VOLUME 1 OF 2

MADISON COUNTY, AND INCORPORATED AREAS

COMMUNITY COMMUNITY NAME NUMBER ALHAMBRA, VILLAGE OF 170270 ALTON, CITY OF 170437 BETHALTO, VILLAGE OF 170438 COLLINSVILLE, CITY OF 170439 EAST ALTON, VILLAGE OF 170440 EDWARDSVILLE, CITY OF 170441 GLEN CARBON, VILLAGE OF 170442 GODFREY, VILLAGE OF 171031 GRANITE CITY, CITY OF 170443 GRANTFORK, VILLAGE OF 170209 HAMEL, VILLAGE OF 170160 HARTFORD, VILLAGE OF 170444 HIGHLAND, CITY OF 170445 LIVINGSTON, VILLAGE OF 170794 Madison MADISON, CITY OF 170446 County MADISON COUNTY (UNINCORPORATED AREAS) 170436 MARINE, VILLAGE OF 170199 MARYVILLE, VILLAGE OF 170299 * NEW DOUGLAS, VILLAGE OF 170316 PIERRON, VILLAGE OF 170317 PONTOON BEACH, VILLAGE OF 170447 PRELIMINARY ROXANA, VILLAGE OF 170448 SOUTH ROXANA, VILLAGE OF 170449 * ST. JACOB, VILLAGE OF 170208 TROY, CITY OF 170255 VENICE, CITY OF 170450 WILLIAMSON, VILLAGE OF 170324 WOOD RIVER, CITY OF 170451 * WORDEN, VILLAGE OF 170825

*NO SPECIAL FLOOD HAZARD AREAS IDENTIFIED

Federal Emergency Management Agency

FLOOD INSURANCE STUDY NUMBER 17119CV001A

NOTICE TO FLOOD INSURANCE STUDY USERS

Communities participating in the National Flood Insurance Program (NFIP) 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. It is advisable to 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 at any time. In addition, FEMA may revise part of this FIS report by the Letter of Map Revision (LOMR) 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.

Selected Flood Insurance Rate Map panels for this community contain information that was previously shown separately on the corresponding Flood Boundary and Floodway Map panels (e.g., floodways, cross sections). In addition, former flood hazard zone designations have been changed as follows: Old Zones New Zone A1 through A30 AE B X C X

Initial Countywide FIS Effective Date:

This preliminary FIS report does not include unrevised Floodway Data tables or unrevised Flood Profiles. These Floodway Data tables and Flood Profiles will appear in the final FIS report.

TABLES OF CONTENTS

Table of Contents – Volume 1

Page 1.0 INTRODUCTION 1

1.1 Purpose of Study 1 1.2 Authority and Acknowledgements 1 1.3 Coordination 4

2.0 AREA STUDIED 5

2.1 Scope of Study 5 2.2 Community Description 9 2.3 Principal Flood Problems 10 2.4 Flood Protection Measures 13

3.0 ENGINEERING METHODS 16

3.1 Hydrologic Analyses 17 3.2 Hydraulic Analyses 23 3.3 Vertical Datum 26

4.0 FLOODPLAIN MANAGEMENT APPLICATIONS 29

4.1 Floodplain Boundaries 29 4.2 Floodways 31

5.0 INSURANCE APPLICATION 75

5.1 Flood Insurance Zones 75

6.0 FLOOD INSURANCE RATE MAP 76

7.0 OTHER STUDIES 76

8.0 LOCATION OF DATA 79

9.0 BIBLIOGRAPHY AND REFERENCES 79

FIGURES

FIGURE 1 – Floodway Schematic 31

i Table of Contents – Volume 1 (continued) Page

TABLES

TABLE 1 – Madison County CCO Meetings 5 TABLE 2 – Limits of Previously Detailed Studies 5 TABLE 3 – Limits of New Detailed Studies 7 TABLE 4 – Letters of Map Change 9 TABLE 5 – Peak Discharge Values 19 TABLE 6 – Manning’s “n” Values 24 TABLE 7 – Summary of Still Water Elevations 25 TABLE 8 – Datum Conversion Calculations by Stream 26 TABLE 9 – Vertical Datum Conversions 27 TABLE 10– Floodway Data Tables 34-74 TABLE 11– Community Map History 77-78

Table of Contents – Volume 2

EXHIBITS Exhibit 1 – Flood Profiles Belt Line Creek Panels 01P Creek 02P – 09P Canteen Creek 10P – 12P Coal Branch Creek 13P – 14P East Alton Ditch 15P East Fork Silver Creek 16P – 17P East Fork Wood River 18P – 20P Honeycut Branch 21P Indian Creek 22P – 24P Joulters Creek 25P – 27P Judys Branch 28P – 32P Judys Branch Tributary 5 33P Judys Branch Tributary 5A 34P Judys Branch Tributary 5B 35P – 36P Judys Branch Tributary 9 37P Judys Branch Tributary 9A 38P Judys Branch Tributary 9B 39P Judys Branch Tributary 10 40P Judys Creek 41P – 43P Judys Creek Tributary B 44P Laurel Branch 45P – 46P Laurel Branch Tributary 1 47P Lindenthal Creek 48P – 50P Lindenthal Creek Tributary 1 51P Lindenthal Creek Tributary 2 52P Lindenthal Creek Tributary 3 53P Lindenthal Creek Tributary 4 54P Mississippi River 55P – 57P Mooney Creek 58P – 61P Mooney Creek Tributary 1 62P

ii Table of Contents – Volume 2 (continued)

EXHIBITS (continued) Exhibit 1 – Flood Profiles (continued) Mooney Creek Tributary 2 Panels 63P Paddock Creek 64P – 66P Sherry Creek – East Fork Sherry Creek 67P Silver Creek 68P – 69P Silver Creek Tributary No. 1 70P Silver Creek Tributary No. 2 71P – 72P Smith Lake Tributary 73P Smith Lake Tributary 2 74P Stanley Creek 75P Sugar Fork 76P Tributary E 77P Tributary F 78P Tributary G 79P Tributary X 80P Tributary Z 81P West Fork Wood River 82P – 84P Wood River 85P

PUBLISHED SEPARATELY Exhibit 2 – Flood Insurance Rate Map Index Flood Insurance Rate Maps

iii FLOOD INSURANCE STUDY

MADISON COUNTY, ILLINOIS – AND INCORPORATED AREAS

1.0 INTRODUCTION

1.1 Purpose of Study

This Flood Insurance Study (FIS) revises and supersedes the FIS reports and/or Flood Insurance Rate Maps (FIRMs) [/Flood Boundary and Floodway Maps] in the geographic area of Madison County, Illinois, including the Cities of Alton, Collinsville, Edwardsville, Granite City, Highland, Madison, Venice, and Wood River; the Villages of Bethalto, East Alton, Glen Carbon, Godfrey, Hartford, Livingston, Pontoon Beach, Roxana, South Roxana, and Worden and unincorporated areas of Madison County (hereinafter referred to collectively as Madison County), and aids in the administration of the National Flood Insurance Act of 1968 and the Flood Disaster Protection Act of 1973. (The Village of Fairmont City appears in the St. Clair County FIS). Please note that the Villages of New Douglas, St. Jacob, and Worden have No Special Flood Hazard Areas Identified. This study has developed flood risk data for various areas of the community that will be used to establish actuarial flood insurance rates. This information will also be used by Madison County to update existing floodplain regulations as part of the Regular Phase of the National Flood Insurance Program (NFIP), and by local and regional planners to further promote sound land use and floodplain development. Minimum floodplain management requirements for participation in the NFIP are set forth in the Code of Federal Regulations at 44 CFR, 60.3.

In some states or communities, floodplain management criteria or regulations may exist that are more restrictive or comprehensive than the minimum Federal requirements. In such cases, the more restrictive criteria take precedence and the State (or other jurisdictional agency) will be able to explain them.

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 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.

Information on the authority and acknowledgments for each of the previously printed FISs and Flood Insurance Rate Maps (FIRMs) for communities within Madison County was compiled, and is shown below.

City of Alton: The hydrologic and hydraulic analyses for the City of Alton were performed by the U.S. Army Corps of Engineers (USACE), St. Louis District, for the Federal Insurance

1 Administration (FIA), under Inter-Agency Agreement No. IAA-H-7-76, Project Order No. 24. This study was completed in July 1978 (Reference 1).

Village of Bethalto: The hydrologic and hydraulic analyses for this study were performed by the USACE, St. Louis District, for the FIA, under Inter-Agency Agreement IAA-H-10-77, Project Order No. 24. This study was completed in December 1978 (Reference 2).

City of Collinsville: The hydrologic and hydraulic analyses for the City of Collinsville were performed by the USACE, St. Louis District, for the FIA, under Inter-Agency Agreement No. IAA-H-10-77, Project Order No. 6. This study was completed in June 1979 (Reference 3).

Village of East Alton: The hydrologic and hydraulic analyses for this study were performed by the Roy F. Weston, Inc. for the FIA, under Contract No. H-3977. This study was completed in October 1977 (Reference 4).

City of Edwardsville: The hydrologic and hydraulic analyses for the City of Edwardsville were obtained from the Flood Insurance Study for the County of Madison, Unincorporated Areas, Illinois. Refer to Madison County (Unincorporated Areas) below (Reference 5).

City of Granite City: The hydrologic and hydraulic analyses for this study were done by the USACE, St Louis District for the FIA under Interagency Agreement IAA-H-7-76 Project Order No. 7 (Reference 6).

Village of Hartford: The hydrologic and hydraulic analyses for this study were performed by the Roy F. Weston, Inc. for the FIA, under Contract No. H-3977. This study was completed in October 1977 (Reference 7).

City Of Highland: The hydrologic and hydraulic analyses for this study were performed by the USACE, St. Louis District for the FIA, under Inter-Agency Agreement EMW-E-1153, Project Order No. 1. This study was completed in May 1985 (Reference 8).

City of Madison: The hydrologic and hydraulic analyses for this study were performed by the USACE, St. Louis District, for the FIA, under Inter-Agency Agreement IAA-H-10-77, Project Order No. 6. This study was completed in August 1978 (Reference 9).

