ST. CLAIR COUNTY, IL - Illinois Flood Maps

Transcription

ST. CLAIR COUNTY,
ILLINOIS
St. Clair County
AND INCORPORATED AREAS
Community
Name
Community
Number
ALORTON, VILLAGE OF
BELLEVILLE, CITY OF
BROOKLYN, VILLAGE OF
CAHOKIA, VILLAGE OF
CASEYVILLE, VILLAGE OF
CENTREVILLE, CITY OF
*COLUMBIA, CITY OF
DUPO, VILLAGE OF
EAST CARONDELET,
VILLAGE OF
EAST ST. LOUIS,
CITY OF
FAIRMONT CITY, VILLAGE OF
FAIRVIEW HEIGHTS, CITY OF
FAYETTEVILLE, VILLAGE OF
FREEBURG, VILLAGE OF
*HECKER, VILLAGE OF
LEBANON, CITY OF
LENZBURG, VILLAGE OF
*No Flood Hazard Areas Identified
170617
170618
170619
170620
170621
170622
170510
170624
170625
170626
170627
170895
170628
170790
171264
170629
170978
Community
Name
Community
Number
MARISSA, VILLAGE OF
MASCOUTAH, CITY OF
MILLSTADT, VILLAGE OF
NEW ATHENS, VILLAGE OF
*NEW BADEN, VILLAGE OF
O’FALLON, CITY OF
SAUGET, VILLAGE OF
SHILOH, VILLAGE OF
SMITHTON, VILLAGE OF
ST. CLAIR COUNTY
(UNINCORPORATED AREAS)
ST. LIBORY, VILLAGE OF
SUMMERFIELD, VILLAGE OF
SWANSEA, VILLAGE OF
WASHINGTON PARK,
VILLAGE OF
Preliminary:
FLOOD INSURANCE STUDY NUMBER
17163CV000B
171058
170630
170838
170632
170050
170633
170635
171043
170892
170616
170634
170636
170637
170638
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) report may not contain all
data available within the Community Map Repository. Please contact the
Community Map Repository for any additional data.
The Federal Emergency Management Agency (FEMA) may revise and republish
part or all of this FIS report at any time. In addition, FEMA may revise part of
this FIS report by the Letter of Map Revision process, which does not involve
republication or redistribution of the FIS report. Therefore, users should consult
with community officials and check the Community Map Repository to obtain the
most current FIS report components.
Initial Countywide FIS Effective Date: November 5, 2003
Revised Countywide FIS Effective Dates: (To Be Determined)
TABLE OF CONTENTS
1.0
INTRODUCTION .................................................................................................................1
1.1 Purpose of Study..............................................................................................................1
1.2 Authority and Acknowledgments ....................................................................................2
1.3 Coordination ....................................................................................................................6
2.0
AREA STUDIED ...................................................................................................................7
2.1 Scope of Study .................................................................................................................8
2.2 Community Description.................................................................................................10
2.3 Principal Flood Problems...............................................................................................11
2.4 Flood Protection Measures ............................................................................................11
3.0
ENGINEERING METHODS .............................................................................................14
3.1 Hydrologic Analyses......................................................................................................15
3.3 Hydraulic Analyses........................................................................................................23
3.3 Vertical Datum...............................................................................................................27
4.0
FLOODPLAIN MANAGEMENT APPLICATIONS ......................................................30
4.1 Floodplain Boundaries...................................................................................................30
4.2 Floodways......................................................................................................................32
5.0
INSURANCE APPLICATIONS ........................................................................................58
6.0
FLOOD INSURANCE RATE MAP ..................................................................................59
7.0
OTHER STUDIES...............................................................................................................60
8.0
LOCATION OF DATA.......................................................................................................60
9.0
BIBLIOGRAPHY AND REFERENCES ..........................................................................60
i
TABLE OF CONTENTS (Continued)
FIGURES
Figure 1 - Floodway Schematic ........................................................................................................ 58
TABLES
Table 1 - Detailed Study Streams ....................................................................................................... 8
Table 2 - Streams Restudied by Detailed Methods............................................................................. 9
Table 3 - Summary of Discharges .................................................................................................... 17
Table 4 - Summary of Stillwater Elevations..................................................................................... 20
Table 5 - Vertical Datum Conversvion............................................................................................. 28
Table 6 - Mississippi River Vertical Datum Conversion.................................................................. 29
Table 7 - Floodway Data................................................................................................................... 33
Table 8 - Community Map History................................................................................................... 61
EXHIBITS
Exhibit 1 - Flood Profiles
Ash Creek
Canteen Creek
Catawba Creek
Douglas Creek
Doza Creek
Engle Creek
Engle Creek Ditch
Hog River
Kaskaskia River
Little Canteen Creek
Little Silver Creek
Loop Creek
Mississippi River
Northwest Tributary to Ogles Creek
Ogles Creek
Ogles Creek Tributary
Prairie Du Pont Diversion Channel
Richland Creek
Schoenberger Creek No. 1
Silver Creek
Unnamed Tributary to Doza Creek
Unnamed Tributary to Loop Creek
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Panel
Panel
ii
01P
02P-03P
04P
05P-06P
07P
08P-09P
10P
11P
12P-14P
15P-16P
17P
18P-22P
23P-24P
25P
26P-28P
29P
30P-31P
32P-38P
39P
40P-41P
42P-49P
50P
51P
TABLE OF CONTENTS (Continued)
Exhibit 1 - Flood Profiles (Continued)
Unnamed Tributary to Ogles Creek
Unnamed Tributary to Richland Creek
West Fork of Richland Creek
Wolf Branch
Exhibit 2 - Flood Insurance Rate Map Index
Flood Insurance Rate Map
iii
Panel
Panel
Panels
Panels
52P
53P
54P-56P
57P-58P
FLOOD INSURANCE STUDY
ST. CLAIR COUNTY, ILLINOIS AND INCORPORATED AREAS
1.0
INTRODUCTION
1.1
Purpose of Study
This Flood Insurance Study (FIS) revises and updates information on the
existence and severity of flood hazards in the geographic area of St. Clair County,
including the Cities of Belleville, Centreville, Columbia, East St. Louis, Fairview
Heights, Lebanon, Mascoutah, and O’Fallon; the Villages of Alorton, Brooklyn,
Cahokia, Caseyville, Dupo, East Carondelet, Fairmont City, Fayetteville,
Freeburg, Hecker, Lenzburg, Marissa, Millstadt, New Athens, New Baden,
Sauget, Shiloh, Smithton, St. Libory, Summerfield, Swansea, and Washington
Park; and the unincorporated areas of St. Clair County (referred to collectively
herein as St. Clair County), and aids in the administration of the National Flood
Insurance Act of 1968 and the Flood Disaster Protection Act of 1973. This study
has developed flood-risk data for various areas of the community that will be used
to establish actuarial flood insurance rates and to assist the community in its
efforts to promote sound floodplain management.
Minimum floodplain
management requirements for participation in the National Flood Insurance
Program (NFIP) are set forth in the Code of Federal Regulations at 44 CFR, 60.3.
Please note that the Cities of Collinsville and Madison are geographically located
in St. Clair and Madison Counties. Please see the separately printed FIS report
and Flood Insurance Rate Map (FIRM) for flood hazard information for the Cities
of Collinsville and Madison. The City of Columbia and the Village of Hecker are
geographically located in St. Clair and Monroe Counties. Only the portions of the
City of Columbia and the Village of Hecker that lie in St. Clair County are
included in this FIS report. The Village of New Baden is geographically located
in St. Clair and Clinton Counties. Only the portion of the Village of New Baden
that is located in St. Clair County is shown in this countywide revision. See the
separately published FIS report and FIRM for flood-hazard information in the
area outside St. Clair County. The Village of Fairmont City is geographically
located in St. Clair and Madison Counties. The Village of Fairmont City is
included in its entirety in this FIS report and FIRM.
Please note that the Villages of Hecker and New Baden and the City of Columbia
have no mapped flood hazard areas within St. Clair County.
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
The Digital Flood Insurance Rate Map (DFIRM) and FIS report for this
countywide study have been produced in digital format. Flood hazard
information was converted to meet the Federal Emergency Management Agency
(FEMA) DFIRM database specifications and Geographic Information System
(GIS) format requirements. The flood hazard information was created and is
provided in a digital format so that it can be incorporated into a local GIS and be
accessed more easily by the community.
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.
Precountywide FIS Report
Information on the authority and acknowledgements for each jurisdiction included
in this countywide FIS report, as compiled from their previously printed FIS
reports, are shown below:
Alorton, Village of:
The hydrologic and hydraulic analyses for the
FIS report dated December 4, 1979, were
prepared by the U.S. Army Corps of Engineers
(USACE), St. Louis District, for the Federal
Insurance Administration (FIA), under InterAgency Agreement No. IAA-H-7-76, Project
Order No. 24. (FIA, 1979e). The work was
completed in November 1977.
Belleville, City of:
FIS report dated May 19, 1980 (FIA, 1980b),
were prepared by the USACE, St. Louis
District, for the FIA, under Inter-Agency
Agreement No. IAA-H-10-77, Project Order
No. 6. The work was completed in September
1978.
Brooklyn, Village of:
FIS report dated September 28, 1979 (FIA,
1979c), were prepared by the USACE, St.
Louis District, for the FIA, under InterAgency Agreement No. IAA-H-10-77, Project
Order No. 6. The work was completed in
January 1978.
2
Cahokia, Village of:
FIS report dated April 17, 1978 (FIA, 1978a),
No. 24. The work was completed in March
1977.
Caseyville, Village of:
1980e), were prepared by the USACE, St.
Order No. 7. The work was completed in June
1979.
Centreville, City of:
1979b), were prepared by the USACE, St.
December 1977.
Dupo, Village of:
FIS report dated August 4, 1980 (FIA, 1980c),
No. 16. The work was completed in January
1979.
East Carondelet, Village of:
1980d), were prepared by the USACE, St.
February 1979.
3
East St. Louis, City of:
FIS report dated May 1, 1979 (FIA, 1979a),
No. 13.
The work was completed in
November 1977.
Fairmont City, Village of:
1979d), were prepared by the USACE, St.
Order No. 6. The work was completed in July
1978.
Fairview Heights, City of:
FIS report dated January 3, 1978 (FIA,
1978b), were prepared by Roy F. Weston,
Inc., for the FIA, under Contract No. H-3977.
The work was completed in March 1977.
Fayetteville, Village of:
FIS report dated December 15, 1980 (FIA,
1980g), were prepared by the USACE, St.
November 1979.
Lebanon, City of:
FIS report dated January 2, 1981 (FIA,
1981a), were prepared by the USACE, St.
Order No. 14. That work was completed in
December 1979.
Mascoutah, City of:
1980f), were prepared by the USACE, St.
October 1979.
4
O’Fallon, City of:
FIS report dated April 15, 1982 (FIA, 1982),
No. 14. The work was completed in October
1980.
Sauget, Village of:
FIS report dated February 1, 1980 (FIA,
1980a), were prepared by the USACE, St.
January 1979.
St. Clair County
(Unincorporated Areas):
FIS reports dated June 15, 1981 (FIA, 1981c)
and August 5, 1985 (FEMA, 1985), were
prepared by the USACE, St. Louis District, for
the FIA, under Inter-Agency Agreement Nos.
IAA-H-7-76 and IAA-H-10-77, Project Order
Nos. 14 and 7, respectively. The work was
completed in June 1979.
Swansea, Village of:
FIS report dated June 1, 1981 (FIA, 1981b),
No. 14.
The work was completed in
December 1979.
Washington Park, Village of:
1978c), were prepared by the USACE, St.
December 1977.
The authority and acknowledgments for the City of Columbia and the Villages of
Freeburg, Hecker, Lenzburg, Marissa, Millstadt, New Athens, New Baden, Shiloh,
Smithton, St. Libory, and Summerfield are not included because there were no
previously printed FIS reports for areas within St. Clair County for those
communities.
5
November 5, 2003
Initial Countywide FIS Report
The updated analyses for Schoenberger Creek No. 2 and Canteen Creek for the
countywide FIS report dated November 5, 2003 (FEMA, 2003), were prepared by
the USACE, St. Louis District, for FEMA, under Inter-Agency Agreement No.
EMW-95-E-4756. The work was completed in April 1997. Hydrologic and
hydraulic analyses for Wolf Branch were prepared by the USACE, St. Louis
District. The work was completed May 1999. New hydrologic and hydraulic
analyses of Silver Creek were prepared by the USACE, St. Louis District. The
work was completed August 1999.
This Countywide Revision
The updated hydrologic and hydraulic analyses for Richland Creek were
performed by the Illinois Department of Natural Resources (IDNR) for FEMA,
under Contract No. HSFE-2004-D-0015, Project Order No. 04-C23. This work
was completed in February 2008.
The updated hydrologic and hydraulic analyses for the Mississippi River AR
zones were taken from the report titled "Upper Mississippi River Floodway
Computation”, prepared by the USACE, St. Paul, Rock Island, and St. Louis
Districts, (USACE, 2004b).
Flood profiles and Base Flood Elevations (BFEs) for the Kaskaskia River and
Silver Creek were revised to reflect updated backwater elevations from the
Mississippi River.
Base map information shown on the FIRM was derived from Sanborn Map
Company, Inc., Digital Orthophoto Quadrangles produced at a scale of 1:1,200,
from National Aerial Photography Program black and white photography dated
2005 or later. The projection used in the preparation of this map is Universal
Transverse Mercator (UTM) Zone 15, and the horizontal datum used is NAD 83,
GRS80 Spheroid.
1.3
Coordination
An initial meeting is held with representatives from FEMA, the community, and
the study contractor to explain the nature and purpose of a FIS, and to identify the
streams to be studied or restudied. A final meeting is held with representatives
from FEMA, the community, and the study contractor to review the results of the
study.
Precountywide Analyses
The initial and final meeting dates for previous FIS reports for St. Clair County and
its communities are listed in the following table:
6
Community Name
Initial Meeting Date Final Meeting Date
Alorton, Village of
Belleville, City of
Brooklyn, Village of
Cahokia, Village of
Caseyville, Village of
Centreville, City of
Dupo, Village of
East Carondelet, Village of
East St. Louis, City of
Fairmont City, Village of
Fairview Heights, City of
Fayetteville, Village of
Lebanon, City of
Madison, City of
Mascoutah, City of
O'Fallon, City of
Sauget, Village of
St. Clair County
(Unincorporated Areas)
Swansea, Village of
Washington Park, Village of
*Data Not Available
January 19, 1976
January 19, 1976
August 26, 1976
January 19, 1976
March 31, 1975
April 1975
August 26, 1976
August 26, 1976
April 1975
August 27, 1976
March 1976
December 15, 1977
December 15, 1977
October 18, 1978
December 15, 1977
December 15, 1977
August 26, 1976
May 26, 1976
March 28, 1979
August 30, 1979
October 18, 1978
September 30, 1977
May 1, 1980
October 17, 1978
January 29, 1980
December 27, 1979
October 18, 1978
March 28, 1979
June 15, 1977
July 22, 1980
September 3, 1980
April 27, 1979
June 16, 1980
September 22, 1981
April 26, 1979
December 4, 1980
December 15, 1977
April l, 1975
*
August 1, 1978
November 5, 2003
For the November 5, 2003, countywide FIS, FEMA notified the county and
incorporated communities with letters dated January 20, 1998, that a countywide FIS
would be prepared.
A final meeting was held on February 21, 2002, and was attended by representatives
of the State, St. Clair County, and FEMA.
For this countywide FIS the initial meeting was held on July 28, 2004, and
attended by representatives of FEMA, State of Illinois, and St. Clair County.
