VOLUME 1 OF 3
CADDO PARISH,
LOUISIANA
AND INCORPORATED AREAS
COMMUNITY NAME
BELCHER, VILLAGE OF
BLANCHARD, TOWN OF
CADDO PARISH
(UNINCORPORATED AREAS)
GILLIAM, VILLAGE OF
GREENWOOD, TOWN OF
HOSSTON, VILLAGE OF
IDA, VILLAGE OF
MOORINGSPORT, TOWN OF
OIL CITY, TOWN OF
RODESSA, VILLAGE OF
SHREVEPORT, CITY OF
VIVIAN, TOWN OF
COMMUNITY NUMBER
220374
220315
220361
220289
220292
220295
220276
220339
220262
220308
220036
220351
Caddo Parish
PRELIMINARY
AUGUST 29, 2011
REVISED:
Federal Emergency Management Agency
FLOOD INSURANCE STUDY NUMBER
22017CV001B
NOTICE TO
FLOOD INSURANCE STUDY USERS
Communities participating in the National Flood Insurance Program have established repositories
of flood hazard data for floodplain management and flood insurance purposes. This Flood
Insurance Study (FIS) may not contain all data available within the repository. It is advisable to
contact the community repository for any additional data.
Part or all of this FIS may be revised and republished at any time. In addition, part of this FIS
may be revised by the Letter of Map Revision process, which does not involve republication or
redistribution of the FIS. It is, therefore, the responsibility of the user to consult with community
officials and to check the community repository to obtain the most current FIS components.
Initial Parishwide FIS Effective Date: April 6, 2000
Revised Parishwide FIS Date: May 17, 2004
TABLE OF CONTENTS – Volume 1
Page
1.0
2.0
3.0
4.0
INTRODUCTION
1
1.1
Purpose of Study
1
1.2
Authority and Acknowledgments
1
1.3
Coordination
3
AREA STUDIED
4
2.1
Scope of Study
4
2.2
Community Description
11
2.3
Principal Flood Problems
13
2.4
Flood Protection Measures
16
ENGINEERING METHODS
17
3.1
Hydrologic Analyses
18
3.2
Hydraulic Analyses
33
3.3
Vertical Datum
37
FLOODPLAIN MANAGEMENT APPLICATIONS
38
4.1
Floodplain Boundaries
38
4.2
Floodways
39
5.0
INSURANCE APPLICATIONS
40
6.0
FLOOD INSURANCE RATE MAP
89
7.0
OTHER STUDIES
89
8.0
LOCATION OF DATA
91
9.0
BIBLIOGRAPHY AND REFERENCES
91
i
TABLE OF CONTENTS – Volume 1 - continued
Page
FIGURES
Figure 1 - Floodway Schematic
40
TABLES
Table 1 - Initial and Final CCO Meetings
4
Table 2 - Streams Studied by Detailed Analysis
6-10
Table 3 - Letters of Map Correction
10
Table 4 - Summary of Discharges
24-32
Table 5 - Summary of Elevations
33
Table 6 - Floodway Data
41-87
Table 7 - Community Map History
90
TABLE OF CONTENTS – continued – Volume 2
EXHIBITS
Exhibit 1 - Flood Profiles
75th Street Drainage Ditch
81st Street Drainage Ditch
Airport Ditch
Audrey Lane Lateral
Avery Ditch
Bayou Pierre
Betty Virginia Lateral
Bickham Bayou
Boggy Bayou
Boggy Bayou Tributary A
Boggy Bayou Tributary B
Brookwood Ditch
Brush Bayou
Buchanan Bayou
Buchanan Bayou Tributary A
Cargill Lateral
Choctaw Bayou
Cooper Road Ditch
Panels
Panels
Panels
Panel
Panel
Panels
Panels
Panels
Panels
Panels
Panels
Panels
Panels
Panels
Panel
Panels
Panels
Panels
ii
01P-04P
05P-06P
07P-10P
11P
12P
13P-26P
27P-28P
29P-31P
32P-43P
44P-47P
48P-53P
54P-56P
57P-64P
65P-70P
71P
72P-73P
74P-80P
81P-82P
TABLE OF CONTENTS – Volume 2 – continued
EXHIBITS - continued
Exhibit 1 - Flood Profiles – continued
Country Club Lateral
Courtesy Lane Channel
Cross Bayou
Cross Bayou Lateral
Cross Bayou Tributary 1
Cross Bayou Tributary 2
Cross Bayou Tributary 3
Panels
Panels
Panel
Panels
Panels
Panels
Panels
83P-85P
86P-87P
88P-89P
90P-92P
93P-94P
95P-96P
97P-98P
TABLE OF CONTENTS – continued – Volume 3
EXHIBITS - continued
Exhibit 1 - Flood Profiles – continued
Cypress Bayou
Ford Park Lateral
Galaxy Lateral
Gilbert Ditch
Gilmer Bayou
Gilmer Bayou Tributary 1
Gilmer Bayou Tributary 2
Gilmer Bayou Tributary 3
Green Oaks Lateral
Green Terrace Lateral
Hollywood Ditch
Industrial Park Lateral
Jenkins Acres Lateral
Lambert Park Lateral
Lincoln Memorial Lateral
Logan Bayou
Lynbrook Lateral
McCain Creek
Murry Lateral
Ockley Ditch
Old River
Page Bayou
Page Bayou Tributary A
Pierremont Ditch
Ranchmoor Lateral
Red River
Rose Park Lateral
Panels
Panels
Panels
Panel
Panels
Panel
Panel
Panel
Panel
Panels
Panels
Panels
Panels
Panels
Panels
Panels
Panels
Panels
Panels
Panels
Panels
Panels
Panel
Panels
Panels
Panels
Panels
iii
99P-102P
103P-104P
105P-106P
107P
108P-111P
112P
113P
114P
115P
116P-118P
119P-121P
122P-124P
125P-126P
127P-128P
129P-132P
133P-138P
139P-141P
142P-151P
152P-153P
154P-156P
157P-158P
159P-164P
165P
166P
167P-168P
169P-172P
173P-174P
TABLE OF CONTENTS – continued – Volume 3
EXHIBITS - continued
Exhibit 1 -Flood Profiles – continued
Sand Beach Bayou
Savanna Lateral
Shirley-Francis Lateral
South Broadmoor Lateral
Southwood High Lateral
St. Vincent Academy Ditch
Summer Grove Ditch
Sycamore Lateral
Twelve Mile Bayou
Werner Park Lateral
Panels
Panels
Panel
Panels
Panels
Panel
Panels
Panel
Panels
Panels
Exhibit 2 - Flood Insurance Rate Map Index
Flood Insurance Rate Map
iv
175P-179P
180P-181P
182P
183P-184P
185P-186P
187P
188P-190P
191P
192P-193P
194P-196P
FLOOD INSURANCE STUDY
CADDO PARISH, LOUISIANA AND INCORPORATED AREAS
1.0
INTRODUCTION
1.1
Purpose of Study
This parishwide FIS investigates the existence and severity of flood hazards in, or
revises and updates previous FISs/Flood Insurance Rate Maps (FIRMs) for the
geographic area of Caddo Parish, Louisiana, including the City of Shreveport; the
Towns of Blanchard, Greenwood, Mooringsport, Oil City, and Vivian; the Villages
of Belcher, Gilliam, Hosston, Ida, and Rodessa; and the unincorporated areas of
Caddo Parish (hereinafter referred to collectively as Caddo Parish).
Please note that the City of Shreveport is geographically located in Caddo and
Bossier Parishes. The City of Shreveport is included in its entirety in this FIS
report.
This FIS aids in the administration of the National Flood Insurance Act of 1968
and the Flood Disaster Protection Act of 1973. This FIS has developed flood risk
data for various areas of the parish that will be used to establish actuarial flood
insurance rates. This information will also be used by Caddo Parish to update
existing floodplain regulations as part of the Regular Phase of the National Flood
Insurance Program (NFIP), and will also be used by local and regional planners to
further promote sound land use and floodplain development. Minimum floodplain
management requirements for participation in the NFIP are set forth in the Code of
Federal Regulations at 44 CFR, 60.3.
In some states or communities, floodplain management criteria or regulations may
exist that are more restrictive or comprehensive than the minimum Federal
requirements. In such cases, the more restrictive criteria take precedence and the
State (or other jurisdictional agency) will be able to explain them.
1.2
Authority and Acknowledgments
The sources of authority for this FIS are the National Flood Insurance Act of 1968
and the Flood Disaster Protection Act of 1973.
Pre-parishwide Analyses
This FIS was prepared to include the unincorporated areas of, and incorporated
communities within, Caddo Parish in a parishwide format. Information on the
authority and acknowledgments for each jurisdiction included in this parishwide
FIS, as compiled from their previously printed FIS reports, is shown below.
1
Caddo Parish
(Unincorporated Areas):
the hydrologic and hydraulic analyses from the
FIS report dated September 5, 1990, were
prepared by the U.S. Army Corps of Engineers
(USACE), Vicksburg District, for the Federal
Emergency Management Agency (FEMA),
under Interagency Agreement No. EMW-86-E2226, Project Order No. 12. This work was
completed in November 1987. The hydrologic
and hydraulic analyses for portions of the
flooding sources were prepared by Owen and
White, Inc., for FEMA during the preparation of
FISs for the City of Shreveport and the Town of
Oil City, under Contract No. H-4701.
the hydrologic and hydraulic analyses from the
FIS report dated May 19, 1997, were performed
by Owen and White, Inc., under Contract No.
89-D028. This work was completed in February
1992.
Greenwood, Town of:
the hydrologic and hydraulic analyses from the
FIS report dated August 3, 1998, were
performed by the U.S. Geological Survey
(USGS), for FEMA, under Contract No. EMW95-E-4757. This work was completed in March
1997.
Oil City, Town of:
the hydrologic and hydraulic analyses from the
FIS report dated July 16, 1980, were prepared
by Owen and White, Inc., for FEMA, under
Contract No. H-4701.
This work was
completed in February 1979.
Shreveport, City of:
the hydrologic and hydraulic analyses from the
FIS report dated January 18, 1984, were
prepared by Owen and White, Inc., for FEMA,
under Contract No. H-4701. This work was
completed in March 1980.
the hydrologic and hydraulic analyses from the
FIS report dated June 5, 1997, were performed
by Owen and White, Inc., under Contract No.
89-D028. This work was completed in February
1992.
There are no previous FISs for the Towns of Blanchard, Mooringsport, and
Vivian; and the Villages of Belcher, Gilliam, Hosston, Ida, and Rodessa; therefore,
2
the previous authority and acknowledgment information for these communities is
not included in this FIS. These communities may not appear in the Community
Map History table (Section 6.0).
May 17, 2004, Parishwide Analyses
The revision affects the unincorporated areas of Caddo Parish and the City of
Shreveport. These detailed analyses were prepared by Owen and White, Inc., for
FEMA, under Contract No. EMT-98-CO-0016. This study was completed in
December 1999.
Parishwide Revision
For this parishwide FIS, revised approximate hydrologic and hydraulic analyses
were prepared by Risk Assessment, Mapping, and Planning Partners (RAMPP) for
FEMA, under Contract No. HSFEHQ-09-D-0369. This work was completed in
April 2011.
Base map information shown on the FIRM was derived from multiple sources
including the City of Shreveport, the Northwest Louisiana Council of
Governments and the USGS. Base map files were provided in digital format.
Additional information was photogrammetrically compiled at a scale of 1:12,000
from aerial photography dated 2004 or later. The projection used in the
preparation of this map is Universal Transverse Mercator (UTM), Zone 15N, and
the horizontal datum used is NAD 83.
Differences in the datum and spheroid used in the production of FIRMs for
adjacent parishes and counties may result in slight positional differences in map
features at the parish boundaries. These differences do not affect the accuracy of
information shown on the FIRM. Users of this FIRM should be aware that minor
adjustments may have been made to specific base map features.
1.3
Coordination
Consultation Coordination Officer’s (CCO) meetings may be held for each
jurisdiction in this parishwide FIS. An initial CCO meeting is held typically with
representatives of FEMA, the community, and the study contractor to explain the
nature and purpose of a FIS, and to identify the streams to be studied by detailed
methods. A final CCO meeting is held typically with representatives of FEMA, the
community, and the study contractor to review the results of the study.
Pre-parishwide Analyses
The dates of the initial and final CCO meetings held for Caddo Parish and the
incorporated communities within its boundaries are shown in Table 1, "Initial and
3
Final CCO Meetings." The information in Table 1 only provides information for
CCO meetings held prior to the April 6, 2000 parishwide study.
TABLE 1 - INITIAL AND FINAL CCO MEETINGS
Community
Initial CCO Date
Final CCO Date
Caddo Parish (Unincorporated Areas)
Greenwood, Town of
Oil City, Town of
Shreveport, City of
September 26, 1985
*
March 13, 1978
March 13, 1978
August 31, 1989
August 7, 1997
July 16, 1979
August 29, 1982
*Data not available
The initial CCO meetings were held with representatives from FEMA, the
communities, and the study contractors to explain the nature and purpose of FIS
reports, and to identify the streams to be studied by detailed methods. The final
CCO meetings were held with representatives from FEMA, the communities, and
the study contractors to review the results of the studies.
Parishwide Revision
For this parishwide FIS, the initial CCO meeting was held on November 2, 2009.
This meeting was attended by representatives of the study contactor, communities,
the State of Louisiana, and FEMA.
2.0
AREA STUDIED
2.1
Scope of Study
This FIS covers the geographic area of Caddo Parish, Louisiana.
Pre-parishwide Analyses
For the Town of Oil City, the shoreline area of Caddo Lake, consisting mainly of
residential development, was selected by the Town of Oil City, FEMA, and the
study contractor to be studied in detail.
The areas studied by detailed methods in the Town of Oil City were selected with
priority given to all known flood hazard areas and areas of projected development
or proposed construction through February 1984.
The limits of the detailed study for the City of Shreveport were determined by
FEMA, the City of Shreveport, and the study contractor at the March 1978
meeting. Because the entire City of Shreveport area was rapidly expanding, the
principal determining factor for selection was the minimum of 1-square-mile
drainage area.
4
Based on the minimum 1-square mile drainage, the following streams in the City of
Shreveport were selected for detailed analysis:
Red River
Boggy Bayou Basin
Boggy Bayou
Gilmer Bayou
Industrial Park Lateral
Lincoln Memorial Lateral
Shirley-Francis Lateral
Southwood High Lateral
Cross Bayou Basin
Cross Bayou
Twelve Mile Bayou
McCain Creek
Cross Bayou Lateral
Bickham Bayou
Country Club Lateral
Galaxy Lateral
Bayou Pierre Basin
Bayou Pierre
Ockley Ditch
Gilbert Ditch
Sand Beach Bayou
South Broadmoor Lateral
Old River
Brush Bayou Basin
Brush Bayou
Brookwood Lateral
75th Street Drainage Ditch
Airport Ditch
Hollywood Lateral
Summer Grove Ditch
Werner Park Lateral
For the City of Shreveport FIS dated June 5, 1997, all of the detailed study
streams of the original City of Shreveport study were restudied, along with 21
additional streams. These streams, along with all others studied by detailed
methods in Caddo Parish, are presented in Table 2, “Streams Studied by Detailed
Analysis.”
The areas studied by detailed methods for the City of Shreveport were selected
with priority given to all known flood hazards and areas of projected development
or proposed construction through March 1985.
The determination of streams to be studied by detailed methods in the 1997 revised
study for the City of Shreveport was discussed by community officials and Owen
and White, Inc., the study contractor, from January 10 through April 4, 1989. The
results of the restudy of individual basins were reviewed by the City of Shreveport
and the study contractor as follows: Cross Bayou basin, May 7 and September 26,
1990; Bayou Pierre basin, January 15, 1991; Brush Bayou basin, May 29, 1991;
and Boggy Bayou basin, February 20, 1992. Throughout the project, contact was
maintained with the Office of the City Engineer, City of Shreveport; FEMA; the
USACE, Vicksburg District; and the USGS.
For the original unincorporated areas of Caddo Parish study, the following
flooding sources were studied by detailed methods: McCain Creek, Logan Bayou,
5
Choctaw Bayou, Page Bayou, Page Bayou Tributary A, Buchanan Bayou,
Buchanan Bayou Tributary A, Brush Bayou, Boggy Bayou, Gilmer Bayou,
Southwood High Lateral, Industrial Park Lateral, Lincoln Memorial Lateral, Cross
Bayou, Ranchmoor Lateral, Summer Grove Ditch, Boggy Bayou Tributary A,
Boggy Bayou Tributary B, Bayou Pierre, Sand Beach Bayou, Galaxy Lateral,
Bickham Bayou, and Old River.
In addition, flooding in the Parish from Wallace, Caddo, and Cross Lakes was also
studied by detailed methods. The areas studied by detailed methods in the original
study for Caddo Parish were selected with priority given to all known flood
hazards and areas of projected development and proposed construction through
November 1992.
The areas studied by detailed methods for the Town of Greenwood were selected
with priority given to all known flood hazards and areas of projected development
or proposed construction through January 1997.
All streams studied by detailed methods within Caddo Parish, along with their
detailed study reaches, are shown in Table 2, “Streams Studied by Detailed
Analysis.”
TABLE 2 – STREAMS STUDIED BY DETAILED ANALYSIS
Flooding Source
Limits of Detailed Study
75th Street Drainage Ditch
From confluence with Brush Bayou to approximately 600
feet upstream of West 68th Street
81st Street Drainage Ditch
From confluence with Brush Bayou to East 74th Street
Airport Ditch
From confluence with Brush Bayou to Meriwether Road
Audrey Lane Lateral
From confluence with Cooper Road Ditch to the corporate
limits of the City of Shreveport (near Doll Street)
Avery Ditch
From confluence with Betty
approximately 900 feet upstream
Bayou Pierre
From State Route 175 to East Dalzell Street
Betty Virginia Lateral
From confluence with Ockley Ditch to approximately 400
feet upstream of Interstate 49
Bickham Bayou
From confluence with Cross Lake to approximately 500 feet
upstream of Pines Road
Boggy Bayou
From confluence with Cypress Bayou to approximately 27.3
miles upstream
6
Virginia
Lateral
to
TABLE 2 – STREAMS STUDIED BY DETAILED ANALYSIS - continued
Flooding Source
Limits of Detailed Study
Boggy Bayou Tributary A
From confluence with Boggy Bayou to Bicknell Ranch
Road
Boggy Bayou Tributary B
From confluence with Boggy Bayou to approximately 1.1
miles upstream of Buncombe Road
Broadmoor AH Zone
From a ridgeline east of Bayou Pierre and north of South
Sand Beach Boulevard
Brookwood Ditch
From confluence with Brush Bayou to Hawthorne Street
Brush Bayou
From confluence with Boggy Bayou to Alta Vista Avenue
Buchanan Bayou
From confluence with Boggy Bayou to State Route 525
(Colquitt Road)
Buchanan Bayou Tributary A
From confluence with Buchanan Bayou to State Route 525
(Colquitt Road)
Caddo Lake
Level pool lake area
Cargill Lateral
From confluence with Airport Ditch to Lotus Lane
Choctaw Bayou
From confluence with Logan Bayou to Millwood Lane
Cooper Road Ditch
From confluence with McCain Creek to confluence with
Audrey Lane Lateral (near Willie Mays Street)
Country Club Lateral
From confluence with Cross Lake to Alabama Street
Courtesy Lane Channel
From confluence with Brush Bayou to approximately 650
feet upstream of Hollywood Avenue
Cross Bayou
From confluence with Red River to Cross Lake Dam
Cross Bayou Lateral
From confluence with Cross Bayou to Weinstock Street
Cross Bayou Tributary
From confluence with Cross Bayou Tributary 2 to
approximately 1,650 feet upstream of U.S. Highway 80
Cross Bayou Tributary 2
From confluence with Cross Bayou Tributary 1 to an
unnamed road approximately 3,000 feet upstream of U.S.