Village of Pontoon Beach: The hydrologic and hydraulic analyses for this study were performed by the USACE, St. Louis District, for the FIA, under Inter-Agency Agreement IAA-H-10-77, Project Order

2 No. 6. This study was completed in January 1978 (Reference 10).

Village of Roxana: The hydrologic and hydraulic analyses for this study were performed by the Roy F. Weston, Inc. for the FIA, under Contract No. H-3977. This study was completed in October 1977 (Reference 11)

Village of South Roxana: The hydrologic and hydraulic analyses for this study were performed by the USACE, St. Louis District, for the FIA, under Inter-Agency Agreement IAA-H-210-77, Project Order No. 6. This study was completed in October 1978 (Reference 12).

City of Venice: The hydrologic and hydraulic analyses for this study were performed by the USACE, St. Louis District, for the FIA, under Inter-Agency Agreement IAA-H-7-76, Project Order No. 7. This study was completed in June 1976. Base flood elevations were assigned in the areas of shallow flooding by Dewberry, Nelson & Davis in January 1977, at the direction of the FIA (Reference 13).

City of Wood River: The hydrologic and hydraulic analyses for this study were performed by the Roy F. Weston, Inc. for the FIA, under Contract No. H-3977. This study was completed in October 1977 (Reference 14).

Madison County: The hydrologic and hydraulic analyses for this study were (Unincorporated Areas) performed 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. A portion of this study was conducted by Turner Collie & Braden Inc., Consulting Engineers, under contract with the St. Louis District. This study was completed in June 1979. (Reference 15).

In addition to incorporating the existing fifteen FIS for communities within Madison County, this countywide FIS includes seventy seven additional approximate studies, four new detailed study areas, redelineation of all other effective profiles, and incorporation of approved Letter of Map Changes (LOMC). The vertical datum was shifted to North American Vertical Datum of 1988 (NAVD88). The digital floodplain data was merged into a single, updated Digital Flood Insurance Rate Map (DFIRM). The DFIRM includes 1995 Digital orthophotography, ten foot contours, political boundaries, road centerlines with street names, railroads with names, airports, rivers, lakes, streams, bridges and other hydraulic structures, and elevation reference marks.

Hydrologic and hydraulic analyses for Mooney Creek and associated tributaries in the City of Edwardsville were prepared by Fuller, Mossbarger, Scott and May Engineers, Inc. (FMSM) for Federal Emergency Management Agency (FEMA) under Contract No. EMC- 2001-CO-0057. This study was completed in May 2003.

3 Hydrologic and hydraulic analyses for Laurel Branch, Lindenthal Creek, and associated tributaries in the City of Highland were prepared by FMSM for FEMA under Contract No. EMC-2001-CO-0057. This study was completed in April 2003.

Hydrologic and hydraulic analyses for Judys Branch, Judys Creek, and associated tributaries in the Village of Glen Carbon were prepared by the Illinois Department of Natural Resources (IDNR) as part of the USACE’s East St. Louis & Vicinity Ecosystem Restoration and Flood Damage Reduction Project. The study was completed in November 2005.

Hydrologic and hydraulic analyses for the Upper Mississippi River System Flow Frequency Study (UMRSFFS) was prepared by the USACE, St. Paul, Rock Island, Omaha, Kansas City, and St. Louis Districts, with participants of a task force including the USACE Head Quarters, USACE Institute for Water Resources, USACE Mississippi Valley Division, USACE Northwestern Division, Geological Survey (USGS), National Weather Service (NWS), Bureau of Reclamation, National Resouces Conservation Service (NRCS), FEMA, Valley Authority (TVA), and the states of Minnesota, Wisconsin, Iowa, Illinois, , Kansas, and Nebraska. This work was completed in January 2004.

Upon completion of the UMRSFFS, the USACE Rock Island, St. Louis, and St. Paul districts performed floodway computations for the Upper Mississippi River for FEMA under Contract No. EMW-2002-IA-0114. This work was completed in June 2004.

Additional approximate hydrologic and hydraulic analyses for this FIS were performed by FMSM for FEMA under Contract No. EMC-2001-CO-0057. This work, which was completed in September 2005, covered unprotected flooding sources affecting Madison County.

1.3 Coordination

The purpose of an initial Consultation Coordination Officer's (CCO's) meeting is to discuss the scope of the FIS. A final CCO meeting is held to review the results of the study. The dates of the initial and final CCO meeting held for the previous FIS for Madison County and the incorporated communities within its boundaries are shown in Table 1 (References 1-15).

Results of the technical aspects of this study were coordinated with, reviewed and approved by IDNR, the State coordinating agency.

Throughout this study, coordination efforts have occurred between FEMA, IDNR, the Illinois State Water Survey (ISWS), USACE, and FMSM regarding the Mississippi River study incorporation and levee issues.

On September 9, 2002, in initial CCO meeting was held concerning this countywide FIS. The results of the study were reviewed at the open house held on MONTH DATE, YEAR, and attended by representatives of Madison County, IDNR, and FEMA. All problems raised at that meeting have been addressed in this study.

4 TABLE 1 –Madison County CCO Meetings Community Name Initial CCO Date Final CCO Date City of Alton January 30, 1976 June 29, 1979 Village of Bethalto January 19, 1976 August 7, 1979 City of Collinsville August 26, 1976 December 19, 1979 Village of East Alton March, 1979 June 5, 1978 City of Edwardsville not published February 15, 1983 City of Granite City March 1, 1975 August 4, 1976 Village of Hartford March, 1976 May 26, 1978 City of Highland March 31, 1983 December 11, 1985 City of Madison August 27, 1976 April 27, 1979 Village of Pontoon Beach September 7, 1976 April 26, 1979 Village of Roxana March, 1976 May 26, 1978 Village of South Roxana August 26, 1976 March 27, 1979 City of Venice March 31, 1975 August 5, 1976 City of Wood River March, 1976 June 5, 1978 Madison County May 27, 1976 January 13, 1981

2.0 AREA STUDIED

2.1 Scope of Study

This FIS covers the geographic area of Madison County, Illinois.

The flooding sources studied previously by detailed methods are shown in Table 2.

TABLE 2 – Limits of Previously Detailed Studies

Flooding Source Limits of Detailed Study Belt Line Creek From Burlington & Quincy Railroad to State Route 111 (City of Alton)

Cahokia Creek Within the limits of Madison County (City of Edwardsville, Unincorporated Madison County)

Canteen Creek From about 1,050 below South Clinton Street to 3,100 feet above Interstate Highway 70 (City of Collinsville, Unincorporated Madison County)

Coal Branch Creek From North Rogers Road to the confluence of Black Creek (City of Alton)

East Alton Ditch From mouth at East Fork Wood River to Kent Street with consideration of specifications for channelization (Reference 16) (Village of East Alton)

East Fork Sherry Creek From mouth at Sherry Creek to just upstream Renken Road (Unincorporated Madison County)

East Fork Silver Creek From confluence with Silver Creek to Ludwig Road (Unincorporated Madison County)

5 TABLE 2 – Limits of Previously Detailed Studies (Continued)

Flooding Source Limits of Detailed Study

East Fork Wood River From confluence with West Fork Wood River to 2,000 feet above Seiler Road (Village of East Alton, Village of Bethalto, Unincorporated Madison County)

Honeycut Branch From confluence with West Fork Wood River to 11,600 feet above Seiler Road (Unincorporated Madison County)

Indian Creek Between the confluence with Cahokia Creek and Moro Road (Unincorporated Madison County)

Joulters Creek From the confluence with Paddock Creek to 450 feet above Renken Road (Unincorporated Madison County)

Paddock Creek From mouth at Cahokia Creek to about 1,600 feet upstream of Stiegliter Road (Unincorporated Madison County)

Sherry Creek From confluence with Cahokia Creek to confluence with East Fork Sherry Creek (Unincorporated Madison County)

Silver Creek From about 10,000 feet below Lebanon Road to about 3,000 feet above Silver Creek Road (Unincorporated Madison County)

Silver Creek Tributary No. 1 From confluence with Silver Creek to 4,800 feet above Conn Road (Unincorporated Madison County)

Silver Creek Tributary No. 2 From confluence with Silver Creek to Missouri Pacific Railroad (Unincorporated Madison County)

Stanley Creek From the confluence with East Fork Wood River to 3,450 feet above Culp Lane (Unincorporated Madison County)

Sugar Fork From confluence with East Fork Silver Creek to 4,750 feet above Mayer Road (Unincorporated Madison County)

Tributary E From 1,150 feet below Unnamed Road crossing to 50 feet above Oakland Road (Unincorporated Madison County)

Tributary F From about 1,600 feet below confluence with Tributary G to about 1,100 feet above confluence with Tributary G (Unincorporated Madison County)

Tributary G From confluence with Tributary F to 50 feet above Sitze Street (Unincorporated Madison County)

Tributary X From confluence with West Fork Wood River to 2,200 feet above third Burlington Northern railroad crossing above Straube Lane (Unincorporated Madison County)

Tributary Z From confluence with Indian Creek to 200 feet above Melody Lane (Unincorporated Madison County)

6 TABLE 2 – Limits of Previously Detailed Studies (Continued)

Flooding Source Limits of Detailed Study

West Fork Wood River From confluence with East Fork Wood River to 2,200 feet above Straube Lane (Village of East Alton, City of Alton, Unincorporated Madison County)

Wood River From mouth at the Mississippi River to confluence with East Fork Wood River (Village of East Alton, City of Alton, Unincorporated Madison County)

Detailed studies were performed to determine shallow ponding conditions. These studies include the area on the western side of the City of Collinsville in the American Bottoms, an area near Wood River Junior High School in the Village of East Alton, the City of Madison, the Village of Pontoon Beach with the exception of the area west of Breckenridge Land and south of Pontoon Avenue, the eastern portion of the Village of Roxana, an area adjacent to in the southwest corner of the Village of Roxana, the Village of South Roxana, the City of Venice, and Tributary 1 and Tributary 2 in the City of Wood River.