The results of the study were reviewed at the open house held on
______________________________, and attended by representatives of
________________. All problems raised at that meeting have been addressed in
this study.
7
2.0
AREA STUDIED
2.1
Scope of Study
This FIS covers the geographic area of St. Clair County, Illinois, including the
incorporated communities listed in Section 1.1. The areas studied by detailed
methods were selected with priority given to all known flood hazards and areas of
projected development or proposed construction.
The streams studied by detailed methods in St. Clair County are listed in Table 1:
Table 1 – Detailed Study Streams
Ash Creek
Canteen Creek
Catawba Creek
Douglas Creek
Doza Creek
Engle Creek
Engle Creek Ditch
Hog River
Kaskaskia River
Little Silver Creek
Loop Creek
Mississippi River
Northwest Tributary to
Ogles Creek
Ogles Creek
Richland Creek
Silver Creek
Wolf Branch
Limits of detailed study are indicated on the Flood Profiles (Exhibit 1) and on the
FIRM (Exhibit 2).
Many areas subject to shallow flooding and ponding areas in St. Clair County are
also studied in detail.
November 5, 2003
As part of the November 5, 2003, initial countywide FIS, portions of Harper Ditch
and Canteen Creek were redelineated. High water marks and field reconnaissance
determined where the water had spilled over spoil banks along each creek.
Schoenberger Creek No. 2 was studied from just upstream of North 89 Street to a
point approximately 1,500 feet upstream of Interstate Highway 161. Updated
analyses were included for Silver Creek from the confluence with Kaskaskia River to
a point approximately 1.25 miles upstream of Lebanon Loyett Road. Wolf Branch
was restudied from the confluence with Richland Creek to a point approximately 900
8
feet upstream of Wabasha Avenue. Several ponding areas along Harding Ditch were
also studied.
Numerous flooding sources in the county were studied by approximate methods.
Approximate analyses were used to study those areas having a low development
potential or minimal flood hazards. The scope and methods of study were proposed
to, and agreed upon by, FEMA and St. Clair County.
The streams restudied by detailed methods in this revision are listed in Table 2.
Table 2 - Streams Restudied by Detailed Methods
Stream
Reach
Mississippi River
From approximately 10,520 feet downstream
of the downstream county boundary to
approximately 4,710 feet upstream of the
upstream county boundary, including the entire
AR flooding zone within St. Clair County
Richland Creek
From approximately 5,200 feet upstream of
Schiermeier Road to approximately 1,100 feet
upstream of North Green Mount Road
For this countywide revision, the FIS report and FIRM were converted to
countywide format, and the flooding information for the entire county, including
both incorporated and unincorporated areas, is shown. Also, the vertical datum
was converted from the National Geodetic Vertical Datum of 1929 (NGVD) to
the North American Vertical Datum of 1988 (NAVD). In addition, the Universal
Transverse Mercator coordinates, previously referenced to the North American
Datum of 1927, are now referenced to the North American Datum of 1983.
The following tabulation presents Letters of Map Correction (LOMCs)
incorporated into this countywide study:
LOMC
Case Number
Date Issued
Project Identifier
LOMR
04-05-0883P
03/01/2004
LOMR
04-05-2329P
05/14/2004
LOMR
LOMR
04-05-2333P
06-05-B005P
04/12/2004
03/08/2007
LOMR
06-05-C230P
01/24/2008
Unnamed Tributary to
Kaskaskia River
Engle Creek and Unnamed
Tributary to Engle Creek
Loop Creek
Orchards Subdivision;
Unnamed Tributary to Loop
Creek
Unnamed Tributary to Richland
Creek
9
2.2
LOMC
Case Number
Date Issued
Project Identifier
LOMR
07-05-4876P
09/28/2007
LOMR
07-05-5847P
01/29/2008
LOMR
08-05-0726P
12/21/2007
Unnamed / Northwest Tributary
to Ogles Creek
Doza Creek and Unnamed
Tributary to Doza Creek
Green Mount Station; Loop
Creek
Community Description
St. Clair County is located in southwestern Illinois, across the Mississippi River
from St. Louis, Missouri. The county encompasses approximately 680 square
miles. Elevations range from near 600 feet NAVD in the northern portion of the
county to 400 feet NAVD along the Mississippi River. The population of St.
Clair County was 261,316 in 2007 (U.S. Census Bureau, 2007). The county is
bordered by Madison County to the north, Clinton County to the northeast,
Washington County to the southeast, Randolph County to the south, Monroe
County to the southwest, and St. Louis County, Missouri, to the west.
The type of climate in south-central Illinois is characterized by warm to hot
summers and cool to cold winters. Generally, more than 60 percent of the
precipitation occurs in the warmer half of the year. The average annual rainfall is
approximately 39 inches. Air temperature ranges from an average maximum of 90
degrees Fahrenheit (oF) in July to an average minimum of 22oF in January.
Winter temperatures rarely go below 0oF. Freezing temperatures normally occur
between mid-October and mid-April (The Weather Channel, 2008).
Vegetation includes mostly agricultural lands with some forests and residential
lawns. The floodplain for all detailed studied streams is primarily agricultural and
residential in nature. Topography consists of moderately rolling uplands with
small streams. The Southern Metropolitan Area Planning Comission (SMAPC)
reports that soils generally consists of silty sediments graded in five-foot
thicknesses, which generally overlie stratified silty sediments (SMAPC, 1970).
The American Bottoms area, the flat area adjacent to the Mississippi River in the
vicinity of East St. Louis, is composed of recent alluvium and glacial valley-train
materials. Its thickness ranges from 80 feet to 120 feet and is underlain by
Mississippian limestone.
Immediately above the bedrock surface is a stratum of glacial outwash overlain by
coarse sands and gravels. Above this stratum is a layer of medium to fine sand.
These deposits may also contain industrial wastes. Meandering loops of the
Mississippi River and creeks have left complex and varied surface deposits.
Approximately 20 percent of the county drains directly into the Mississippi River
through the American Bottoms. The remaining portion of the county drains
10
through Richland Creek, Silver Creek or the Kaskaskia River. The general flow
direction is southerly.
2.3
Principal Flood Problems
Low-lying areas of St. Clair County are subject to periodic flooding by overflows
from the streams studied in detail for this FIS.
Notable floods have occurred on Richland Creek in 1908, 1912, 1915, 1916,
1919, 1927, 1942, 1946, and 1957. The flood of 1957 was the largest flood on
record. The storm of 1957 was the result of a severe rainstorm of short duration.
The storm was centered approximately 7 miles southwest of Belleville, where
16.54 inches of rain fell in less than 12 hours causing $2.7 million in damage in
the Belleville area.
USGS streamflow gages exist on Richland Creek near Hecker and Silver Creek,
near the Village of Freeburg. Based on the results of the hydrologic analysis for
the unincorporated areas of St. Clair County FIS, dated August 5, 1985, the
recurrence interval for Richland Creek at the streamflow gage near Hecker was
approximately 20-percent-annual-chance for the November 1972 flood. The
recurrence interval for the April 1975 flood of Silver Creek, at the streamflow
gage near Freeburg, was 20-percent-annual-chance based on a limited period of
record. Floods also occurred on Richland and Silver Creeks in 1943, 1946, 1957,
1969, 1972, 1979, 1986, 1990, 1993, 1995, 1996, and 2005 (USACE, 1974 and
USGS, 2008a).
A high recorded Mississippi River stage at St. Louis for the 117-year period of
record occurred in April 1973 (USGS, 1977). This flood was determined to have
a 2.9 percent-annual-chance recurrence interval. However, inundation of the
Mississippi River floodplain did not occur within the urbanized areas of St. Clair
County since they were protected by the extensive system of existing levees and
related flood control structures. During the April 1973 flood, damage was
experienced in the industrial and commercial areas within the American Bottoms.
The Southwestern Illinois Metropolitan and Regional Planning Comission
(SIMRPC) attributed the damage to ponding of interior runoff during high
Mississippi River stages when backwater blocked the gravity drainage systems
(SIMRPC, 1975). The highest recorded stage occurred in August 1993 (USGS,
2008b). The American Bottoms experienced extensive flood damages due to
interior runoff in August 1915, July 1942, August 1946, July 1952, June 1957 and
May 1961 (SIMRPC, 1975). The 1946 flood approximated a 1-percent-annualchance event, with an average depth of rainfall of 11.8 inches.
2.4
Flood Protection Measures
Levees exist in the study area that provide the communities with some degree of
protection against flooding. However, it has been ascertained that some of these
11
levees may not protect the communities from rare events such as the 1-percentannual-chance flood. The criteria used to evaluate protection against the 1percent-annual-chance flood are 1) adequate design, including freeboard; 2)
structural stability; and 3) proper operation and maintenance. Levees that do not
protect against the 1-percent-annual-chance flood event are not considered in the
hydraulic analysis of the 1-percent-annual-chance floodplain.
The East St. Louis and Vicinity, Illinois, flood control project authorized by the
Flood Control Act of 1936, provides urban design flood protection from the
Mississippi River floods (U.S. House, 1936). Protection from the 1-percentannual-chance-flood is provided, primarily by levees located outside the local
community boundaries, to all bottom lands between the bluffs on the east and the
Mississippi River and Chain of Rocks Canal on the west, and extends from Prairie
Du Pont Canal on the south side to Cahokia Creek diversion channel on the north.
The project included raising and enlarging 16.7 miles of levee, 3.1 miles of
concrete floodwall, gravity drainage structures, and alterations at bridge crossings.
The levee and floodwall portion of the project was essentially completed by 1964.
An extensive system of flood protection structures exists along the Mississippi
River in St. Clair County. This system includes levees, stormwater pumping
stations and gravity outlet structures. The levees offer protection against floods
with recurrence intervals of equal or less than a 1-percent-annual-chance
occurrence. The area of St. Clair County protected by these structures includes
primarily the American Bottoms plus areas located along the major streams which
outfall into the Mississippi River. The Eastside Levee and Sanitary District
operates 13 stormwater pumping stations and maintains 52 miles of drainage
ditches and stormwater sewer systems serving various cities and industries within
the American Bottoms.
Carlyle Reservoir is on the Kaskaskia River approximately 50 river miles
upstream of the St. Clair County boundary. This reservoir, constructed by the
USACE, was completed in 1967 and serves recreation, flood control, water
supply and navigation needs. The Kaskaskia River channel, between its mouth
and the City of Fayetteville, has been widened, straightened and deepened for
navigational purposes. Flood protection structures along the Kaskaskia River
within St. Clair County include a levee system and a stormwater pumping station,
which protect the area surrounding the City of New Athens.
The Kaskaskia River Levee systems provide protection from the 1% annual
chance flood.
The Blue Waters Ditch pump station reduces the 1-percent-annual-chance
floodplain in the City of Cahokia.
12
FEMA specifies that all levees must have a minimum of 3 foot freeboard against
the 1-percent-annual-chance flood to be considered a safe flood protection
structure.
South of Belleville, along Richland Creek, most of the levee stations are believed
to represent agricultural levees, which may protect fields during smaller flood
events. Most of these levees overtop during the 1-percent-annual-chance flood, or
do not maintain adequate freeboard.
North of State Highway 15 in Belleville, along Richland Creek, the levee stations
represent the ring levees protecting the sewage treatment plant and sewage disposal
ponds. On the landward side, the single levee feature was assumed to be
ineffective, as the feature was not continuous in upstream or downstream cross
sections.
Several major levee systems in the American Bottoms Region provide protection
from flooding of the main stem Mississippi River. While protection afforded by
the these systems is significant, findings brought forward by the USACE in August
2007 show that certain systems do not meet the requirements set forth in the Code
of Federal Regulations, Title 44, Section 65.10 (44 CFR 65.10), entitled “Mapping
of Areas Protected by Levee Systems”. Specific deficiencies were identified in the
following five systems:
Wood River Drainage & Levee District
Chain of Rocks Levee
Metro East Sanitary District
Prairie Du Pont Levee & Sanitary District
Fish Lake Drainage & Levee District
44 CFR 65.10 establishes minimum design, operation, and maintenance standards
for the accreditation of levee and levee systems in the NFIP. When FEMA learns
that a flood control system no longer provides adequate protection in accordance
with these standards, the affected FIRM panels are revised to show flood risk based
on the system not providing that protection.
Affected communities with established restoration plans for levees that are newly
de-accredited may request a special flood control restoration zone (Zone AR) if the
restoration can be accomplished within a specified length of time and the
community can demonstrate conformance to all appropriate provisions contained in
44 CFR 65.14. A community that does not receive Federal funds for the purpose
of constructing the restoration project is given a maximum of 5 years for
completion of restoration activities from the date of submittal of the community's
application for the Zone AR designation. A community that receives Federal funds
for the purpose of designing and/or constructing the restoration project is given a
maximum of 10 years for completion of restoration activities (or meet the
13
requirements of 44 CFR 61.12) from the date of submittal of the community's
application for the Zone AR designation.
Upon completion of restoration activities, affected communities should provide
written evidence to FEMA that the rehabilitated system(s) meets the requirements
of 44 CFR 65.10. Communities will often work through the levee owner for the
submission of required documents. Communities that receive Federal funds for the
purpose of design and/or construction of the restoration should provide evidence of
support for this certification from the USACE or appropriate Federal agency
involved in the design or construction.
Meetings held on August 29, 2007, at the East West Gateway Council of
Governments (St. Louis, Missouri) and September 29 at the Southwestern Illinois
College (Belleville, Illinois), provided initial information to community officials
and levee owners on the status of the levee evaluations and FEMA’s deaccreditation process. FEMA and the USACE participated in presenting
information at both meetings. Letters mailed in October 2007 to elected officials
and levee owners provided notice of FEMA’s intent to de-accredit the
aforementioned flood protection systems for purposes of flood risk identification as
shown on FIRMs projected for publication. The October 2007 letter also provided
guidance for the submission of data used to support an application for Zone AR
designation.
On January 29, 2008, a consolidated application for Zone AR designation was
submitted by the East West Gateway Council of Governments on behalf of the
impacted communities in Monroe, St. Clair and Madison Counties. The
application presents information on behalf of 25 incorporated communities and the
three listed counties. FEMA responded to individual communities in letters dated
___________________, 2008, identifying application deficiencies and establishing
submittal timeframes to allow finalization of Zone AR designations. The January
29, 2008, application establishes the start date for a maximum 10-year timeframe
for completion of restoration plans if Federal funds are used, or a maximum 5-year
timeframe if Federal funds are not used.
3.0
ENGINEERING METHODS
For the flooding sources studied by detailed methods in the community, standard
hydrologic and hydraulic study methods were used to determine the flood hazard
data required for this study. Flood events of a magnitude that 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
14
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 that equals or
exceeds the 1-percent-annual-chance (100-year) flood in any 50-year period is
approximately 40 percent (4 in 10); for any 90-year period, the risk increases to
approximately 60 percent (6 in 10). The analyses reported herein reflect flooding
potentials based on conditions existing in the community at the time of completion
of this study. Maps and flood elevations will be amended periodically to reflect
future changes.
3.1
Hydrologic Analyses
Hydrologic analyses were carried out to establish peak discharge-frequency
relationships for each flooding source studied by detailed methods affecting the
community.
The hydrologic analyses described in the previously printed FIS reports for
communities within St. Clair County have been compiled from the FIS reports
and are summarized below.
The National Weather Service (NWS) has had a recording gage located at the
Lambert St. Louis Airport since 1936. This station index number is 7455.
Precipitation records are available for the St. Louis area for the period from 1871
to date. These records were used with the USACE HEC-1 computer program to
determine the discharge frequency relationships for Schoenberger Creek No. 1 in
the City of East St. Louis (HEC, 1973).