Highway 80
7
TABLE 2 – STREAMS STUDIED BY DETAILED ANALYSIS - continued
Flooding Source
Limits of Detailed Study
Cross Bayou Tributary 3
From Union Pacific Railroad to approximately 1,000 feet
upstream of U.S. Highway 80
Cross Lake
Level pool lake area
Cypress Bayou
From Wallace Lake Dam to just upstream of U.S. Highway
171.
Ford Park Lateral
From confluence with Cross Lake to Debbie Street
Galaxy Lateral
From confluence with Cross Lake to Jefferson Paige Road
Gilbert Ditch
From confluence with Ockley Ditch to Linden Street
Gilmer Bayou
From confluence with Boggy Bayou to Buncombe Road
Gilmer Bayou Tributary 1
From Limit of Detailed Study (at Town of Greenwood
corporate limits) to approximately 6,000 feet upstream
Gilmer Bayou Tributary 2
From approximately 550 feet downstream of Waterwood
Drive to just downstream of Kimberly Road
Gilmer Bayou Tributary 3
From confluence with Gilmer Bayou Tributary 2 to just
downstream of Adams Lane
Green Oaks Lateral
From confluence with Cooper Road Ditch to Pearl Street
Green Terrace Lateral
From confluence with Boggy Bayou to Cedar Creek Drive
Hollywood Ditch
From confluence with Airport Ditch to approximately 2,000
feet upstream of Hollywood Avenue
Industrial Park Lateral
From confluence with Gilmer Bayou to approximately 2,500
feet upstream of Bert Kouns Industrial Loop
Jenkins Acres Lateral
From confluence with Airport Ditch to downstream of
Amelia Avenue
Lambert Park Lateral
From confluence with Summer Grove Ditch to Cynthia
Street
Lincoln Memorial Lateral
From confluence with Industrial Park Lateral to West 70th
Street
8
TABLE 2 – STREAMS STUDIED BY DETAILED ANALYSIS - continued
Flooding Source
Limits of Detailed Study
Logan Bayou
From confluence with Cross Lake to Pine Hill Road
Lynbrook Lateral
From confluence with Brush Bayou to St. Vincent Avenue
McCain Creek
From confluence with Twelve Mile Bayou to State Route
173
Murry Lateral
From confluence with Hollywood Ditch to upstream of
Interstate 20
Ockley Ditch
From confluence with Bayou Pierre to approximately 1,650
feet upstream of Kings Highway
Old River
From confluence with Sand Beach Bayou to approximately
3,750 feet upstream of East 70th Street
Page Bayou
From confluence with Cross Lake to Jefferson Paige Road
Page Bayou Tributary A
From confluence with Page Bayou to a lake spillway
approximately 1,780 feet upstream
Pierremont Ditch
From confluence with Bayou Pierre to Creswell Avenue
Ranchmoor Lateral
From confluence with Brush Bayou to downstream of
Interstate 49
Red River
From approximately 5.3 miles downstream of 70th Street to
approximately 1.6 miles upstream of Interstate Highway
220
Rose Park Lateral
From confluence with Country Club Lateral to Claiborne
Street
Sand Beach Bayou
From confluence with Bayou Pierre to approximately 600
feet upstream of Louisiana State Highway 1 (Youree Drive)
Savanna Lateral
From confluence with Summer Grove Ditch to Mansfield
Road
Shirley-Francis Lateral
From confluence with Industrial Park Lateral to Woolworth
Road
9
TABLE 2 – STREAMS STUDIED BY DETAILED ANALYSIS - continued
Flooding Source
Limits of Detailed Study
South Broadmoor Lateral
From confluence with Sand Beach Bayou to East Kings
Highway
Southwood High Lateral
From confluence with Gilmer Bayou to approximately 1,500
feet upstream of Dean Road
St. Vincent Academy Ditch
From confluence with Ockley Ditch to just upstream of
Stephenson Street
Summer Grove Ditch
From Williamson Way to Bert Kouns Industrial Loop
Sycamore Lateral
From confluence with Cross Bayou Lateral to Weinstock
Street
Twelve Mile Bayou
From confluence with Cross Bayou to Grimmet Road
Wallace Lake
Level pool lake area
Werner Park Lateral
From confluence with Brush Bayou to Corbitt Street
Parishwide Revision
Floodplain boundaries of stream that have been previously studied by detailed
methods were delineated using the best available topographic data. No new
hydrologic or hydraulic analyses were performed for those streams.
This FIS also incorporates the determinations of letters issued by FEMA resulting
in map changes (Letter of Map Revision [LOMR], Letter of Map Revision - based
on Fill [LOMR-F], and Letter of Map Amendment [LOMA], as shown in Table 3,
"Letters of Map Correction."
TABLE 3 - LETTERS OF MAP CORRECTION
Community
Flooding Source(s)/Project Identifier
Date Issued
Type
City of Shreveport
Audrey Lane Lateral
May 11, 2010
LOMR
All or portions of numerous flooding sources in the parish 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 Caddo
Parish.
10
2.2
Community Description
Caddo Parish is located in the northwest corner of Louisiana, approximately 300
miles northwest of New Orleans and approximately 150 miles east of Dallas,
Texas. The Parish is bordered by the unincorporated areas of Miller County,
Arkansas, to the north; the unincorporated areas of Bossier Parish to the east; the
unincorporated areas of DeSoto and Red River Parishes to the south; and the
unincorporated areas of Marion, Panola, and Cass Counties, Texas, to the west.
The 2010 population for Caddo Parish was estimated to be 254,969 (Reference 1).
The physiography of Caddo Parish consists of rolling and hilly uplands, generally
sloping intermediate terraces, and bottom lands within the main valleys.
Louisiana has a humid-subtropical climate, directly influenced by the Gulf of
Mexico, which is approximately 200 miles to the south of Caddo Parish. Climatic
conditions in northern Louisiana are usually moderate in character with large,
sudden changes being rare. Temperatures are moderate throughout the year, with
the average summer temperature in the region at approximately 81 degrees
Fahrenheit (°F) while the average winter temperature is approximately 51°F
(Reference 5). Because periods of prolonged freezing rarely occur, snow and ice
have no effect on flood runoff from streams originating within the State (Reference
6). The average annual rainfall varies across the Parish, with an average of 51
inches in the City of Shreveport (Reference 5) and an average of 50 inches in the
Town of Oil City (Reference 5).
The Parish is located in the oak-hickory-pine ecological zone of Louisiana. The
two major plant communities that occur in the zone are a pine-hardwood-forest
type in the higher elevations and bottom land hardwoods along the lower, floodprone areas (Reference 7). Natural waters range from intermittent headwaters
through marshes to mature, slow-moving meandering streams. Manmade waters
include larger lakes and reservoirs, as well as many small ponds and lakes.
The Town of Greenwood is located in the central part of Caddo Parish,
approximately 2 miles west of the City of Shreveport and approximately 2 miles
east of the Louisiana-Texas border.
The Town is surrounded by the
unincorporated areas of Caddo Parish.
The Town of Greenwood study area has a relatively steep terrain. Cross and
Gilmer Bayous drain the western and eastern sections of the Town, respectively,
and each has three tributaries.
The Town of Oil City is approximately 15 miles northwest of the City of
Shreveport. Situated on the east end of Caddo Lake, the town limits encompass
about 1,190 acres, approximately 50 acres of which are part of Caddo Lake.
There are approximately 6,000 feet of shoreline in the Town.
11
Caddo Lake, primarily a recreational body of water, took its present shape in 1914
with the construction of a dam on Cypress Bayou. The dam is located 4 miles
southeast of the Town of Oil City. The structure was designed to maintain a
minimum pool elevation of 168.3 feet referenced to the North American Vertical
Datum of 1988 (NAVD 88) on the lake.
The City of Shreveport is predominantly located in Caddo Parish, in the northwest
corner of Louisiana, 187 miles east of Dallas, Texas, and 320 miles northwest of
New Orleans, Louisiana. The existing channel of the Red River forms most of the
eastern corporate limit of the City of Shreveport, while the old channel forms the
Caddo Parish boundary. This results in some land area of Bossier Parish being
within the corporate limits of the City of Shreveport.
The City of Shreveport is the center of commerce for northwest Louisiana, and has
an extensive diversified industrial economy. The growth patterns in the City of
Shreveport are typical of a large urban community, with private residences,
apartments, and shopping centers expanding away from the central business
district. The principal direction of movement has been to the south. Northward
movements have been limited by the geographical barriers of Cross Lake, the Red
River, and their floodplains. In the last few years, however, the availability of land
above the floodplains has dwindled, and construction has begun to infringe on low
lands.
The Red River, which forms the easterly boundary of the City of Shreveport, is
one of the principal rivers in the State of Louisiana. Its mouth is formed at the Old
River control structure, which regulates the diversion of low water from the
Mississippi River. The City of Shreveport sits at mile 277 of the Red River, which
has a drainage area of 60,614 square miles at this point. The City is protected
from possible flooding of the river by the natural high ground of the central
business district and a system of artificial levees for the remaining portions of its
length.
Runoff from the northern portion of the City of Shreveport flows into the Cross
Bayou basin, which intersects the Red River, just north of the central business
district. The majority of the area runoff flows into the Boggy Bayou or Brush
Bayou basins, which flow into Wallace Lake and then connect with Bayou Pierre.
Bayou Pierre parallels the Red River from the City of Shreveport to Natchitoches
(70 miles) before their confluence.
The Cross Bayou basin, which drains the northern section of the City of
Shreveport, contains several streams. Twelve Mile Bayou is a major drainage
stream (3,259 square miles) controlled by several upstream reservoirs and is 8,800
feet upstream from the confluence of Cross Bayou with the Red River. Cross
Bayou flows easterly to the Red River. Cross Lake is a water-supply reservoir.
The dam and spillway are located on Cross Bayou 20,200 feet upstream from the
Red River. McCain Creek flows into Twelve Mile Bayou and provides drainage
for the northernmost sections of the City of Shreveport and its corresponding
developed suburban areas. Cooper Road Ditch, Green Oaks Lateral, and Audrey
Lane Lateral are tributaries of McCain Creek. Cross Bayou Lateral flows into
12
Cross Bayou downstream of Cross Lake. Country Club Lateral, Rose Park
Lateral, Bickham Bayou, Ford Park Lateral, and Galaxy Lateral flow into Cross
Lake.
The topography of this basin in the City of Shreveport area ranges from 149.8 feet
NAVD 88 to 339.8 feet NAVD 88 in the upper reaches of McCain Creek. Flat
topography is common only along the bottom lands stretching along the north
shore of Cross Lake and the north bank of Cross Bayou.
The Brush Bayou basin drains most of the south-central portion of the City of
Shreveport. Each of its tributary streams is completely urbanized and flows
directly into Brush Bayou except for Hollywood Ditch, Jenkins Acres Lateral, and
Murry Lateral, which are tributaries of Airport Ditch. The topography of the area
varies from 159.8 feet NAVD 88 along Brush Bayou at the southerly corporate
limits to 279.8 feet NAVD 88 in the northwestern corner of the basin. Some flat
topography does exist along Brush Bayou and Airport Ditch.
The Boggy Bayou basin drains the southwestern section of the City of Shreveport.
The area is largely undeveloped. In the study portion of this basin, the flows from
all tributaries must pass through Gilmer Bayou before reaching Boggy Bayou.
Shirley-Francis and Lincoln Memorial Laterals are also tributaries to Industrial
Park Lateral. The topography of the area varies from 159.8 feet NAVD 88 along
Boggy Bayou to 319.8 feet NAVD 88 at the headwaters of Industrial Park Lateral.
Relatively flat topography extends from the downstream reaches of Boggy Bayou,
Gilmer Bayou, and Industrial Park Lateral.
The Bayou Pierre basin, which drains the southeastern portion of the City of
Shreveport, is quite unique. The northern portion of the basin and the portion
west of Bayou Pierre are heavily urbanized as the land is relatively high. In the
area west of Bayou Pierre and south of Southfield Road, the development has
increased. The land here is quite flat, ranging from elevations of 139.8 to 164.8
feet NAVD 88, and the portion between Southfield Road and Kings Highway is
heavily urbanized. In the study area, Gilbert Ditch, St. Vincent Academy Ditch,
Avery Ditch, and Betty Virginia Lateral are tributaries of Ockley Ditch, which is a
tributary of Bayou Pierre. Both the Old River and South Broadmoor Lateral are
tributaries of Sand Beach Bayou. Sand Beach Bayou joints Bayou Pierre near the
downstream limit of the study.
2.3
Principal Flood Problems
The low-lying areas of Caddo Parish are subject to periodic headwater flooding
caused by the inability of streams to handle heavy localized rainfalls of short
duration. Backwater flooding on the Red River and its tributaries mainly affects
areas located in the City of Shreveport.
Severe flooding can occur in the Parish at any time of the year, but appears to be
more frequent during the summer and fall. The storm of June 9, 1986 produced 5
to 6 inches of rain in a 10-hour period, and the June 27, 1986 storm, resulting from
Hurricane Bonnie, produced 7.06 inches of rain in 15 hours.
13
The June 27th storm caused flooding along Pines Road near the Huntingdon Golf
Course, between 70th Street and Buncombe Road, at the Forest Mobile Estates on
the Industrial Loop, at the Blue Ridge Mobile Home Park on Buncombe Road,
and in the Colquitt Road Estates and Edgewood subdivisions, southwest of the
City of Shreveport corporate limits. Several sections of the Colquitt Road bridge
over Gilmer Bayou were washed away (Reference 9).
This storm also caused flooding on McCain Creek near State Route 173 in the
Martin Luther King Drive area and on a major portion of the development around
Cross Lake; floodwaters reached a level of 175.3 feet northeast of Cross Lake in
the City of Shreveport.
In the Wallace Lake area, south of the corporate limits of the City of Shreveport,
principal flooding occurs in the Kingston Farms and Meadow Lake Subdivisions,
along Linwood Avenue and Barron Road, in a mobile home park at B&S Landing,
and in the vicinity of several mobile homes at Debroeck Landing. Flooding in
these areas can be either backwater from Wallace Lake, headwater from Boggy
Bayou and its tributaries, or a combination of both.
Flooding in the Bayou Pierre-Sand Beach Bayou area south of the City of
Shreveport corporate limits mainly occurs on Youree Drive north of Kings
Highway and on Gilbert Drive near the southern portion of Querbes Golf Course.
Streams in Caddo Parish have relatively flat slopes and a moderate degree of
channel meandering.
These conditions encourage vegetation growth and
sedimentation, which in turn reduce flow velocity and increase flood depths and
durations. Inadequate bridge and culvert openings and the dumping of trash in
stream beds also increase the potential for flood damage.
The most intense rainfall occurs during localized thunderstorms, which produce
large amounts of rainfall and are usually of short duration. Another source of
heavy rainfall is from tropical storms. These storms originate over ocean waters
and move slowly inland. During this slow inland movement, extremely heavy
rainfall can occur over much of Louisiana.
In the Town of Greenwood, flooding mainly occurs during the winter and spring,
but can occur during any season. Flooding impact on tributaries caused by major
downstream courses is defined as backwater flooding. In addition, flooding
impacts caused by in-stream hydraulic losses (normal backwater) are defined as
headwater flooding.
The shoreline areas of Caddo Lake are susceptible to substantial flooding. On
May 5, 1958, Caddo Lake crested at 182.71 feet NAVD 88 on the Mooringsport
gage. This is the highest recorded level of the lake. On May 3, 1966, Caddo Lake
crested at 180.50 feet NAVD 88, causing considerable flooding of low-lying areas.
On April 30, 1973, the level of Caddo Lake reached 175.58 feet NAVD 88
(Reference 10). More recently, the lake level reached 175.60 feet NAVD 88 in
March 2001 and 175.20 feet NAVD 88 in October 2009 (Reference 44).
14
The principal flooding season for Caddo Lake occurs from January through May.
High water levels in Caddo Lake are the result of extended periods of precipitation
rather than from a sudden storm. For example, in the 10 days preceding May 5,
1958, nearly 14 inches of rainfall were recorded over the area (Reference 11).
In the Cross Bayou basin, a principal flooding area has been the West Agurs area,
which is part of the original Red River and headwater flooding from the CypressTwelve Mile Bayou basins. On April 5, 1945, and May 5, 1958, with a peak stage
at 169.8 feet NAVD 88, virtually the entire area to the Texas and Pacific Railroad
levee flooded (Reference 14). The greatest floods caused by backwater from
Twelve Mile Creek and the Red River were in May 1892 and August 1949
(Reference 2). After 1958, the next highest stage reached 157.83 NAVD 88 which
occurred in 1973 (Reference 45).
McCain Creek and Cooper Road Ditch are partially urbanized and, with somewhat
smaller basins, are affected by 24-hour storms. Most of the other laterals in the
City of Shreveport, which are tributaries to Cross Lake and Cross Bayou, are
highly urbanized with sudden peak discharge from short duration, intense rainfall.
The Brush Bayou basin drains most of the south-central portion of the City of
Shreveport. Most of its tributary streams are completely urbanized. Some flat
topography does exist along Brush Bayou, Hollywood Ditch, and Airport Ditch.
Most of these streams react to short duration, intense rainfall. Flooding is
common in the Mooretown area along Hollywood Ditch.
The Boggy Bayou basin drains the southwestern section of the City of Shreveport.
The area is largely undeveloped. Relatively flat topography extends from the
downstream reaches of Boggy Bayou, Gilmer Bayou, and Industrial Park Lateral.
These streams are generally most sensitive to full-day heavy rainfalls.
The Bayou Pierre basin drains the southeastern portion of the City of Shreveport.
The northern portion of the basin and the portion west of Bayou Pierre are heavily
urbanized as the land is relatively high. In the area east of Bayou Pierre and south
of Southfield Road, the development has increased and the land is quite flat. In the
upper reaches of the basin, this area is sensitive to short duration, intense storms.
In the lower reaches, this area is affected by longer duration storms.