The following streams were restudied or newly studied in detail and included in this study:

TABLE 3 – Limits of New Detailed Studies

Flooding Source Limits of Detailed Study

Judys Branch From 1,100 feet below State Highway 157 to about 3,800 feet above State Highway 159 (Village of Glen Carbon)

Judys Branch Tributary 5 From mouth at Judys Branch to confluence with Tributaries 5a and 5b (Village of Glen Carbon)

Judys Branch Tributary 5a From confluence with Tributaries 5 and 5b to 700 feet above State Highway 159 (Village of Glen Carbon)

Judys Branch Tributary 5b From confluence with Tributaries 5 and 5a to 3,700 feet above State Highway 159 (Village of Glen Carbon)

Judys Branch Tributary 9 From mouth at Judys Branch to confluence with Tributaries 9a and 9b (Village of Glen Carbon)

Judys Branch Tributary 9a From confluence with Tributaries 9 and 9b to 150 feet above Ash Road (Village of Glen Carbon)

Judys Branch Tributary 9b From confluence with Tributaries 9 and 9a to about 500 feet above confluence (Village of Glen Carbon)

Judys Branch Tributary 10 From mouth at Judys Branch to about 100 feet below abandoned railroad (Village of Glen Carbon)

Judys Creek From mouth at Judys Branch to about 9,500 feet above I-270 (Village of Glen Carbon)

7

TABLE 3 – Limits of New Detailed Studies (Continued)

Flooding Source Limits of Detailed Study

Judys Creek Tributary B From mouth at Judys Creek to 1,250 feet above Timberwolfe Drive (Village of Glen Carbon)

Laurel Branch From mouth at Lindenthal Creek to about 3,950 feet above Willow Creek Drive (City of Highland)

Laurel Branch Tributary 1 From mouth at Laurel Branch to about 800 feet above Willow Creek Drive (City of Highland)

Lindenthal Creek From Iberg Road to 200 feet below Plaza Drive (City of Highland)

Lindenthal Creek Tributary 1 From mouth at Lindenthal Creek to 1,350 feet above Troxler Avenue (City of Highland)

Lindenthal Creek Tributary 2 From mouth at Lindenthal Creek to 50 feet above US Highway 40 (City of Highland)

Lindenthal Creek Tributary 3 From mouth at Lindenthal Creek to about 1,150 feet above mouth (City of Highland)

Lindenthal Creek Tributary 4 From mouth at Lindenthal Creek to about 1,700 feet above mouth (City of Highland)

Mississippi River Within the limits of Madison County (City of Venice, City of Madison, Village of Hartford, City of Wood River, Village of East Alton, City of Alton, Unincorporated Madison County)

Mooney Creek From confluence with Cahokia Creek to Goshen Road (City of Edwardsville, Unincorporated Madison County)

Mooney Creek Tributary 1 From mouth at Mooney Creek to about 750 feet above Stonebrooke Drive (City of Edwardsville)

Mooney Creek Tributary 2 From mouth at Mooney Creek to about 1850 feet above Alderwood Court (City of Edwardsville)

Approximate analyses are usually used to study areas having a low development potential or minimal flood hazards. In 2004, new approximate analyses were performed to protect areas where flood hazards were not previously identified. In addition, some approximate studies were performed to replace existing approximate study areas.

This countywide FIS also incorporates the determination of letters issued by the Federal Emergency Management Agency (FEMA) resulting in map revisions (Letter of Map Revisions (LOMR)) and map amendments (Letter of Map Amendments (LOMA)), as shown in Table 4, “Letters of Map Change.”

Letters of Map Amendment (LOMA) incorporated for this study are summarized in the Summary of Map Amendment (SOMA) included in the Technical Support Data Notebook

8 (TSDN) associated with this FIS update. Copies of the TSDN may be obtained from the Community Map Repository.

TABLE 4 – Letters of Map Change

Community Flooding Source(s) and Project Date Issued Type Identifier City of Granite City Unnamed Ponding Area September 8, 2000 LOMR Zone Change from AH to X

Madison Unincorporated Smith Lake Tributary December 28, 1999 LOMR Areas, County of Updated hydrologic and hydraulic analyses

City of Wood River Smith Lake Tributary/ April 12, 2000 LOMR Smith Lake Tributary 2 Updated hydrologic and hydraulic analyses

2.2 Community Description

Madison County is in southwestern Illinois, directly across the Mississippi River from St. Louis, Missouri. Madison County is bordered on the north by Jersey County, Macoupin County, and Montgomery County, Illinois. It is bordered on the east by Bond County and Clinton County, Illinois. It is bordered on the south by St. Clair County and Clinton County, Illinois. It is bordered on the west by Jersey County, Illinois; St. Charles County, Missouri; and the City of St. Louis, Missouri. The county encompasses approximately 725 square miles. Elevations range from near 650 feet in the northeastern portion of the county to 400 feet along the Mississippi River. The 2000 population of the county was 258,941. The economy of the area is primarily based on manufacturing industries along the Mississippi River and agriculture in the remaining portion of the county (Reference 17).

The climate of south- is characterized by warm to hot summers (July to August) and cool to cold winters (December to February). Generally, more than 60 percent of the precipitation occurs in the warmer half of the year (April to September). The average annual rainfall is 38 inches per year of as little as 24 inches per year. Air temperature ranges from an average maximum of 89 degrees Fahrenheit (oF) in July to an average minimum of 25 oF in January (Reference 18).

The topography of the region is diverse, including flood plains, bluffs, and rugged valley areas. The main features of the area have been shaped by continental glaciations, resistant bedrock, and subsequent erosion. The bluffs of the area are created by vertical and lateral erosion and built upon by deposits of loess.

Pennsylvanian and Mississippi aged systems are the prevalent bedrock of the area. Most of the bedrock is limestone; however, some sandstone does exist in the flood plain areas. The prominent limestone bluffs are of Mississippian age. Parts of the area show bedrock outcroppings and have shallow bedrock as a result of thin glacial drift where deposits and erosions were controlled by resistant limestone.

Vegetation consists mostly of agricultural lands with some timberlands. The rest of the vegetation is residential lawns. Topography consists of moderately rolling uplands broken

9 by small streams draining to the American Bottoms or the Kaskaskia River. Soils generally consist of silty sediments graded in five-foot thickness, which generally overlie stratified silty sediments (Reference 19).

Approximately 15 percent of the county is located in a flat area adjacent to the Mississippi River between the Cities of Wood River and Granite City. This area is named the “American Bottoms.” It formerly served as part of the Mississippi River flood plain until the river was protected by an extensive system of levees. All major streams in the county flow in a southwesterly direction. The western half of the county drains directly into the Mississippi River. The eastern half drains into tributaries of the Kaskaskia River before entering the Mississippi River.

Development within the American Bottoms is primarily commercial and industrial while the upland flood plains are predominantly undisturbed with sparse agricultural and residential development.

2.3 Principal Flood Problems

Communities of Madison County are subject to periodic flooding by overflows from the streams studied in detail in this FIS, especially, Cahokia Creek, Indian Creek, and Canteen Creek. Shallow ponding and overbank flooding within the county is generally caused by the low-lying topography and lack of relief, especially in the area called the American Bottoms. In addition, during flood events, gravity flow to the levee is occasionally blocked forms an impoundment.

In the City of Alton, flooding occurs periodically as a result of heavy local rainfall along the study reaches of Coal Branch and Belt Line Creeks; however, stage records for these short duration floods are not available.

In the Village of Bethalto, flooding caused by local storms occurs periodically along the East Fork Wood River and along the three small tributary streams, however there are no available records on past floods.

In the City of Collinsville, flooding occurs periodically along Canteen Creek as a result of localized storms and in the American Bottoms area because of ponding from hillside runoff. Three small streams studied by approximate methods also experience some flooding from localized storms. Major flooding occurred from large storms in 1946, 1957, and 1961. Records are available for the 1957 flood and show it reached an elevation of 440.7 (NAVD88) on the Canteen Creek gage which is located about 400 feet upstream of the State Route 157 crossing. The 1957 flood had an estimated recurrence interval of approximately 200 years. The leveed portion of Canteen Creek west of State Route 157 overtops at a flow of approximately 3,000 cubic feet per second (cfs) causing damage adjacent to the creek. This levee offers no protection from even the 10-percent-annual- chance flood.

In the Village of East Alton, topography is the cause of most of the flooding problems in the community. The lack of relief throughout most of East Alton encourages internal ponding and overbank flooding of drainage ditches, such as East Alton Ditch. The problem is further aggravated by overland runoff approaching sheet flow conditions, from the steep sloped bluff area. Flooding in the floodplain of East Alton Ditch results from inadequate conveyance of the channel and culverts and the interior drainage runoff behind the levee

10 which forms an impoundment during periods when the gravity drainage through the levee is blocked. The presence of railroad lines in the community act as partial barriers to overland flow.

In the City of Edwardsville, the only flood on record was the April 1973 flood on the Cahokia Creek. That flood was estimated to have a five-year recurrence interval although no discharge was estimated at the time.

In the City of Granite City, although a levee system offers protection from the Mississippi River flooding, interior runoff collects in the low-lying areas of the community and in areas without storm sewers. Low-lying areas are flooded for hours and even days because of inadequate drainage systems. Major interior flooding occurred in 1946, 1957, 1961, and 1968. The groundwater level in very high and several factors have aggravated the situation in recent years. After the 1973 flood, groundwater reached very high levels and contributed to approximately 45 sewer breaks. Groundwater has also been responsible for damages to residences by causing foundation cracks, damaging furnishings and appliances, and leaving a residue from the sanitary sewer system.

In the Village of Hartford, the majority of the community lies on the land side of the levee. This area is subject to street flooding caused by blocked gravity flow drainage outlets at the base of the levee and shallow flooding due to inadequate surface drainage toward the levee. The presence of the railroad lines in the community acts as partial barriers to overland flow both out of and into Hartford.

In the City of Highland, the only flood on record was the June 1957 flood on Lindenthal Creek. No discharge was estimated at the time.