Flood flow frequency data for Canteen Creek was derived from a log-Pearson
Type III statistical analysis. The gage and period of record was for the USGS
gage on Canteen Creek near Caseyville (1939 to date, USGS 05589500) (USGS,
1939 to date). Regionally optimized unit graph and loss rate parameters were
used in the Canteen Creek basin HEC-1 (HEC, 1973) model with frequency
rainfall amounts obtained from Technical Paper No. 40 (NWS, 1961). The 0.2percent-annual-chance flood discharges were obtained with rainfall data
extrapolated from that published in Technical Paper No. 40. The frequency curve
derived from the HEC-1 model was then adjusted to closely match the computed
frequency curve. Although the drainage area for Canteen Creek at State Highway
157 is greater than the drainage area at State Highway 159, peak discharges at
State Highway 157 are less because a significant amount of water goes into
storage.
For Ash Creek, Catawba Creek, Douglas Creek, Engle Creek, Engle Creek Ditch,
Hog River, Kaskaskia River, Little Canteen Creek, Little Silver Creek, Loop
Creek, Ogles Creek, Ogles Creek Tributary, Prairie Du Pont Diversion Channel,
Richland Creek from the downstream county boundary to approximately 5,200
15
feet upstream of Schiermeier Road, and West Fork Richland Creek, peak
discharges for floods of 10-, 2-, and 1-percent-annual-chance recurrence intervals
were developed by hydrologic basin modeling using the USACE HEC-1 program
(HEC, 1973). The computer program utilizes frequency rainfall amounts obtained
from Technical Papers No. 40 and 49, optimized unit hydrographs, and storage
routing (NWS, 1961 and NWS, 1964). Discharges for the 0.2-percent-annualchance floods were extrapolated from rainfall data analyzed by the method
published in Technical Paper No. 40 (NWS, 1961). All areas subject to shallow
flooding had peak volume values for the 10- and 1-percent-annual-chance floods
determined by these same methods.
On upper Engle Creek, the rational method flows were adopted because it was
judged that these flows were more reasonable than those of the regression
equations. The divided flow for Engle Creek Ditch was determined by a trialand-error method which balanced the water surface elevation (WSEL) of the
Ditch with that of Engle Creek.
On the Kaskaskia River, discharges decrease between the confluence of Silver
Creek and the upstream confluence of the Elkhorn River because of the effect of
storage above the Silver Creek confluence. Discharges decrease along Silver
Creek because of the storage effect of its floodplain.
November 5, 2003
Initial Countywide Analyses
For Schoenberger Creek No. 2, Harding Ditch, Canteen Creek, and various
ponding areas, flood elevations experienced in May 1995 exceeded elevations
published in previous FISs. Rainfall gage data published in Climatological Data,
Illinois (NOAA, 1995) indicate that 96 hour rainfall totals at the Edwardsville,
Cahokia, and Belleville gages are near those predicted for a 1-percent-annualchance storm event by Technical Paper No. 40. Therefore, this event was chosen
as the basis for reevaluating flood hazards in these areas.
The frequency-discharges for Silver Creek were based on the Regional Frequency
Analysis for Streams in the St. Louis District.
All peak discharges for Wolf Creek were estimated by applying synthetic unit
hydrograph methodology to the HEC-1 rainfall-runoff mathematical model
developed by the USACE (HEC, 1973). Parameters for Clark-unit hydrographs
and exponential loss rate functions were determined from regional relationships
developed from an optimization study of observed floods at 14 streamflow gages
in the vicinity of St. Clair County. Rainfall data for Richland Creek, provided by
the NWS (NWS, 1961 and 1964), were used to develop the 10-, 2-, 1-, and 0.2percent-annual-chance synthetic storm events. Rainfall data for Wolf Branch
were developed using Bulletin 70 (Huff and Angel, 1989) from the Illinois
Department of Energy and Natural Resources.
16
The hydrologic analyses for the upstream portion of Richland Creek (from
approximately 5,200 feet upstream of Schiermeier Road to approximately 1,100
feet upstream of North Green Mount Road) were performed from regression
equations taken from SIR 2004-5103, “Estimating Flood-Peak Magnitudes and
Frequencies for Rural Streams in Illinois” (Soong et. al, 2004). The results of these
equations were adjusted for urbanization using WSP-2207, “Flood Characteristics
of Urban Watersheds in the United States” (Sauer et. al, 1983).
Mississippi River floodplain elevations were determined by the January 2004
Upper Mississippi River System Flow Frequency Study (UMRSFFS) (USACE,
2004a). The UMRSFFS was developed by five USACE Districts (St. Paul, Rock
Island, Omaha, Kansas City, and St. Louis) and coordinated through
representatives from seven federal agencies and seven states. The study addresses
flooding of the Illinois River from Lockport to the mouth, the Missouri River
below the Gavins Point Dam to the mouth, and the Mississippi River from St. Paul
to the confluence with the Ohio River. Technical aspects of the study include
impacts of levees, land use change, and climate variation. Hydrology was
accomplished based on 100 years of record from 1898 to 1998 using a log-Pearson
Type III distribution for unregulated flows at gages. In situations where historic
records were not adequate to develop discharge frequency relationships or to verify
the results, hydrologic modeling was used to create synthetic flows based on
rainfall.
Peak discharge-drainage area relationships for St. Clair County, Illinois are shown
in Table 3.
Table 3 - Summary of Discharges
Peak Discharges (cubic feet per second)
10-PercentAnnualChance
2-PercentAnnual-Chance
4.1
1,490
2,750
3,490
4,470
22.6
4,300
7,000
8,400
11,000
20.1
4,500
7,100
8,600
11,100
CATAWBA CREEK
At confluence with Richland
Creek
2.05
2,040
2,800
3,130
3,520
DOUGLAS CREEK
Just upstream of confluence
with Richland Creek
20.6
6,200
9,300
10,600
12,800
Flooding Source and Location
ASH CREEK
At confluence with Loop
Creek
CANTEEN CREEK
At North Main Street /State
Highway 57
At State Highway 159/North
Illinois Street
Drainage Area
(square miles)
17
0.2-PercentAnnual-Chance
Table 3 – Summary of Discharges (Continued)
19.53
*
*
2,285
*
18.76
*
*
2,220
*
1.87
1.23
700
550
1,200
950
1,500
1,200
2,000
1,600
0.75
250
450
560
780
ENGLE CREEK DITCH
At confluence with Engle
Creek
0.75
118
266
354
647
HOG RIVER
At confluence with Silver
Creek
2.6
815
1,190
1,360
1,680
5,210
47,500
69,800
80,300
108,600
4,702
41,000
59,900
68,500
101,100
4,410
42,400
62,100
70,700
109,900
7.95
3,100
4,940
5,780
7,340
7.2
2,433
3,914
4,581
5,910
5.89
2,600
4,200
4,900
6,470
47.9
6,050
10,380
12,760
16,790
33.0
16.6
5,840
4,300
9,060
6,300
10,700
7,330
13,750
9,570
25.1
5,170
8,270
9,440
13,450
697,000
670,000
850,000
910,000
1,120,000
DOZA CREEK
Approximately 770 feet
downstream of Winter
Road
Approximately 1,660 feet
upstream of Winter Road
ENGLE CREEK
At Scott Troy Road
Just downstream of Illinois
Terminal Railroad
Just upstream of
convergence of Engle
Creek Ditch
KASKASKIA RIVER
of Richland Creek
of Silver Creek
of Elkhorn River
LITTLE CANTEEN CREEK
At North Main Street /State
Highway 157
upstream of North Main
Street /State Highway 157
upstream of Circle Drive
LITTLE SILVER CREEK
Creek
At CSX/Strack Lane
At Midgely Neiss Road
LOOP CREEK
Creek
MISSISSIPPI RIVER
At St. Louis Gage
Drainage Area
(square miles)
*Data Not Available
18
NORTHWEST TRIBUTARY
TO OGLES CREEK
At confluence with Unnamed
Tributary to Ogles Creek
OGLES CREEK
Creek
At Illinois Terminal Railroad
At Interstate Highway 64
OGLES CREEK TRIBUTARY
At confluence with Ogles
Creek
PRAIRIE DU PONT
DIVERSION CHANNEL
At confluence with
Mississippi River
RICHLAND CREEK
At State Highway 156
of West Fork of Richland
Creek
of Douglas Creek
Just downstream of Strip
Mine Road
Just upstream of SchleutterGermaine Road
At West F Street
Just downstream of the
confluence of Wolf Branch
Just upstream of the
confluence of Wolf Branch
Just downstream of Old
Collinsville Road
downstream of Hartman
1Lane
At North Green Mount Road
SCHOENBERGER CREEK
NO. 1
SCHOENBERGER CREEK
NO. 2
At State Highway 157
SILVER CREEK
At confluence with Kaskaskia
River
0.38
*
*
15.9
3,480
5,140
6,260
8,160
8.5
2.2
2,230
800
3,290
1,400
3,860
1,750
4,820
2,300
0.54
300
500
700
900
38.5
12,000
17,700
19,500
21,800
129.4
96.8
20,300
16,100
31,500
24,600
37,300
29,000
45,800
35,500
56.3
10,700
15,700
17,900
22,100
44.496
6,545
6,545
12,684
14,935
37.125
5,208
5,208
9,914
11,668
18.44
14.355
2,384
2,128
4,761
4,072
5,669
4,971
7,742
6,476
1.766
338
668
842
1,124
11.877
2,057
4,132
5,145
6,479
9.407
1,908
3,771
4,751
6,308
2.229
493
963
1,210
1,607
*
*
*
*
*
12.0
4,610
7,430
8,860
11,860
476.4
12,400
19,000
22,000
29,000
Drainage Area
(square miles)
*Data Not Available
19
155
*
UNNAMED TRIBUTARY TO
DOZA CREEK
downstream of Hillstown
Road
LOOP CREEK
At confluence with Loop
Creek
OGLES CREEK
At Pausch Road
At Merriam Parkway
At Longfellow Drive
RICHLAND CREEK
At State Highway 15
1Westbound
WEST FORK OF RICHLAND
CREEK
with Richland Creek
Just upstream of State
Highway 159
WOLF BRANCH
with Richland Creek
Drainage Area
(square miles)
9.97
*
*
3,915
*
1.85
*
*
931
*
1.23
0.46
0.77
*
*
*
*
*
*
881
316
539
*
*
*
3.79
*
*
3,100
*
26.9
5,100
8,300
10,100
1,600
23.0
5,000
7,900
9,600
12,000
1.8
1,300
1,545
1,750
2,215
*Data Not Available
Stillwater elevations for ponding areas within St. Clair County are shown in Table 4.
Table 4 - Summary of Stillwater Elevations
Water Surface Elevations (Feet NAVD*)
Flooding Source
VILLAGE OF ALORTON
Between Interstate Highway 255 and State
Highway 157
Approximately 600 feet southwest of the
intersection of Pocket Road and State
Highway 15 and Missouri Avenue
**
**
411
**
**
**
411
**
*National American Vertical Datum of 1988
**Data Not Available
20
Table 4 – Summary of Stillwater Elevations (Continued)
Flooding Source
VILLAGE OF CAHOKIA
Areas east of Illinois Central Railroad
Areas between Falling Stream Road and
U.S. Highway 50
Areas south of Camp Jackson Road
Areas north and west of Jerome Lane
Areas between Range Lane and the Missouri
Pacific Railroad
Area between Camp Jackson and Jerome
Lane
Between Illinois Terminal Railroad and Camp
Jackson Road
Approximately 20 feet south of the
intersection of Fox Meadow Lane and Paris
Avenue
VILLAGE OF CASEYVILLE
At intersection of Sterling Place and
Bermuda Avenue
At intersection of Countryside Drive and
Acorde Drive
North of Harding Ditch, west of Black Lane
Approximately 1,000 feet northwest of
intersection with Interstate Highway 64 and
State Highway 157
CITY OF CENTREVILLE
At the intersection of Lake Drive and East
Side Levee and Sanitary Canal District
At the intersection of Belleview Avenue and
th
North 80 Street
Approximately 1,000 feet west of the
intersection of State Highway 15 (New
Missouri Avenue and Harding Ditch)
Along Harding Drainage Ditch
Area bounded by 55th Street and 51st Street
and north of Lake Boulevard
East Side Levee and Sanitary District Canal
CITY OF EAST ST. LOUIS
Approximately 500 feet northwest of
intersection of Summit Avenue and
Michigan Avenue
Approximately 300 feet northeast of the
intersection of Louisville and Nashville
Railroad and Kings Highway (State
Highway 50)
Approximately 400 feet east of intersection of
nd
Ohio Avenue and North 62 Street
Approximately 500 feet southwest of
intersection of State Street and Terrace
Drive
**
**
**
**
397
405
**
**
**
**
**
**
**
**
406
406
408
**
**
**
**
**
409
**
**
**
404
**
**
**
404
**
**
**
422
**
**
**
422
**
**
**
418
**
**
**
422
**
**
**
414
**
**
**
414
**
**
**
411
**
**
**
**
**
411
411
**
**
**
**
411
**
**
**
414
**
**
**
415
**
**
**
414
**
**
**
414
**
21
Flooding Source
CITY OF EAST ST. LOUIS (CONTINUED)
Intersection of Marybelle Avenue and North
70th Street
Approximately 600 feet south of intersection
th
of St. Clair Avenue and North 47 Street
VILLAGE OF FAIRMONT CITY
Approximately 1,000 feet west of Collinsville
Road
Southwest area of the Village of Fairmont
City Ponding
North of Cahokia Canal, west of Madison
Road, and east of Industrial Avenue
Approximately 1,000 feet west of the
intersection of Collinsville Road and
Cookson Road
At intersection of Site Road and Park Road
Approximately 400 feet east of intersection
of Pocket Road and Site Road
At intersection of Park Drive and Major
Street
Approximately 800 feet west of intersection
of Stowers Road and Bernia Street
At intersection of Watts Street and Brinson
Drive
Approximately 0.5 mile east of intersection
of Watts Street and Brinson Drive
At intersection of Caseyville Road and
Bunkum Road
nd
At intersection of North 82 Street and
Bunkum Road
At intersection of Rock Springs Road and
McKinley Avenue
North of Old Cahokia Canal and south of
County Road boundary
Approximately 1,000 feet northeast of the
intersection of Mullins Creek Road and
Prairie Du Pont Creek
South of Cahokia Canal, north of CSX
Transportation and southwest of Old
Cahokia Canal
Approximately 1,000 feet east of the
intersection of Rock Springs Road and St.
Clair Avenue
Approximately 750 feet west of the
th
intersection of Lake Drive and North 88
Street
Approximately 400 feet south of intersection
of U.S. Highway 255 (County Highway 3)
**
**
418
**
**
**
414
**
**
**
403
**
414
**
**
**
**
**
407
**
**
**
403
**
**
**
**
**
411
411
**
**
**
**
418
**
**
421
**
**
**
**
418
**
**
**
418
**
**
**
422
**
**
**
422
**
**
**
415
**
**
**
403
**
**
**
418
**
**
**
403
**
**
**
415
**
**
**
414
**
**
**
404
**
22
Flooding Source
VILLAGE OF FAIRMONT CITY
(CONTINUED)
Approximately 700 feet southeast of the
intersection of State Highway 157 and
Carol Street
VILLAGE OF WASHINGTON PARK, CITY OF
EAST ST. LOUIS
Approximately 300 feet south of the
intersection of St. Clair Avenue and
Louisville and Nashville Railroad
Approximately 500 feet north of the
VILLAGE OF WASHINGTON PARK
Approximately 700 feet east of the
**
**
411
**
**
**
414
**
**
**
414
**
**
417
**
**
**Data not available
3.2
Hydraulic Analyses
Analyses of the hydraulic characteristics of flooding from the sources studied
were carried out to provide estimates of the elevations of floods of the selected
recurrence intervals. Users should be aware that flood elevations shown on the
FIRM represent rounded whole-foot elevations and may not exactly reflect the
elevations shown on the Flood Profiles or in the Floodway Data Table in the FIS
report. Flood elevations shown on the FIRM are primarily intended for flood
insurance rating purposes. For construction and/or floodplain management
purposes, users are cautioned to use the flood elevation data presented in this FIS
report in conjunction with the data shown on the FIRM.