The following table correlates the rainfall with its anticipated frequency of return
based on data from the Shreveport Regional Airport rain gage, and frequency
curves from the National Oceanic and Atmospheric Administration (NOAA)
(Reference 17).
15
Date
Critical
Amount (inches)
Time Span
(hours)
Frequency of
Return (years)
12.44
6.63
4.65
5.72
3.74
4.03
2.73
4.43
3.07
3.27
3.19
3.45
2.58
4.52
5.94
3.50
4.51
3.64
2.56
10.44
2.34
24
48
12
24
4
12
1
2
12
6
2
2
1
6
6
6
6
12
1
12
1
400
N/A
4
4
5
2
10
40
1
2
5
7
7
7
30
3
7
2
7
200
5
July 25, 1933
May 6, 1935
September 15, 1968
November 17, 1969
July 29, 1972
June 7, 1974
September 17, 1976
May 7, 1978
January 19, 1979
May 4, 1979
May 9, 1981
June 5, 1983
July 3, 1985
June 9, 1986
July 27, 1986
November 15, 1987
June 4, 1989
May 12, 1990
May 31, 1990
April 12, 1991
April 17, 1991
Note: Rainfall causing Red River flooding of May 1990 occurred in Oklahoma
and Arkansas. The Red River crest on May 16, 1990, was at 34.5 feet (165.78
NAVD 88). The flood reached a 1-percent-annual-chance flood elevation
(References 16 and 18).
2.4
Flood Protection Measures
The frequent flooding by backwater from the Red River was virtually eliminated by
the cleanup of massive log jams, the channelization and sloping of various sections,
and the construction of levees along its lower banks. Even after these
improvements, some backwater flooding was still occurring in the West Agurs area
and this was accompanied by headwater flooding from Twelve Mile Bayou. The
West Agurs area is now protected by a ring levee. Improvements along Twelve
Mile Bayou include a levee along the east bank of the bayou in 1961 and the
establishment of Ferrell’s Bridge Reservoir and Caddo Lake.
Although constructed for water supply, it is likely that the Cross Lake Reservoir
has served as protection for downstream floodplains. Other improvements in the
Cross Bayou basin include channel widening and paving of several streams and
ditches.
Numerous improvements have been made within the Brush Bayou basin including
several enlargement and realignment of channels completed by the USACE
16
(Reference3). Completion of additional work in October 1983 led to the transfer
of operation and maintenance responsibilities to Caddo Parish officials.
The City of Shreveport has conducted several channel improvements in the Brush
Bayou basin including channel paving, enlargement and widening of several
streams and ditches including Werner Parks Lateral, Brush Bayou, 75th Street
Drainage Ditch, Hollywood Ditch, Airport Ditch, Brookwood Lateral, and
Summer Grove Ditch.
Projects within the Boggy Bayou basin include channel improvements of Boggy
Bayou and Gilmer Bayou.
Very little channel improvement has taken place in the sparsely populated alluvial
plain of the Bayou Pierre basin. The State of Louisiana carried out some channel
improvements on the alluvial plain of Bayou Pierre in the early 1960s (Reference
19). The densely populated upstream portions of the basin are where the channels
are mostly improved.
McCain Creek has been enlarged from its mouth to Pine Hill Road by the
Louisiana Department of Public Words in cooperation with the Cad Levee District.
The work, completed in 1958, lowered headwater flood stages
The Wallace Lake dam on Cypress Bayou was completed in December 1946 by
USACE. The dam protects 90,000 acres of rich farmland and relieves the
backwater flooding on Bayou Pierre above the confluence of Cypress Bayou by
detaining flows from Cypress Bayou (Reference 20).
There are no known flood-protection measures in the Towns of Blanchard,
Mooringsport, Oil City, and Vivian; and, the Villages of Ida and Rodessa.
3.0
ENGINEERING METHODS
For the flooding sources studied in detail in the parish, standard hydrologic and hydraulic
study methods were used to determine the flood hazard data required for this FIS. Flood
events of a magnitude which are expected to be equaled or exceeded once on the average
during any 10-, 50-, 100-, or 500-year period (recurrence interval) have been selected as
having special significance for floodplain management and for flood insurance rates.
These events, commonly termed the 10-, 50-, 100-, and 500-year floods, have a 10-, 2-,
1-, and 0.2-percent chance, respectively, of being equaled or exceeded during any year.
Although the recurrence interval represents the long term average period between floods
of a specific magnitude, rare floods could occur at short intervals or even within the same
year. The risk of experiencing a rare flood increases when periods greater than 1 year are
considered. For example, the risk of having a flood which equals or exceeds the 100-year
flood (1-percent chance of annual exceedence) in any 50-year period is approximately 40
percent (4 in 10), and, for any 90-year period, the risk increases to approximately 60
percent (6 in 10). The analyses reported herein reflect flooding potentials based on
conditions existing in the parish at the time of completion of this FIS. Maps and flood
elevations will be amended periodically to reflect future changes.
17
3.1
Hydrologic Analyses
Hydrologic analyses were carried out to establish the peak discharge-frequency
relationships for the flooding sources studied in detail affecting the parish.
Pre-parishwide Analyses
The discharge-frequency analysis for Cross Bayou from the Red River to Twelve
Mile Bayou and for Twelve Mile Bayou, both in the City of Shreveport, was based
on USGS gage data. A gage station on Twelve Mile Bayou at Dixie, Louisiana
(Reference 6), is located 17.3 miles upstream of the mouth of the bayou.
Discharge-frequency data for this station were used to develop the peak discharges
of these streams. These discharges were then translated to other locations by
taking the square root of the relative drainage areas. For the rest of the streams
studied by detailed methods in the City of Shreveport, the HEC-1 computer
program (Reference 21) was used to model rainfall-runoff relationships.
The development of hydrologic procedures for analyzing flood conditions is a vital
concern. A comparison was made of computed discharge by various methods
including: the National Resources Conservation Service (NRCS) (formerly the Soil
Conservation Service) peak discharge method, USGS regression equation, NRCS
unit hydrograph, Clark unit hydrograph, and Texas Water Board unit hydrograph.
Loss rate methods were compared as well as using the NRCS, Holton, and initial
uniform loss methods. The selected procedures for unit hydrograph and loss rates
were Clark unit hydrograph with Holton loss rates.
For calculating Clark unit-hydrograph parameters, an equation developed by Espey
Huston was used to determine values Tc and R (Reference 22). Loss-rate
parameters were selected based on the soil types and land use of each subbasin.
The modified-Puls routing method was used in this analysis. Volume discharge
relationships were computed using the USACE HEC-2 computer program
(Reference 23); NOAA Technical Memorandum NWS Hydro-35, “Five- to 60Minute Precipitation Frequency for the Eastern and Central United States”
(Reference 24); and U.S. Weather Bureau Technical Paper Nos. 40, “Rainfall
Frequency Atlas of the United States,” and 49, “Two- to 10-Day Precipitation for
Return Periods of 2 to 100 Years in the Contiguous United States” (References 25
and 26), were used for rainfall data. Hypothetical storm patterns are based on
triangular distribution using PH Input Cards (Reference 21). High-water elevations
and observed rainfall data, obtained from the Weather Service Office, Shreveport,
Louisiana, for the June 27, 1986, and April 12, 1991, storms were used to check
the reliability of hydrologic and hydraulic models.
For the City of Shreveport FIS dated June 5, 1997, the study was revised to
incorporate the results of a restudy of Bayou Pierre and tributaries of Bayou
Pierre, Sand Beach Bayou, Pierremont Ditch, South Broadmoor Lateral, and the
Old River and to incorporate the results of an appeal resolution dated October 17,
1996. The Flood Insurance Rate Map was also revised to incorporate a Letter of
Map Revision (LOMR) dated May 10, 1989.
18
Bayou Pierre was revised from the downstream corporate limits to approximately
104,000 feet above the De Soto Parish boundary. The elevations of a flood having
a 1-percent change of being equaled or exceeded in any given year (base flood)
along Bayou Pierre increased through the revised reach. The maximum base flood
elevation (BFE) increase, approximately 1.5 feet, occurred at the downstream
corporate limits. The width of the SFHA, the area inundated by the base flood,
also increased along Bayou Pierre. The maximum increase in SFHA width,
approximately 150 feet, occurred just downstream of Flournoy Lucas Road. The
entire length of Sand Beach Bayou was revised. The BFEs along Sand Beach
Bayou decreased by a maximum of approximately 0.5 foot at the downstream
corporate limits. The entire length of Pierremont Ditch was revised with the
appeal resolution to include a channelization project completed in 1996. The
entire length of South Broadmoor Lateral was revised. The BFEs decreased
approximately 0.5 foot along the entire length. The entire length of the Old River
was revised. The BFEs along Ockley Ditch also increased downstream of Gilbert
Street due to backwater elevations from Bayou Pierre. The maximum increase,
approximately 0.2 foot, occurred at the confluence with Bayou Pierre.
For the streams in the Town of Greenwood (Cross and Gilmer Bayou Tributaries
1, 2, and 3), no streamflow information as available; therefore, peak-discharge
estimates are based on the study entitled “Magnitude and Frequency of Floods for
Small Watersheds in Louisiana,” completed by the USGS, in cooperation with the
Louisiana Department of Transportation and Development (Reference 27). In that
study, physical and climatic characteristics of small streams in Louisiana were
regressed against the flood estimates for the 50%-, 20%-, 10%-, 4%-, 2%-, and
1%-annual chance recurrence intervals using non-linear multiple regression
techniques. These equations were used to estimate the magnitude of peak
discharges at ungaged sites such as those within the Town of Greenwood. Basin
slopes used in the computation of design and discharge along a tributary were
based on the general basin slope of that tributary.
For the unincorporated areas of Caddo Parish, the hydrologic analyses for Gilmer
Bayou, Southwood High Lateral, Industrial Park Lateral, Lincoln Memorial
Lateral, Galaxy Lateral, Bickham Bayou, Old River, McCain Creek, Bayou Pierre,
South Broadmoor Lateral, Summer Grove Ditch, and portions of Sand Beach
Bayou and Brush Bayou were taken from the November 1, 1985, Flood Insurance
Study for the City of Shreveport (Reference 18).
The computed flows for Gilmer Bayou were generally higher than those in the
studies mentioned previously; this discrepancy is understandable given the recent
channelization on the streambed. The flows appear to be reasonable, and models
on Boggy Bayou were successfully calibrated using these flows.
For the rest of the streams studied by detailed methods in Caddo Parish, the
methods of analysis varied from stream to stream to correlate the procedures of
this study as closely as possible with the procedures used on these streams in
previous studies. Discharges were developed synthetically because there were only
19
a few gage stations within the study area. Snyder’s unit graph coefficients were
developed for each of the stream drainage basins.
Rainfall data for the 1-percent-annual-chance flood frequency were determined
from the U.S. Weather Bureau Technical Paper Nos. 40 and 49 (References 25
and 26). The 12-hour rainfall amounts were distributed into 0.5-hour increments
and arranged in a sequence considered to be critical for runoff. Observed rainfall
from the June 27, 1986, storm was used to help calibrate the hydrologic and
hydraulic models.
Flood frequency-discharge values for the streams studied by detailed methods,
except for Bayou Pierre and Sand Beach Bayou, were determined using the
USACE HEC-1 computer program (Reference 28). Hydrographs for the 1percent-annual-chance flood frequency and the June 27, 1986, storm were
developed by applying tabulated rainfall data to the unit hydrographs computed
using HEC-1. Initial losses and infiltration loss rates were adjusted in relationship
to the average imperviousness of each subbasin. The prevalent value for initial loss
was 0.5 inch, and the infiltration loss rate was 0.05 inch per hour. Runoff was
routed through the basins using the modified-Puls method.
To check for reliability, the discharge-frequency data were compared to peak
discharge flows computed in USACE Flood Plain Information Studies, the Flood
Insurance Study for the City of Shreveport, and a USGS Regional Flow-Frequency
Analysis for Louisiana (References 2, 3, 4, 19, 18, and 6, respectively). In this
comparison, flows developed for each stream were compared and each generally
coincided, with the exception of Bayou Pierre, Sand Beach Bayou, and Gilmer
Bayou.
The computed flows for Bayou Pierre and Sand Beach Bayou were significantly
lower than those in the Bayou Pierre Special Flood Hazard Information Report
(Reference 19). Attempts to calibrate models using flows computed by HEC-1
were unsuccessful; therefore, a drainage area-versus-discharge curve was
developed for establishing the 1-percent annual chance flood for Bayou Pierre and
Sand Beach Bayou.
Analyses of peak elevations on Caddo Lake were based on records of the lake
gages at Mooringsport (40 years) and on the Twelve Mile Bayou gage near Dixie
(36 years) (Reference 29).
Due to its proximity to the Town of Mooringsport, lake levels at the Towns of Oil
City and Mooringsport were assumed to be the same.
The data at Mooringsport gage site list selected observed discharges and the
corresponding stage discharges and readings. However, no analysis has been done
to establish any discharge- or stage-frequency relationship.
For the data at the gage site on Twelve Mile Bayou, the USGS performed a Log
Person Type-II analysis to determine a discharge-frequency relationship at this site
(Reference 30).
20
To relate this data to the Mooringsport stage and discharge readings, the 5%-,
2%-and 1%-annual-chance flood discharges at the Twelve Mile Bayou gage were
converted to equivalent discharges at Mooringsport. This conversion procedure is
shown below:
Drainage Area at Mooringsport gage:
Drainage Area at Twelve Mile Bayou gage:
2,708 square miles
3,194 square miles
Actual Discharge at Twelve Mile
Bayou gage (May 5, 1958):
138,400 cubic feet
per second (CFS)
The converted equivalent discharge at Mooringsport will be:
2,708/3,1941.0 x 38,400 =
32,557 cfs
As compared with:
Actual Discharge at Mooringsport gage (May 5, 1958):
32,766 cfs
This resultant discharge-frequency relationship was correlated with the
Mooringsport discharge and stage data to determine corresponding stage at
specific recurrence intervals.
Flood elevations inundated by Caddo Lake are based on the stillwater elevation of
the lake.
The storm-surge elevations for the 10%-, 2%-, 1%-, and 0.2%-annual-chance
floods have been determined for Caddo Lake. The analyses reported herein reflect
the stillwater elevations and do not include the contributions from wave-action
effects such as wave-crest height and wave run-up. Nonetheless, the additional
hazard due to wave-action effect should be considered in the planning of future
development.
A HEC-1 computer model was developed for Cross Lake. The procedure included
inflow hydrographs from each of the four major tributary basins plus direct rainfall.
Storage data were obtained from the USACE study for the Louisiana Dam Safety
Program. Outflow from spillway was calculated based on normal operating
procedure for the control gates.
To determine the 1%-annual chance flood elevation for Wallace Lake, a stagefrequency curve, based on a period of record from 1927 to 1973, was applied from
Wallace Lake Dam upstream of the points at which headwater effects office from
Boggy, Cypress, Brush, and Buchanan Bayous.
For the unincorporated areas of Caddo Parish FIS dated May 19, 1997, the Bayou
Pierre channel storage volumes (modified-Puls) in the HEC-1 program were
recalculated based on the new starting water-surface elevations (WSELs) at
Highway 175 to produce discharges used in the HEC-2 program. The discharge
21
Highway 175 to produce discharges used in the HEC-2 program. The discharge
for a flood having a 1-percent chance of being equaled exceeded in any given year
(base flood) is 14,283 cfs at Highway 175.
April 6, 2000, Parishwide Analyses
This study was revised to convert the FIRMs and Flood Insurance Study reports
for Caddo Parish and Incorporated Areas into the parishwide format. In addition,
the mapping for the new parishwide FIRM was converted into digital format.
The mapping for Caddo Parish and Incorporated Areas has been prepared using
digital data. The mapping for Caddo Parish and Incorporated Areas has been
prepared using digital data. Previously published FIRM data produced manually
have been converted to vector digital data by a digitizing process. The Northwest
Louisiana Council of Governments has provided road and highway name and
centerline data. The centerline data were computer plotted with the digitized
floodplain data to produce the parishwide FIRM.
Some minor floodplain differences will exist between this digital FIRM and the
previous manual FIRMs due to the differences between the digital road base and
the vector road network shown on the previous maps. These road base differences
exist for a variety of reason, including but not limited to:
•
•
•
•
•
•
Better accuracy in the digital road base
Change in the road width representation
More roads shown on the digital Flood Insurance Rate Map
Change in the map scale
Addition of previously issued LOMRs
Correction of previous mapping errors
As part of this digital conversion, other deliberate changes to the floodplain
representation have been made. The panel layout of the digital FIRM has been
revised based on the layout of the USGS quadrangle maps of the Parish area.
Individual map panel scales were determined so that the flood data represented
were at similar scale to that shown on the previous FIRM. As a result of this
revised layout, panel edges will exist where none existed before and others will be
removed. BFEs represented on the FIRM have been adjusted at some of these new
and old panel edge locations to more clearly represent the actual BFEs for those
particular Special Flood Hazard Areas (SFHAs).
May 17, 2004, Parishwide Analyses
This study was revised to incorporate the results of the analysis of Caddo Lake
within the unincorporated areas of Caddo Parish and the Towns of Mooringsport
and Oil City. This detailed analysis was prepared by Owen and White, Inc., in
June 2000, using a stage-frequency computation for a gauging station located at
the Caddo Lake Dam. In 1959, the Lake O’ the Pines reservoir upstream of Caddo
Lake was placed in operation, which had a significant effect on the WSELs of
Caddo Lake. A stage-frequency analysis, using the USACE Flood Frequency
22
Analysis computer program, HEC-FFA, Version 3.1 (Reference 31), was
performed for the 39 years of annual maximum flood stage values recorded for
Caddo Lake since the opening of Lake O’ the Pines in 1959. The Base Flood
Elevation and the 1-percent-annual-chance floodplain boundary delineation for
Caddo Lake were revised from the Caddo Lake Dam to the State boundary
between Louisiana and Texas.
The frequency-elevation relationships for Caddo Lake are presented in Table 5,
“Summary of Elevations.”
This study was also revised to reflect new, detailed hydrographic and hydraulic
analyses alone a portion of Cypress Bayou from Wallace Lake to just upstream of
U.S. Highway 171, and to reflect an updated analysis of stage-frequency data for
Wallace Lake.
Discharges for Cypress Bayou area based on gauging station at U.S. Highway 171.
This station has a record of 59 years from 1939 to 1997. Peak annual discharges
are available for this entire portion of record. A log-Pearson Type III analysis was
performed on this gauge data using the HEC-FFA computer program (Reference
17). For downstream locations, discharges were computed by comparing the
gauge discharges with discharges computed by the methods described in Floods in
Louisiana, Magnitude and Frequency, Fifth Edition (Reference 32).