In the City of Madison, the Village of Pontoon Beach, and the Village of South Roxana, flooding from local runoff, which causes ponding in the lower areas, has always been a problem in the city (Reference 20). Even after an increase in levee protection in 1936 (Reference 21), flood damages continue to occur within the protected area of the city as a result of local runoff and ponding. Most frequently flooded is the low-lying ground along former sloughs. Water collects in these low areas during storm runoff periods. Very little development has occurred in the lowest part of these former sloughs; consequently, small rainfall amounts cause little damage. However, during severe storm periods the low areas do not have sufficient capacity to store all the runoff, causing inundation and damage to surrounding developed areas. The floods of 1946, 1957, 1961, and 1969 caused considerable damages in the American Bottoms area, including the City of Madison, the Village of Pontoon Beach, and the Village of South Roxana. These floods were caused by heavy local rainfall, which caused ponding in the low areas. The 1946 storm was approximately a 1-percent-annual-chance flood event, with an average of 11.8 inches of rainfall during the storm. The 1957 storm was an even greater flood event than in 1946, with 14.4 inches of rainfall in less than 16 hours. The 1961 storm was approximately a 2- percent-annual-chance event, with about 7.2 inches of rainfall occurring during the peak 48-hour period of the storm (Reference 22). In 1969, a much smaller flood than the three discussed above caused some flooding in the American Bottoms area.

In the Village of Roxana, the principal flood problem in the community results from inadequate drainage. Shallow depressions in Roxana and adjacent areas allow the accumulation of stormwater. This ponded water must infiltrate into the soil or evaporate. The areas which have historically been places of shallow ponding and street flooding are

11 the low-lying lots along Old Edwardsville Road and the area surrounding the intersection of Chaffer and Tydeman Avenues. Historically, a USGS gage on Indian Creek near Wanda, just north of the village, reported a flood greater than a 50-year recurrence interval for the August 1946 flood.

In the City of Venice, drainage in the American Bottoms continues to be a problem. Many of the difficulties arise from the extremely slight land slope, and the high water table that exists in the area. Additionally, substantial and repetitive flood damages have occurred in the bottom lands when ditches, channels, and structures within the leveed area are unable to carry runoff from the eastern bluffs in addition to the rain that falls directly on the area. Seepage and ponding during high river stages are the major sources of flooding.

In the City of Wood River, topography is the cause of most of the flooding problems in the community resulting in shallow flooding due to inadequate surface drainage. The lack of relief throughout most of the city encourages internal ponding and overbank flooding of drainage ditches such as Tributaries 1 and 2. The problem is further aggravated by overland runoff, approaching sheet flow conditions, from the steep sloped bluff area. Flooding due to local runoff in the areas of Tributaries 1 and 2 results from inadequate conveyance of the channel and culverts and the absence of an outlet. The runoff from the ridge area south of Airline Drive in Madison County drains to the 6th Street Detention area through overland flow down the steep bluffs. The major stream feeding the detention area is Tributary 1. In the past, this pond has filled and overflowed into adjacent areas of Madison County and the City of Wood River. Residential areas in Wood River, west of the detention area known as Eastwood Subdivision and Lincoln Addition, have experienced shallow flooding and overflows from the detention area. The principal problem in these residential areas is that no channel or culvert exists to direct runoff into undeveloped areas. The shallow ponds created during storms have taken several weeks to evaporate or infiltrate into the soil. This is considered a health hazard as well as a potential source of subsidence and other foundation damage. Runoff from the area south of Tributary 1 in Madison County drains south toward Illinois Route 111 by overland flow where it accumulates in low areas in the City of Wood River. No channel or culverts provide outlets for the water in this area. The locations of overflow points are peculiar to the intensity/duration characteristics of the rainfall. However, the principal path of flow of the overbank flooding is south towards Illinois Route 111. Large storm overflow will fill the depressions north of Illinois Route 111 and overflow southward into that residential area of Wood River known as Glendale Gardens. Glendale Gardens, like Lincoln Addition, has no channel or culverts to direct runoff into undeveloped areas. Therefore, runoff within the area ponds and must infiltrate into the soil or evaporate. Tributary 2 flows adjacent to Glendale Gardens. During storms with a 10-year recurrence or greater intensity, overbank flooding occurs along portions of Avalon Street. Thus Glendale Gardens receives overbank flooding from Tributaries 1 and 2 and has no outlet for this runoff or incident rainfall. During major storms, sufficient volumes of water have accumulated in this area to cross southward over portions of , making it impassable. This causes shallow flooding as far west as Central Avenue and as far south as Tennyson Avenue in the City of Wood River. Tributary 2 is the major stream which drains the ridge area in Belk Park east of Illinois Route 143. All the runoff from the bluffs in this area accumulates in a depression known as Smith Lake, which lies southeast of Wood River in portions of Madison County and the Village of Roxana. Runoff, which accumulates in this area, rises during major storms until it covers Illinois Route 143 southeast of Wood River causing shallow flooding in the area adjacent to Illinois Route 143 and Rock Hill Road in the City of Wood River.

12 Floods have occurred on the Mississippi River during all seasons. However, an analysis of the dominant seasonal characteristics of floods that have occurred within the study area indicates that the flood season is April through June, with 75 percent of the floods occurring during this period. Some of the most serious Mississippi River floods were associated with spring thaws.

Major floods on the Mississippi River have occurred in 1844, 1851, and 1903, prior to completion of the levee system almost completed inundating the City of Granite City. The flood events in 1844 and 1851 caused major damages in the City of Madison and almost completed inundated the City of Venice. These two floods produced estimated discharges of 1,300,000 cfs and 1,022,000 cfs respectively, at St. Louis, Missouri, and are estimated to be larger that 1-percent-annual-chance flooding events (Reference 23). Levee protection for areas including the City of Madison, was increased after authorization in 1936 (Reference 21). Since the increased protection, flooding has not been experienced by the City of Madison from the Mississippi River on the landside of the levee. The levee system offers protection from floods of the 0.2-percent-annual-chance recurrence interval in the Village of Roxana.

The highest recorded Mississippi River stage at St. Louis for the 117-year period of record occurred in April 1973 (Reference 24). This flood has been determined to have a 35-year recurrence interval. However, inundation of the Mississippi River flood plain did not occur within the urbanized areas of Madison County, since they are protected by the extensive system of existing levees and related flood protection structures. During the April 1973 flood, some damage was experienced in the industrial and commercial areas near the City of Alton because the levee does not protect all of the city and due to Mississippi River backwater blocking the gravity drainage system in these areas (Reference 25). During this event, the river stage at Alton was 432.23 feet (Reference 26). River stages at Alton have been recorded since 1904.

2.4 Flood Protection Measures

Three drainage and levee districts are located within Madison County. The Wood River Drainage and Levee District is located in the American Bottoms and operates and maintains most of the flood protection works along the Mississippi River, Wood River, and the Cahokia Diversion Channel. The Cahokia Creek Drainage and Levee District maintains a levee system on Cahokia Creek upstream of Edwardsville. The Foster Drainage and Levee District was responsible for straightening the channel of the East Fork of Wood River and is now inactive.

An extensive system of flood protection structures exists along the Mississippi River in Madison County. This system includes levees, stormwater pumping stations, and gravity outlet structures (Reference 25). The pumping stations and gravity structures are designed to protect primarily against localized flooding, with the levees containing the stream overflow. The area of Madison County protected by these structures includes primarily the American Bottoms plus other areas located along the major streams which outfall into the Mississippi River.

The East St. Louis and Vicinity, Illinois flood control project offers urban design flood protection from Mississippi River overflows for the City of Madison, Village of Pontoon Beach, and City of Venice. The project was authorized by the Flood Control Act of June 22, 1936. Protection is provided primarily by levees to all bottomlands between the bluffs

13 on the east and the Mississippi River and Chain of Rocks Canal on the west, and extends from the 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, and construction of 3.1 miles of concrete floodwall, gravity drainage structures, and alterations at bridge crossings (Reference 21). The levee and floodwall portion of the project was essentially completed by 1964.

The Wood River Drainage and Levee District provides protection in the Village of East Alton, the Village of Hartford, the Village of Roxana, and the City of Wood River. The levee, with a net levee grade elevation of 443 feet (Reference 27), extends from the Cahokia diversion channel north to Lock and Dam No. 26 at Alton, Illinois. In addition to the levee, there are gravity drainage structures, pump facilities, levee roads with flood gates, and seepage control wells. In 1957, Congress authorized the COE to investigate interior flooding in the Wood River Drainage and Levee District. The results of that study were that improvements in the settled areas of the district were not economically feasible (Reference 28).

In the City of Alton, the Mississippi River levee extends from the Missouri Pacific Railroad bridge embankment downstream along the bank of the Mississippi River. A flank levee extends up the right bank of the Wood River to high ground at Broadway. The degree of flooding from the Mississippi River to the unprotected part of Alton is reduced by upstream reservoirs. The upper Missouri River and upper Mississippi River Reservoirs reduce flood flows which reduce flood stages at Alton. There are no flood protection measures for Coal Branch Creek, Belt Line Creek, and West Fork Wood River within Alton. Also, Lock and Dam No. 26 on the Mississippi provides no flood protection measures.

In the Village of East Alton, eight pumping stations along the Wood River and East Fork Wood River and under the operating jurisdiction of the Olin Mathieson Corporation. Under Illinois House Bills 285 and 1041, the Illinois Division of Water Resources studied interior flooding problems and during 1978 implemented a program for control of stormwater runoff on East Alton Ditch. The plan called for channelization from the ponding area behind the levee, about 1,000 feet east of the Burlington Northern and Conrail tracks to Douglas Street. Increased conveyance was made at culverts on Main Street, Washington Avenue, Sixth Street, and Wood River Avenue. Stormwater is now removed from the area more rapidly as a result of the improvements. The plan also called for an additional pumping station at the base of the levee to prevent formation of impoundment behind the levee during periods of blocked gravity drainage. There are no other regulatory measures in the village which control drainage or floodplain development

In the City of Madison, a project designed to reduce the occurrence of flooding in the bottomlands was under study in 1980 (Reference 29).

In the Village of Pontoon Beach, the levees surrounding Long Lake west of State Highway 111 generally give protection from 1-percent-annual-chance floods. The levees to the east of State Highway 111 and those in the southern part of the community do not give 1- percent-annual-chance flood protection.

In the Village of South Roxana, a levee extends from Wood River on the north, downstream along the bank of the Mississippi River. A flank levee extends up the right bank of the Cahokia Creek diversion channel.