The hydraulic analysis described in the previously printed FIS reports for
communities within St. Clair County have been compiled from the FIS reports
and are summarized below.
For Ogles Creek, Ogles Creek Tributary, Engle Creek and Engle Creek Ditch,
channel and valley cross sections were obtained by photogrammetric methods.
The photogrammetry was used to draw four-foot contour lines for delineating
flood limits on workmaps (USACE, 1979). However, the mapping was done to
a contour interval accuracy of two feet, which provided data for the valley cross
sections to plus or minus one foot of the actual elevations. For Ash Creek,
23
Canteen Creek, Catawba Creek, Douglas Creek, Hog River, Kaskaskia River,
Little Canteen Creek, Little Silver Creek, Loop Creek, Prairie Du Pont Diversion
Channel, Richland Creek from the downstream county boundary to
approximately 5,200 feet upstream of Schiermeier Road, Schoenberger Creek
No. 1, and West Fork of Richland Creek, cross sections were obtained by field
surveys and from topographic maps (USACE, 1975). All bridges and culverts
were field checked to obtain elevation data and structural geometry. The
location and extent of the cross sections were determined during field
inspections.
The Canteen Creek hydraulic analysis required special treatment below State
Highway 157. There are levees along the channel from this point downstream.
Peak flows of all floods studied, including the 10-percent-annual-chance flood,
would spill over the channel just below State Highway 157 and run through the
overbank area. When the floodwater spills over the channel bank, the water
levels downstream in the overbank area are lower than the levels in the channel
at the same location. Profiles were computed and drawn for both the channel
and overbank downstream of State Highway 157. The channel capacity for the
stream segment between State Highways 40 and 157 was determined for each
frequency flood. The capacity was then subtracted from the total peak flow and
the remainder was used to compute water-surface profiles in the overbank area.
The USACE HEC-2 computer program was used for this analysis (HEC, 1972).
For Ash Creek, Catawba Creek, Douglas Creek, Engle Creek, Engle Creek
Ditch, Hog River, Kaskaskia River, Little Canteen Creek, Little Silver Creek,
Loop Creek, Ogles Creek, Ogles Creek Tributary, Prairie Du Pont Diversion
Channel, Richland Creek from the downstream county boundary to
approximately 5,200 feet upstream of Schiermeier Road, Schoenberger Creek
No. 1, and West Fork Richland Creek, WSELs of floods of the selected
recurrence intervals were computed using the USACE HEC-2 computer program
(HEC, 1972).
Starting WSELs were estimated as normal depth for all streams listed above
other than Catawba Creek, which used the elevations for Richland Creek at its
confluence with Catawba Creek.
The depth of the shallow flooding areas were determined by averaging
planimetered areas of equal elevations from topographic maps obtained from
aerial photographs (USACE, 1975). By comparing these elevations with the
computed runoff volumes, ponding locations were determined.
Cross section data obtained from aerial photographs were used to prepare storageelevation curves for the Blue Waters Ditch and Dead Creek areas. Rating curves
were developed for each bridge and culvert in the area. Flooding along Dead
Creek and Blue Waters Ditch is primarily a matter of interconnected storage ponds
with little flow. This is due to the relatively flat slopes in the drainage courses and
the constrictions caused by undersized culverts. For this reason, WSELs were
24
determined using the USACE HEC-1 Flood Hydrograph Package (HEC, 1973).
The computed WSELs were used to delineate the areas subject to 1-percentannual-chance flooding under shallow ponding conditions. This was accomplished
using topographic maps at a scale of 1:4,800 with a contour interval of 2 feet
(USACE, 1975).
To consider the effects of Harding Ditch on the adjacent shallow flooding areas,
the capacity of the ditch was estimated using the height of the levees as the
stream bank. It was determined that during the 1-percent-annual-chance flood,
the WSEL in the ditch exceeds the elevation of the levee in some reaches and
will overtop the levee. The flow estimated to overtop the levee was added to the
flow estimated for the ponding areas analysis and a new elevation was
computed.
The elevations for the lower reach of Engle Creek and Rock Spring Branch,
which were studied by approximate methods, were presented in the
“Reconnaissance Study, O’Fallon, St. Clair County, Illinois”, prepared by the
Southwestern Illinois Metropolitan and Regional Planning Commission
(SIMRPC, 1976b).
For streams studied by approximate methods, information from a previous
USACE study and from an Illinois Department of Transportation (IDOT) study
was used to estimate the limits of flooding (USACE, unpublished and IDOT,
1978).
November 5, 2003
Initial Countywide Analyses
For Schoenberger Creek No. 2, Harding Ditch, and various ponding areas, flood
elevations experienced in May 1995 exceeded elevations published in previous
FISs. High water mark elevations were obtained by field survey of these areas
following the May 1995 flood.
These high water elevations and
photogrammetric maps were used to determine the limits of flooding.
A HEC-RAS model for Silver Creek was created to incorporate updated
hydrology and new geometry along the stream from approximately 500 feet
downstream of Norfolk Southern Railroad to just upstream of Interstate
Highway 64.
Wolf Branch WSELs were computed using HEC-2 (HEC, 1976).
Starting WSELs for Wolf Branch were calculated using the slope/area method.
25
For this revision, cross sections for the upstream portion of Richland Creek
(from approximately 5,200 feet upstream of Schiermeier Road to approximately
1,100 feet upstream of North Greenwood Road) were obtained using digital
topography and field survey. The WSELs were computed using the USACE’s
HEC-RAS (Version 3.1.3) computer program (HEC, 2005). Starting WSELs
were determined by using normal depth routines in HEC-RAS. The hydraulic
model was prepared using digital elevation data from the County along with data
from the National Elevation Dataset, without surveying bathymetric data. Where
bridge or culvert data were readily available, these data were reflected in the
hydraulic model. Where these structural data were not readily available, field
measurements of these structures were made to approximate their geometry in
the hydraulic models.
Two detailed study tributaries join Richland Creek within the study area: Wolf
Branch and Catawba Creek. The backwater effects of Richland Creek along these
tributaries were reduced due to the drop in BFEs along Richland Creek.
Cross sections for the Mississippi River were obtained from channel hydrographic
surveys in conjunction with Scientific Assessment and Strategy Team (SAST)
floodplain digital terrain data collected in 1995 and 1998. The UMRSFFS
(discussed in Section 3.1) is based on an unsteady flow model (UNET). Levee
failure was assumed at the top of existing levee grade based on an upstream and a
downstream point. The UNET model was calibrated by both stage and discharge
at gaging locations primarily by adjusting roughness coefficients and estimated
lateral inflows. Some special considerations and techniques were required to
address especially complex flow reaches and levee failure impacts.
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).
Channel roughness factors (Mannings “n”) used in the hydraulic computations
were based on field inspection. The Manning’s “n” values for all detailed studied
streams are listed in the following table:
Manning's "n" Values
Stream
Channel “n”
Overbank “n”
Ash Creek
Canteen Creek
Catawba Creek
Douglas Creek
0.035-0.080
0.035-0.080
0.067-0.098
0.035-0.070
0.035-0.140
0.040-0.070
0.030-0.048
0.050-0.140
26
Manning's "n" Values (Continued)
Stream
Stream
Doza Creek
Engle Creek
Engle Creek Ditch
Hog River
Kaskaskia River
Little Silver Creek
Loop Creek
Mississippi River
Northwest Tributary to Doza Creek
Ogles Creek
Richland Creek
Silver Creek
Wolf Branch
Stream
*
0.012-0.065
0.012-0.065
0.035-0.070
0.035-0.070
0.040-0.080
0.035-0.070
0.035-0.070
*
*
0.012-0.065
0.012-0.065
0.035-0.070
0.035-0.070
0.040
*
0.050-0.070
*
*
*
*
0.035-0.070
0.012-0.055
*
0.030-0.090
0.030-0.090
0.050-0.140
0.050-0.140
0.040-0.070
0.050-0.140
0.050-0.140
*
*
0.030-0.090
0.030-0.090
0.050-0.140
0.030-0.098
0.070
*
0.050-0.090
*
*
*
*
0.050-0.140
0.050-0.120
*Data Not Available
The profile baselines depicted on the FIRM represent the hydraulic modeling
baselines that match the flood profiles on this FIS report. As a result of improved
topographic data, the profile baseline, in some cases, may deviate significantly
from the channel centerline or appear outside the Special Flood Hazard Area.
The hydraulic analyses for this study were based on unobstructed flow. The
flood elevations shown on the Flood Profiles (Exhibit 1) are thus considered
valid only if hydraulic structures remain unobstructed, operate properly, and do
not fail.
3.3
Vertical Datum
All flood elevations shown in this FIS report and on the FIRM are referenced to
NAVD. Structure and ground elevations in the community must, therefore, be
referenced to NAVD. It is important to note that adjacent communities may be
referenced to NGVD. This may result in differences in BFEs across the
corporate limits between the communities. The average conversion factor that
was used to convert the data in this FIS report to NAVD was calculated using the
27
National Geodetic Survey’s (NGS) VERTCON online utility (NGS, 2007). The
data points used to determine the conversion are listed in Table 5.
Table 5 – Vertical Datum Conversion
Stream Name
Ash Creek
Canteen Creek
Catawba Creek
Douglas Creek
Doza Creek
Engle Creek
Engle Creek Ditch
Hog River
Kaskaskia River
Little Silver Creek
Loop Creek
Northwest Tributary to Ogles
Creek
Ogles Creek
Prairie Du Pont Diversion
Channel
Richland Creek (From the
downstream county
1boundary to 5,200 feet
1upstream of Schiermeier
1Road)
Schoenberger No. 1
Schoenberger No. 2
Silver Creek
Unnamed Tributary to Doza
Creek
Unnamed Tributary to Loop
Creek
Unnamed Tributary to Ogles
Creek
Unnamed Tributary to
Richland Creek
Wolf Branch
Minimum
Conversion
(Feet)
-0.407
-0.377
-0.413
-0.427
-0.459
-0.381
-0.381
-0.427
-0.413
-0.361
-0.407
-0.407
-0.390
Maximum
Conversion
(Feet)
-0.427
-0.430
-0.413
-0.427
-0.469
-0.394
-0.381
-0.427
-0.525
-0.371
-0.453
-0.427
-0.394
Average
Conversion
(Feet)
-0.416
-0.404
-0.413
-0.427
-0.465
-0.386
-0.381
-0.427
-0.455
-0.368
-0.429
-0.418
-0.393
Maximum
Offset (Feet)
0.011
0.027
0.000
0.000
0.006
0.008
0.000
0.000
0.070
0.007
0.024
0.011
0.003
-0.351
-0.354
-0.033
-0.453
-0.361
-0.075
-0.404
-0.359
-0.053
0.053
0.005
0.022
-0.427
-0.518
-0.462
0.056
-0.427
-0.394
-0.423
-0.466
-0.459
-0.407
-0.466
-0.466
-0.443
-0.400
0.442
-0.466
0.016
0.007
0.024
0.000
-0.427
-0.427
-0.427
0.000
-0.390
-0.394
-0.391
0.003
-0.427
-0.427
-0.427
0.000
-0.384
-0.400
-0.476
-0.407
-0.428
-0.402
0.048
0.005
BFEs and profile elevations reported in the Upper Mississippi River System Flow
Frequency Study (USACE, 2004a) were incorporated into this FIS report and
associated DFIRM. This information was converted from NGVD to NAVD based
on data presented in Table 6. A conversion factor was calculated using the latitude
28
and longitude of each Mississippi River cross section. The conversion factor for
each cross section was used to prepare the Mississippi River Floodway Data
Tables, Flood Profiles, and DFIRM.
Table 6 –Mississippi River Vertical Datum Conversions
Cross
Section
ID
169.79
170.15
170.60
171.01
171.46
171.88
172.41
172.97
173.46
174.00
174.38
175.33
175.80
176.19
176.56
176.96
177.44
177.91
178.31
178.86
178.89
179.00
179.12
179.17
179.53
180.01
180.03
180.11
180.22
180.77
181.33
181.90
182.44
182.50
182.90
NAD83
Latitude
(dec. deg.)
38.494
38.499
38.504
38.514
38.520
38.525
38.531
38.538
38.543
38.550
38.555
38.563
38.568
38.573
38.578
38.585
38.591
38.598
38.605
38.613
38.614
38.615
38.616
38.617
38.622
38.628
38.629
38.630
38.631
38.640
38.648
38.657
38.663
38.666
38.671
NAD83
Longitude
(dec. deg.)
90.247
90.245
90.242
90.252
90.249
90.246
90.243
90.240
90.235
90.229
90.226
90.214
90.206
90.201
90.198
90.193
90.189
90.184
90.179
90.178
90.178
90.178
90.178
90.178
90.176
90.175
90.175
90.175
90.174
90.174
90.175
90.175
90.178
90.178
90.179
NGVD
Base Flood
Elevation
(feet)
419.9
420.1
420.3
420.6
420.9
421.1
421.4
421.8
422.1
422.4
422.6
423.1
423.4
423.6
423.9
424.1
424.4
424.8
425.1
425.5
425.5
425.6
425.7
425.7
425.9
426.3
426.3
426.4
426.4
426.8
427.2
427.6
428.0
428.0
428.6
NAVD
Base Flood
Elevation
(feet)
419.9
420.1
420.3
420.5
420.8
421.0
421.3
421.7
422.0
422.3
422.5
423.0
423.3
423.5
423.8
424.0
424.3
424.7
424.9
425.3
425.3
425.4
425.5
425.5
425.7
426.1
426.1
426.2
426.2
426.6
427.0
427.5
427.8
427.9
428.5
NGVD to NAVD
Elevation
Change
(feet)
0.0
-0.0
-0.0
-0.1
-0.1
-0.1
-0.1
-0.1
-0.1
-0.1
-0.1
-0.1
-0.1
-0.1
-0.1
-0.1
-0.1
-0.1
-0.2
-0.2
-0.2
-0.2
-0.2
-0.2
-0.2
-0.2
-0.2
-0.2
-0.2
-0.2
-0.2
-0.1
-0.2
-0.1
-0.1
For additional information regarding conversion between NGVD and NAVD, visit
the NGS website at www.ngs.noaa.gov, or contact the NGS at the following
address:
29
Vertical Network Branch, N/CG13
National Geodetic Survey, NOAA
Silver Spring Metro Center 3
1315 East-West Highway
Silver Spring, Maryland 20910
(301) 713-3191
Temporary vertical monuments are often established during the preparation of a
flood hazard analysis for the purpose of establishing local vertical control.
Although these monuments are not shown on the FIRM, they may be found in the
Technical Support Data Notebook associated with the FIS report and FIRM for this
community. Interested individuals may contact FEMA to access these data.
To obtain current elevation, description, and/or location information for
benchmarks shown on this map, please contact the Information Services Branch of
the NGS at (301) 713-3242, or visit their website at www.ngs.noaa.gov.