The Wallace lake reservoir was completed in 1946, and stage records are available
since then. A stage-frequency analysis was performed to determine the 10-, 2- 1-,
and 0.2-percent-annual-chance WSELs. Stages were plotted according to Weibull
plotting positions, and a stage-frequency curve was estimated. The frequencyelevation relationships for Wallace Lake are presented in Table 5, “Summary of
Elevations.” These resulting WSELs were further verified by a HEC-FFA analysis
performed on discharges that were determined from a rating curve provided by the
USACE, Vicksburg District.
Parishwide Revision
There are no new hydrologic analyses for the streams studied by detailed methods.
For streams studied by approximate methods, the discharges were computed for all
ungaged streams, using the USGS Regression Equations for Louisiana (Reference
33). Peak flood discharges were calculated for the 1-percent annual chance storm
event.
Based on physiography, elevation, and precipitation, Louisiana is divided into two
hydrologic regions. The west part of Caddo Parish falls within the Pine Hills
region, and the eastern part of the Parish falls within the Non-Pine Hills region.
The majority of the Parish is rural, and hence an assumption was made that all the
basins will be considered entirely rural.
There are some USGS stream gages with significant length of record in the study
area. The streams with sufficient records include Cypress Bayou, Red River,
23
Twelvemile Bayou, Kelly Bayou, Black Bayou, and Paw Paw Bayou. For these
streams, it was decided to compute the discharges using flood frequency analysis
as outlined in Technical Bulletin 17B (Reference 34). The PeakFQ (PKFQWIN)
Program, Version 5.2, was used for computation of the 1-percent annual chance
storm event discharge values.
Peak discharge-drainage area relationships for the streams studied by detailed
methods are shown in Table 4, “Summary of Discharges.”
TABLE 4 - SUMMARY OF DISCHARGES - continued
FLOODING SOURCE
AND LOCATION
75TH STREET DRAINIAGE
DITCH
At mouth
At West 68th Street
DRAINAGE
AREA
(sq. miles)
10-PERCENT
ANNUAL
CHANCE
PEAK DISCHARGES cfs)
2-PERCENT
1-PERCENT
ANNUAL
ANNUAL
CHANCE
CHANCE
0.2-PERCENT
ANNUAL
CHANCE
1.4
*
1,484
750
1,797
970
1,963
1,067
2,231
1,221
0.8
0.6
1,178
862
1,346
1,047
1,425
1,134
1,555
1,279
10.0
5,731
7,376
8,235
9,382
4.4
1.0
2,707
784
2,557
1,036
2,788
1,164
3,063
1,321
AUDREY LANE
LATERAL
At mouth
At Doll Street Extended
0.8
0.3
420
160
575
216
653
245
757
282
AVERY DITCH
At mouth
0.03
73
93
101
116
41.0
*
*
14,283
*
27.8
14.4
9.9
*
6,662
6,697
*
7,636
7,265
12,493
8,058
7,508
*
8,526
7,717
81ST STREET DRAINAGE
DITCH
At mouth
At Linwood Avenue
AIRPORT DITCH
At mouth
Upstream of Hollywood
Lateral
At Meriwether Road
BAYOU PIERRE
At State Route 175
Just downstream of
confluence of Sand Beach
Bayou
At Flournoy Lucas Road
At East 70th Street
*Data not available
24
TABLE 4 - SUMMARY OF DISCHARGES - continued
FLOODING SOURCE
AND LOCATION
BAYOU PIERRE
(continued)
At Pierremont Road
Upstream of Ockley Ditch
At Kings Highway
DRAINAGE
AREA
(sq. miles)
10-PERCENT
ANNUAL
CHANCE
PEAK DISCHARGES cfs)
2-PERCENT
1-PERCENT
ANNUAL
ANNUAL
CHANCE
CHANCE
0.2-PERCENT
ANNUAL
CHANCE
8.1
1.9
1.0
6,827
2,179
1,449
7,504
2,620
1,683
7,735
2,823
1,773
7,999
3,108
1,932
BETTEY VIRGINIA
LATERAL
At mouth
Upstream of Avery Ditch
0.4
0.02
1,093
143
1,373
184
1,492
202
1,693
231
BICKHAM BAYOU
At mouth
At Jefferson Paige Road
At Pines Road
5.3
2.9
0.8
3,850
2,530
794
5,222
3,471
1,041
5,863
3,858
1,160
6,724
4,224
1,326
148.0
79.0
49.1
41.3
11.8
*
11,244
6,678
*
*
*
16,099
9,538
*
*
24,800
19,018
11,078
11,100
9,600
*
22,916
13,241
*
*
BOGGY BAYOU
TRIBUTARY A
At confluence with Boggy
Bayou
At Buncombe Road
4.1
3.1
*
*
*
*
3,900
3,600
*
*
BOGGY BAYOU
TRIBUTARY B
At Confluence with Boggy
Bayou
At State Route 169
8.6
3.3
*
*
*
*
4,160
3,660
*
*
BROADMOOR LATERAL
*
*
*
1,533
*
BROOKWOOD DITCH
At Mouth
1.5
1,931
2,499
2,746
3,116
BOGGY BAYOU
At confluence with Cypress
Bayou
At State Route 171
Upstream of Gilmer Bayou
At Woolworth Road
At State Route 169
*Data not available
25
TABLE 4 - SUMMARY OF DISCHARGES - continued
FLOODING SOURCE
AND LOCATION
BRUSH BAYOU
At confluence with Boggy
Bayou
At Flournoy Lucas Road
At Texas and Pacific
Railroad
Upstream of Airport Ditch
At Hollywood Avenue
DRAINAGE
AREA
(sq. miles)
10-PERCENT
ANNUAL
CHANCE
PEAK DISCHARGES cfs)
2-PERCENT
1-PERCENT
ANNUAL
ANNUAL
CHANCE
CHANCE
0.2-PERCENT
ANNUAL
CHANCE
25.4
25.3
*
18,134
*
22,631
12,740
24,952
*
26,389
17.4
5.0
1.3
13,050
5,167
1,005
16,141
6,405
1,185
17,650
7,029
1,271
19,291
7,766
1,385
18.0
16.6
*
*
*
*
6,150
6,000
*
*
9.0
*
*
4,500
*
3.5
*
*
2,150
*
BUCHANAN BAYOU
TRIBUTARY A
At confluence with
Buchanan Bayou
At State Route 525
3.5
1.2
*
*
*
*
2,153
827
*
*
CARGILL LATERAL
At mouth
0.4
401
532
854
661
CHOCTAW BAYOU
At confluence with Logan
Bayou
At Blanchard Furr Road
At Blanchard Latex Road
14.9
8.3
3.7
*
*
*
*
*
*
7,200
5,590
3,317
*
*
*
COOPER ROAD DITCH
At mouth
Upstream of Green Oaks
2.5
1.5
1,460
809
1,944
1,102
2,177
1,248
2,488
1,437
BUCHANAN BAYOU
At confluence with Boggy
Bayou
At State Route 171
At Keithville Springridge
Road
Downstream of State Route
525
*Data not available
26
TABLE 4 - SUMMARY OF DISCHARGES - continued
FLOODING SOURCE
AND LOCATION
DRAINAGE
AREA
(sq. miles)
10-PERCENT
ANNUAL
CHANCE
PEAK DISCHARGES cfs)
2-PERCENT
1-PERCENT
ANNUAL
ANNUAL
CHANCE
CHANCE
0.2-PERCENT
ANNUAL
CHANCE
COUNTY CLUB
LATERAL
At mouth
At Jewella Avenue
2.1
1.1
2,881
2,000
3,728
2,583
4,118
2,829
4,761
3,266
COURTESY LANE
CHANNEL
At mouth
At Union Avenue
1.1
0.5
1,466
826
1,813
1,066
1,984
1,168
2,248
1,338
26,600
6,149
40,800
1,066
47,100
1,168
71,000
1,338
*
*
2,303
*
1,950
2,456
2,665
2,945
CROSS BAYOU
At mouth
At outflow from Cross Lake
At Town of Greenwood
corporate limits
3,517
253
9.71
CROSS BAYOU
LATERAL
At mouth
1.3
CROSS BAYOU
TRIBUTARY 1
At confluence with Cross
Bayou Tributary 2
At State Highway 169
At Union Pacific Railroad
At Interstate 20
At U.S. Highway 80
6.59
6.50
6.24
5.30
5.20
*
*
*
*
*
*
*
*
*
*
1,736
1,723
1,687
1,544
1,528
*
*
*
*
*
CROSS BAYOU
TRIBUTARY 2
At confluence with Cross
Bayou Tributary 1
At Speedway drive
At Union Pacific Railroad
At Interstate 20
At U.S. Highway 80/79
3.02
3.00
2.87
2.20
1.97
*
*
*
*
*
*
*
*
*
*
1,219
1,214
1,183
1,010
942
*
*
*
*
*
*Data not available
27
TABLE 4 - SUMMARY OF DISCHARGES - continued
FLOODING SOURCE
AND LOCATION
CROSS BAYOU
TRIBUTARY 3
At Interstate 20
At Greenwood Heights
At U.S. Highway 80
CROSS LAKE
At spillway
CYPRESS BAYOU
At Linwood Avenue
At U.S. Highway 171
DRAINAGE
AREA
(sq. miles)
0.546
0.298
0.117
10-PERCENT
ANNUAL
CHANCE
PEAK DISCHARGES cfs)
2-PERCENT
1-PERCENT
ANNUAL
ANNUAL
CHANCE
CHANCE
0.2-PERCENT
ANNUAL
CHANCE
*
*
*
*
*
*
369
235
110
*
*
*
253.1
18,987
30,215
34,670
42,387
84
66
23,171
12,900
33,676
22,100
38,959
26,600
53,000
38,500
FORD PARK LATERAL
At mouth
0.4
515
677
749
857
GALAXY LATERAL
At mouth
At Jefferson Paige Road
3.0
1.3
1,450
688
2,191
930
2,495
1,044
2,904
1,191
GILBERT DITCH
At mouth
At Linden Street
1.3
*
1,795
2,310
2,178
2,971
2,350
3,225
2,638
3,698
28.1
6,202
9,033
10,733
13,224
5.0
3,471
4,639
5,219
5,894
*
631
*
843
1,343
951
*
1,081
*
*
*
*
823
451
*
*
GILMER BAYOU
At mouth
At Bert Kouns Industrial
Loop
At Town of Greenwood
corporate limits
At Buncombe Road
GILMER BAYOU
TRIBUTARY 1
Approximately 3,000 feet
upstream of corporate
limits
At Kimberly Road
2.92
0.9
1.32
0.548
*Data not available
28
TABLE 4 - SUMMARY OF DISCHARGES - continued
PEAK DISCHARGES cfs)
2-PERCENT
1-PERCENT
ANNUAL
ANNUAL
CHANCE
CHANCE
FLOODING SOURCE
AND LOCATION
DRAINAGE
AREA
(sq. miles)
GILMER BAYOU
TRIBUTARY 2
At Waterwood Drive
At Bea Lane
At Golden Meadow Road
At Beebe Drive
At Kimberly Road
1.60
1.35
0.589
0.390
0.262
*
*
*
*
*
*
*
*
*
*
949
851
490
388
264
*
*
*
*
*
GILMER BAYOU
TRIBUTARY 3
At Golden Meadow Road
At Winburn Drive
0.441
0.395
*
*
*
*
393
362
*
*
GREEN OAKS LATERAL
At mouth
0.3
391
505
563
650
GREEN TERACE
LATERAL
At mouth
1.0
717
929
1,045
1,188
HOLLYWOOD DITCH
At mouth
At Hayward Court
Upstream of Hollywood
3.6
1.0
1.4
3,310
988
1,291
4,191
1,289
1,695
4,608
1,440
1,858
5,148
1,639
2,069
19.8
5,437
7,638
9,030
10,716
7.2
2,004
2,794
3,195
3,726
JENKINS ACRES
LATERAL
At mouth
0.6
370
503
602
727
LAMBERT PARK
LATERAL
At mouth
At Francais Drive
0.5
0.1
979
304
1,263
392
1,377
425
1,547
488
INDUSTRIAL PARK
LATERAL
At mouth
At Bert Kouns Industrial
Loop
10-PERCENT
ANNUAL
CHANCE
*Data not available
29
0.2-PERCENT
ANNUAL
CHANCE
TABLE 4 - SUMMARY OF DISCHARGES - continued
FLOODING SOURCE
AND LOCATION
LINCOLN MEMORIAL
LATERAL
At mouth
At Flournoy Lucas Road
DRAINAGE
AREA
(sq. miles)
10-PERCENT
ANNUAL
CHANCE
PEAK DISCHARGES cfs)
2-PERCENT
1-PERCENT
ANNUAL
ANNUAL
CHANCE
CHANCE
0.2-PERCENT
ANNUAL
CHANCE
5.4
1.5
1,921
1,717
2,814
2,352
3,333
2,677
3,974
3,068
3.7
*
*
8,170
*
3.4
1.2
*
*
*
*
2,680
2,460
*
*
0.8
0.3
678
276
854
364
933
408
1,040
467
25.9
16
5.8
4,367
2,579
*
6,033
3,641
*
6,690
4,181
4,500
7,537
4,979
*
MURRY LATERAL
At mouth
At Interstate 20
0.6
0.1
1,013
192
1,234
217
1,333
225
1,466
240
OCKLEY DITCH
At mouth
Upstream of Gilbert Ditch
At Woodrow Street
4.9
*
*
5,335
4,009
2,054
6,288
4,556
2,054
6,726
4,776
2,668
7,335
5,136
2,969
OLD RIVER
At mouth
At Chelsea Street
3.4
1.0
803
391
1,150
525
1,328
597
1,516
690
10.0
8.1
*
*
*
*
6,100
4,700
*
*
LOGAN BAYOU
At confluence with Cross
Lake
At confluence of Choctaw
Bayou
At Roy Road
LYNBROOK LATERAL
At mouth
At St. Vincent Avenue
McCAIN CREEK
At mouth
At Pine Hills Road
At State Route 173
PAGE BAYOU
At confluence with Cross
Lake
At Jefferson Paige Road
*Data not available
30
TABLE 4 - SUMMARY OF DISCHARGES - continued
FLOODING SOURCE
AND LOCATION
DRAINAGE
AREA
(sq. miles)
10-PERCENT
ANNUAL
CHANCE
PEAK DISCHARGES cfs)
2-PERCENT
1-PERCENT
ANNUAL
ANNUAL
CHANCE
CHANCE
0.2-PERCENT
ANNUAL
CHANCE
PAGE BAYOU
TRIBUTARY A
At confluence with Page
Bayou
At spillway
4.1
0.7
*
*
*
*
4,359
3,760
*
*
PIERREMONT DITCH
At mouth
At Gilbert Drive
1.6
0.7
2,081
1,549
2,831
2,163
3,220
2,329
3,776
2,815
RANCHMOOR LATERAL
At mouth
1.7
967
1,338
1,516
1,730
125,000
165,000
205,000
227,2001
0.3
611
817
888
998
12.3
7.4
4.9
1.4
*
2,402
1,998
1,126
*
4,051
3,473
2,168
5,062
4,640
4,226
2,514
*
5,673
5,021
2,965
RED RIVER
Downstream of Cross Bayou
ROSE PARK LATERAL
At mouth
SAND BEACH BAYOU
Just upstream of confluence
with Bayou Pierre
At Flournoy Lucas Road
Downstream of Old River
At East 70th Street
60,613
SAVANA LATERAL
At mouth
At Summer Grove Drive
At Bert Kouns Industrial
Loop
0.7
0.5
1,055
812
1,292
978
1,384
1,048
1,532
1,147
0.4
573
687
742
793
SHIRLEY-FRANCIS
LATERAL
At Woolworth Road
0.9
686
947
1,081
1,243
*Data not available
1
Standard Project Flood used in place of 0.2% annual chance flood. Red River not restudied from 1980 Flood
Insurance Study
31
TABLE 4 - SUMMARY OF DISCHARGES - continued
FLOODING SOURCE
AND LOCATION
DRAINAGE
AREA
(sq. miles)
10-PERCENT
ANNUAL
CHANCE
PEAK DISCHARGES cfs)
2-PERCENT
1-PERCENT
ANNUAL
ANNUAL
CHANCE
CHANCE
0.2-PERCENT
ANNUAL
CHANCE
SOUTH BROADMOOR
LATERAL
At mouth
1.5
361
495
567
658
SOUTHWOOD HIGH
LATTERAL
At mouth
1.7
1,082
1,443
1,638
1,861
ST. VINCENT ACADEMY
DITCH
At mouth
At St. Vincent Avenue
0.8
0.7
1,311
1,344
1,674
1,733
1,861
1,889
2,144
2,166
2.5
3,764
4,904
5,387
6,124
0.8
0.5
1,256
736
1,596
930
1,748
1,020
1,991
1,166
0.3
414
535
588
673
0.4
614
747
813
930
25,600
39,200
45,400
68,300
1,287
1,339
1,605
1,732
1,811
1,910
2,011
2,184
SUMMER GROVE DITCH
At Williamson Way
At Southern Pacific
Railroad
At Mansfield Road
At Bert Kouns Industrial
Loop
SYCAMORE LATERAL
At mouth
TWELVE MILE BAYOU
At mouth
WERNER PARK
LATERAL
At mouth
At Corbett Street
3,259
1.3
0.3
*Data not available
32
The frequency-elevation data relationships for Caddo, Wallace, and Cross Lakes
are presented in Table 5, “Summary of Elevations.”
TABLE 5 - SUMMARY OF ELEVATIONS
FLOODING SOURCE
AND LOCATION
10-PERCENT
ANNUAL
CHANCE
ELEVATION (feet NAVD)
2-PERCENT
1-PERCENT
ANNUAL
ANNUAL
CHANCE
CHANCE
0.2-PERCENT
ANNUAL
CHANCE
CADDO LAKE
At Caddo Lake Dam
175.1
179.1
180.6
183.6
CROSS LAKE
At the City of
Shreveport corporate
limits
173.8
176.2
176.9
178.3
WALLACE LAKE
At Wallace Lake Dam
153.9
158.9
159.6
160.2
3.2
Hydraulic Analyses
Analyses of the hydraulic characteristics of flooding from the source studied were
carried out to provide estimates of the elevations of floods of the selected recurrence
intervals. Users should be aware that flood elevations shown on the FIRM represent
rounded whole-foot elevations and may not exactly reflect the elevations shown on the
Flood Profiles or in the Floodway Data tables in the FIS report. For construction
and/or floodplain management purposes, users are encouraged to use the flood
elevation data presented in this FIS in conjunction with the data shown on the FIRM.
Pre-parishwide Analyses
Information on the hydraulic analyses for each of the previously printed FIS reports for
communities within Bossier Parish was compiled, and is presented below.
For the City of Shreveport, cross-section data for channels and bridges were taken
from field surveys. Elevation data for overbank areas were obtained from 2-foot
contour maps (Reference 35).