14 In the City of Wood River, proposals have been made to improve drainage characteristics of Tributaries 1 and 2 and to provide an outlet for shallow ponding in Lincoln Addition and Glendale Gardens (Reference 25). Under Illinois House Bill 285 and 1041, mentioned above, a program was implemented for improvement of stormwater detention at the 6th Street Detention Area. The specifications called for expansion and excavation of the existing pond and the installation of two pumps with a total capacity of 38 cfs. The pumps would discharge flood storage to the East Fork Wood River and maintain a flood storage capacity of 382 acre-feet above a permanent pool six feet deep (Reference 30). In March 1977, the City Council of Wood River enacted an ordinance to control drainage and construction in special flood hazard areas. The ordinance specifically identified the existing Flood Hazard Boundary Map (Reference 31) as the basis for areas affected by the ordinance and areas of historical shallow flooding experience. The ordinance required that all residential structures have the lowest floor elevated to one foot above the base flood elevation. Non-residential structures have the option of floodproofing measures to this elevation (Reference 32).

No other legislative or structural flood protection measures were in effect prior to the initiation of this FIS.

Several major levee systems located below the natural bluff line, in areas known locally as 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 Corps of Engineers 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 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 National Flood Insurance Program. When FEMA learns that a flood control system no longer provides adequate protection in accordance with these standards, the affected Flood Insurance Rate Map (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 requirements of 44 CFR 61.12) from the date of submittal of the community's application for the Zone AR designation.

15 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 Corps of Engineers 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 levees evaluations and FEMA’s de-accreditation process. FEMA and the Corps of Engineers 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 Flood Insurance Rate Maps 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 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.

16 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.

This FIS report includes information from previously published FIS reports as well as new information. Unless indicated otherwise, the information provided in this section was obtained from the previously published FIS for Madison County.

Peak discharges for, Cahokia Creek, Canteen Creek, East Fork Silver Creek, East Fork Wood River, Honeycut Branch, Indian Creek, Joulters Creek, Paddock Creek, Sherry Creek, Silver Creek, Silver Creek Tributary No. 1, Silver Creek Tributary No. 2, Stanley Creek, Sugar Fork, Tributary E, Tributary F, Tributary G, Tributary X, Tributary Z, West Fork Wood River, and Wood River in the City of Alton, City of Edwardsville, the Village of East Alton, and unincorporated areas of Madison County were estimated by applying synthetic unit hydrograph methodology to the HEC-1 rainfall-runoff mathematical model developed by the COE (Reference 33). Parameters for Clark unit hydrographs and exponential loss rate functions were determined from regional relationships developed from an optimization study of observed floods at fourteen stream-flow gages in the vicinity of Madison County. Rainfall data provided by the National Weather Service (Reference 18) were used to develop the 10-, 2-, 1-, and 0.2-percent-annual-chance synthetic storm events. Channel and reservoir routings for the flood hydrographs were performed using the modified Puls method (Reference 34). The 10-percent-annual-chance discharge values decrease downstream for Cahokia Creek from the upstream county boundary to just upstream of the confluence of Sherry Creek and for Silver Creek form the confluence of East Fork Silver Creek to the downstream county boundary because of channel storage available in these reaches. Additionally, East Fork Silver Creek discharges decrease downstream from the confluence of Sugar Fork to its mouth because of available channel storage.

Since there were no streamflow records for Belt Line Creek, Coal Branch Creek, and East Fork Wood River within the Villages of Bethalto and East Alton, peak discharges for floods of 10-, 2-, and 1-percent-annual-chance recurrence intervals were developed by hydrologic basin modeling, using HEC-1 (Reference 33). The computer program utilized frequency rainfall amounts obtained from the U.S. National Weather Service Technical Paper No. 40 (Reference 22), optimized unit hydrographs, and storage routing. Discharges for the 0.2-percent-annual-chance floods were obtained with rainfall data extrapolated from that published in Technical Paper No. 40. Downstream decrease in peak discharge along Belt Line Creek is due to the Crest Drive culvert restricting discharge and producing a storage effect of the upstream side of the culvert.

Flood discharges for Shields Branch and approximate studies in the Village of Bethalto were based on regional equations developed by the St. Louis District COE (Reference 35). These empirical equations related peak discharge to drainage area and channel slope.

For the portion of Canteen Creek within the City of Collinsville, a frequency curve was derived from a log-Pearson Type III statistical analysis for about 37 years of record (1939 – 1976) for the USGS gage on Canteen Creek near Caseyville (Reference 36). Regionally optimized unit graph and loss rate parameters were used in the Canteen Creek basin HEC-1 model (Reference 33) with frequency rainfall amounts obtained from the U. S. National Weather Service Technical Paper No. 40 (Reference 22). The 0.2-annual-percent-chance

17 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. A reduction of peak flow along Canteen Creek occurs due to overbank storage in the floodplain at State Route 157.

Floods having recurrence intervals from 50- to 1-percent-annual-chance on East Alton Ditch have been studied extensively by the Illinois Division of Water Resources. The discharge-frequency data for East Alton Ditch used in this study were based on Grays method of synthetic hydrographs used in designing the channel improvements for East Alton Ditch (Reference 37). This method is very similar to the SCS TR20 method (Reference 38) for determining hydrographs for basins with less than a 10 square mile area. These hydrographs were then routed downstream with the state routing model. Two other methods (References 39 and 40) were also developed for comparison with the values used by the state. All methods produced similar results; however, the discharge values used, developed by Gray’s method, are the largest discharges.

For Laurel Branch, Lindenthal Creek, Mooney Creek and associated tributaries in the Cities of Edwardsville and Highland, peak discharges were estimated by applying synthetic unit hydrograph methodology to the HEC-HMS rainfall-runoff mathematical model developed by the COE (Reference 41). Parameters for SCS unit hydrographs were determined from a field review and digital soils and land use data. Rainfall data provided by the Bulletin 70 (Reference 42) was used to develop 10-, 2-, 1-, and 0.2-percent-annual-chance synthetic storm events.

For Judys Branch, Judys Creek, and associated tributaries in the Village of Glen Carbon, peak discharges were estimated by applying synthetic unit hydrograph methodology to the HEC-HMS rainfall-runoff mathematical model developed by the COE (Reference 41). Parameters for SCS unit hydrographs were determined from a field review and digital soils and land use data. Rainfall data provided by the St. Louis Anomaly section of Frequency Distributions of Heavy Rainstorms in Illinois (Reference 43) was used to develop 10-, 2-, 1-, and 0.2-percent-annual-chance synthetic storm events.

Mississippi River floodplain elevations were determined by the January 2004 Upper Mississippi River System Flow Frequency Study (UMRSFFS) (Reference 44). The UMRSFFS was developed by five USACE Districts (St. Paul, Rock Island, Omaha, Kansas City, 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 . 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 synthetic flows based on rainfall.

In the Village of East Alton, the Village of Roxana, and the City of Wood River, for areas determined to be experiencing ponding caused by inadequate drainage, the volume of the floodwaters was determined by utilizing the 1-percent-annual-chance 24-hour rainfall data, based on the Illinois Division of Water Resources data and the relationships of streamflow, hydrologic soil type, land use, and drainage area defined by the SCS (Reference 40). The resultant 1-percent-annual-chance runoff volume was determined through use of the SCS

18 National Engineering Handbook, Section 4, Hydrology (Reference 45). Moisture condition III was selected due to the unusual conditions present in the area.

In the City of Granite City, in order to establish the amount of water that would pond as a result of the 1-percent-annual-chance flood, the 1-percent-annual-chance frequency rainfall was determined from the U.S. National Weather Service Technical Paper 40 (Reference 22). The volume of runoff that would pond in various sections of the community was determined from the rainfall.

In the City of Madison and the Village of South Roxana, peak volume values for the 1- percent-annual-chance flood for the areas subject to shallow flooding conditions, were developed by hydrologic basin modeling, using HEC-1 (Reference 33). The computer program utilizes frequency rainfall amounts obtained from the U. S. National Weather Service Technical Paper No. 40 (Reference 22), optimized unit hydrographs, and storage routing.

In the Village of Pontoon Beach, peak volumes for the 10-, 2-, 1-, and 0.2-percent-annual- chance floods for Long Lake, Horseshoe Lake and other areas subject to shallow flooding conditions were developed by hydrologic basin modeling using HEC-1 (Reference 33).

Reservoir routings were conducted for Holiday Shores Lake and Dunlap Lake.

For new approximate studies in the county, regression equations were used to calculate the 1-percent-annual-chance flood discharges (Reference 46).

Peak discharges for the 10-, 2-, 1-, and 0.2-percent-annual-chance floods of each flooding source studied in detail in the community are shown in Table 5.

TABLE 5 – Peak Discharge Values

Peak Discharge (cfs) Drainage 10% 2% 1% 0.2% Area (Sq Annual Annual Annual Annual Flooding Source and Location Miles) Chance Chance Chance Chance Belt Line Creek At mouth 1.16 722 1,169 1,300 1,513 Belt Line Road 0.99 1,041 1,437 1,587 1,883 Cahokia Creek US Route 67 262.3 13,200 21,700 26,700 36,300 Above Indian Creek confluence 221.2 10,800 20,300 25,300 34,200 Above Mooney Creek confluence 192.3 10,700 19,900 24,800 33,800 Above Sherry Creek confluence 119.5 10,100 16,700 20,700 26,500 At Madison County Line 78.3 10,300 16,300 19,700 24,100 Canteen Creek State Route 157 22.6 4,300 7,000 8,400 11,000 State Route 159 20.1 4,500 7,100 8,600 11,100 Mulberry Street 16.2 4,100 6,600 8,000 10,300 County Highway 32 10.3 3,900 6,300 7,500 9,600 Coal Branch Creek At mouth 5.25 2,456 3,584 3,954 4,589 Just upstream of Black Creek confluence 0.83 816 1,162 1,285 1,490