4.0
FLOODPLAIN MANAGEMENT APPLICATIONS
The NFIP encourages State and local governments to adopt sound floodplain
management programs. Therefore, each FIS provides 1-percent-annual-chance (100year) flood elevations and delineations of the 1- and 0.2-percent-annual-chance (500year) floodplain boundaries and 1-percent-annual-chance floodway to assist
communities in developing floodplain management measures. This information is
presented on the FIRM and in many components of the FIS report, including Flood
Profiles, Floodway Data Table, and Summary of Stillwater Elevations Table. Users
should reference the data presented in the FIS report as well as additional information
that may be available at the local 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 (100-year) flood has been adopted by FEMA as the base flood for
floodplain management purposes. The 0.2-percent-annual-chance (500-year) flood
is employed to indicate additional areas of flood risk in the community. Between
cross sections, the boundaries were interpolated using: topographic maps developed
from aerial photographs at a scale of 1:4,800 with a contour interval of 2 feet;
topographic maps at a scale of 1:4,800 with a contour interval of 4 feet; and
topographic maps at a scale of 1:24,000 with a contour interval of 10 feet (USACE,
1975; USACE, 1979; Surdex Corporation, 1979; Surdex Corporation, 1975; USGS,
various dates). For the Mississippi River, the 1- and 0.2-percent-annual-chance
floodplain boundaries have been delineated using topographic maps at a scale of
1:24,000 with a contour interval of 10 feet. The delineation used flood elevations
determined at each cross section and interpolated the floodplain boundary between
cross-sections.
30
For the streams studied by approximate methods, the 1-percent-annual-chance
floodplain boundaries were delineated using: topographic maps at a scale of 1:4,800
feet with a contour interval of 4 feet; the Reconnaissance Study O'Fallon, St. Clair
County, Illinois; topographic maps at a scale of 1:24,000 with a contour interval of
10 feet; previously published Flood Hazard Boundary Maps; USGS Flood Prone
Areas Maps; Southwestern Illinois Metropolitan Regional Planning Commission
100-year Flood Plain Maps; and the USGS publication, Depth and Frequency of
Floods in Illinois (Kenneth Balk and Associates, 1975; SIMRPC, 1976; USGS,
various dates; FIA, 1976; USGS, no date; SIMRPC, 1976a; and USGS, 1976).
As indicated in Section 2.4, FEMA and the USACE have ascertained that certain
levee systems providing protection from Mississippi River flooding do not meet
the full requirements set forth in 44 CFR 65.10. A listing provided in Section 2.4
shows five systems do not meet the requirements set forth in 44 CFR 65.10 at the
time of publication of this study. These systems are therefore not shown as
providing protection from the base flood on FIRMs published with this study.
Instead, the maps contain Special Flood Hazard Areas designated as Zone AR, the
flood insurance zone for areas designated as flood control restoration zones. The
Zone AR designation requires the administration of special floodplain management
requirements as stipulated in the 44 CFR 60.3(f). The establishment of this flood
zone permits communities to regulate development through minimum floodplain
management requirements appropriate to the temporary nature of flood hazards
during the period when 1-percent-annual-chance flood protection is being restored.
Even after the completion of specific restoration projects, there may be areas
within the designated Zone AR which will be vulnerable to residual flooding from
sources other than those protected by the rehabilitated system(s). In these areas,
dual flood zones are shown (Zone AR/A, AR/AE and AR/AH), which shows that
these areas are subject to flooding as a result of a de-accredited flood control
system (Zone AR) as well as flooding from an underlying or residual flooding
source (Zones A, AE and AH) that will remain on the FIRM once the flood control
system is restored. These dual flood insurance zone designations imply special
considerations for floodplain management regulations and for flood insurance
rates.
The 1- and 0.2-percent-annual-chance floodplain boundaries are shown on the
FIRM (Exhibit 2). On this map, the 1-percent-annual-chance floodplain boundary
corresponds to the boundary of the areas of special flood hazards (Zones A, AE,
AH, AR/A, AR/AE and AR/AH); and the 0.2-percent-annual-chance floodplain
boundary corresponds to the boundary of areas of moderate flood hazards. In cases
where the 1- and 0.2-percent-annual-chance floodplain boundaries are close
together, only the 1-percent-annual-chance floodplain boundary has been shown.
Small areas within the floodplain boundaries may lie above the flood elevations but
cannot be shown due to limitations of the map scale and/or lack of detailed
topographic data.
31
For the streams studied by approximate methods, only the 1-percent-annualchance floodplain boundary is shown on the FIRM (Exhibit 2).
4.2
Floodways
Encroachment on floodplains, such as structures and fill, reduces flood-carrying
capacity, increases flood heights and velocities, and increases flood hazards in
areas beyond the encroachment itself. One aspect of floodplain management
involves balancing the economic gain from floodplain development against the
resulting increase in flood hazard. For purposes of the NFIP, a floodway is used
as a tool to assist local communities in this aspect of floodplain management.
Under this concept, the area of the 1-percent-annual-chance floodplain is divided
into a floodway and a floodway fringe. The floodway is the channel of a stream,
plus any adjacent floodplain areas, that must be kept free of encroachment so
that the 1-percent-annual-chance flood can be carried without substantial
increases in flood heights. Minimum Federal standards limit such increases to 1
foot, provided that hazardous velocities are not produced. The floodways in this
study 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. At the
recommendation of the Department of Water Resources, Illinois State Water
Survey (ISWS), a floodway having no more than a 0.1-foot surcharge has been
delineated for this FIS (ISWS, 1975).
The floodways presented in this FIS report and on the FIRM 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 have been tabulated for selected cross sections
(Table 7). In cases where the floodway and 1-percent-annual-chance floodplain
boundaries are either close together or collinear, only the floodway boundary has
been shown.
32
FLOODING SOURCE
CROSS SECTION
ASH CREEK
A
B
C
D
E
F
G
H
1
DISTANCE
840
1,588
3,038
4,778
6,828
9,889
11,839
13,039
1-PERCENT-ANNUAL-CHANCE-FLOOD
WATER SURFACE ELEVATION
FLOODWAY
WIDTH
(FEET)
793
633
561
574
629
800
488
72
SECTION
AREA
(SQUARE
FEET)
2,192
3,514
3,164
1,926
2,729
1,262
1,243
373
MEAN
VELOCITY
(FEET PER
SECOND)
REGULATORY
1.4
0.9
1.0
1.7
1.1
2.2
2.2
7.0
425.7
426.3
426.3
426.3
426.7
430.5
433.9
435.8
(FEET NAVD)
WITHOUT
FLOODWAY
WITH
FLOODWAY
(FEET NAVD)
(FEET NAVD)
421.42
424.43
424.83
425.83
426.7
430.5
433.9
435.8
421.5
424.5
424.9
425.8
426.8
430.6
434.0
435.9
1
Feet above confluence with Loop Creek
Elevation computed without consideration of flooding controlled by Loop Creek
3
Elevation computed without consideration of backwater effects from Loop Creek
2
TABLE 7
FEDERAL EMERGENCY MANAGEMENT AGENCY
FLOODWAY DATA
ST. CLAIR COUNTY, IL
ASH CREEK
INCREASE
(FEET)
0.1
0.1
0.1
0.0
0.1
0.1
0.1
0.1
FLOODING SOURCE
CROSS SECTION
CANTEEN CREEK
A
B
C
D
E
F
G
H
I
1
DISTANCE
13,434
16,632
19,906
20,011
24,288
26,664
28,618
32,525
34,109
FLOODWAY
WIDTH
(FEET)
3,371
2,473
94
400
581
1,301/4112
758/7272
105
265
SECTION
AREA
(SQUARE
FEET)
2,237
2,025
1,282
2,368
3,312
2,452
5,717
1,273
1,378
MEAN
VELOCITY
(FEET PER
SECOND)
REGULATORY
2.5
2.8
6.6
3.5
2.6
3.5
1.5
6.6
6.0
422.5
428.7
438.7
440.4
447.1
450.4
456.2
460.9
464.4
(FEET NAVD)
WITHOUT
FLOODWAY
WITH
FLOODWAY
(FEET NAVD)
(FEET NAVD)
422.5
428.7
438.7
440.4
447.1
450.4
456.2
460.9
464.4
422.6
428.8
438.7
440.4
447.2
450.5
456.2
461.0
464.5
1
Feet above confluence with Cahokia Canal
Total width/width within St. Clair County (excluding the Area Not Included for the City of Collinsville)
2
TABLE 7
FLOODWAY DATA
CANTEEN CREEK
INCREASE
(FEET)
0.1
0.1
0.0
0.0
0.1
0.1
0.0
0.1
0.1
FLOODING SOURCE
CROSS SECTION
CATAWBA CREEK
A
B
C
D
E
FLOODWAY
1
DISTANCE
686
1,742
2,429
3,168
3,643
WIDTH
(FEET)
578
287
87
100
220
SECTION
AREA
(SQUARE
FEET)
5,822
1,673
572
888
2,242
MEAN
VELOCITY
(FEET PER
SECOND)
REGULATORY
0.6
1.6
4.6
3.0
1.0
493.4
494.7
495.9
504.2
511.6
(FEET NAVD)
WITHOUT
FLOODWAY
WITH
FLOODWAY
(FEET NAVD)
(FEET NAVD)
490.32
494.7
495.9
504.2
511.6
490.4
494.8
496.0
504.2
511.6
1
Feet above confluence with Richland Creek
Elevation computed without consideration of backwater effects from Richland Creek
2
TABLE 7
FLOODWAY DATA
CATAWBA CREEK
INCREASE
(FEET)
0.1
0.1
0.1
0.0
0.0
FLOODING SOURCE
CROSS SECTION
DOUGLAS CREEK
A
B
C
1
DISTANCE
900
6,917
11,088
FLOODWAY
WIDTH
(FEET)
3,1142
1,058
90
SECTION
AREA
(SQUARE
FEET)
9,866
4,384
1,056
MEAN
VELOCITY
(FEET PER
SECOND)
REGULATORY
1.8
2.4
9.9
432.5
440.7
448.6
(FEET NAVD)
WITHOUT
FLOODWAY
WITH
FLOODWAY
(FEET NAVD)
(FEET NAVD)
432.5
440.7
448.6
432.6
440.8
448.6
1
Combined floodway width with Richland Creek
2
TABLE 7
FLOODWAY DATA
DOUGLAS CREEK
INCREASE
(FEET)
0.1
0.1
0.0
FLOODING SOURCE
CROSS SECTION
DOZA CREEK
A
B
C
D
E
1
DISTANCE
468
1,526
3,590
5,629
9,899
FLOODWAY
WIDTH
(FEET)
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
REGULATORY
500
1,276
1,150
1,145
158
1,423
2,104
5,857
4,763
635
2.9
1.6
0.1
0.1
0.3
407.6
408.5
412.1
412.1
415.6
(FEET NAVD)
WITHOUT
FLOODWAY
WITH
FLOODWAY
(FEET NAVD)
(FEET NAVD)
407.6
408.5
412.1
412.1
415.6
407.6
408.5
412.1
412.1
415.6
1
Feet above limit of detailed study (limit of detailed study is approximately 800 feet downstream of Winter Road)
TABLE 7
FLOODWAY DATA
DOZA CREEK
INCREASE
(FEET)
0.0
0.0
0.0
0.0
0.0
FLOODING SOURCE
CROSS SECTION
HOG RIVER
A
B
C
D
1
DISTANCE
7,973
9,895
12,408
13,897
FLOODWAY
WIDTH
(FEET)
265
59
240
48
SECTION
AREA
(SQUARE
FEET)
698
428
812
228
MEAN
VELOCITY
(FEET PER
SECOND)
REGULATORY
1.9
2.7
1.4
5.0
417.6
417.6
417.6
417.6
(FEET NAVD)
WITHOUT
FLOODWAY2
WITH
FLOODWAY
(FEET NAVD)
(FEET NAVD)
410.8
412.7
414.5
416.0
410.9
412.8
414.6
416.1
1
Feet above confluence with Silver Creek
Elevation computed without consideration of backwater effects from Silver Creek
2
TABLE 7
FLOODWAY DATA
HOG RIVER
INCREASE
(FEET)
0.1
0.1
0.1
0.1
FLOODING SOURCE
CROSS SECTION
KASKASKIA RIVER
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
1
DISTANCE
110,352
119,328
130,416
138,336
148,896
149,952
155,232
159,456
170,544
189,024
190,608
194,832
195,360
203,280
208,032
219,120
231,792
244,464
FLOODWAY
WIDTH
(FEET)
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
REGULATORY
5,647/4,4362
7,431/2,3502
4,036/3,6502
5,341/1,3002
5,730
5,214
4,100
5,807
7,300
2,500
2,260
3,230
4,092
10,015
11,467
10,507
13,497
14,209
105,077
136,261
71,932
60,049
95,958
77,585
20,938
74,976
92,659
21,075
23,353
24,712
30,054
48,936
122,298
137,935
116,507
136,302
0.8
0.6
1.1
1.3
0.8
1.0
3.8
0.9
0.8
3.3
3.0
2.8
2.3
1.4
0.6
0.5
0.6
0.5
392.2
392.2
392.2
392.6
392.9
392.9
393.9
394.3
394.8
395.4
395.9
396.9
397.2
399.7
400.1
400.4
400.7
401.2
(FEET NAVD)
WITHOUT
FLOODWAY
WITH
FLOODWAY
(FEET NAVD)
(FEET NAVD)
391.63
391.93
392.2
392.6
392.9
392.9
393.9
394.3
394.8
395.4
395.9
396.9
397.2
399.7
400.1
400.4
400.7
401.2
391.7
392.0
392.3
392.7
393.0
393.0
394.0
394.4
394.9
395.5
396.0
397.0
397.3
399.7
400.2
400.5
400.8
401.3
1
Feet above confluence with Mississippi River
Total width/width within county boundary
3
Elevation computed without consideration of backwater effects from Mississippi River
2
TABLE 7
FLOODWAY DATA
KASKASKIA RIVER
INCREASE
(FEET)
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.0
0.1
0.1
0.1
0.1
FLOODING SOURCE
CROSS SECTION
LITTLE CANTEEN
CREEK
A
B
C
D
E
F
G
H
I
J
FLOODWAY
1
DISTANCE
350
4,550
4,710
5,085
5,955
6,335
6,775
8,500
12,799
13,969
WIDTH
(FEET)
630
908
880
250
125
150