For the unincorporated areas of Caddo Parish, cross-section date for channels, bridges,
and overbank areas were taken from field surveys, USGS quadrangle maps, and Caddo
Parish drainage study amps with 2-foot contour intervals (Reference 36). Along certain
portions of the stream studied by detailed methods, a profile baseline is shown on the
maps to represent distances as indicated on the flood profiles and floodway data table.
For the Town of Greenwood, cross section data used in the hydraulic analyses were
obtained from field surveys conducted on July 9-11 and July 22-24, 1996 and available
topographic maps (Reference 37). Elevations and structural-geometry data were
33
obtained for bridges, culverts, and roadways so that their effects on the 1%-annual
chance flood profile could be assessed.
Starting water-surface elevations for each stream were determined by various methods.
For Cross Bayou, the average annual stage on the Red River was used. Cross Bayou
Lateral used the computed state on Cross Bayou based on average annual flows. Cross
Lake was based on average lake stages from January to April. For streams flowing into
Cross Lake, the normal pool elevation was used. Green Terrace Lateral, Brookwood
Lateral, Ranchmoor Lateral, 75th Street Drainage Ditch, and 81st Street Drainage Ditch
used the calculated water-surface elevations on the receiving stream at the time of peak
flow on the tributary.
Starting water-surface elevations for Bayou Pierre; Boggy Bayou; Cross Bayou
Tributaries 1, 2, and 3; and Gilmer Bayou Tributaries 1, 2, and 3 were determined by
the slope-area method.
The starting water-surface elevations for all other streams were determined by
coincident stages on receiving streams.
Water-surface elevations of floods of the selected recurrence interval for the streams
studied by detailed methods were computed using the USACE HEC-2 computer
program (Reference 38). Flood profiles were drawn showing computed water-surface
profiles for floods of the selected recurrence interval. Stage-storage relationships were
developed for each stream by initially running an arbitrary range of discharged through
the defined project area. These were run through the HEC-1 model to route the
hydrographs through the study area using the modified-Puls method. High-water marks
from the June 27, 1986, storm were used to verify the HEC-2 models because it was a
large storm that set record stage levels in the study area.
Water-surface elevations of floods of the selected recurrence intervals for Cross Bayou
Tributaries 1, 2, and 3 and Gilmer Bayou Tributaries 1, 2, and 3 were computed using
the USGS WSPRO computer program (Reference 46). The 1%-annual-chance flood
discharges for these tributaries to Cross and Gilmer Bayous were decreased within the
hydraulic model in an upstream direction based on the decreasing drainage area.
Elevations on cross and Gilmer Bayous and associated tributaries were based on
detailed analyses, filed investigations, and available topography. In the Town of
Greenwood, steep topographic relief resulted in normal headwater elevations along
most of the tributaries and localized backwater near the various hydraulic structures.
The computed profiles, with the exception of Boggy Bayou, compared well to studies
previously performed in the area. In the portion of Boggy Bayou from Gilmer Bayou
to U.S. Route 171, the profile varied from previous analyses by 2 to 3 feet because of
extensive channelization that has been carried out since the previous studies were
prepared. One other discrepancy, of less than 0.5 foot, appeared at the new culvert at
the Pine Hill Road crossing over McCain Creek. The downstream portion of the
profile for Gilmer Bayou was adjusted to eliminate any discrepancy with the profile for
Boggy Bayou at the point of confluence.
34
An extensive AH Zone is presented for the Broadmoor area in the City of Shreveport.
Flood waters overflow the Bayou Pierre ridgeline and enter the low-lying Broadmoor
area. Outflow characteristics from Bayou Pierre were determined through the splitflow option of the HEC-2 computer program. Backwater calculations were performed
upstream from Sand Beach Bayou using overbank conveyance.
The resulting water-surface elevations for the revised study for the City of Shreveport
differ throughout the system from those presented in the original study. It is the intent
of the revised study to use the improved topographic maps and advanced hydrographic
procedures to provide a more cohesive and representative projection of flood
conditions
For the unincorporated areas of Caddo Parish FIS dated May 19, 1997, starting
WSELs for each stream were determined by various methods. Cross Lake was
based on average lake stages from January to April. For streams flowing into
Cross Lake, the normal pool elevation was used. The starting conditions for
Bayou Pierre were changed from the slope-area method to a known starting
WSEL, 144.1 feet NAVD 88, based on a USACE gauged-data analysis. The new
starting WSEL resulted in a maximum decrease in BFE of 8.9 feet at State Route
175. The starting conditions for Boggy and Sand Beach Bayous, the Old River,
and South Broadmoor Lateral were determined using the slope-area method. The
starting WSELs for all other streams were determined by coincident stages on
receiving streams.
The resulting WSELs for the revised study differ throughout the system from those
presented in the original study. It is the intent of the revised study to utilize the
improved topographic maps and advanced hydrologic procedures to provide a
more cohesive and representative projection of flood conditions.
May 17, 2004, Parishwide Analyses
For the May 17, 2004, FIS report, the hydraulic analysis for Cypress Bayou was
performed with the USACE HEC-RAS computer program (Reference 38).
The starting WSEL of Cypress Bayou for all floods was the flood stage elevation
on Wallace Lake. The USACE, Vicksburg District, provided surveyed cross
sections within Wallace Lake and upstream on Cypress Bayou through Linwood
Avenue. Fourteen cross sections between Linwood Avenue and U.S. Highway
171, including two bridges, were surveyed across the floodplain, with cross section
widths varying between 2,000 and 4,000 feet. Additional cross sections
downstream of Linwood Avenue were obtained from a 1988 USACE study of
Boggy Bayou and Wallace Lake.
35
Parishwide Revision
There are no new hydraulic analyses for the streams studied by detailed methods.
Cross sections were determined from topographic maps and field surveys. All
bridges, dams, and culverts were field surveyed to obtain elevation data and
structural geometry.
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.
For streams studied by approximate methods, WSELs were determined using base
product methods.
Hydraulic analyses were carried out using HEC-RAS
(Reference 39). Cross sections were cut from the available topographic data using
HEC-GeoRAS with an ESRI ArcMAP GIS platform (Reference 40). RAMPP
Redelineation and GeoTerrain tool was used to process all the streams (Reference
41).
Channel roughness factors (Manning’s “n” values) used in the hydraulic computations
were assigned on the basis of field observation and engineering judgment, using field
survey descriptions and 1986 aerial photography of portions of the study area. For all
of the streams studied by detailed methods except Cypress Bayou, channel “n” values
ranged from 0.015 to 0.120 and overbank values ranged from 0.060 to 0.250.
Manning’s “n” values for the main channel of Cypress Bayou range from 0.040 to
0.070, with the overbank values ranging from 0.050 to 0.120. For the streams
studied by approximate methods, Manning’s “n” values for the main channel range
from 0.040 to 0.170.
Qualifying bench marks within a given jurisdiction that are cataloged by the
National Geodetic Survey (NGS) and entered into the National Spatial Reference
System (NSRS) as First or Second Order Vertical and have a vertical stability
classification of A, B, or C are shown and labeled on the FIRM with their 6character NSRS Permanent Identifier.
Bench marks cataloged by the NGS and entered into the NSRS vary widely in
vertical stability classification. NSRS vertical stability classifications are as
follows:
•
Stability A: Monuments of the most reliable nature, expected to hold
position/elevation well (e.g., mounted in bedrock)
36
•
Stability B: Monuments which generally hold their position/elevation well
(e.g., concrete bridge abutment)
•
Stability C: Monuments which may be affected by surface ground
movements (e.g., concrete monument below frost line)
•
Stability D: Mark of questionable or unknown vertical stability (e.g.,
concrete monument above frost line, or steel witness post)
In addition to NSRS bench marks, the FIRM may also show vertical control
monuments established by a local jurisdiction; these monuments will be shown on
the FIRM with the appropriate designations. Local monuments will only be placed
on the FIRM if the community has requested that they be included, and if the
monuments meet the aforementioned NSRS inclusion criteria.
To obtain current elevation, description, and/or location information for bench
marks shown on the FIRM for this jurisdiction, please contact the Information
Services Branch of the NGS at (301) 713-3242, or visit their Web site at
www.ngs.noaa.gov.
It is important to note that temporary vertical monuments are often established
during the preparation of a flood hazard analysis for the purpose of establishing
local vertical control. Although these monuments are not shown on the FIRM,
they may be found in the Technical Support Data Notebook associated with this
FIS and FIRM. Interested individuals may contact FEMA to access this data.
3.3
Vertical Datum
All FIS reports and FIRMs are referenced to a specific vertical datum. The
vertical datum provides a starting point against which flood, ground, and structure
elevations can be referenced and compared. Until recently, the standard vertical
datum in use for newly created or revised FIS reports and FIRMs was the National
Geodetic Vertical Datum of 1929 (NGVD 29). With the finalization of NAVD 88,
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
NAVD 88. Effective information was converted from NGVD 29 to NAVD 88.
An average conversion factor of -0.21 foot was applied to convert all effective
Base Flood Elevations (BFEs). Structure and ground elevations in the community
must, therefore, be referenced to NAVD 88. It is important to note that adjacent
communities may be referenced to NGVD 29. This may result in differences in
BFEs across the corporate limits between the communities.
For more information on NAVD 88, see Converting the National Flood
Insurance Program to the North American Vertical Datum of 1988, FEMA
Publication FIA-20/June 1992, or contact the NGS Information Services,
NOAA, N/NGS12, National Geodetic Survey, SSMC-3, #9202, 1315 East-West
37
Highway, Silver Spring, Maryland 20910-3282, (301) 713-3242 (Internet
address http://www.ngs.noaa.gov).
4.0
FLOODPLAIN MANAGEMENT APPLICATIONS
The NFIP encourages State and local governments to adopt sound floodplain management
programs. To assist in this endeavor, each FIS provides 1-percent-annual-chance
floodplain data, which may include a combination of the following: 10-, 2-, 1-, and 0.2percent-annual-chance flood elevations; delineations of the 1- and 0.2-percent-annualchance floodplains; and 1-percent-annual-chance floodway. This information is presented
on the FIRM and in many components of the FIS, including Flood Profiles, Floodway
Data tables, and Summary of Stillwater Elevation tables. Users should reference the data
presented in the FIS as well as additional information that may be available at the local
community map repository before making flood elevation and/or floodplain boundary
determinations.
4.1
Floodplain Boundaries
To provide a national standard without regional discrimination, the 1-percentannual-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 parish. For the streams studied in
detail, the 1- and 0.2-percent-annual-chance floodplain boundaries have been
delineated using the flood elevations determined at each cross section.
The boundaries were interpolated between cross sections using topographic data
obtained from Louisiana State University (LSU) Atlas and 10 meter DEMs
(References 42 and 43). The LSU website provides LiDAR mass points,
breaklines, and 5 meter DEMs for the state of Louisiana. The LSU LiDAR data
only covers the State of Louisiana. Caddo Parish borders with the State of Texas
and some streams flow from areas outside the parish. The 10 meter DEMs were
integrated with the LSU LiDAR data to provide complete coverage.
The 1- and 0.2-percent-annual-chance floodplain boundaries are shown on the
FIRM (Exhibit 2). On this map, the 1-percent-annual-chance floodplain boundary
corresponds to the boundary of the areas of special flood hazards (Zones A and
AE), and the 0.2-percent-annual-chance floodplain boundary corresponds to the
boundary of areas of moderate flood hazards. In cases where the 1- and 0.2percent-annual-chance floodplain boundaries are close together, only the 1percent-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-annualchance floodplain boundary is shown on the FIRM (Exhibit 2).
38
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 FIS are presented to local agencies as minimum standards
that can be adopted directly or that can be used as a basis for additional floodway
studies. The floodways presented in this FIS were computed for certain stream
segments on the basis of equal conveyance reduction from each side of the
floodplain. Floodway widths were computed at cross sections. Between cross
sections, the floodway boundaries were interpolated. The results of the floodway
computations are tabulated for selected cross sections (Table 6). The computed
floodways are shown on the FIRM (Exhibit 2). In cases where the floodway and
1-percent-annual-chance floodplain boundaries are either close together or
collinear, only the floodway boundary is shown.
No floodways were computed for Boggy Bayou Tributary A, Boggy Bayou
Tributary B, Buchanan Bayou, Buchanan Bayou Tributary A, Choctaw Bayou,
Cross Bayou Tributary 1, Cross Bayou Tributary 2, Cross Bayou Tributary 3,
Cypress Bayou, Gilmer Bayou Tributary 1, Gilmer Bayou Tributary 2, Gilmer
Bayou Tributary 3, Logan Bayou, Page Bayou, Page Bayou Tributary A, Red
River, and for portions of Bayou Pierre, Boggy Bayou, Brush Bayou and McCain
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 6 for certain downstream cross
sections of 75th Street Drainage Ditch, 81st Street Drainage Ditch, Bickham Bayou,
Brookwood Ditch, Country Club Lateral, Cross Bayou, Ford Park Lateral, Galaxy
Lateral, Green Terrace Lateral, Old River, Pierremont Ditch, Ranchmoor Lateral,
Sand Beach Bayou, South Broadmoor Lateral, Twelve Mile Bayou, and Werner
Park Lateral 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.
Encroachment into areas subject to inundation by floodwaters having hazardous
velocities aggravates the risk of flood damage, and heightens potential flood
39
hazards by further increasing velocities. A listing of stream velocities at selected
cross sections is provided in Table 6, "Floodway Data." In order to reduce the risk
of property damage in areas where the stream velocities are high, the community
may wish to restrict development in areas outside the floodway.
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 WSEL of
the 1-percent-annual-chance flood by more than 1.0 foot at any point. Typical
relationships between the floodway and the floodway fringe and their significance
to floodplain development are shown in Figure 1.
FLOODWAY SCHEMATIC
5.0
Figure 1
INSURANCE APPLICATIONS
For flood insurance rating purposes, flood insurance zone designations are assigned to a
community based on the results of the engineering analyses. The zones are as follows:
Zone A
Zone A is the flood insurance rate zone that corresponds to the 1-percent-annualchance floodplains that are determined in the FIS by approximate methods.
Because detailed hydraulic analyses are not performed for such areas, no BFEs or
depths are shown within this zone.