19 TABLE 5 – Peak Discharge Values (Continued)

Peak Discharge (cfs) Drainage 10% 2% 1% 0.2% Area (Sq Annual Annual Annual Annual Flooding Source and Location Miles) Chance Chance Chance Chance East Alton Ditch At mouth 0.48 350 502 612 780 East Fork Silver Creek At mouth 98.2 7,000 12,500 15,200 19,200 At Sugar Fork confluence 88 7,300 12,950 15,500 19,500 At Highland Silver Lake Dam 47.5 4,500 7,450 9,000 11,300 East Fork Wood River At mouth 66.2 7,900 12,400 15,300 19,700 At State Highway 140 Bridge 58.9 7,900 12,300 15,000 19,500 McCoy Road 44.8 7,500 11,600 14,200 18,800 Honeycut Branch At mouth 17.5 2,900 4,700 5,700 7,700 Indian Creek At mouth 39.7 5,200 8,600 10,900 14,200 Roosevelt Road 18.1 3,100 4,900 6,000 7,300 Joulters Creek At mouth 6.3 500 900 1,100 1,400 Judys Branch Downstream of State Highway 157 7.75 2245 3623 4,736 6,847 Just downstream Judys Creek confluence 7.00 2229 3604 4,706 6,719 Upstream of Collinsville Street 4.45 1540 2504 3,264 4,539 Just downstream of Tributary 5 confluence 4.05 1489 2410 3,139 4,292 Upstream of Glen Crossing Road 2.72 1078 1744 2,256 3,021 Upstream of I-270 2.09 957 1559 1,857 2,459 Just downstream of Tributary 9 confluence 1.99 886 1438 1,858 2,465 Just downstream of Tributary 10 confluence 1.67 732 1194 1,545 2,036 At State Highway 159 1.43 608 1001 1,299 1,724 Upstream of abandoned railroad (1st crossing) 0.34 177 289 372 487 Judys Branch Tributary 5 At mouth 1.01 393 643 842 1,129 Judys Branch Tributary 5a At Tributary 5b confluence 0.29 126 208 270 359 Judys Branch Tributary 5b At Tributary 5a confluence 0.21 98 162 211 278 Upstream of State Hwy 159 0.05 31 49 63 81 Judys Branch Tributary 9 At mouth 0.32 124 197 254 338 Judys Branch Tributary 9a At Tributary 9b confluence 0.16 80 125 158 206 Judys Branch Tributary 9b At Tributary 9a confluence 0.05 16 29 39 53 Judys Branch Tributary 10 At mouth 0.24 126 195 247 321

20 TABLE 5 – Peak Discharge Values (Continued)

Peak Discharge (cfs) Drainage 10% 2% 1% 0.2% Area (Sq Annual Annual Annual Annual Flooding Source and Location Miles) Chance Chance Chance Chance Judys Creek At mouth 1.85 714 1142 1,477 1,987 Downstream of Norfolk & Western Railroad (4th crossing) 1.31 546 874 1,129 1,503 Just downstream of Tributary B confluence 1.12 498 801 1,029 1,356 Just downstream of lake 0.73 326 527 681 895 Upstream of Norfolk & Western Railroad (1st crossing) 0.08 26 43 56 77 Judys Creek Tributary B At mouth 0.31 163 260 332 433 Laurel Branch At mouth 1.66 418 671 808 1,249 Above Tributary 1 confluence 1.21 304 486 585 903 Laurel Branch Tributary 1 At mouth 0.05 19 27 31 45 Lindenthal Creek At Iberg Road 5.58 1475 2325 2,787 4,277 Above Laurel Branch confluence 3.28 900 1402 1,675 2,552 At Broadway Street 2.81 785 1215 1,449 2,201 Above Tributary 1 confluence 1.10 284 452 543 835 Lindenthal Creek Tributary 1 At mouth 0.97 310 461 542 806 Above Tributary 2 confluence 0.64 201 300 353 527 Above Tributary 4 confluence 0.52 155 235 279 420 Lindenthal Creek Tributary 2 At mouth 0.27 87 129 152 226 Above Tributary 3 confluence 0.09 27 41 49 74 Lindenthal Creek Tributary 3 At mouth 0.16 48 73 86 129 Lindenthal Creek Tributary 4 At mouth 0.11 36 53 62 92 Mississippi River River Mile 179.6 St. Louis Gage 697,000 670,000 850,000 910,000 1,120,000 Crossover with Missouri River 360,000 486,000 610,000 720,000 River Mile 218.0 Grafton Gage 171,300 360,000 446,000 488,000 585,000 Mooney Creek State Route 152 12.3 3,700 5,600 6,200 7,300 At Marine Road 5.05 1053 1822 2,244 3,605 Above Tributary 1 confluence 2.06 434 751 925 1,487 Above Tributary 2 confluence 1.79 366 641 793 1,280 Mooney Creek Tributary 1 At mouth 0.67 157 261 318 501 Mooney Creek Tributary 2 At mouth 0.26 60 101 123 195

21 TABLE 5 – Peak Discharge Values (Continued)

Peak Discharge (cfs) Drainage 10% 2% 1% 0.2% Area (Sq Annual Annual Annual Annual Flooding Source and Location Miles) Chance Chance Chance Chance Paddock Creek At mouth 25.6 3,600 5,400 6,800 8,500 Above Yorkville Road 14.3 3,300 5,000 5,900 7,300 Sherry Creek At mouth 28.1 5,600 8,900 11,200 13,700 Silver Creek At St. Clair County Line 284 16,900 28,900 33,700 43,500 At East Fork Silver Creek Confluence 256.9 17,000 28,900 33,700 43,400 At Tributary No. 1 Confluence 79.9 13,100 20,600 23,700 30,000 At Tributary No. 2 Confluence 58.2 12,200 17,300 19,400 24,100 Silver Creek Tributary No. 1 At mouth 9.9 2,860 4,170 4,800 5,900 Silver Creek Tributary No. 2 At mouth 11.7 2,930 4,290 4,950 6,120 Smith Lake Tributary Just upstream of Route 143 2.42 82 130 165 871 2,265 feet upstream of Route 143 2.05 234 391 506 847 Below Smith Lake trib 2 confluence 1.72 90 147 188 739 At Bonita Street 0.35 56 97 128 159 Smith Lake Tributary 2 At confluence with Smith Lake Trib 1.28 29 29 83 132 Stanley Creek At mouth 1.7 1,300 1,900 2,300 2,700 Sugar Fork At mouth 30.2 4,500 6,700 7,600 9,050 Tributary E Cross section C 0.9 1,020 1,540 1,880 2,240 Inwood Lane 0.5 780 1,120 1,290 1,450 Tributary F Below Tributay G confluence 0.5 1,070 1,460 1,640 1,820 Above Tributary G confluence 0.3 650 850 940 1,030 Tributary G At mouth 0.2 470 650 740 810 Tributary X At mouth 7.7 3,400 5,000 5,900 7,200 Tributary Z At mouth 2.4 1,200 1,800 2,100 2,600 West Fork Wood River At mouth 56.0 9,200 14,500 17,600 23,800 At State Highway 140 54.2 9,200 14,600 18,200 24,700 Below Lick Creek confluence 38.5 8,300 13,300 16,200 21,000 Below Honeycut Branch confluence 36.8 7,900 12,500 15,300 19,900 Below Tributary X confluence 17.4 5,900 8,900 10,700 13,400

22 TABLE 5 – Peak Discharge Values (Continued)

Peak Discharge (cfs) Drainage 10% 2% 1% 0.2% Area (Sq Annual Annual Annual Annual Flooding Source and Location Miles) Chance Chance Chance Chance Wood River At mouth 123.0 15,956 25,460 30,450 39,800 At West Fork confluence 120.8 15,880 25,354 30,330 39,200

3.2 Hydraulic Analyses

Analyses of the hydraulic characteristics of flooding from the sources studied were carried out to provide estimates of the elevations of floods of the selected recurrence intervals. Users should be aware that flood elevations shown on the Flood Insurance Rate Map (FIRM) represent rounded whole-foot elevations and may not exactly reflect the elevations shown on the Flood Profiles or in the Floodway Data table in the FIS report. Flood elevations shown on the FIRM are primarily intended for flood insurance rating purposes. For construction and/or floodplain management purposes, users are cautioned to us the flood elevation data presented in this FIS report in conjunction with the data shown on the FIRM.

Detail-studied streams that were not re-studied as part of this map update may include a "profile base line" on the maps. This "profile base line" provides a link to the flood profiles included in the Flood Insurance Study report. The detail studied stream centerline may have been digitized or redelineated as part of this revision. The "profile base lines" for these streams were based on the best available data at the time of their study and are depicted as they were on the previous FIRMs. In some cases where improved topographic data was used to redelineate floodplain boundaries, the "profile base line" may deviate significantly from the channel centerline or may be outside the SFHA.

Channel and valley cross sections of streams studies in detail were obtained by field surveys. All bridges, dams, culverts, and levees along these streams were field surveyed to obtain elevations and structural geometry.

Locations of selected cross sections used in the hydraulic analyses are shown on the Flood Profiles (Exhibit 1). For stream segments for which a floodway is computed (Section 4.2), selected cross section locations are shown on the Flood Boundary and Floodway Map (Exhibit 2).

Roughness factors (Manning's "n") used in the hydraulic computations were chosen by engineering judgment and based on field observation, topographic maps, (Reference 47), and HEC-2 model calibrations (Reference 48). Table 6 shows the channel and overbank "n" values reported in the previous Flood Insurance Study organized by communities for the flooding sources studied by detailed methods.

The channel “n” values for Lindenthal Creek, Laurel Branch, and the associated tributaries in the City of Highland ranged from .030 to .045 and the overbank “n” values ranged from .035 to .095. The channel “n” values for Mooney Creek and the associated tributaries in the City of Edwardsville ranged from .030 to .035 and the overbank “n” values ranged from .035 to .075. The channel “n” values for Judys Branch and the associated tributaries in the

23 Village of Glen Carbon ranged from .060 to .109 and the overbank “n” values ranged from .030 to .500. The channel “n” values for Judys Creek and the associated tributaries in the Village of Glen Carbon ranged from .050 to .100 and the overbank “n” values ranged from .010 to .100. TABLE 6 – Manning’s “n”

Community Channel "n" Values Overbank "n" Values City of Alton .040 - .065 .035 - .080 Village of Bethalto .045 - .060 .045 - .100 City of Collinsville .040 - .065 .035 - .080 Village of East Alton .045 - .060 .045 - .100 City of Edwardsville .035 - .070 .050 - .140 City of Wood River .030 - .040 .060 - .080 Unincorporated Areas .035 - .070 .050 - .140

The channel “n” values for Lindenthal Creek, Laurel Branch, and the associated tributaries in the City of Highland ranged from .030 to .045 and the overbank “n” values ranged from .035 to .095. The channel “n” values for Mooney Creek and the associated tributaries in the City of Edwardsville ranged from .030 to .035 and the overbank “n” values ranged from .035 to .075. The channel “n” values for Judys Branch and the associated tributaries in the Village of Glen Carbon ranged from .060 to .109 and the overbank “n” values ranged from .030 to .500. The channel “n” values for Judys Creek and the associated tributaries in the Village of Glen Carbon ranged from .050 to .100 and the overbank “n” values ranged from .010 to .100.