202
434
296
434
SECTION
AREA
(SQUARE
FEET)
2,447
1,239
2,576
1,165
989
517
1,215
2,281
931
1,474
MEAN
VELOCITY
(FEET PER
SECOND)
REGULATORY
2.4
4.7
2.2
5.0
5.8
11.2
4.8
2.0
4.9
3.1
426.8
439.0
442.4
444.9
446.7
447.5
451.6
455.6
468.0
470.9
(FEET NAVD)
WITHOUT
FLOODWAY
WITH
FLOODWAY
(FEET NAVD)
(FEET NAVD)
426.8
439.0
442.4
444.9
446.7
447.5
451.6
455.6
468.0
470.9
426.9
439.1
442.4
444.9
446.7
447.5
451.6
455.7
468.1
471.0
1
Feet above confluence with Harding Ditch
TABLE 7
FLOODWAY DATA
LITTLE CANTEEN CREEK
INCREASE
(FEET)
0.1
0.1
0.0
0.0
0.0
0.0
0.0
0.1
0.1
0.1
FLOODING SOURCE
CROSS SECTION
LITTLE SILVER CREEK
A
B
C
D
E
F
G
H
I
J
K
L
M
N
1
DISTANCE
2,700
10,190
16,542
19,024
27,646
29,256
30,344
38,264
40,100
43,185
45,135
46,729
48,778
54,141
FLOODWAY
WIDTH
(FEET)
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
REGULATORY
2,1002
1,566
285
1,641
1,082
149
1,206
898
712
1,154
1,165
807
2,834
680
6,405
10,381
2,503
9,599
7,018
1,621
9,669
5,337
5,313
6,743
2,031
3,469
8,161
2,999
5.5
1.2
5.1
1.3
1.5
6.6
1.2
2.1
2.1
1.1
3.6
1.7
0.7
1.9
430.6
431.4
433.5
435.7
441.5
441.8
443.3
447.3
450.7
453.3
453.9
454.9
456.3
461.9
1
Combined floodway width of Little Silver Creek and Silver Creek
3
Elevation computed without consideration of flooding controlled by Silver Creek
2
TABLE 7
(FEET NAVD)
WITHOUT
FLOODWAY
WITH
FLOODWAY
(FEET NAVD)
(FEET NAVD)
430.63
430.84
433.5
435.7
441.5
441.8
443.3
447.3
450.7
453.3
453.9
454.9
456.3
461.9
430.6
430.9
433.6
435.8
441.6
441.9
443.4
447.4
450.8
453.4
454.0
455.0
456.4
462.0
4
0.0
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
Elevation computed without consideration of backwater effects from
Silver Creek
FLOODWAY DATA
INCREASE
(FEET)
LITTLE SILVER CREEK
FLOODING SOURCE
CROSS SECTION
LOOP CREEK
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
FLOODWAY
1
DISTANCE
9,546
12,778
17,424
19,663
20,539
26,664
27,667
29,821
35,270
35,719
40,740
43,243
48,682
50,582
54,226
WIDTH
(FEET)
1,831
1,488
1,267
1,600
1,275
433
884
710
790
984
1,362
680
390
384
245
SECTION
AREA
(SQUARE
FEET)
1,443
7,231
2,524
6,072
7,388
2,012
6,443
1,285
2,939
4,183
4,334
3,584
1,487
1,503
807
MEAN
VELOCITY
(FEET PER
SECOND)
REGULATORY
6.5
1.3
4.2
1.8
1.6
6.0
1.9
5.6
2.4
1.7
5.6
4.0
4.5
4.4
8.3
421.3
423.2
427.7
428.8
429.6
438.0
441.6
443.3
453.3
453.8
463.7
468.7
484.6
494.9
502.9
(FEET NAVD)
WITHOUT
FLOODWAY
WITH
FLOODWAY
(FEET NAVD)
(FEET NAVD)
421.3
423.2
427.7
428.8
429.6
438.0
441.6
443.3
453.3
453.8
463.7
468.7
484.6
494.9
502.9
421.3
423.2
427.8
428.9
429.7
438.1
441.7
443.4
453.4
453.9
463.7
468.7
484.7
494.9
502.9
1
TABLE 7
FLOODWAY DATA
LOOP CREEK
INCREASE
(FEET)
0.0
0.0
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.0
0.0
0.1
0.0
0.0
FLOODING SOURCE
CROSS
SECTION
FLOODWAY
1
DISTANCE
WIDTH2
(FEET)
WITHIN
ILLINOIS
SECTION
MEAN
2
AREA
VELOCITY WIDTH
(SQUARE (FEET PER (FEET)
FEET)
SECOND) TOTAL
REGULATORY
FROM UNET
MODEL
(FEET NAVD)
WITHOUT
WITH
FLOODWAY FLOODWAY
(FEET NAVD) (FEET NAVD)
MISSISSIPPI
RIVER
5,268
419.9
169.79
169.79
3,820/03
N/A
N/A
N/A
170.15
170.15
3,668/03
N/A
N/A
5,111
420.1
N/A
3
170.60
170.60
N/A
N/A
4,771
420.4
N/A
3,737/0
5,104
420.5
171.01
171.01
2,137/1,4993
N/A
N/A
N/A
171.46
171.46
3,891
N/A
5,211
420.8
N/A
N/A
171.88
171.88
N/A
6,037
421.0
N/A
4,047
N/A
172.41
172.41
N/A
5,117
421.3
N/A
3,993
N/A
172.97
172.97
N/A
4,690
421.7
N/A
3,614
N/A
173.46
173.46
N/A
5,386
422.0
N/A
3,927
N/A
174.00
174.00
3,768
N/A
N/A
5,533
422.3
N/A
174.38
174.38
N/A
4,773
422.5
N/A
3,578
N/A
175.33
175.33
N/A
5,876
423.0
N/A
5,039
N/A
175.80
175.80
N/A
6,647
423.3
N/A
5,365
N/A
176.19
176.19
N/A
6,058
423.5
N/A
4,454
N/A
176.56
176.56
N/A
4,740
423.8
N/A
3,819
N/A
424.1
176.96
176.96
N/A
3,963
N/A
2,946
N/A
424.3
177.44
177.44
N/A
3,498
N/A
2,299
N/A
424.7
177.91
177.91
N/A
2,578
N/A
2,320
N/A
1
Miles above confluence with Ohio River
2
Widths are reported as widths to state line and composite width
3
Illinois width / width within St. Clair County
*
Floodway Data Tables for Mississippi River are a special case. See Flood Insurance Study Text for full explanation.
TABLE 7
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
FLOODWAY DATA
MISSISSIPPI RIVER*
INCREASE
(FEET)
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
FLOODING SOURCE
CROSS
SECTION
FLOODWAY
1
DISTANCE
WIDTH2
(FEET)
WITHIN
ILLINOIS
SECTION
AREA
(SQUARE
FEET)
MEAN
2
VELOCITY WIDTH
(FEET PER (FEET)
SECOND) TOTAL
REGULATORY
FROM UNET
MODEL
(FEET NAVD)
WITH
WITHOUT
FLOODWAY
FLOODWAY
(FEET
(FEET NAVD)
NAVD)
MISSISSIPPI
RIVER
(CONTINUED)
N/A
N/A
N/A
425.0
178.31
178.31
3,660
2,704
N/A
N/A
N/A
178.86
178.86
1,787
2,788
425.3
N/A
N/A
N/A
178.89
178.89
1,775
2,979
425.3
N/A
N/A
N/A
179.00
179.00
2,475
425.4
1,385
N/A
N/A
N/A
179.12
179.12
2,466
425.5
1,293
N/A
N/A
N/A
179.17
179.17
2,494
425.5
1,280
N/A
N/A
N/A
179.53
179.53
2,501
425.7
1,142
N/A
N/A
N/A
180.01
180.01
2,368
426.1
1,025
N/A
N/A
N/A
180.03
180.03
2,356
426.1
1,022
N/A
N/A
N/A
180.11
180.11
2,373
426.2
1,919
N/A
N/A
N/A
180.22
180.22
2,344
426.2
1,965
N/A
N/A
N/A
180.77
180.77
2,245
426.6
1,075
N/A
N/A
N/A
181.33
181.33
2,396
427.0
1,267
N/A
N/A
N/A
181.90
181.90
2,621
427.5
1,460
3
N/A
N/A
N/A
427.8
182.44
182.44
2,321
646/0
N/A
N/A
N/A
182.50
182.50
670/03
2,583
427.9
3
N/A
N/A
N/A
182.90
182.90
619/0
2,809
428.5
1
Miles above confluence with Ohio River
2
Widths are reported as widths to state line and composite width
3
Illinois width / width within St. Clair County
*
Floodway Data Tables for Mississippi River are a special case. See Flood Insurance Study Text for full explanation.
TABLE 7
FLOODWAY DATA
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
MISSISSIPPI RIVER*
INCREASE
(FEET)
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
FLOODING SOURCE
CROSS SECTION
OGLES CREEK
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
1
DISTANCE
1,637
6,288
8,765
12,836
18,110
20,492
22,604
27,356
28,887
33,744
39,970
45,144
47,890
48,980
49,570
51,600
52,855
53,860
54,940
FLOODWAY
WIDTH
(FEET)
500
573
251
552
547
253
311
93
39
32
137
131
58
149
263
160
230
60
40
SECTION
AREA
(SQUARE
FEET)
3,681
4,608
1,622
2,370
2,351
1,754
1,652
661
474
329
557
637
336
1,115
1,508
620
350
310
250
MEAN
VELOCITY
(FEET PER
SECOND)
REGULATORY
1.7
1.4
3.8
2.6
2.5
3.0
2.9
6.9
6.6
8.4
4.3
2.8
4.8
0.9
0.7
2.2
3.7
3.7
4.6
448.1
460.9
461.7
470.0
478.9
483.8
490.4
494.2
499.8
511.9
525.7
535.8
544.6
550.2
550.3
553.8
556.9
560.6
565.6
(FEET NAVD)
WITHOUT
FLOODWAY
WITH
FLOODWAY
(FEET NAVD)
(FEET NAVD)
447.02
460.9
461.7
470.0
478.9
483.8
490.4
494.2
499.8
511.9
525.7
535.8
544.6
550.2
550.3
553.8
556.9
560.6
565.6
447.0
461.0
461.8
470.1
479.0
483.9
490.5
494.2
499.9
511.9
525.8
535.9
544.7
550.3
550.4
553.9
556.9
560.7
565.7
1
Elevation computed without consideration of backwater effects from Silver Creek
2
TABLE 7
FLOODWAY DATA
OGLES CREEK
INCREASE
(FEET)
0.0
0.1
0.1
0.1
0.1
0.1
0.1
0.0
0.1
0.0
0.1
0.1
0.1
0.1
0.1
0.1
0.0
0.1
0.1
FLOODING SOURCE
CROSS SECTION
OGLES CREEK
TRIBUTARY
A
B
C
FLOODWAY
1
DISTANCE
340
645
1,060
WIDTH
(FEET)
179
180
220
SECTION
AREA
(SQUARE
FEET)
806
751
379
MEAN
VELOCITY
(FEET PER
SECOND)
REGULATORY
0.8
0.8
1.5
550.2
550.2
550.2
(FEET NAVD)
WITHOUT
FLOODWAY2
WITH
FLOODWAY
(FEET NAVD)
(FEET NAVD)
549.0
549.1
549.3
549.1
549.2
549.4
1
Feet above confluence with Ogles Creek
Elevation computed without consideration of backwater effects from Ogles Creek
2
TABLE 7
FLOODWAY DATA
OGLES CREEK TRIBUTARY
INCREASE
(FEET)
0.1
0.1
0.1
FLOODING SOURCE
CROSS SECTION
FLOODWAY
1
DISTANCE
WIDTH
(FEET)
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
RICHLAND CREEK
A
83,447
1,594
15,584
2.4
B
91,238
2,800
7,362
5.1
C
91,502
2,675
17,419
2.1
D
28,363
1.3
98,947
2,9472
E
107,237
1,601
10,311
2.8
F
108,240
2,009
13,276
2.2
G
112,834
2,803
13,968
2.0
H
115,790
1,745
10,081
2.7
I
115,949
1,788
10,359
2.7
J
14,865
1.7
120,014
3,1143
3
K
9,866
1.8
120,965
3,800
L
126,298
1,566
8,447
2.1
M
129,149
1,170
3,197
5.1
N
132,950
1,991
10,886
1.7
O
135,010
1,678
7,979
2.3
P
138,970
1,882
2,165
2.3
Q
142,521
1,300
2,253
5.7
R
143,370
1,373
7,185
1.3
S
148,388
1,279
4,420
2.6
T
149,821
1,807
3,121
4.3
1
Feet above confluence with Kaskaskia River
2
Combined floodway width of Richland Creek and West Fork of Richland Creek
3
Combined floodway width of Richland Creek and Douglas Creek
4
Elevation computed with consideration of levee/without consideration of levee
TABLE 7
REGULATORY
(FEET NAVD)
416.8
420.4
422.1
423.7
425.5
426.0
428.3
429.8
429.9
432.4
432.8
436.5
440.2
443.4
444.8
447.4
451.1
455.2
456.8/456.34
457.3/457.04
WITHOUT
FLOODWAY
WITH
FLOODWAY
(FEET NAVD)
(FEET NAVD)
416.8
420.4
422.1
423.7
425.5
426.0
428.3
429.8
429.9
432.4
432.8
436.5
440.2
443.4
444.8
447.4
451.1
455.2
456.3
457.0
416.9
420.4
422.1
423.7
425.6
426.1
428.4
429.9
430.0
432.5
432.9
436.6
440.2
443.4
444.9
447.4
451.1
455.2
456.3
457.0
FLOODWAY DATA
RICHLAND CREEK
INCREASE
(FEET)
0.1
0.0
0.0
0.0
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.0
0.0
0.1
0.0
0.0
0.0
0.0
0.0
FLOODING SOURCE
CROSS SECTION
FLOODWAY
1
DISTANCE
WIDTH
(FEET)
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
RICHLAND CREEK
(CONTINUED)
U
151,852
1,112
2,480
5.2
V
155,169
146
1,773
4.6
W
156,220
440
3,982
2.5
X
159,107
172
2,054
4.3
Y
162,067
173
1,393
4.3
Z
163,004
123
777
7.4
AA
164,862
718
1,666
4.8
AB
165,223
469
1,321
5.8
AC
168,074
259
1,132
5.8
AD
168,726
290
2,173
3.7
AE
169,846
247
2,871
2.6
AF
175,862
507
3,327
2.7
AG
177,149
343
2,240
3.3
AH
177,870
290
2,555
2.5
AI
181,044
549
2,952
3.1
AJ
183,561
556
2,520
3.6
AK
185,715
380
1,625
4.3
AL
187,701
512
2,109
4.1
AM
189,879
528
2,153
3.9
AN
191,699
342
1,498
4.4
1
2
Elevation computed with consideration of levee/without consideration of levee
TABLE 7
REGULATORY
(FEET NAVD)
460.5/460.32
463.8/462.42
470.4/470.12
472.6/472.42
474.0/473.92
475.2
478.7
479.0/478.92
489.1
490.7
493.2
496.3
496.7
500.5
501.7
504.6
506.8
509.6
512.5
513.9
WITHOUT
FLOODWAY
WITH
FLOODWAY
(FEET NAVD)
(FEET NAVD)
460.3
462.4
470.1
472.4
473.9
475.2
478.7
478.9
489.1
490.7
493.2
496.3
496.7
500.5
501.7
504.6
506.8
509.6
512.5
513.9
460.4
462.4
470.1
472.4
474.0
475.2
478.7
478.9
489.2
490.8
493.2
496.3
496.8
500.5
501.7
504.6
506.8
509.6
512.5
513.9
FLOODWAY DATA
RICHLAND CREEK
INCREASE
(FEET)
0.1
0.0
0.0
0.0
0.1
0.0
0.0
0.0
0.1
0.1
0.0
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
FLOODING SOURCE
CROSS SECTION
RICHLAND CREEK
(CONTINUED)
AO
AP
AQ
AR
AS
AT
AU
FLOODWAY
1
DISTANCE
WIDTH
(FEET)
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
REGULATORY
583
505
477
436
465
208
339
1,649
1,355
1,653
1,242
1,413
554
754
4.6
5.4
4.0
3.5
3.1
6.9
3.8
516.5
520.4
522.1
524.1
525.2
526.2
529.6
193,918
196,037
197,129
198,933
199,888
200,809
202,087
(FEET NAVD)
WITHOUT
FLOODWAY
WITH
FLOODWAY
(FEET NAVD)
(FEET NAVD)
516.5
520.4
522.1
524.1
525.2
526.2
529.6
516.5
520.4
522.1
524.1
525.2
526.2
529.6
1
TABLE 7
FLOODWAY DATA
RICHLAND CREEK
INCREASE
(FEET)
0.0
0.0
0.0
0.0
0.0
0.0
0.0
FLOODING SOURCE
CROSS SECTION
SCHOENBERGER
CREEK NO. 1
A
B
C
D
E
F
G
H
I
FLOODWAY
1
DISTANCE
WIDTH
(FEET)
17,688
18,427
19,483
20,064
20,856
21,595
22,334
23,126
24,288
25
57
56
17
14
85
160
14
11
SECTION
AREA
(SQUARE
FEET)
227
227
265
151
127
293
463
86
47
MEAN
VELOCITY
(FEET PER
SECOND)
REGULATORY
2.0
1.6
0.9
1.2
1.5
0.6
0.4
1.9
2.4
410.0
410.2
410.6
410.7
410.7
410.8
410.9
410.9
411.0
(FEET NAVD)
WITHOUT
FLOODWAY
WITH
FLOODWAY
(FEET NAVD)
(FEET NAVD)
410.0
410.2
410.6
410.7
410.7
410.8
410.9
410.9
411.0
410.0
410.3
410.7
410.8
410.8
410.9
411.0
411.0
411.1
1
Feet above confluence with Cahokia Canal
TABLE 7
FLOODWAY DATA
SCHOENBERGER CREEK NO. 1
INCREASE
(FEET)
0.0
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
FLOODING SOURCE
CROSS SECTION
SCHOENBERGER
CREEK NO. 2
J
K
L
M
N
O
FLOODWAY
1
DISTANCE
8,395
13,330
16,170
19,220
21,410
22,870
WIDTH
(FEET)
51
95
112
174
57
167
SECTION
AREA
(SQUARE
FEET)
729
1,105
1,122
1,122
487
795
MEAN
VELOCITY
(FEET PER
SECOND)
REGULATORY
11.9
6.6
3.0
3.0
6.9
4.2
436.7
448.1
456.0
466.4
472.6
481.8
(FEET NAVD)
WITHOUT
FLOODWAY
WITH
FLOODWAY
(FEET NAVD)
(FEET NAVD)
436.7
448.1
456.0
466.4
472.6
481.8
436.8
448.2
456.1
466.5
472.7
481.9
1
Feet above confluence with Harding Ditch