40
FLOODING SOURCE
CROSS SECTION
75
1
2
TH
Street Drainage Ditch
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
DISTANCE
145
1,470
3,325
4,000
4,240
4,620
5,200
5,715
5,935
6,100
6,446
6,817
7,075
7,360
7,610
7,910
1
WIDTH
(FEET)
55
250
170
325
200
195
100
100
100
160
160
160
180
240
40
40
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
377
955
416
650
841
816
442
521
591
927
662
834
1,025
1,220
235
257
5.2
2.0
4.4
2.6
2.0
2.0
3.4
2.8
2.4
1.5
2.0
1.6
1.2
1.0
4.8
4.4
REGULATORY
182.0
185.1
188.1
190.7
192.0
192.7
194.6
197.7
198.5
198.8
199.3
201.4
202.0
202.4
204.6
206.5
WITHOUT
FLOODWAY
181.2
185.1
188.1
190.7
192.0
192.7
194.6
197.7
198.5
198.8
199.3
201.4
202.0
202.4
204.6
206.5
WITH
FLOODWAY
INCREASE
181.7
186.1
188.6
191.4
192.9
193.7
195.5
198.5
199.3
199.7
200.2
201.9
202.9
203.4
205.1
207.2
0.5
1.0
0.5
0.7
0.9
1.0
0.9
0.8
0.8
0.9
0.9
0.5
0.9
1.0
0.5
0.7
2
Feet above confluence with Brush Bayou
Elevation computed without consideration of backwater effects from Brush Bayou
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
75TH STREET DRAINAGE DITCH
FLOODING SOURCE
CROSS SECTION
81
1
2
ST
Street Drainage Ditch
A
B
C
D
E
F
G
H
I
J
K
L
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
DISTANCE
100
1,670
2,910
3,450
4,625
5,082
5,578
5,940
6,236
6,370
6,725
7,270
1
WIDTH
(FEET)
47
43
24
20
20
60
26
18
60
60
50
100
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
284
129
98
101
120
304
143
120
330
274
215
35
5.0
9.8
11.5
10.7
9.0
3.5
6.2
6.8
2.5
2.6
2.8
1.5
REGULATORY
181.3
182.3
187.6
190.3
199.9
201.0
202.4
202.7
206.0
206.0
206.2
207.5
WITHOUT
FLOODWAY
180.0
182.3
187.6
190.3
199.9
201.0
202.4
202.7
206.0
206.0
206.2
207.5
WITH
FLOODWAY
INCREASE
180.6
182.3
187.6
190.3
199.9
201.6
203.2
203.5
206.7
206.7
207.1
208.3
0.6
0.0
0.0
0.0
0.0
0.6
0.8
0.8
0.7
0.7
0.9
0.8
2
Feet above confluence with Brush Bayou
Elevation computed without consideration of backwater effects from Brush Bayou
FEDERAL EMERGENCY MANAGEMENT AGENCY
TABLE 6
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
81ST STREET DRAINAGE DITCH
FLOODING SOURCE
1
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Airport Ditch
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
240
1,200
2,550
2,890
4,540
6,276
8,100
9,300
10,920
11,990
12,340
13,420
15,900
18,540
19,900
20,930
22,000
23,200
1
WIDTH
(FEET)
312
82
180
91
126
90
179
78
90
120
65
198
133
535
370
200
200
150
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
3,031
932
1,331
1,096
1,203
1,005
1,238
442
363
652
461
787
1,321
2,763
727
1,125
528
602
4.7
8.8
5.9
7.2
6.0
7.0
5.6
6.3
7.0
3.6
5.0
2.7
0.9
0.7
2.6
1.1
2.3
1.9
REGULATORY
183.3
184.8
186.9
189.6
190.2
191.2
193.5
193.8
197.2
204.0
204.8
206.3
218.6
218.7
220.1
221.6
222.9
226.7
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
183.3
184.8
186.9
189.6
190.2
191.2
193.5
193.8
197.2
204.0
204.8
206.3
218.6
218.7
220.1
221.6
222.9
226.7
184.0
185.4
187.3
189.9
190.6
191.8
193.5
193.8
197.2
204.3
205.3
207.3
219.6
219.7
220.1
222.1
223.7
227.5
0.7
0.6
0.4
0.3
0.4
0.6
0.0
0.0
0.0
0.3
0.5
1.0
1.0
1.0
0.0
0.5
0.8
0.8
Feet above confluence with Brush Bayou
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
AIRPORT DITCH
FLOODING SOURCE
1
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Audrey Lane Lateral
A
B
C
D
E
615
1,205
1,970
2,680
4,280
1
WIDTH
(FEET)
51
24
18
50
60
SECTION
AREA
(SQUARE
FEET)
240
90
48
174
206
MEAN
VELOCITY
(FEET PER
SECOND)
2.2
5.3
9.3
2.1
1.2
REGULATORY
187.3
187.3
189.7
194.8
200.0
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
187.3
187.3
189.7
194.8
200.0
187.8
187.8
189.7
195.4
200.3
0.5
0.5
0.0
0.6
0.3
Feet above confluence with Cooper Road Ditch
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
AUDREY LANE LATERAL
FLOODING SOURCE
CROSS SECTION
Avery Ditch
A
B
1
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
DISTANCE
1
60
990
WIDTH
(FEET)
37
30
SECTION
AREA
(SQUARE
FEET)
123
17
MEAN
VELOCITY
(FEET PER
SECOND)
0.8
2.5
REGULATORY
196.3
209.1
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
196.3
209.1
196.4
209.1
0.1
0.0
Feet above confluence with Betty Virginia Lateral
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
AVERY DITCH
FLOODING SOURCE
1
2
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Bayou Pierre
1
A-F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z
32,510
34,710
35,310
38,010
40,510
43,010
45,560
47,701
49,384
50,980
52,350
55,190
56,795
58,300
60,480
63,110
65,610
68,335
70,305
70,855
2
WIDTH
(FEET)
708
344
605
178
163
216
156
160
176
160
196
160
171
160
644
236
196
220
196
196
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
7,527
4,151
7,365
2,700
2,692
3,062
2,443
2,658
2,816
2,589
3,193
2,740
2,351
2,772
3,092
3,001
3,223
3,363
2,959
2,834
1.7
3.0
1.7
3.0
3.0
2.7
3.3
3.0
2.9
3.2
2.6
3.1
3.5
2.9
2.5
2.4
2.3
2.2
2.6
2.7
REGULATORY
155.4
155.5
155.6
155.9
156.5
157.1
157.5
158.6
159.0
159.3
159.4
159.7
160.1
160.5
161.2
162.2
163.3
164.4
164.8
164.9
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
155.4
155.5
155.6
155.9
156.5
157.1
157.5
158.6
159.0
159.3
159.4
159.7
160.1
160.5
161.2
162.2
163.3
164.4
164.8
164.9
155.4
155.5
155.7
156.1
156.6
157.1
157.5
158.6
159.2
159.5
159.8
160.2
160.7
161.1
161.9
163.2
164.2
165.2
165.6
165.7
0.0
0.0
0.1
0.2
0.1
0.0
0.0
0.0
0.2
0.2
0.4
0.5
0.6
0.6
0.7
1.0
0.9
0.8
0.8
0.8
Data not available
Feet above State Highway 175
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
BAYOU PIERRE
FLOODING SOURCE
1
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Bayou Pierre (continued)
AA
AB
AC
AD
AE
AF
AG
AH
AI
AJ
AK
AL
72,385
73,775
76,285
77,685
78,210
79,085
80,778
82,075
84,445
85,553
85,949
87,462
1
WIDTH
(FEET)
190
170
220
180
440
300
126
173
60
100
150
250
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
2,559
2,250
2,620
1,929
1,456
1,529
849
1,141
492
753
1,246
1,721
3.0
3.5
3.0
4.8
1.9
1.7
2.8
1.9
3.6
2.4
1.4
1.6
REGULATORY
165.1
165.6
166.1
166.1
166.7
167.0
167.5
168.4
170.0
171.9
172.1
172.4
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
165.1
165.6
166.1
166.1
166.7
167.0
167.5
168.4
170.0
171.9
172.1
172.4
165.9
166.3
166.8
166.8
167.4
167.7
168.4
169.1
170.0
172.1
172.4
173.4
0.8
0.7
0.7
0.7
0.7
0.7
0.9
0.7
0.0
0.2
0.3
1.0
Feet above State Highway 175
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
BAYOU PIERRE
FLOODING SOURCE
1
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Betty Virginia Lateral
A
B
C
D
E
F
G
H
I
J
220
416
625
990
1,429
1,930
2,144
2,604
3,130
3,510
1
WIDTH
(FEET)
270
170
80
60
60
48
40
33
37
25
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
1,674
889
442
220
284
163
133
107
192
17
0.8
1.1
1.3
2.6
1.7
2.5
3.1
3.8
1.1
4.8
REGULATORY
172.4
172.4
172.5
175.1
178.1
181.2
183.9
185.8
196.3
199.2
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
172.4
172.4
172.5
175.1
178.1
181.2
183.9
185.8
196.3
199.2
173.2
173.2
173.2
175.6
178.9
181.8
184.0
186.4
196.3
199.3
0.8
0.8
0.7
0.5
0.8
0.6
0.1
0.6
0.0
0.1
Feet above confluence with Ockley Ditch
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
BETTY VIRGINIA LATERAL
FLOODING SOURCE
1
2
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Bickham Bayou
A
B
C
D
E
F
G
H
I
J
139
1,900
3,700
4,750
6,290
7,550
9,600
11,228
12,450
13,900
1
WIDTH
(FEET)
250
445
230
147
150
180
265
150
120
31
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
742
2,762
1,021
730
1,192
953
1,074
776
640
135
7.9
1.6
4.4
5.5
3.2
3.9
2.2
2.7
2.4
8.6
REGULATORY
176.9
177.1
178.8
182.3
187.9
189.5
197.8
202.0
204.5
212.4
WITHOUT
FLOODWAY
173.4
177.1
178.8
182.3
187.9
189.5
197.8
202.0
204.5
212.4
WITH
FLOODWAY
INCREASE
173.4
177.6
179.5
183.2
188.4
190.4
198.5
202.2
205.5
212.4
0.0
0.5
0.7
0.9
0.5
0.9
0.7
0.2
1.0
0.0
2
Feet above confluence with Cross Lake
Elevation computed without consideration of backwater effects from Cross Lake
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
BICKHAM BAYOU
FLOODING SOURCE
CROSS SECTION
Boggy Bayou
1
A-H
I
J
K
L
M
N
1
O-AA
1
2
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
DISTANCE
40,200
40,630
42,840
44,700
46,075
48,320
2
WIDTH
(FEET)
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
1,300
1,850
2,100
2,700
2,800
2,100
8,306
11,282
11,762
16,877
13,414
14,141
2.3
1.0
0.9
0.7
0.7
0.8
REGULATORY
168.3
168.7
170.0
170.6
170.9
171.6
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
168.3
168.7
170.0
170.6
170.9
171.6
169.2
169.6
170.8
171.5
171.9
172.5
0.9
0.9
0.8
0.9
1.0
0.9
No floodway calculated
Feet above confluence with Cypress Bayou
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
BOGGY BAYOU
FLOODING SOURCE
1
2
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Brookwood Ditch
A
B
C
D
E
F
285
2,030
2,820
4,225
6,126
6,850
1
WIDTH
(FEET)
90
230
42
29
35
39
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
978
636
288
182
162
176
2.8
4.3
7.3
9.8
8.5
6.9
REGULATORY
171.3
172.1
175.2
177.6
188.5
192.4
WITHOUT
FLOODWAY
107.5
172.1
175.2
177.6
188.5
192.4
WITH
FLOODWAY
INCREASE
170.9
173.1
176.1
177.8
188.5
192.4
0.4
1.0
0.9
0.2
0.0
0.0
2
Feet above confluence with Brush Bayou
Elevation computed without consideration of backwater effects from Brush Bayou
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
BROOKWOOD DITCH
FLOODING SOURCE
1
2
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Brush Bayou
1
A-C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
12,260
13,920
15,363
17,950
19,200
20,640
22,420
24,040
25,370
26,890
29,365
30,825
31,790
32,150
35,370
35,987
37,280
39,700
41,580
43,282
44,830
45,055
2
WIDTH
(FEET)
287
240
510
350
300
279
228
239
400
270
165
186
170
312
89
45
56
80
45
43
40
31
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
2,910
2,909
4,875
3,698
4,144
4,300
3,122
3,763
3,146
2,331
2,252
2,356
2,181
3,032
903
360
390
465
398
278
104
292
8.5
8.5
4.7
6.2
5.5
5.2
6.6
5.3
6.1
8.0
7.8
7.3
6.5
4.7
7.0
11.5
10.2
7.4
7.6
4.0
9.4
3.3
REGULATORY
162.4
165.9
167.8
168.7
170.3
171.1
172.1
173.2
174.2
175.3
178.6
181.3
182.5
183.3
186.0
187.6
190.4
194.5
197.4
201.6
205.5
214.7
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
162.4
165.9
167.8
168.7
170.3
171.1
172.1
173.2
174.2
175.3
178.6
181.3
182.5
183.3
186.0
187.6
190.4
194.5
197.4
201.6
205.5
214.7
163.4
166.3
168.4
169.7
170.7
171.4
172.4
173.6
174.4
175.8
179.2
181.8
183.5
184.0
186.4
187.7
190.5
194.7
198.3
202.4
205.5
214.7
1.0
0.4
0.6
1.0
0.4
0.3
0.3
0.4
0.2
0.5
0.6
0.5
1.0
0.7
0.4
0.1
0.1
0.2
0.9
0.8
0.0
0.0
No floodway calculated
Feet above Confluence with Boggy Bayou
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
BRUSH BAYOU
FLOODING SOURCE
1
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Cargill Lateral
A
B
C
D
E
F
80
1,460
1,691
2,562
3,260
4,495
1
WIDTH
(FEET)
37
41
40
34
40
40
SECTION
AREA
(SQUARE
FEET)
122
267
250
61
65
247
MEAN
VELOCITY
(FEET PER
SECOND)
4.4
1.8
1.8
6.0
5.5
1.4
REGULATORY
193.9
207.1
207.4
209.5
215.7
224.2
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
193.9
207.1
207.4
209.5
215.7
224.2
194.2
207.3
208.0
209.6
216.2
225.1
0.3
0.2
0.6
0.1
0.5
0.9
Feet above confluence with Airport Ditch
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
CARGILL LATERAL
FLOODING SOURCE
1
2
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Cooper Road Ditch
A
B
C
D
E
F
G
310
2,050
4,000
5,960
8,060
9,520
10,472
1
WIDTH
(FEET)
84
65
58
49
58
41
120
SECTION
AREA
(SQUARE
FEET)
780
331
362
297
238
157
415
MEAN
VELOCITY
(FEET PER
SECOND)
2.8
6.2
5.3
4.9
4.2
5.9
1.9
REGULATORY
166.3
166.3
169.1
172.8
175.3
181.1
185.9
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
160.3
162.8
169.2
173.2
175.4
181.1
186.5
0.6
0.0
0.1
0.4
0.1
0.0
0.6
2
159.7
2
162.8
169.1
172.8
175.3
181.1
185.9
Feet above confluence with McCain Creek
Elevation computed without consideration of backwater effects from Red River
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
COOPER ROAD DITCH
FLOODING SOURCE
1
2
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Country Club Lateral
A
B
C
D
E
F
G
H
I
J
K
L
0
1,300
1,550
2,650
3,500
4,230
4,490
4,915
5,340
5,820
6,465
6,992
1
WIDTH
(FEET)
63
212
310
200
155
158
130
90
54
40
40
14
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
413
745
1,164
821
535
530
734
502
230
164
228
94
10.0
4.6
3.0
3.6
5.1
4.5
3.1
4.2
5.6
7.9
5.4
13.0
REGULATORY
176.9
179.3
180.0
185.2
189.2
191.5
193.5
197.4
198.3
200.0
205.2
210.0
WITHOUT
FLOODWAY
171.2
179.3
180.0
185.2
189.2
191.5
193.5
197.4
198.3
200.0
205.2
210.0
WITH
FLOODWAY
INCREASE
172.2
179.7
180.8
186.0
189.9
192.4
193.8
197.8
199.1
200.8
206.1
210.0
1.0
0.4
0.8
0.8
0.7
0.9
0.3
0.4
0.8
0.8
0.9
0.0
2
Feet above confluence with Cross Lake
Elevation computed without consideration of backwater effects from Cross Lake
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
COUNTRY CLUB LATERAL
FLOODING SOURCE
1
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Courtesy Lane Channel
A
B
C
D
E
F
G
H
160
820
2,130
3,360
4,700
5,530
7,405
8,135
1
WIDTH
(FEET)
38
40
41
35
85
211
90
50
SECTION
AREA
(SQUARE
FEET)
195
323
221
177
306
471
78
182
MEAN
VELOCITY
(FEET PER
SECOND)
10.2
6.1
8.6
10.3
5.4
3.3
4.6
6.4
REGULATORY
186.1
192.0
193.3
196.1
200.7
202.5
207.9
208.8
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
186.1
192.0
193.3
196.1
200.7
202.5
207.9
208.8
186.6
193.0
193.8
196.1
201.1
203.2
208.1
209.7
0.5
1.0
0.5
0.0
0.4
0.7
0.2
0.9
Feet above confluence with Brush Bayou
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
COURTESY LANE CHANNEL
FLOODING SOURCE
1
2
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Cross Bayou
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
760
1,460
1,830
2,200
3,670
5,490
6,670
8,590
9,240
10,000
12,770
14,040
16,180
18,260
20,170
1
WIDTH
(FEET)
312
505
284
223
314
493
380
335
616
142
250
250
300
300
300
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
5,914
10,799
5,342
5,577
6,670
8,285
8,768
6,791
7,267
1,296
3,218
2,500
2,519
3,303
3,987
8.0
4.4
8.8
8.4
7.1
5.7
5.4
6.9
3.0
8.0
3.2
4.1
4.1
3.1
2.6
REGULATORY
166.3
166.3
166.3
166.3
166.3
166.3
166.3
166.3
166.3
166.3
166.3
166.3
166.3
166.3
166.3
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
154.4
155.6
154.8
155.3
157.5
158.3
160.1
160.8
155.8
154.7
158.8
160.4
161.1
163.5
164.8
1.0
0.9
1.0
0.9
0.6
0.5
0.8
0.3
0.7
0.9
0.2
0.2
0.3
0.6
0.8
2
153.4
2
154.7
2
153.8
2
154.4
2
156.9
2
157.8
2
159.3
2
160.5
2
155.1
2
153.8
2
158.6
2
160.2
2
160.8
2
162.9
2
164.0
Feet above confluence with Red River
Elevation computed without consideration of backwater effects from Red River
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
CROSS BAYOU
FLOODING SOURCE
1
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Cross Bayou Lateral
A
B
C
D
E
F
G
H
I
J
K
1,188
2,040
2,872
3,350
3,822
4,637
5,060
5,820
5,970
6,130
6,441
1
WIDTH
(FEET)
60
60
65
42
40
100
192
12
9
9
6
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
1,082
901
432
297
381
454
603
48
41
40
41
2.5
2.8
5.8
7.5
6.7
4.3
3.1
8.8
10.2
10.6
10.2
REGULATORY
169.9
170.0
170.6
175.2
176.7
180.1
181.7
183.2
186.1
189.0
195.7
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
169.9
170.0
170.6
175.2
176.7
180.1
181.7
183.2
186.1
189.0
195.7
169.9
170.0
171.5
175.2
177.3
180.8
181.8
183.9
186.5
189.2
195.9
0.0
0.0
0.9
0.0
0.6
0.7
0.1
0.7
0.4
0.2
0.2
Feet above confluence with Cross Bayou
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
CROSS BAYOU LATERAL
FLOODING SOURCE
1
2
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Ford Park Lateral
A
B
C
D
E
123
1,600
2,870
3,520
4,310
1
WIDTH
(FEET)
96
33
90
43
14
SECTION
AREA
(SQUARE
FEET)
430
109
357
97
35
MEAN
VELOCITY
(FEET PER
SECOND)
1.7
6.1
1.6
5.6
9.1
REGULATORY
176.9
180.1
186.7
191.0
196.9
WITHOUT
FLOODWAY
171.8
180.1
186.7
191.0
196.9
WITH
FLOODWAY
INCREASE
172.6
180.6
187.7
191.6
196.9
0.8
0.5
1.0
0.6
0.0
2
Feet above confluence with Cross Lake
Elevation computed without consideration of backwater effects from Cross Lake
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
FORD PARK LATERAL
FLOODING SOURCE
1
2
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Galaxy Lateral
A
B
C
D
E
F
220
1,920
4,050
6,550
7,850
9,050
1
WIDTH
(FEET)
410
293
250
90
59
32
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
3,226
1,877
684
452
385
208
0.8
1.3
3.1
4.0
2.8
5.0
REGULATORY
176.9
177.0
179.1
186.8
190.0
195.4
WITHOUT
FLOODWAY
176.8
177.0
179.1
186.8
190.0
195.4
WITH
FLOODWAY
INCREASE
176.9
177.1
179.5
187.7
190.7
195.5
0.1
0.1
0.4
0.9
0.7
0.1
2
Feet above confluence with Cross Lake
Elevation computed without consideration of backwater effects from Cross Lake
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
GALAXY LATERAL
FLOODING SOURCE
1
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Gilbert Ditch
A
B
C
D
E
415
750
1,400
2,105
2,530
1
WIDTH
(FEET)
350
260
250
120
100
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
1,980
1,478
1,012
680
678
1.2
1.7
2.8
4.5
4.8
REGULATORY
167.9
167.9
168.3
169.8
170.9
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
167.9
167.9
168.3
169.8
170.9
168.3
168.7
169.2
170.7
171.7
0.4
0.8
0.9
0.9
0.8
Feet above confluence with Ockley Ditch
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
GILBERT DITCH
FLOODING SOURCE
1
2
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Gilmer Bayou
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
350
2,080
3,640
6,480
7,760
9,330
10,750
11,650
12,660
13,340
14,550
15,880
17,155
18,420
20,365
21,480
22,600
23,720
25,380
1
WIDTH
(FEET)
2
1,850
220
245
190
165
109
134
85
65
450
120
100
72
55
60
86
85
50
45
SECTION
AREA
(SQUARE
FEET)
2
11,287
2,703
2,748
2,268
1,576
902
927
884
750
2,304
823
750
453
353
404
417
302
200
142
MEAN
VELOCITY
(FEET PER
SECOND)
1.0
4.0
3.9
4.7
3.6
6.3
5.6
4.1
4.8
1.6
4.3
4.7
6.0
7.1
5.4
4.6
5.4
6.8
6.7
REGULATORY
168.7
168.7
169.0
170.1
171.1
172.3
175.0
177.9
182.8
184.3
187.7
189.9
191.5
193.6
197.1
198.4
200.6
203.6
210.5
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
168.7
168.7
169.0
170.1
171.1
172.3
175.0
177.9
182.8
184.3
187.7
189.9
191.5
193.6
197.1
198.4
200.6
203.6
210.5
169.6
169.7
169.9
170.9
171.8
172.7
175.1
177.9
183.3
184.8
188.5
190.8
192.2
194.0
197.3
198.6
200.6
203.6
210.5
0.9
1.0
0.9
0.8
0.7
0.4
0.1
0.0
0.5
0.5
0.8
0.9
0.7
0.4
0.2
0.2
0.0
0.0
0.0
Feet above confluence with Boggy Bayou
Combined Gilmer Bayou/Boggy Bayou floodway
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
GILMER BAYOU
FLOODING SOURCE
1
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Green Oaks Lateral
A
B
C
400
2,200
2,690
1
WIDTH
(FEET)
70
30
15
SECTION
AREA
(SQUARE
FEET)
125
134
69
MEAN
VELOCITY
(FEET PER
SECOND)
4.5
2.3
3.3
REGULATORY
176.4
185.4
188.6
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
176.4
185.4
188.6
176.6
186.0
188.9
0.2
0.6
0.3
Feet above confluence with Cooper Road Ditch
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
GREEN OAKS LATERAL
FLOODING SOURCE
1
2
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Green Terrace Lateral
A
B
C
D
E
F
G
H
150
2,330
4,165
5,980
7,735
9,380
10,950
12,510
1
WIDTH
(FEET)
37
150
45
37
15
50
50
16