Starting water-surface elevations shown on the flood profile drawings for Cahokia Creek and Wood River are the peak Mississippi River stages for the selected recurrence intervals. Starting water-surface elevations for Belt Line Creek, Coal Branch Creek, Judys Creek, Lindenthal Creek, Mooney Creek, Tributaries E and F are based on normal depth computations with energy slopes equal to the slope of the channel bottoms. Starting water- surface elevations for the remaining tributaries are the main stem corresponding stages for the selected recurrence intervals. The starting water-surface elevations for Canteen Creek and Silver Creek were taken from the St. Claire County Flood Insurance Study (Reference 49).

Water-surface elevations of the 10-, 2-, 1-, and 0.2-percent-annual-chance floods of streams previously studied in detail were computed through use of the COE HEC-2 step-backwater computer program (Reference 48). Water-surface elevations for floods of the selected recurrence intervals on Laurel Branch, Lindenthal Creek, Mooney Creek, and associated tributaries were computed through use of the USACE HEC-RAS Version 3.0.1 software (Reference 50). Water-surface elevations for floods of the selected recurrence intervals on Judys Branch, Judys Creek, and associated tributaries were computed through use of the USACE HEC-RAS Version 3.1.2 software (Reference 51).

Cross sections for the Mississippi River were 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

24 address especially complex flow reaches and levee failure impacts. The confluences of the Missouri and Illinois Rivers with the Mississippi relied primarily on the Weibull approach (Reference 44).

Still water lake elevations and areas of shallow ponding have been determined within Madison County. The elevations are shown in Table 7. Shallow ponding elevations reported below were previously reported in the FIS for the City of Madison, the Village of Roxana, and the Village of South Roxana. Additional areas of shallow ponding not reported in this table are identified on the FIRM panels.

TABLE 7 – Summary of Still Water Elevations

ELEVATION (NAVD88) 10% 2% 1% 0.2% Annual Annual Annual Annual FLOODING SOURCE LOCATION Chance Chance Chance Chance Horseshoe Lake Village of Pontoon Beach 413.5 414.2 414.5 414.7 Long Lake Village of Pontoon Beach 415.5 416.0 416.5 416.7 City of Madison – About 700 feet west of the intersection of West Second Street and Shallow Ponding Webster Street 408.5 - 410.5 - City of Madison – Along Kohl Shallow Ponding Street and Race Street 411.7 - 412.5 - City of Madison – East of Shallow Ponding Farrish Street 407.6 - 410.4 - Village of Roxana/ Village of South Roxana – Adjacent to Shallow Ponding Illinois Route 111 426.6 - 428.4 - * “-“ indicates data is not available

Additional hydraulic analyses of the shallow ponding areas in Madison County were carried out to provide estimates of the flood elevations in these areas. The shallow ponding areas were numerous and scattered in the American Bottoms and near the Cities of Collinsville, Granite City, Madison, Venice, Wood River and the Villages of East Alton, Hartford, Pontoon Beach, Roxana, and South Roxana due primarily to inadequate storm sewer capacity and very little flow between interconnected storage ponds. These analyses were based on field inspection, aerial photographs (Reference 52 and 53), storm sewer maps (Reference 54), topographic maps (References 47 and 55-57), and historical studies (References 58 and 59). Water-surface elevations in the drainage courses and ponding areas were determined from storage elevation curves and computed flood volumes. This, along with local input and historical data, was used to determine the ponding locations.

The hydraulic analyses for this study are based only on the effects of unobstructed flow. The flood elevations as shown on the profiles (Exhibit 1) are, therefore, considered valid only if hydraulic structures, in general, remain unobstructed and if channel and overbank conditions remain essentially the same as ascertained during this study.

Flood profiles were drawn showing the computed water-surface elevations to an accuracy of 0.5 foot for floods of the selected recurrence intervals. In cases where two or more profiles are close together, due to limitations of the profile scale, only the higher profile has been shown.

25

All elevations are referenced from North American Vertical Datum of (NAVD88); elevation reference marks used in the study are shown on the maps.

3.3 Vertical Datum

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

Effective information for this FIS report was converted from NGVD29 to NAVD88 based on data presented in Table 8, with the exception of the Mississippi River. The vertical datum shift for Madison County varies on a stream by stream basis and was calculated in accordance with FEMA’s specifications. Structure and ground elevations in the community must, therefore, be referenced to NAVD88. It is important to note that adjacent communities in other counties not presented in this FIS may be referenced to NGVD29. This may result in differences in BFEs across the corporate limits between communities.

Table 8 – Datum Conversion Calculation by Stream

Stream Name Change Change (feet) Maximum (meters) Offset Belt Line Creek -0.017 -0.056 0.02 Cahokia Creek -0.119 -0.390 0.01 Canteen Creek -0.146 -0.479 0.06 Coal Branch Creek -0.047 -0.154 0.05 East Alton Ditch 0.018 0.060 0.01 East Fork Sherry Creek -0.113 -0.371 0.10 East Fork Silver Creek -0.142 -0.467 0.04 East Fork Wood River -0.041 -0.133 0.20 Honeycut Branch -0.113 -0.370 0.20 Indian Creek -0.055 -0.180 0.05 Joulters Creek -0.103 -0.339 0.01 Judys Branch -0.167 -0.547 0.02 Judys Branch Tributary 5 -0.170 -0.558 0.00 Judys Branch Tributary 5a -0.170 -0.558 0.00 Judys Branch Tributary 5b -0.169 -0.554 0.00 Judys Branch Tributary 9 -0.162 -0.531 0.00 Judys Branch Tributary 9a -0.159 -0.520 0.01 Judys Branch Tributary 9b -0.160 -0.526 0.00 Judys Branch Tributary 10 -0.163 -0.535 0.00 Judys Creek -0.156 -0.513 0.04 Judys Creek Tributary B -0.147 -0.482 0.01 Mooney Creek -0.134 -0.439 0.04 Paddock Creek -0.105 -0.344 0.03 Sherry Creek -0.112 -0.369 0.01 Silver Creek -0.142 -0.465 0.04 Silver Creek Tributary No. 1 -0.143 -0.469 0.01 Silver Creek Tributary No. 2 -0.134 -0.441 0.02 Smith Lake Tributary 0.015 0.049 0.01

26 Table 8 – Datum Conversion Calculation by Stream (Continued)

Stream Name Change Change (feet) Maximum (meters) Offset Smith Lake Tributary 2 0.015 0.049 0.01 Stanley Creek -0.036 -0.118 0.10 Sugar Fork -0.151 -0.494 0.00 Tributary E 0.012 0.038 0.01 Tributary F 0.015 0.049 0.01 Tributary G 0.013 0.043 0.00 Tributary X -0.123 -0.405 0.02 Tributary Z -0.044 -0.143 0.03 West Fork Wood Rver -0.078 -0.257 0.22 Wood River 0.031 0.101 0.06

BFEs and profile elevations reported in the Upper Mississippi River System Flow Frequency Study (Reference 44) were incorporated into this FIS report and associated DFIRMs. This information was converted from NGVD29 to NAVD88 based on data presented in Table 9. A conversion factor was calculated using the latitude 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 DFIRMs.

Table 9 –Mississippi River Vertical Datum Conversions

NGVD29 to NGVD29 NAVD88 NAVD88 Cross NAD83 NAD83 Base Flood Base Flood Elevation Section Latitude Longitude Elevation Elevation Change ID (dec. deg.) (dec. deg.) (feet) (feet) (feet) 182.44 38.662 90.184 428 427.9 -0.1 182.50 38.665 90.185 428 427.9 -0.1 182.52 38.665 90.185 428 427.9 -0.1 182.53 38.665 90.185 428 427.9 -0.1 182.90 38.670 90.184 428.3 428.2 -0.1 183.26 38.674 90.187 428.6 428.6 0.0 183.27 38.675 90.186 428.6 428.5 -0.1 183.28 38.675 90.186 428.6 428.5 -0.1 183.30 38.675 90.187 428.6 428.5 -0.1 183.38 38.677 90.183 428.6 428.5 -0.1 183.98 38.685 90.190 429.1 429.1 0.0 184.56 38.692 90.197 429.5 429.6 0.1 185.18 38.699 90.197 429.9 430.0 0.1 185.76 38.706 90.197 430.1 430.2 0.1 186.36 38.710 90.197 430.3 430.4 0.1 186.82 38.717 90.194 430.4 430.5 0.1 187.41 38.723 90.191 430.6 430.7 0.1 188.00 38.728 90.188 430.8 430.9 0.1 188.43 38.731 90.186 431.1 431.2 0.1 188.88 38.734 90.183 431.3 431.4 0.1 189.47 38.741 90.174 431.7 431.8 0.1 190.29 38.754 90.164 432.2 432.3 0.1 190.32 38.754 90.164 432.2 432.3 0.1 190.37 38.756 90.165 432.2 432.3 0.1 190.46 38.757 90.165 432.2 432.3 0.1 190.47 38.757 90.165 432.2 432.3 0.1

