0L 13,604 2,120 7,301 0.0 6.7 6.7 7.7 1.0M 14,113 1,639 3,377 0.1 6.7 6.7 7.7 1.0N 14,558 248 518 0.5 6.7 6.7 7.7 1.0O 15,639 971 2,280 0.1 6.7 6.7 7.7 1.0P 15,898 403 793 0.2 6.8 6.8 7.7 1.0Q 16,425 1,145 3,064 0.0 6.8 6.8 7.8 1.0R 16,675 1,019 2,425 0.1 6.8 6.8 7.8 1.0S 16,980 544 3,277 0.0 6.8 6.8 7.8 1.0

¹Feet above confluence with Tomoka River2Includes backwater from Tomoka River3Elevation computed without consideration of backwater effects from Tomoka River





LAUREL CREEK

TA

BL

E 8


TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 1

8


SECTION AREA

(SQUARE FEET)



WITHOUT FLOODWAY

(FEET NAVD)

WITH FLOODWAY

(FEET NAVD)

INCREASE (FEET)

Thompson CreekA 90 67 247 1.4 5.52 1.63 1.6 0.0B 1,356 60 444 0.8 5.6 5.6 6.2 0.6C 1,734 87 467 0.6 5.6 5.6 6.3 0.7D 3,512 95 617 0.5 7.5 7.5 8.4 0.9E 4,163 54 460 0.7 7.5 7.5 8.4 0.9F 5,028 49 345 0.8 7.5 7.5 8.5 1.0G 5,741 238 1,339 0.2 7.5 7.5 8.5 1.0H 6,856 402 2,852 0.0 7.5 7.5 8.5 1.0I 8,353 411 1,769 0.1 7.5 7.5 8.5 1.0

¹Feet above U.S. Highway 12Includes backwater from Tomoka River3Elevation computed without consideration of backwater effects from Tomoka River





THOMPSON CREEK

TA

BL

E 8


TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 8

TA

BL

E 1

8

64

g. Bibliography and References

1. Aeromap, U.S., Inc., Topographic Map of Ormond Beach, Florida, Scale 1:200, Contour Interval 1 Foot: City of Ormond Beach, Florida, 1995.

2. Federal Emergency Management Agency, Flood Insurance Study, Volusia County, Florida and Incorporated Areas, Washington, D.C., April 15, 2002.

3. Woolpert, Inc., Orlando, FL, 2006/2007 Volusia County LiDAR DTM Project, 1”=100’, Contour Interval 1 foot: Volusia County, FL, 2007.

4. U.S. Army Corps of Engineers (USACE), Hydrologic Engineering Center (HEC), Hydrologic Modeling System (HMS), Version 3.4, August 2009.

5. U.S. Department of Commerce, Technical Paper No. 40: Rainfall Frequency Atlas of the United States for Durations from 30 Minutes to 24 Hours and Return Periods from 1 to 100 Years, Washington D.C., May 1961.

6. U.S. Department of Agriculture, Natural Resources Conservation Service, Technical Release 55: Urban Hydrology for Small Watersheds, June 1986

7. Kent, K. M., National Engineering Handbook, Section 4 – Hydrology, August 1972.

8. Camp Dresser & McKee, Inc., East Volusia Regional Water Authority Nova Canal Flood Control and Integrated Water Resource Program Final Report, July 2010.

9. U.S. Environmental Protection Agency, SWMM Computer Program, Version 5.0.021, September 2010.

10. Streamline Technologies, Inc., Interconnected Channel and Pond Routing Model, Version Unknown.

11. Environmental Consulting and Technology, Inc., B-21 Watershed Management Plan, August 2009.

12. Camp Dresser & McKee, Inc., Deep Creek Basin Stormwater Master Plan, July 2009.

13. U.S. Army Corps of Engineers (USACE) Hydrologic Engineering Center (HEC), River Analysis System (RAS), Version 4.1.0, January 2010.

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