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
241
448
210
140
80
244
131
40
4.3
2.1
4.3
5.6
7.9
2.0
2.6
6.4
REGULATORY
167.8
167.8
172.8
177.8
187.0
191.9
204.8
215.4
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
162.4
167.9
173.5
178.0
187.3
192.8
205.1
215.6
1.0
0.3
0.7
0.2
0.3
0.9
0.3
0.2
2
161.4
2
167.6
172.8
177.8
187.0
191.9
204.8
215.4
Feet above confluence with Boggy Bayou
Elevation computed without consideration of backwater effects from Boggy Bayou
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
GREEN TERRACE LATERAL
FLOODING SOURCE
1
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Hollywood Ditch
A
B
C
D
E
F
G
H
I
J
K
L
M
460
1,460
3,280
4,720
5,930
6,630
7,135
7,400
7,730
8,360
9,270
10,600
11,770
1
WIDTH
(FEET)
112
104
103
55
56
110
140
140
160
280
150
58
30
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
741
660
586
570
397
623
515
697
941
1,492
634
240
141
6.2
6.7
7.0
6.7
8.9
5.4
6.6
4.6
3.4
1.5
2.9
6.8
10.2
REGULATORY
193.6
194.3
198.2
205.0
205.6
208.5
208.7
210.7
211.7
212.5
213.0
215.0
217.1
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
193.6
194.3
198.2
205.0
205.6
208.5
208.7
210.7
211.7
212.5
213.0
215.0
217.1
194.0
194.6
198.5
205.3
206.5
209.5
209.2
211.5
212.4
213.4
214.0
215.4
217.1
0.4
0.3
0.3
0.3
0.9
1.0
0.5
0.8
0.7
0.9
1.0
0.4
0.0
Feet above confluence with Airport Ditch
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
HOLLYWOOD DITCH
FLOODING SOURCE
1
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Industrial Park Lateral
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
250
1,385
2,375
3,725
4,425
5,825
6,925
8,205
9,065
13,412
14,568
15,848
16,918
18,417
19,402
21,170
22,722
24,191
26,141
27,394
1
WIDTH
(FEET)
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
144
1,043
950
930
1,100
1,348
1,060
1,080
592
479
673
171
162
915
700
150
141
135
139
95
1,439
5,044
4,102
3,857
2,394
3,058
3,599
5,071
1,664
1,723
2,132
798
976
1,622
909
843
870
924
711
490
6.3
1.8
2.2
2.3
3.6
2.8
2.4
1.7
3.2
2.9
2.3
5.3
4.3
2.6
4.5
4.8
4.6
3.5
4.5
6.5
REGULATORY
170.6
176.0
176.7
178.0
178.7
180.9
182.6
184.4
185.1
190.9
192.0
193.7
197.5
199.3
200.8
204.0
206.0
208.3
210.1
213.3
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
170.6
176.0
176.7
178.0
178.7
180.9
182.6
184.4
185.1
190.9
192.0
193.7
197.5
199.3
200.8
204.0
206.0
208.3
210.1
213.3
171.3
176.0
176.7
178.0
178.7
180.9
182.6
184.5
185.2
190.9
192.0
193.7
197.5
199.3
200.8
204.2
206.2
208.5
210.3
214.0
0.7
0.0
0.0
0.0
0.0
0.0
0.0
0.1
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.2
0.2
0.2
0.2
0.7
Feet above confluence with Gilmer Bayou
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
INDUSTRIAL PARK LATERAL
FLOODING SOURCE
1
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Jenkins Acres Lateral
A
B
C
D
E
190
1,150
2,260
3,220
3,465
1
WIDTH
(FEET)
92
460
40
40
40
SECTION
AREA
(SQUARE
FEET)
370
750
245
95
110
MEAN
VELOCITY
(FEET PER
SECOND)
1.6
0.8
2.4
6.1
5.3
REGULATORY
190.2
191.3
197.3
200.3
202.0
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
190.2
191.3
197.3
200.3
202.0
190.4
191.7
197.5
200.6
202.5
0.2
0.4
0.2
0.3
0.5
Feet above confluence with Airport Ditch
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
JENKINS ACRES LATERAL
FLOODING SOURCE
1
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Lambert Park Lateral
A
B
C
D
E
F
G
130
1,350
3,070
3,830
4,230
4,585
4,951
1
WIDTH
(FEET)
75
51
17
28
12
10
12
SECTION
AREA
(SQUARE
FEET)
429
151
56
98
51
31
36
MEAN
VELOCITY
(FEET PER
SECOND)
3.2
7.7
8.9
4.3
7.0
10.0
6.9
REGULATORY
171.9
174.4
180.0
191.2
192.4
196.0
199.0
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
171.9
174.4
180.0
191.2
192.4
196.0
199.0
172.6
175.1
180.1
191.4
192.7
196.0
199.1
0.7
0.7
0.1
0.2
0.3
0.0
0.1
Feet above confluence with Summer Grove Ditch
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
LAMBERT PARK LATERAL
FLOODING SOURCE
1
2
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Lincoln Memorial Lateral
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
1,450
2,930
3,730
3,950
4,230
4,480
6,630
8,430
10,430
11,505
13,590
15,840
16,146
18,730
21,180
23,295
23,870
1
WIDTH
(FEET)
2
1,080
110
400
500
500
500
432
300
450
425
320
92
100
350
350
290
200
SECTION
AREA
(SQUARE
FEET)
2
7,431
617
764
2,129
2,122
1,691
3,168
1,944
2,945
2,841
1,975
643
736
1,368
1,106
469
801
MEAN
VELOCITY
(FEET PER
SECOND)
2.9
5.3
4.2
1.5
1.5
1.8
1.0
1.6
1.0
1.0
1.4
4.2
3.6
1.3
1.5
1.8
1.1
REGULATORY
186.0
187.1
190.2
192.0
192.2
192.3
197.6
201.6
205.3
206.6
208.5
211.5
214.4
217.2
222.6
230.9
231.9
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
186.0
187.1
190.2
192.0
192.2
192.3
197.6
201.6
205.3
206.6
208.5
211.5
214.4
217.2
222.6
230.9
231.9
186.4
187.4
190.3
192.7
193.1
193.3
198.6
202.4
206.3
207.5
209.4
212.2
214.9
217.5
223.6
231.7
232.7
0.4
0.3
0.1
0.7
0.9
1.0
1.0
0.8
1.0
0.9
0.9
0.7
0.5
0.3
1.0
0.8
0.8
Feet above confluence with Industrial Park Lateral
Combined Lincoln Memorial Lateral/ Industrial Park Lateral floodway
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
LINCOLN MEMORIAL LATERAL
FLOODING SOURCE
1
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Lynbrook Lateral
A
B
C
D
E
160
1,550
2,330
3,685
4,880
1
WIDTH
(FEET)
24
80
35
21
18
SECTION
AREA
(SQUARE
FEET)
171
336
212
77
52
MEAN
VELOCITY
(FEET PER
SECOND)
5.5
2.9
4.8
9.1
7.9
REGULATORY
177.4
180.1
181.6
184.6
188.1
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
177.4
180.1
181.6
184.6
188.1
178.1
181.0
182.1
185.1
188.1
0.7
0.9
0.5
0.5
0.0
Feet above confluence with Brush Bayou
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
LYNBROOK LATERAL
FLOODING SOURCE
1
2
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
McCain Creek
A
B
C
D
E
F
G
H
I
J
2,000
4,100
5,400
7,150
10,050
12,250
15,050
16,900
20,450
22,360
1
WIDTH
(FEET)
140
174
140
141
85
75
100
83
83
81
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
1,482
1,557
1,463
1,319
802
630
722
649
820
695
4.5
4.2
4.4
4.0
6.0
7.4
6.2
6.8
5.3
6.0
REGULATORY
166.3
166.3
166.3
166.3
166.3
166.3
169.9
171.8
175.8
178.0
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
156.0
156.9
157.4
160.7
162.2
166.0
169.8
172.6
176.2
178.2
0.8
0.6
0.6
0.5
0.3
0.3
0.9
0.8
0.4
0.2
2
155.2
2
156.3
2
156.8
2
160.2
2
161.9
2
165.7
169.9
171.8
175.8
178.0
Feet above confluence with Twelve Mile Bayou
Elevation computed without consideration of backwater effects from Red River
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
MCCAIN CREEK
FLOODING SOURCE
1
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Murry Lateral
A
B
C
D
E
F
340
1,500
2,470
3,240
4,100
4,670
1
WIDTH
(FEET)
240
100
39
180
13
14
SECTION
AREA
(SQUARE
FEET)
875
271
96
175
42
35
MEAN
VELOCITY
(FEET PER
SECOND)
1.5
4.4
11.1
3.4
10.3
9.0
REGULATORY
212.8
213.8
217.0
221.9
228.4
232.2
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
212.8
213.8
217.0
221.9
228.4
232.2
213.6
214.3
217.3
222.5
228.5
232.2
0.8
0.5
0.3
0.6
0.1
0.0
Feet above confluence with Hollywood Ditch
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
MURRY LATERAL
FLOODING SOURCE
1
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Ockley Ditch
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
260
830
1,500
3,269
4,170
4,567
4,874
5,151
5,595
6,304
6,584
6,990
7,380
8,500
9,520
9,700
10,432
10,984
11,180
12,030
13,520
14,640
1
WIDTH
(FEET)
140
120
400
340
170
310
350
320
360
310
280
280
280
234
252
230
320
80
65
40
301
60
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
1,427
1,270
2,524
2,012
1,345
1,864
2,125
1,587
1,671
1,019
1,600
1,748
1,358
1,849
1,009
889
1,482
389
262
279
1,429
304
4.7
5.3
1.9
2.4
3.6
2.6
2.3
2.9
2.7
4.6
3.0
2.7
2.1
1.8
3.0
3.2
1.9
4.2
6.2
5.5
0.9
3.4
REGULATORY
166.2
166.4
167.8
168.8
171.3
171.8
172.2
172.3
172.7
174.9
176.4
178.2
178.2
188.1
188.1
188.1
192.7
193.3
193.3
197.2
208.5
210.0
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
166.2
166.4
167.8
168.8
171.3
171.8
172.2
172.3
172.7
174.9
176.4
178.2
178.2
188.1
188.1
188.1
192.7
193.3
193.3
197.2
208.5
210.0
167.2
167.3
168.3
169.5
171.9
172.5
172.9
173.0
173.3
175.4
177.3
178.6
178.7
188.9
189.0
189.0
193.5
193.7
193.5
197.4
208.9
211.0
1.0
0.9
0.5
0.7
0.6
0.7
0.7
0.7
0.6
0.5
0.9
0.4
0.5
0.8
0.9
0.9
0.8
0.4
0.2
0.2
0.4
1.0
Feet above confluence with Bayou Pierre
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
OCKLEY DITCH
FLOODING SOURCE
1
2
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Old River
A
B
C
D
E
F
G
H
I
J
K
300
2,100
4,226
6,125
6,915
8,470
9,544
10,810
12,270
14,405
16,135
1
WIDTH
(FEET)
62
70
81
68
99
107
83
76
153
171
176
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
269
376
455
429
642
523
410
499
925
1,788
1,680
4.9
3.5
2.8
2.9
1.6
1.9
2.4
1.3
0.7
0.3
0.4
REGULATORY
159.7
159.7
159.7
159.7
159.7
159.7
159.7
159.7
159.7
161.6
161.6
WITHOUT
FLOODWAY
WITH
FLOODWAY
2
150.1
2
153.1
2
155.5
2
156.5
2
156.8
2
157.2
2
157.7
2
158.1
2
158.2
161.6
161.6
Feet above confluence with Sand Beach Bayou
Elevation computed without consideration of backwater effects from Sand Beach Bayou
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
OLD RIVER
150.1
153.1
155.5
156.5
156.8
157.2
157.7
158.1
158.2
161.6
161.6
INCREASE
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
FLOODING SOURCE
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Pierremont Ditch
A
B
C
D
E
350
1,260
1,760
2,340
3,820
1
WIDTH
(FEET)
28
26
28
22
26
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
192
149
173
148
124
16.6
16.5
14.2
16.6
19.9
REGULATORY
164.6
164.7
164.8
164.8
164.8
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
151.9
153.9
156.8
158.2
162.9
0.0
0.0
0.0
0.0
0.0
2
151.9
2
153.9
3
156.8
3
158.2
3
162.9
1
Feet above confluence with Bayou Pierre
Elevation computed without consideration of flooding effects from Bayou Pierre
3
Elevation computed without consideration of backwater effects from Bayou Pierre
2
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
PIERREMONT DITCH
FLOODING SOURCE
1
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Ranchmoor Lateral
A
B
C
D
E
F
G
H
160
920
1,535
2,420
3,400
5,010
6,735
6,970
1
WIDTH
(FEET)
214
370
400
395
325
200
80
80
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
1,038
2,399
2,783
2,419
759
894
577
500
1.5
0.6
0.5
0.6
1.8
1.4
2.0
2.4
REGULATORY
166.5
167.3
167.6
168.0
168.2
170.7
180.4
180.5
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
166.8
167.2
167.3
167.4
168.3
171.5
181.2
181.4
0.5
0.7
0.7
0.8
1.0
0.8
0.8
0.9
2
166.3
2
166.5
2
166.6
2
166.6
2
167.3
170.7
180.4
180.5
Feet above confluence with Brush Bayou
Elevation computed without consideration of flooding effects from Brush Bayou
2
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
RANCHMOOR LATERAL
FLOODING SOURCE
1
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Rose Park Lateral
A
B
C
D
E
F
G
170
1,200
1,500
1,950
2,377
2,750
3,000
1
WIDTH
(FEET)
310
50
65
50
40
26
40
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
1,164
154
192
128
162
83
194
3.0
4.6
3.3
4.4
3.2
5.0
1.9
REGULATORY
180.0
187.1
190.8
195.1
198.6
203.0
206.2
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
180.0
187.1
190.8
195.1
198.6
203.0
206.2
180.8
187.9
191.7
195.7
199.6
203.8
207.1
0.8
0.8
0.9
0.6
1.0
0.8
0.9
Feet above confluence with Country Club Lateral
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
ROSE PARK LATERAL
FLOODING SOURCE
1
2
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Sand Beach Bayou
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
650
2,150
3,465
5,720
7,910
9,880
11,220
13,364
13,660
14,900
17,120
19,830
22,300
25,000
27,830
29,130
30,070
1
WIDTH
(FEET)
247
586
490
114
134
141
107
161
167
216
195
180
214
178
159
143
130
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
1,168
1,959
1,560
936
1,280
1,389
1,155
1,241
1,535
1,860
1,746
1,902
1,830
1,688
1,570
1,535
918
4.3
2.6
3.1
5.2
3.8
3.3
4.0
3.8
3.0
2.4
2.4
1.5
1.6
1.7
1.6
1.0
1.1
REGULATORY
155.7
155.8
155.9
156.0
156.0
156.0
156.4
158.5
158.8
159.2
159.7
160.1
160.1
160.2
161.1
161.2
161.2
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
146.9
149.3
150.8
152.9
154.9
155.8
156.4
158.5
158.8
159.2
159.7
160.2
160.3
160.6
161.5
161.6
161.6
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.1
0.2
0.4
0.4
0.4
0.4
2
146.9
2
149.3
2
150.8
2
152.9
2
154.9
2
155.8
156.4
158.5
158.8
159.2
159.7
160.1
160.1
160.2
161.1
161.2
161.2
Feet above confluence with Bayou Pierre
Flooding controlled by Bayou Pierre
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
SAND BEACH BAYOU
FLOODING SOURCE
1
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Savanna Lateral
A
B
C
D
E
F
122
835
1,825
2,310
3,420
4,433
1
WIDTH
(FEET)
20
20
17
30
15
40
SECTION
AREA
(SQUARE
FEET)
177
129
92
177
111
196
MEAN
VELOCITY
(FEET PER
SECOND)
7.8
10.1
12.3
5.9
6.7
3.1
REGULATORY
183.0
183.9
189.2
191.7
194.9
213.6
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
183.0
183.9
189.2
191.7
194.9
213.6
183.0
184.5
189.2
192.3
195.8
214.5
0.0
0.6
0.0
0.6
0.9
0.9
Feet above confluence with Summer Grove Ditch
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
SAVANNA LATERAL
FLOODING SOURCE
1
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Shirley-Francis Lateral
A
B
C
180
1,000
2,160
1
WIDTH
(FEET)
221
192
50
SECTION
AREA
(SQUARE
FEET)
717
540
350
MEAN
VELOCITY
(FEET PER
SECOND)
1.5
2.0
3.0
REGULATORY
206.1
208.1
212.1
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
206.1
208.1
212.1
206.3
208.6
212.8
0.2
0.5
0.7
Feet above confluence with Industrial Park Lateral
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
SHIRLEY-FRANCIS LATERAL
FLOODING SOURCE
1
2
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
South Broadmoor Lateral
A
B
C
D
E
F
G
H
I
J
80
2,120
3,984
4,540
5,410
6,750
8,325
10,443
11,880
12,250
1
WIDTH
(FEET)
30
31
32
33
34
84
64
54
48
44
SECTION
AREA
(SQUARE
FEET)
85
84
94
103
110
439
317
225
166
156
MEAN
VELOCITY
(FEET PER
SECOND)
6.7
4.8
3.8
3.3
2.8
0.6
0.7
0.3
0.2
0.1
REGULATORY
158.6
158.6
158.6
158.6
158.6
158.6
158.6
158.6
158.6
158.6
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
145.2
147.5
150.3
150.5
150.8
157.9
157.9
158.6
158.7
158.7
0.0
0.0
0.8
0.5
0.3
0.3
0.3
0.3
0.3
0.3
2
145.2
2
147.5
2
149.5
2
150.0
2
150.5
2
157.6
2
157.6
2
158.3
2
158.4
2
158.4
Feet above confluence with Sand Beach Bayou
Elevation computed without consideration of backwater effects from Sand Beach Bayou
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
SOUTH BROADMOOR LATERAL
FLOODING SOURCE
1
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Southwood High Lateral
A
B
C
D
200
2,600
5,380
6,765
1
WIDTH
(FEET)
97
180
150
150
SECTION
AREA
(SQUARE
FEET)
340
676
895
792
MEAN
VELOCITY
(FEET PER
SECOND)
4.8
2.2
1.4
1.5
REGULATORY
176.9
185.3
194.1
195.7
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
176.9
185.3
194.1
195.7
176.9
186.2
194.6
196.5
0.0
0.9
0.5
0.8
Feet above confluence with Gilmer Bayou
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
SOUTHWOOD HIGH LATERAL
FLOODING SOURCE
1
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
St. Vincent Academy Ditch
A
B
C
D
E
290
725
1,185
1,530
1,775
1
WIDTH
(FEET)
160
145
42
45
45
SECTION
AREA
(SQUARE
FEET)
923
547
301
486
474
MEAN
VELOCITY
(FEET PER
SECOND)
2.0
3.4
6.2
3.8
4.0
REGULATORY
178.3
178.4
180.7
187.0
187.1
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
178.3
178.4
180.7
187.0
187.1
178.9
179.0
181.2
187.0
188.0
0.6
0.6
0.5
0.0
0.9
Feet above confluence with Ockley Ditch
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
ST. VINCENT ACADEMY DITCH
FLOODING SOURCE
1
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Summer Grove Ditch
A
B
C
D
E
F
G
H
I
J
8,365
10,510
11,353
12,532
13,953
15,930
16,770
17,200
18,100
19,045
1
WIDTH
(FEET)
200
60
98
80
50
35
36
24
60
23
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
1,385
574
604
414
322
157
104
141
235
68
3.9
6.5
6.0
8.1
5.4
7.8
9.8
6.7
3.4
9.7
REGULATORY
169.2
171.9
172.8
175.1
183.4
189.0
197.0
200.7
202.2
204.6
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
169.2
171.9
172.8
175.1
183.4
189.0
197.0
200.7
202.2
204.6
170.2
172.6
173.7
175.3
183.4
189.0
197.0
201.1
202.9
204.6
1.0
0.7
0.9
0.2
0.0
0.0
0.0
0.4
0.7
0.0
Feet above confluence with Brush Bayou
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
SUMMER GROVE DITCH
FLOODING SOURCE
CROSS SECTION
Sycamore Lateral
A
B
1
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
DISTANCE
1
170
840
WIDTH
(FEET)
22
20
SECTION
AREA
(SQUARE
FEET)
137
89
MEAN
VELOCITY
(FEET PER
SECOND)
5.9
9.1
REGULATORY
181.9
184.5
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
181.9
184.5
182.0
184.9
0.1
0.4
Feet above confluence with Cross Bayou Lateral
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
SYCAMORE LATERAL
FLOODING SOURCE
1
2
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Twelve Mile Bayou
A
B
C
D
E
F
G
H
I
J
K
L
M
430
1,750
4,370
5,850
7,320
9,670
11,160
12,800
14,180
15,295
15,771
17,187
18,305
1
WIDTH
(FEET)
695
285
263
245
292
245
217
264
300
429
428
400
288
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
10,882
7,240
9,329
6,236
7,040
6,944
6,091
6,851
7,477
9,863
12,209
8,553
8,540
4.3
6.3
4.9
7.3
6.4
6.5
7.5
6.6
6.0
4.6
3.7
5.3
5.3
REGULATORY
166.3
166.3
166.3
166.3
166.3
166.3
166.3
166.3
166.3
166.3
166.3
166.3
166.3
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
161.6
161.7
162.6
162.8
163.1
163.7
164.0
164.9
165.6
166.0
166.2
166.4
166.6
0.3
0.1
0.2
0.2
0.2
0.2
0.3
0.3
0.3
0.2
0.3
0.3
0.3
2
161.3
2
161.6
2
162.4
2
162.6
2
162.9
2
163.5
2
163.7
2
164.6
2
165.3
2
165.8
2
165.9
2
166.1
2
166.3
Feet above confluence with Cross Bayou
Elevation computed without consideration of backwater effects from Red River
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
TWELVE MILE BAYOU
FLOODING SOURCE
BASE FLOOD
WATER-SURFACE ELEVATION
(FEET NAVD)
FLOODWAY
CROSS SECTION
DISTANCE
Werner Park Lateral
A
B
C
D
E
F
G
H
I
J
K
810
2,075
2,880
3,290
3,560
3,910
4,245
4,590
4,915
5,210
5,575
1
WIDTH
(FEET)
40
31
130
120
170
140
150
270
320
220
180
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
223
198
681
682
740
831
821
1,241
1,442
777
559
8.1
9.2
2.7
2.7
2.5
2.2
2.3
1.5
1.3
2.4
3.4
REGULATORY
199.8
202.3
206.7
207.0
207.9
209.2
209.8
210.5
210.9
211.5
212.5
WITHOUT
FLOODWAY
WITH
FLOODWAY
INCREASE
199.8
202.3
206.7
207.0
207.9
209.2
209.8
210.5
210.9
211.5
212.5
200.1
202.9
207.5
207.8
208.0
210.2
210.7
211.4
212.0
212.5
213.1
0.3
0.6
0.8
0.8
0.1
1.0
0.9
0.9
3
1.1
1.0
0.6
1
Feet above confluence with Brush Bayou
Elevation computed without consideration of backwater effects from Brush Bayou
3
EG=1.0
2
TABLE 6
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
CADDO PARISH, LA
AND INCORPORATED AREAS
WERNER PARK LATERAL
Zone AE
Zone AE is the flood insurance rate zone that corresponds to the 1-percent-annualchance floodplains that are determined in the FIS by detailed methods. In most
instances, whole-foot base flood elevations derived from the detailed hydraulic
analyses are shown at selected intervals within this zone.