TABLE 7
FLOODWAY DATA
SCHOENBERGER CREEK NO. 2
INCREASE
(FEET)
0.1
0.1
0.1
0.1
0.1
0.1
FLOODING SOURCE
CROSS SECTION
FLOODWAY
1
DISTANCE
WIDTH
(FEET)
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
REGULATORY
SILVER CREEK
A
7,100
1,318
15,104
1.5
B
14,715
367
19,430
4.4
C
18,250
743
8,770
2.5
D
29,500
2,920
29,850
0.8
E
36,500
763
7,207
3.1
F
45,542
323
4,742
4.6
G
49,650
744
10,998
2.0
H
51,800
240
5,063
4.4
I
54,400
295
6,088
3.6
J
63,250
656
13,671
1.2
K
72,270
1,950
20,995
1.1
L
72,310
1,950
20,995
1.1
M
83,700
4,530
77,490
0.4
N
93,150
5,314
57,434
0.4
O
106,325
6,247
75,939
0.3
P
112,125
249
3,355
6.6
Q
118,165
3,100
34,105
0.7
R
125,540
2,919
23,375
7.4
S
130,867
2,132
23,651
0.9
T
137,117
2,303
21,824
1.0
U
145,432
1,676
12,706
1.7
1
2
Elevation computed without consideration of backwater effects from Kaskaskia River
TABLE 7
(FEET NAVD)
394.3
395.5
396.5
397.2
398.7
407.2
408.9
409.7
412.1
416.9
417.3
417.3
417.5
417.6
419.5
420.3
421.7
422.3
426.3
426.6
427.3
WITHOUT
FLOODWAY
WITH
FLOODWAY
(FEET NAVD)
(FEET NAVD)
393.92
395.5
396.5
397.2
398.7
407.2
408.9
409.7
412.1
416.9
417.3
417.3
417.5
417.6
419.5
420.3
421.7
422.3
426.3
426.6
427.3
FLOODWAY DATA
393.9
395.5
396.6
397.2
398.8
407.3
409.0
409.8
412.1
417.0
417.4
417.4
417.6
417.7
419.5
420.3
421.8
422.4
426.3
426.6
427.4
SILVER CREEK
INCREASE
(FEET)
0.0
0.0
0.1
0.0
0.1
0.1
0.1
0.1
0.0
0.1
0.1
0.1
0.1
0.1
0.0
0.0
0.1
0.1
0.0
0.0
0.1
FLOODING SOURCE
CROSS SECTION
UNNAMED TRIBUTARY
TO DOZA CREEK
A
B
C
D
FLOODWAY
1
DISTANCE
220
1,052
2,324
2,873
WIDTH
(FEET)
850
875
900
850
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
REGULATORY
3,352
2,938
3,337
2,254
1.2
1.3
1.3
2.6
412.1
412.2
415.5
415.6
(FEET NAVD)
WITHOUT
FLOODWAY
WITH
FLOODWAY
(FEET NAVD)
(FEET NAVD)
412.1
412.2
415.5
415.6
412.1
412.2
415.5
415.6
INCREASE
(FEET)
0.0
0.0
0.0
0.0
1
Feet above confluence with Doza Creek
TABLE 7
FLOODWAY DATA
UNNAMED TRIBUTARY TO DOZA CREEK
FLOODING SOURCE
CROSS SECTION
WEST FORK OF
RICHLAND CREEK
A
B
C
D
E
F
G
H
I
J
K
1
DISTANCE
3,168
10,100
10,877
17,424
22,229
30,835
35,534
45,778
53,909
58,291
63,202
FLOODWAY
WIDTH
(FEET)
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
REGULATORY
2,9472
1,393
1,659
1,608
97
1,039
1,152
514
550
618
62
28,363
3,584
2,608
6,056
1,215
2,932
3,534
2,197
1,664
2,393
651
1.3
2.8
3.9
1.7
7.9
2.9
2.3
3.4
4.1
2.8
8.4
423.7
425.6
427.5
435.9
443.2
451.1
457.5
476.5
491.9
499.8
510.4
(FEET NAVD)
WITHOUT
FLOODWAY
WITH
FLOODWAY
(FEET NAVD)
(FEET NAVD)
423.63
425.6
427.5
435.9
443.2
451.1
457.5
476.5
491.9
499.8
510.4
423.7
425.7
427.6
435.9
443.2
451.1
457.6
476.6
492.0
499.9
510.5
INCREASE
(FEET)
1
Combined floodway width of Richland Creek and West Fork Richland Creek
3
Elevation computed without consideration of flooding controlled by Richland Creek
2
TABLE 7
FLOODWAY DATA
WEST FORK OF RICHLAND CREEK
0.1
0.1
0.1
0.0
0.0
0.0
0.1
0.1
0.1
0.1
0.1
FLOODING SOURCE
CROSS SECTION
WOLF BRANCH
A
B
C
D
E
FLOODWAY
1
DISTANCE
WIDTH
(FEET)
2,040
4,298
4,550
4,970
6,215
458
16
230
32
54
SECTION
AREA
(SQUARE
FEET)
3,977
170
1,276
407
333
MEAN
VELOCITY
(FEET PER
SECOND)
REGULATORY
0.5
11.6
1.5
4.9
5.9
506.5
508.1
514.6
516.6
522.6
(FEET NAVD)
WITHOUT
FLOODWAY
WITH
FLOODWAY
(FEET NAVD)
(FEET NAVD)
506.5
508.1
514.6
516.6
522.6
506.5
508.2
514.6
516.6
522.6
1
TABLE 7
FLOODWAY DATA
WOLF BRANCH
INCREASE
(FEET)
0.0
0.1
0.0
0.0
0.0
FLOODING SOURCE
CROSS SECTION
SILVER CREEK
(CONTINUED)
V
W
X
Y
Z
AA
AB
AC
AD
AE
AF
1
DISTANCE
149,377
150,947
156,347
161,507
162,632
166,722
171,972
177,372
180,572
185,522
187,022
FLOODWAY
WIDTH
(FEET)
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
REGULATORY
1,184
2,1002
4,063
403
2,607
4,346
4,751
821
1,521
662
1,410
11,523
10,080
28,979
3,744
14,537
38,237
39,387
6,794
12,760
6,743
13,204
1.9
5.0
0.8
5.9
1.5
0.6
0.6
3.2
1.7
3.3
1.7
428.2
430.5
431.9
435.7
437.8
438.4
438.8
441.1
444.2
448.1
449.9
(FEET NAVD)
WITHOUT
FLOODWAY
WITH
FLOODWAY
(FEET NAVD)
(FEET NAVD)
428.2
430.5
431.9
435.7
437.8
438.4
438.8
441.1
444.2
448.1
449.9
428.2
430.5
431.9
435.8
437.8
438.5
438.9
441.2
444.3
448.2
450.0
1
Combined floodway width with Little Silver Creek
2
TABLE 7
FLOODWAY DATA
SILVER CREEK
INCREASE
(FEET)
0.0
0.0
0.0
0.1
0.0
0.1
0.1
0.1
0.1
0.1
0.1
Due to the limitation of the UNET (as described in Section 3.2) with floodway
encroachment modeling, floodway calculations for the Mississippi River are
based on the June 2004 Upper Mississippi River Floodway Computation
(USACE, 2004b) performed by the St. Paul, Rock Island, and St. Louis Districts
of the USACE. The study extends from Cairo, Illinois, to Hastings, Minnesota,
covering 815 miles.
The objective of the study was to produce a floodway consistent with the results
of the UMRSFFS (discussed in Section 3.1). A steady flow HEC-RAS model was
built and calibrated to the 1-percent-annual-chance flood UMRSFFS profile only.
The model was not calibrated to other frequency events or to “natural” conditions.
This model was then used to compute the floodway.
When states on opposite banks defined the floodway based on differing allowable
increases in elevation to the UMRSFFS 1-percent-annual-chance flood profile,
two floodway computations were performed. Floodway computations were based
on equal reduction in conveyance from both banks using first one state’s criteria
and then the other state’s criteria. The floodway computation using the criteria of
the state on the left bank was used to set the floodway boundary of the left bank.
Likewise the floodway computation using the criteria of the state on the right
bank was used to set the right bank floodway. A third composite floodway run
was performed using the floodway boundaries identified in the previous
calculations for the left and right bank limits respectively. The appropriate
floodway boundary on each bank was delineated and used in the HEC-RAS
model resulting in a composite encroached 1-percent-annual-chance flood profile.
When a levee defined the floodway, the floodway boundaries were placed at the
landside toe of the levee. Illinois has a more restrictive allowable rise than Iowa
or Missouri, therefore the composite floodway run produces a profile that exceeds
the Illinois limit of 0.1 foot rise and are not reported in the FIS for Illinois
Counties.
As a result of this approach, the Floodway Data Tables for the Mississippi River
are a special case. Floodway widths are reported in two columns; the width of the
floodway within the state of Illinois and the total width of the composite
floodway. Floodway section areas, floodway mean velocities, and 1-percentannual-chance flood WSELs with floodways are not reported from the steady
state hydraulic models. However, regulatory 1-percent-annual-chance flood
WSELs are reported from the UNET model.
In the State of Illinois, any portion of a stream or watercourse that lies within the
floodway fringe of a studied (AE) stream may have a state regulated floodway.
The FIRM may not depict these state regulated floodways.
57
Floodways restricted by anthropogenic features such as bridges and culverts are
drawn to reflect natural conditions and may not agree with the model computed
widths listed in the Floodway Data table in this FIS report.
The area between the floodway and 1-percent-annual-chance floodplain
boundaries is termed the floodway fringe. The floodway fringe encompasses the
portion of the floodplain that could be completely obstructed without increasing
the water surface elevation of the 1-percent-annual-chance flood more than 1 foot
at any point. Typical relationships between the floodway and the floodway fringe
and their significance to floodplain development are shown in Figure 1.
Figure 1 - Floodway Schematic
No floodways were computed for Engle Creek, Engle Creek Ditch, Northwest Tributary
to Ogles Creek, Prairie Du Pont Diversion Channel, Unnamed Tributary to Loop Creek,
Unnamed Tributary to Ogles Creek, and Unnamed Tributary to Richland Creek.
5.0
INSURANCE APPLICATIONS
For flood insurance rating purposes, flood insurance zone designations are assigned to a
community based on the results of the engineering analyses. These zones are as follows:
58
Zone A
Zone A is the flood insurance risk zone that corresponds to the 1-percent-annual-chance
floodplains that are determined in the FIS by approximate methods. Because detailed
hydraulic analyses are not performed for such areas, no BFEs or base flood depths are
shown within this zone.
Zone AE
Zone AE is the flood insurance risk zone that corresponds to the 1-percent-annual-chance
floodplains that are determined in the FIS by detailed methods. In most instances, wholefoot BFEs derived from the detailed hydraulic analyses are shown at selected intervals
within this zone.
Zone AH
Zone AH is the flood insurance risk zone that corresponds to the areas of 1-percentannual-chance shallow flooding (usually areas of ponding) where average depths are
between 1 and 3 feet. Whole-foot BFEs derived from the detailed hydraulic analyses are
shown at selected intervals within this zone.
Zone AR
Zone AR is the flood insurance risk zone that corresponds to an area of special flood
hazard formerly protected from the 1-percent-annual-chance flood event by a floodcontrol system that was subsequently decertified. Zone AR indicates that the former
flood-control system is being restored to provide protection from the 1-percent-annualchance or greater flood event.
Zone X
Zone X is the flood insurance risk zone that corresponds to areas outside the 0.2-percentannual-chance floodplain, areas within the 0.2-percent-annual-chance floodplain, areas of
1-percent-annual-chance flooding where average depths are less than 1 foot, areas of 1percent-annual-chance flooding where the contributing drainage area is less than 1 square
mile, and areas protected from the 1-percent-annual-chance flood by levees. No BFEs or
base flood depths are shown within this zone.
6.0
FLOOD INSURANCE RATE MAP
The FIRM is designed for flood insurance and floodplain management applications.
For flood insurance applications, the map designates flood insurance risk zones as
described in Section 5.0 and, in the 1-percent-annual-chance floodplains that were
studied by detailed methods, shows selected whole-foot BFEs or average depths.
59
Insurance agents use the zones and BFEs in conjunction with information on structures
and their contents to assign premium rates for flood insurance policies.
For floodplain management applications, the map shows by tints, screens, and symbols,
the 1- and 0.2-percent-annual-chance floodplains, floodways, and the locations of
selected cross sections used in the hydraulic analyses and floodway computations.
The countywide FIRM presents flooding information for the entire geographic area of St.
Clair County. Previously, FIRMs were prepared for each incorporated community and
the unincorporated areas of the County identified as flood-prone. Historical data relating
to the maps prepared for each community are presented in Table 8.
7.0
OTHER STUDIES
FISs have been prepared for Clinton County, Illinois and Incorporated Areas (FEMA,
2007); Randolph County, Illinois (Unincorporated Areas) (FEMA, 1986); and St. Louis
County, Missouri and Incorporated Areas (FEMA, 2000).
supersedes or is compatible with all previous studies on
Information pertaining to revised and unrevised flood hazards for each jurisdiction within
St. Clair County has been compiled into this FIS. Therefore, this FIS supersedes all
previously printed FIS reports and FIRMs for all of the jurisdictions within St. Clair
County. Stre
ams studied in this rep
This report either supersedes or is compatible with all previous studies on streams studied
in this report and should be considered
8.0
LOCATION OF DATA
Information concerning the pertinent data used in the preparation of this study can be
obtained by contacting FEMA, Federal Insurance and Mitigation Division, 536 South
Clark Street, Sixth Floor, Chicago, Illinois 60605.
9.0
BIBLIOGRAPHY AND REFERENCES
Federal Emergency Management Agency, Flood Insurance Study, St. Clair County,
Illinois (Unincorporated Areas), August 5, 1985.