Zone AH
Zone AH is the flood insurance rate zone that corresponds to the areas of 1percent-annual-chance shallow flooding (usually areas of ponding) where average
depths are between 1 and 3 feet. Whole-foot base flood elevations derived from
the detailed hydraulic analyses are shown at selected intervals within this zone.
Zone AO
Zone AO is the flood insurance rate zone that corresponds to the areas of 1percent-annual-chance shallow flooding (usually sheet flow on sloping terrain)
where average depths are between 1 and 3 feet. Average whole-foot depths
derived from the detailed hydraulic analyses are shown within this zone.
Zone AR
Area of special flood hazard formerly protected from the 1-percent-annual-chance
flood event by a flood control system that was subsequently decertified. Zone AR
indicates that the former flood control system is being restored to provide
protection from the 1-percent-annual-chance or greater flood event.
Zone A99
Zone A99 is the flood insurance rate zone that corresponds to areas of the 1percent-annual-chance floodplain that will be protected by a Federal flood
protection system where construction has reached specified statutory milestones.
No base flood elevations or depths are shown within this zone.
Zone V
Zone V is the flood insurance rate zone that corresponds to the 1-percent-annualchance coastal floodplains that have additional hazards associated with storm
waves. Because approximate hydraulic analyses are performed for such areas, no
base flood elevations are shown within this zone.
Zone VE
Zone VE is the flood insurance rate zone that corresponds to the 1-percent-annualchance coastal floodplains that have additional hazards associated with storm
waves. Whole-foot base flood elevations derived from the detailed hydraulic
analyses are shown at selected intervals within this zone.
88
waves. Whole-foot base flood elevations derived from the detailed hydraulic
analyses are shown at selected intervals within this zone.
Zone X
Zone X is the flood insurance rate zone that corresponds to areas outside the 0.2percent-annual-chance floodplain, areas within the 0.2-percent-annual-chance
floodplain, and to areas of 1-percent-annual-chance flooding where average depths
are less than 1 foot, areas of 1-percent-annual-chance flooding where the
contributing drainage area is less than 1 square mile, and areas protected from the
1-percent-annual-chance flood by levees. No base flood elevations or depths are
shown within this zone.
Zone D
Zone D is the flood insurance rate zone that corresponds to unstudied areas where
flood hazards are undetermined, but possible.
6.0
FLOOD INSURANCE RATE MAP
The FIRM is designed for flood insurance and floodplain management applications. For
flood insurance applications, the map designates flood insurance rate zones as described in
Section 5.0 and, in the 1-percent-annual-chance floodplains that were studied by detailed
methods, shows selected whole-foot 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 are shown where applicable.
The current FIRM presents flooding information for the entire geographic area of Caddo
Parish. Previously, separate Flood Hazard Boundary Maps and/or FIRMs were prepared
for each incorporated community with identified flood hazard areas and the
unincorporated areas of the parish. Historical map dates relating to pre-parishwide maps
prepared for each community, prior to the April 6, 2000 parishwide map, are presented in
Table 7, "Community Map History."
7.0
OTHER STUDIES
The USACE has prepared Flood Plain Information Reports on McCain Creek, Gilmer
Bayou, Brush Bayou, Logan Bayou, and Choctaw Bayou (References 2, 3, and 4). The
USACE has also prepared a Special Flood Hazard Information Report on Bayou Pierre
and Sand Beach Bayou and Tributaries and a Detailed Information Report on Brush
Bayou (References 18 and 12).
Information pertaining to revised and unrevised flood hazards for each jurisdiction within
Caddo Parish has been compiled into this FIS. Therefore, this FIS supersedes all
previously printed FIS Reports, FHBMs, FBFMs, and FIRMs for all of the incorporated
and unincorporated jurisdictions within Caddo Parish.
89
INITIAL NFIP
MAP DATE
FLOOD HAZARD
BOUNDARY MAP
REVISIONS DATE
INITIAL FIRM
DATE
Belcher, Village of
June 27, 1978
None
April 6, 2000
Caddo Parish
(Unincorporated Areas)
March 7, 1978
None
September 5, 1990
Greenwood, Town of
August 3, 1998
None
August 3, 1998
Mooringsport, Town of
June 25, 1976
None
April 6, 2000
December 27, 1974
October 3, 1975
July 16, 1980
January 3, 1975
January 9, 1976
January 18, 1984
COMMUNITY
NAME
Oil City, Town of
Shreveport, City of
FIRM
REVISIONS DATE
May 19, 1997
November 1, 1985
April 17, 1995
June 5, 1997
TABLE 7
FEDERAL EMERGENCY MANAGEMENT AGENCY
CADDO PARISH, LA
AND INCORPORATED AREAS
COMMUNITY MAP HISTORY
This is a multi-volume FIS. Each volume may be revised separately, in which case it
supersedes the previously printed volume. Users should refer to the Table of Contents in
Volume 1 for the current effective date of each volume; volumes bearing these dates
contain the most up-to-date flood hazard data.
8.0
LOCATION OF DATA
Information concerning the pertinent data used in preparation of this FIS can be obtained
by contacting FEMA, Federal Insurance and Mitigation Division, Federal Regional Center,
800 North Loop 288, Denton, Texas 76201-3698.
9.0
BIBLIOGRAPHY AND REFERENCES
1. U.S. Department of Commerce, Bureau of the Census. (Retrieved July 9, 2011).
http://2010.census.gov.
2. U.S. Department of the Army, Corps of Engineers, Flood Plain Information.
(1971). McCain Creek and Gilmer Bayou, Shreveport, Louisiana. New Orleans,
Louisiana.
3. U.S. Department of the Army, Corps of Engineers, Flood Plain Information.
(1974). Shreveport, Louisiana, No. 2, Brush Bayou and Tributaries. New Orleans,
Louisiana.
4. U.S. Department of the Army, Corps of Engineers, Flood Plain Information.
(1974). Shreveport, Louisiana, No. 3, Logan and Choctaw Bayous. New Orleans,
Louisiana.
5. U.S. Department of Commerce, National Oceanic and Atmospheric
Administration, National Weather Service. (Retrieved April 1, 2011). Monthly
Weather Summary. http://www.weather.gov.
6. U.S. Department of the Interior, Geological Survey, with the Louisiana
Department of Transportation and Development. (1985). Water Resources
Technical Report No. 36, Floods in Louisiana, Magnitude and Frequency. Forth
Edition, F.N. Lee.
7. U.S. Department of the Army, Corps of Engineers. (1985). Caddo Lake
Enlargement, Louisiana and Texas, Summary of Results. Vicksburg, Mississippi.
8. U.S Department of Commerce, Bureau of the Census. (1971). 1970 Census of
Population, Number of Inhabitants, Louisiana. Washington, D.C.
9. Office of the Mayor. (July 22, 1986). Report on City Drainage Systems,
Shreveport, Louisiana.
10. U.S. Department of the Army, Corps of Engineers, New Orleans District. Daily
State Readings, 1938-1977.
91
11. U.S. Department of Commerce, National Oceanic and Atmospheric
Administration. (1978). Climatological Data, Louisiana, July 1978. Asheville,
North Carolina.
12. U.S. Department of the Army, Corps of Engineers, New Orleans District. (1972).
Brush Bayou, Louisiana, Detailed Project Report, New Orleans, Louisiana.
13. U.S. Department of the Army, Engineer District. (1948). Bayou Pierre in the
Vicinity of Shreveport, Louisiana. New Orleans, Louisiana.
14. U.S. Department of the Army, Engineer District. (1972) Type II Comprehensive
Basin Study, Red River Below Denison Dam. New Orleans, Louisiana.
15. The Shreveport Journal. (July 25, 1933; May 6, 1935; April 29, 1953; September
13, 1961; September 16, 1968; November 18, 1969).
16. The Shreveport Times. (July 30, 1972; June 8, 1974; September 18, 1976; May 7,
1978; May 8, 1978; January 20, 1978; January 21, 1979; April 1, 1979; May 5,
1979; May 31, 1979; May 17, 1980; May 10, 1981; December 15, 1982;
December 16, 1982, February 6, 1983; May 22, 1983; June 6, 1983; June 11,
1985; June 10, 1986; June 28, 1986; November 16, 1987; April 3, 1989, May 5,
1989; June 8, 1989; July 4; 1989; May 9, 1990; May 16, 1990; May 31, 1990;
April 13, 1991; April 14, 1991; April 15, 1991; April 16, 1991; April 17, 1991;
April 19, 1991).
17. U.S. Department of Commerce, National Oceanic and Atmospheric
Administration. Technical Paper No. 25, Rainfall, Intensity, Duration Frequency
Curves. Washington, D.C.
18. Federal Emergency Management Agency. (November 1, 1985). Flood Insurance
Study, City of Shreveport, Caddo and Bossier Parishes, Louisiana.
19. U.S. Department of the Army, Corps of Engineers. (1974). Special Flood Hazard
Information on Bayou Pierre, Sand Bayou and Tributary in and Near Shreveport,
Louisiana. New Orleans, Louisiana.
20. U.S. Department of the Army, Corps of Engineers. (May 1975). Wallace Lake,
Master Reservoir Regulation Manual. New Orleans, Louisiana.
21. U.S. Department of the Army, Corps of Engineers, Hydrologic Engineering
Center. (September 1981). HEC-1 Flood Hydrograph Package. Davis California.
22. Espy Huston, Inc. Development of Hydraulic Methodologies for Fort Bend
County, Texas. Austin Texas.
23. U.S. Department of the Army, Corps of Engineers, Hydrologic Engineering
Center. (September 1988). HEC-2 Water Surface Profiles, Generalized Computer
Program. Davis, California.
24. U.S. Department of Commerce, National Oceanic and Atmospheric
Administration. (June 1977) Technical Memorandum NWS Hydro-35, Five- to 6092
Minute Precipitation Frequency for the Eastern and Central United States. Silver
Spring, Maryland.
25. U.S. Department of Commerce, Weather Bureau. (1961). Technical paper No. 40,
Rainfall Frequency Atlas of the United States. Washington, D.C.
26. U.S. Department of Commerce, Weather Bureau. Technical Paper No. 49, Twoto 10-Day Precipitation for Return Periods of 2 to 100 Years in the Contiguous
United States. Washington, D.C.
27. U.S. Department of the Interior, Geological Survey, in cooperation with the
Louisiana Department of Transportation and Development, Office of Highways.
(1979). Research Study No. GS-2H, Magnitude and Frequency of Floods for
Small Watersheds in Louisiana. A.S. Lowe.
28. U.S. Department of the Army, Corps of Engineers, Hydrologic Engineering
Center. (October 1970). HEC-1 Flood Hydrograph Package. Davis, California.
29. U.S. Department of the Army, Corps of Engineers, New Orleans District.
Observed Discharges, 1953-1977.
30. U.S. Department of the Interior, Geological Survey. (1976). Floods in Louisiana,
Magnitude and Frequency. Third Edition, Braxtel L. Neely, Jr., Louisiana
Department of Highways. Baton Rouge, Louisiana.
31. U.S. Army Corps of Engineers, Hydrologic Engineering Center. (February 1995).
HEC-FFA – Flood Frequency Analysis. Version 3.1. Davis, California.
32. U.S. Department of the Interior, Geological Survey. (1998). Technical Report
Number 60, Floods in Louisiana Magnitude and Frequency. Fifth Edition.
33. U.S. Department of the Interior, Geological Survey. (2001). U.S. Geological
Survey Fact Sheet 099-01: The National Flood Frequency Program – Methods of
Estimating Flood Magnitudes and Frequency in Rural Areas in Louisiana.
34. U.S. Department of the Interior. (March 1982). Guidelines for Determining Flood
Flow Frequency (Bulletin 17B of the Hydrologic Subcommittee).
35. Western Air Maps, Inc. (February 1986). City of Shreveport, Louisiana,
Topographic Map. Lenexa, Kansas.
36. S.M. Cothern and Associates, Inc. (1975). Comprehensive Drainage Study Map
of the Shreveport Metropolitan Planning Area. Caddo Parish Police Jury,
Shreveport, Louisiana.
37. U.S. Department of the Interior, Geological Survey. (Greenwood, Louisiana,
1982; Waskom, Texas-Louisiana, 1962). 7.5-Minute Series Topographic Maps.
Scale 1:24,000, Contour Interval 10 feet.
93
38. U.S. Army Corps of Engineers, Hydrologic Engineering Center. (September
1998). HEC-RAS – River Analysis System, Version 2.2. Davis, California.
39. U.S. Army Corps of Engineers, Hydrologic Engineering Center. (March 2008).
HEC-RAS – River Analysis System, Version 4.0. Davis, California.
40. U.S. Army Corps of Engineers, Hydrologic Engineering Center. (September
2009). HEC-GeoRAS GIS Tools for Support of HEC-RAS using ArcGIS,
Version 4.2.93. Davis, California.
41. RAMPP. GeoFIRM Toolset – Redelineation and GeoTerrain, Version 5.0.
42. Louisiana State University. Atlas website – 2005 LiDAR data and LiDAR
metadata files. http://atlas.lsu.edu/central/.
43. U.S. Department of the Interior, Geological Survey. Seamless Data Distribution
System – 10 meter Digital Elevation Model. http://seamless.usgs.gov/.
44. http://water.weather.gov/ahps2/hydrograph.php?wfo=shv&gage=lcol1
45. http://nwis.waterdata.usgs.gov/la/nwis/peak
46. U.S. Department of the Interior, Geological Survey, in cooperation with the
Federal Highway Administration, Office of Research and Development, WSPRO
Bridge Waterways Analysis Model Research Report, J.O. Shearman, W.H. Kirby,
V.R Schneider, and H.N. Flippo, 1985.
94