Federal Emergency Management Agency, Flood Insurance Study, Randolph County,
Illinois (Unincorporated Areas), June 3, 1986.
Federal Emergency Management Agency, Flood Insurance Study, St. Louis County,
Missouri and Incorporated Areas, August 23, 2000. NF
Federal Emergency Management Agency, Flood Insurance Study, St. Clair County and
Incorporated Areas, Illinois, Washington, D.C., November 5, 2003.
NFIP.
60
COMMUNITY
NAME
INITIAL
IDENTIFICATION
FLOOD HAZARD
BOUNDARY MAP
REVISION DATE
FIRM
EFFECTIVE DATE
FIRM
REVISION DATE
Alorton, Village of
April 5, 1974
June 18, 1976
June 4, 1980
None
Belleville, City of
May 3, 1974
September 24, 1976
November 19, 1980
None
Brooklyn, Village of
March 1, 1974
April 2, 1976
March 28, 1980
None
Cahokia, Village of
March 29, 1974
April 2, 1976
October 17,1978
June 27, 1980
Caseyville, Village of
December 10, 1976
None
March 16, 1981
None
Centreville, City of
January 13, 1978
None
March 4, 1980
None
Columbia, City of*
N/A
None
N/A
None
Dupo, Village of
May 3, 1974
July 2, 1976
February 4, 1981
None
East Carondelet, Village of
May 3, 1974
April 2, 1976
March 2, 1981
None
East St. Louis, City of
November 16, 1973
June 25, 1976
November 1, 1979
None
Fairmont City, Village of
October 8, 1976
None
March 28, 1980
None
Fairview Heights, City of
April 2, 1976
None
July 3, 1978
None
Fayetteville, Village
February 22, 1974
June 4, 1976
June 15, 1981
None
Freeburg, Village of
March 22, 1974
June 4, 1976
January 18, 1980
None
*No Flood Hazard Areas identified within St. Clair County
TABLE 8
COMMUNITY MAP HISTORY
COMMUNITY
NAME
INITIAL
IDENTIFICATION
FLOOD HAZARD
BOUNDARY MAP
REVISION DATE
FIRM
EFFECTIVE DATE
FIRM
REVISION DATE
Hecker, Village of*
N/A
None
N/A
None
Lebanon, City of
November 16, 1973
February 27, 1976
July 2, 1981
None
Lenzburg, Village of
November 5, 2003
None
November 5, 2003
None
Marissa, Village of
November 5, 2003
None
November 5, 2003
None
Mascoutah, City of
March 1, 1974
May 28, 1976
June 15, 1981
None
Millstadt, Village of
TBD
None
TBD
None
New Athens, Village of
March 22, 1974
June 4, 1976
March 23, 1984
None
New Baden, Village of*
N/A
None
N/A
None
O’Fallon, City of
February 22, 1974
October 31, 1975
October 15, 1982
None
Sauget, Village of
December 13, 1974
None
August 1, 1980
July 9, 1982
Shiloh, Village of
November 5, 2003
None
November 5, 2003
None
Smithton, Village of
March 29, 1974
June 4, 1976
June 25, 1976
None
St. Clair County
(Unincorporated Areas)
May 21, 1976
None
December 15, 1981
August 5, 1985
St. Libory, Village of
September 6, 1974
June 11, 1976
February 25, 1983
None
*No Flood Hazard Areas identified within St. Clair County
TABLE 8
COMMUNITY
NAME
INITIAL
IDENTIFICATION
FLOOD HAZARD
BOUNDARY MAP
REVISION DATE
FIRM
EFFECTIVE DATE
FIRM
REVISION DATE
Summerfield, Village of
May 3, 1974
May 28, 1976
August 10, 1979
September 28, 1984
Swansea, Village of
April 5, 1974
June 4, 1976
December 1, 1981
Washington Park, Village of
October 8, 1976
None
June 15, 1979
None
None
TABLE 8
Federal Emergency Management Agency, Flood Insurance Study, Clinton County,
Illinois and Incorporated Areas, August 2, 2007.
Federal Insurance Administration, Flood Hazard Boundary Map, St. Clair County,
Illinois (Unincorporated Areas), May 21, 1976.
Federal Insurance Administration, Flood Insurance Study, Village of Cahokia, St. Clair
County, Illinois, Flood Insurance Study Report, April 17, 1978a; Flood Insurance Rate
Map, October 17, 1978.
Federal Insurance Administration, Flood Insurance Study, City of Fairview Heights, St.
Clair County, Illinois, Flood Insurance Study Report, January 3, 1978b; Flood Insurance
Rate Map, June 3, 1978.
Federal Insurance Administration, Flood Insurance Study, Village of Washington Park,
St. Clair County, Illinois, Flood Insurance Study Report, December 15, 1978c; Flood
Insurance Rate Map, June 15, 1979.
Federal Insurance Administration, Flood Insurance Study, City of East St. Louis, St. Clair
County, Illinois, Flood Insurance Study Report, May 1, 1979a; Flood Insurance Rate
Map, November 1, 1979.
Federal Insurance Administration, Flood Insurance Study, City of Centreville, St. Clair
County, Illinois, Flood Insurance Study Report, September 4, 1979b; Flood Insurance
Rate Map, March 4, 1980.
Federal Insurance Administration, Flood Insurance Study, Village of Brooklyn, St. Clair
County, Illinois, Flood Insurance Study Report, September 28, 1979c; Flood Insurance
Federal Insurance Administration, Flood Insurance Study, Village of Fairmont City, St.
Clair County, Illinois, Flood Insurance Study Report, September 28, 1979d; Flood
Insurance Rate Map, March 28, 1980.
Federal Insurance Administration, Flood Insurance Study, Village of Alorton, St. Clair
County, Illinois, Flood Insurance Study Report, December 4, 1979e; Flood Insurance
Federal Insurance Administration, Flood Insurance Study, Village of Sauget, St. Clair
County, Illinois, Flood Insurance Study Report, February 1, 1980a; Flood Insurance Rate
Map, August 1, 1980.
Federal Insurance Administration, Flood Insurance Study, City of Belleville, St. Clair
County, Illinois, Flood Insurance Study Report, May 19, 1980b; Flood Insurance Rate
Map, November 19, 1980.
Federal Insurance Administration, Flood Insurance Study, Village of Dupo, St. Clair
County, Illinois, Flood Insurance Study Report, August 4, 1980c; Flood Insurance Rate
Map, February 4, 1981.
Federal Insurance Administration, Flood Insurance Study, Village of East Carondelet, St.
Clair County, Illinois, Flood Insurance Study Report, September 2, 1980d; Flood
Insurance Rate Map, March 2, 1981.
64
Federal Insurance Administration, Flood Insurance Study, Village of Caseyville, St. Clair
County, Illinois, Flood Insurance Study Report, September 16, 1980e; Flood Insurance
Federal Insurance Administration, Flood Insurance Study, City of Mascoutah, St. Clair
County, Illinois, Flood Insurance Study Report, December 15, 1980f; Flood Insurance
Federal Insurance Administration, Flood Insurance Study, Village of Fayetteville, St.
Clair County, Illinois, Flood Insurance Study Report, December 15, 1980g; Flood
Insurance Rate Map, June 15, 1981.
Federal Insurance Administration, Flood Insurance Study, City of Lebanon, St. Clair
County, Illinois, Flood Insurance Study Report, January 2, 1981a; Flood Insurance Rate
Map, July 2, 1981.
Federal Insurance Administration, Flood Insurance Study, Village of Swansea, St. Clair
County, Illinois, Flood Insurance Study Report, June 1, 1981b; Flood Insurance Rate
Map, December 1, 1981.
Federal Insurance Administration, Flood Insurance Study, St. Clair County, Illinois
(Unincorporated Areas), Flood Insurance Study Report, June 15, 1981c; Flood Insurance
Rate Map, December 15, 1981.
Federal Insurance Administration, Flood Insurance Study, City of O’Fallon, St. Clair
County, Illinois, Flood Insurance Study Report, April 15, 1982; Flood Insurance Rate
Map, October 15, 1982.
Huff, F.A., and J.R. Angel, Frequencey Distributions and Hydroclimatic Characteristics
of Heavy Rainstorms in Illinois, Bulletin 70, 1989.
Hydrologic Engineering Center, HEC-1 Flood Hydrograph Package, U.S. Army Corps of
Engineers, Davis, California, 1973.
Hydrologic Engineering Center, HEC-2 Water Surface Profiles, U.S. Army Corps of
Engineers, Davis, California, 1972.
Hydrologic Engineering Center, HEC-2 Water Surface Profiles, U.S. Army Corps of
Engineers, Davis, California, November 1976.
Hydrologic Engineering Center, HEC-RAS River Analysis System, Version 3.1.3, U.S.
Army Corps of Engineers, Davis, California, May 2005.
Illinois Department of Transportation, Division of Water Resources, Strategic Planning
Study, Canteen Creek Watershed, Madison and St. Clair Counties, Illinois, September
1978.
Illinois State Geological Survey, Statewide ArcSDE Raster Mosaic of USGS DRGs.
Champaign, Illinois, 2003.
65
Illinois State Water Survey Division and Illinois Division of Water Resources,
Governor's Task Force on Flood Control, State of Illinois Guidelines for Flood Plain
Studies, March 1975.
Kenneth Balk and Associates, Inc., Drainage Study and Storm Water Program for the
City of Fairview Heights, Illinois, St. Louis, Missouri, 1975.
National Weather Service, Rainfall Frequency Atlas of the United States, 30-Minute to
24-Hour Durations, 1- to 100-Year Return Periods, Technical Paper 40, U.S. Department
of Commerce, 1961.
National Weather Service, Two- to Ten-Day Precipitation for Return Periods of 2 to 100
years in the Contiguous United States, Technical Paper 49, U.S. Department of
Commerce, 1964.
National Geodetic Survey, VERTCON – North American Vertical Datum Conversion
Utility. Retrieved
January 15, 2007, from http://www.ngs.noaa.gov/cgibin/VERTCON/vert_con.prl.
National Oceanographic and Atmospheric Administration, Climatological Data, Illinois,
May 1995.
Sauer, V. B., W. O. Thomas, Jr., V. A. Stricker and K. V. Wilson, Flood Characteristics
of Urban Watersheds in the United States., WSP 2207, U.S. Geological Survey, 1983.
Soong, D.T., A.L. Ishii, J.B. Sharpe and C F. Avery, 2004. Estimating Flood-Peak
Magnitudes and Frequencies for Rural Streams in Illinois, SIR 2004-5103, U.S.
Geological Survey, 2004.
Southwestern Metropolitan Area Planning Commission, Land Characteristics Study, St.
Clair County, Illinois, June 1970.
Southwestern Illinois Metropolitan and Regional Planning Commission, Plan for Major
Drainage: The American Bottoms and Hillside Drainage Area Planning Basin,
Collinsville, Illinois, August 1975.
Southwestern Illinois Metropolitan and Regional Planning Commission, Plan for Major
Drainage: The Richland Creek Planning Basin, Collinsville, Illinois, June 1976a.
Southwestern Illinois Metropolitan and Regional Planning Commission, Reconnaissance
Study, O'Fallon, St. Clair County, Illinois, Illinois Department of Transportation,
Division of Water Resources, 1976b.
Surdex Corporation, Aerial Photography, St. Louis, Missouri, April 4, 1979.
Surdex Corporation, Orthographic Maps, Scale 1:4,800, Contour Interval 4 feet: Village
of Swansea, Illinois, 1975.
U.S. Army Corps of Engineers, St. Louis District, Flood Plain Information, Silver Creek
and Tributaries, St. Clair County, Illinois - No. 1, St. Louis, Missouri, September 1974.
66
U.S. Army Corps of Engineers, St. Louis District, Topographic Maps, Scale 1:4,800,
Contour Interval 2 feet: East St. Louis and Vicinity, Illinois, 1975.
U.S. Army Corps of Engineers, St. Louis District, Aerial Photography, Scale 1:4,800,
Contour Interval 4 feet: Village of Fayetteville, City of Mascoutah, City of O'Fallon,
Illinois, 1979.
U.S. Army Corps of Engineers, Kansas District, Omaha District, Rock Island District, St.
Paul District, and St. Louis District, Upper Mississippi River System Flow Frequency
Study, January 2004a.
U.S. Army Corps of Engineers, Rock Island District, St. Paul District, and St. Louis
District, Upper Mississippi River Floodway Computation, June 30, 2004b.
U.S. Army Corps of Engineers, St. Louis District, East St. Louis and Vicinity, Illinois,
Interior Flood Control Project, (unpublished).
U.S. Census Bureau, American Factfinder, St. Clair County, Illinois, 2007. Retrieved
April 29, 2008, from http://factfinder.census.gov.
U.S. Geological Survey, Water Resources Data for Illinois, Part l, Surface Water
Records, 1939 to date.
U.S. Geological Survey, 7.5 Minute Series Topographic Maps, Scale 1:24,000, Contour
Interval 10 Feet: Alton, Illinois-Missouri, 1954, photorevised 1968; Baldwin, Illinois,
1970; Bethalto, Illinois, 1952, photorevised 1968, Cahokia, Illinois-Missouri, 1954,
photorevised 1968 and 1974; Collinsville, Illinois, 1955, photorevised 1968 and 1974;
Freeburg, Illinois, 1954, photorevised 1968 and 1974; Granite City, Illinois, 1954,
photorevised 1968 and 1974; Highland, Illinois, 1957; Lebanon, Illinois, 1954,
photorevised 1968 and 1974; Mascoutah, Illinois, 1954, photorevised 1968 and 1974;
Millstadt, Illinois, 1954, photorevised 1968 and 1974; Monks Mound, I1linois,1954,
photorevised 1968 and 1974; New Athens East, Illinois, 1954, photorevised 1968 and
1974; New Athens West, Illinois, 1954, photorevised 1968 and 1974; O'Fallon, Illinois,
1954, photorevised 1968 and 1974; Paderborn, Illinois, 1954, photorevised 1968 and
1974; Red Bud, Illinois, 1970; St. Jacob, Illinois 1954, photorevised 1968 and 1974; St.
Libory, Illinois, 1964; Tilden, Illinois, 1965; Trenton, Illinois, 1957; Veedy, Illinois,
1957; Webster Groves, Missouri-Illinois, 1954, photorevised 1968 and 1974, U.S.
Department of the Interior, various dates.
U.S. Geological Survey, Depth and Frequency of Floods in Illinois, Byron J. Prugh, Jr.,
1976.
U.S. Geological Survey, Water Resources Data for Illinois, Water Year 1976, Water Data
Report IL-76-1 Champaign, Illinois, 1977.
U.S. Geological Survey, EROS Data Center, National Elevation Dataset, p. Raster digital
data; 1/3 arc second (10 meter) posting DEM, Sioux Falls, South Dakota, 1999.
U.S. Geological Survey, Peak Streamflow for the Nation, USGS 05595200 Richland
Creek Near Hecker, IL. Retrieved April 29, 2008a, from http://nwis.waterdata.usgs.gov.
67
U.S. Geological Survey, Peak Streamflow for the Nation, USGS 07010000 Mississippi
River at St. Louis, MO. Retrieved April 29, 2008b, from http://nwis.waterdata.usgs.gov.
U.S. Geological Survey, Map of Flood-Prone Areas, Scale 1:24,000, Contour Intervals 10
Feet: Freeburg Quadrangle; Champaign, Illinois, no date.
U.S. House, 74th Congress, H.R. 8455, Flood Control Act of 1936, Public Law No. 738,
1936.
The Weather Channel, Monthly Averages for Belleville, IL. Retrieved April 29, 2008,
from http://www.weather.com.
68

ST. CLAIR COUNTY, IL - Illinois Flood Maps

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