27 Table 9 –Mississippi River Vertical Datum Conversions (Continued)

NGVD29 to NGVD29 NAVD88 NAVD88 Cross NAD83 NAD83 Base Flood Base Flood Elevation Section Latitude Longitude Elevation Elevation Change ID (dec. deg.) (dec. deg.) (feet) (feet) (feet) 190.48 38.757 90.165 432.2 432.3 0.1 190.50 38.757 90.165 432.2 432.3 0.1 190.64 38.759 90.163 432.3 432.4 0.1 190.79 38.761 90.163 432.3 432.4 0.1 190.81 38.761 90.160 432.4 432.5 0.1 190.82 38.761 90.160 432.4 432.5 0.1 190.85 38.762 90.162 432.4 432.5 0.1 191.36 38.769 90.161 432.6 432.7 0.1 191.92 38.778 90.158 432.8 432.9 0.1 192.41 38.786 90.155 432.9 433.0 0.1 192.91 38.794 90.151 433.1 433.3 0.2 193.28 38.801 90.149 433.2 433.4 0.2 193.79 38.808 90.147 433.4 433.6 0.2 194.16 38.812 90.145 433.6 433.8 0.2 194.63 38.812 90.144 433.7 433.9 0.2 194.97 38.812 90.142 433.8 434.0 0.2 195.56 38.813 90.142 434.1 434.3 0.2 196.09 38.814 90.140 434.2 434.4 0.2 196.48 38.816 90.140 434.4 434.6 0.2 196.82 38.818 90.139 434.5 434.7 0.2 197.31 38.822 90.138 434.6 434.8 0.2 197.71 38.824 90.139 434.7 434.9 0.2 198.28 38.825 90.140 434.8 435.0 0.2 198.81 38.831 90.141 434.9 435.1 0.2 199.34 38.839 90.144 435.0 435.2 0.2 199.83 38.830 90.149 435.1 435.3 0.2 200.31 38.834 90.158 435.2 435.4 0.2 200.54 38.844 90.163 435.3 435.5 0.2 200.70 38.845 90.166 435.4 435.6 0.2 200.85 38.838 90.168 435.5 435.7 0.2 201.29 38.845 90.180 435.7 435.9 0.2 201.85 38.851 90.184 436.0 436.2 0.2 202.50 38.859 90.194 436.4 436.6 0.2 202.63 38.875 90.190 436.5 436.6 0.1 202.66 38.875 90.191 436.5 436.6 0.1 202.68 38.875 90.192 436.5 436.6 0.1 203.04 38.879 90.195 436.6 436.7 0.1 203.36 38.878 90.207 436.6 436.7 0.1 203.86 38.883 90.213 436.7 436.8 0.1 204.38 38.886 90.222 436.8 436.8 0.0 204.96 38.891 90.230 436.9 436.9 0.0 205.48 38.895 90.236 437.0 437.0 0.0 206.07 38.899 90.244 437.1 437.0 -0.1 206.60 38.903 90.252 437.1 437.0 -0.1 207.12 38.906 90.260 437.2 437.0 -0.2 207.72 38.909 90.267 437.3 437.1 -0.2 208.29 38.913 90.276 437.4 437.2 -0.2

28 For more information on NAVD88, see the FEMA publication entitled Converting the National Flood Insurance Program to the North American Vertical Datum of 1988 (Reference 60), or contact the Vertical Network Branch, National Geodetic Survey, Coast and Geodetic Survey, National Oceanic and Atmospheric Administration, Silver Spring, Maryland 20910 (http://www.ngs.noaa.gov).

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

4.0 FLOODPLAIN MANAGEMENT APPLICATIONS

The NFIP encourages State and local governments to adopt sound floodplain management programs. Therefore, each Flood Insurance Study provides 1-percent annual chance flood elevations and delineations of the 1- and 0.2-percent annual chance floodplain boundaries and the regulatory floodway to assist communities in developing floodplain management measures.

4.1 Floodplain Boundaries

To provide a national standard without regional discrimination, the 1-percent-annual- 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. For each stream studied by detailed methods, the 1- and 0.2-percent-annual-chance floodplain boundaries have been delineated using the flood elevations determined at each cross section. Between cross sections, the boundaries were interpolated using digital base map information provided by the Madison County Information Systems. This data includes 1995 digital orthophotography and contours at ten foot intervals; referenced to a Illinois State Plane West coordinate system, NAD83 horizontal datum, and NAVD88 vertical datum (Reference 61).

For areas of shallow ponding, the 1-percent-annual-chance flood boundary was previously delineated based on topographic maps at a scale of 1:24000 with a contour interval of 10 feet (Reference 47). These areas were digitized onto the DFIRM panels.

Approximate 1-percent-annual-chance floodplain boundaries were delineated using digital base map information described above. Approximate floodplains from the previous FIRMs were redelineated using cross sections with interpolated 1-percent-annual-chance water- surface elevations.

The 1- and 0.2-percent-annual-chance floodplain boundaries are shown on the FIRM (Exhibit 2). On this map, the l-percent-annual-chance floodplain boundary corresponds to the boundary of the areas of special flood hazards (Zones A, AE, AH, AO, and AR); 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 l-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.

29 For the Mississippi River and stream segments located in the American Bottoms Region, these delineations were generally based on topographic data acquired by the Corps of Engineer in support of the UMRSFFS (discussed in Section 3). This data was collected at contour-equivalent accuracies of 4 feet using photogrammetric methods compiled as digital elevation model (DEM) and digital terrain model (DTM) data. The DEM data are 15-foot posting grids with a vertical resolution of 0.1 foot. The DTM data are mass points and breaklines that adequately define elevated roads, railroads, levees and major topography changes. The DEM/DTM data are all in ASCII XYZ format. Flight dates for the multi- state, multi-year photogrammetry started in 1998 and continued through 2001.

As indicated in Section 2.4, FEMA and the US Army Corps 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 Flood Insurance Rate Maps 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 Flood Insurance Rate Map 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 Flood Insurance Rate Map (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.

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

30 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 l-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 l-percent-annual-chance flood can be carried without substantial increases in flood heights. Minimum Federal standards limit such increases to 1.0 foot, provided that hazardous velocities are not produced. Minimum standards of the State of Illinois limit such increases in flood heights to 0.1 foot, provided that hazardous velocities are not produced (References 62 and 63). 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.

The floodway presented in this FIS report and on the FIRM was computed for certain stream segments on the basis of equal conveyance reduction from each side of the floodplain. Floodway widths were computed at cross sections. Between cross sections, the floodway boundaries were interpolated. The results of the floodway computations have been tabulated for selected cross sections. In cases where the floodway and l-percent- annual-chance floodplain boundaries are either close together or collinear, only the floodway boundary has been shown.

The 1-percent-annual-chance flood is completely contained within the levees along the Wood River – East Fork Wood River below the Village of East Alton corporate limits. Above the Village of East Alton, a floodway and cross sectioning are shown.

No floodway or cross sections are shown for lakes within Madison County which impound the flow along streams and no encroachment is possible. Examples are Holiday Lake on

FIGURE 1 – Floodway Schematic Joulters Creek, Highland Silver Lake on East Fork Silver Creek, and Dunlap Lake on

31 Mooney Creek. No floodway or cross sections are shown for the downstream portions of the Wood River and Cahokia Creek since these areas are in the Mississippi River flood plain and no free flow analysis is available.

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 (Reference 64) 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 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 profile, two floodways were computed for the reach. For each 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 appropriate floodway boundary on each bank was delineated and used in the HEC-RAS model resulting in a composite encroached 1-percent-annual-chance profile. When a levee defined the floodway, the floodway boundaries were placed at the landside toe of the levee.

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-percent-annual-chance flood water surface elevations with floodways are not reported from the steady state hydraulic models. However, regulatory 1-percent-annual-chance flood water surface elevations 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.

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 Flood Insurance Study report.

The area between the floodway and l-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 l- percent-annual-chance flood more than 0.1 foot at any point. Typical relationships between the floodway and the floodway fringe and their significance to floodplain development are shown in Figure 1.

In the redelineation efforts, the floodways were not recalculated. As a result, there were areas where the previous floodway did not fit within the boundaries of the redelineated 1- percent-annual-chance floodplain. In these areas, the floodway was reduced. Water

32 surface elevations, with and without a floodway, the mean velocity in the floodway, and the location and area at each surveyed cross section as determined by hydraulic methods can be seen in Table 10, Floodway Data Table. The width of the floodway depicted by the FIRM panels and the amount of reduction to fit the floodway inside the 1-percent-annual-chance floodplain, if necessary, is also listed.

33 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE A 0.36 180 555 2.6 447.6 447.6 447.7 0.1 B 0.68 144 337 4.2 452.0 452.0 452.1 0.1

1Miles above mouth

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS BELT LINE CREEK 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE A 19,590 553 7,422 3.6 436.2 436.2 436.3 0.1 B 21,489 524 6,007 4.5 437.1 437.1 437.2 0.1 C 23,865 600 7,250 3.7 440.1 440.1 440.1 0.0 D 26,664 2,336 2 20,665 1.2 440.9 440.9 440.9 0.0 E 29,040 1,145 10,471 2.4 441.2 441.2 441.2 0.0 F 31,451 369 4,587 5.5 442.0 442.0 442.0 0.0 G 36,168 891 9,279 2.7 14 445.5 445.5 445.6 0.1 H 41,448 1,475 6,887 3.7 448.9 448.9 449.0 0.1 I 43,137 264 4,105 6.1 450.3 450.3 450.3 0.0 J 45,936 897 8,742 2.9 452.2 452.2 452.3 0.1 K 46,569 244 3,595 7.0 452.6 452.6 452.7 0.1 L 47,620 998 12,035 2.1 454.7 454.7 454.7 0.0 M 48,100 1,106 12,455 2.0 455.0 455.0 455.0 0.0 N 49,632 898 11,702 2.2 455.6 455.6 455.6 0.0 O 51,216 2,295 27,476 3.9 457.1 457.1 457.1 0.0 P 51,849 2,285 22,542 1.1 457.1 457.1 457.1 0.0 Q 54,650 2,949 31,955 0.8 457.4 457.4 457.4 0.0 R 61,950 3,185 24,363 1.0 458.8 458.8 458.9 0.1 S 70,541 1,083 5,750 4.5 461.9 461.9 461.9 0.0 T 73,708 935 6,643 3.9 466.6 466.6 466.6 0.0 U 74,448 175 3,543 7.3 467.5 467.5 467.6 0.1 V 77,616 3,652 31,638 0.8 471.1 471.1 471.2 0.1 W 98,736 3,150 13,985 1.6 476.1 476.1 476.2 0.1 X 105,600 2,157 10,551 2.0 479.2 479.2 479.3 0.1 Y 112,200 3,131 18,546 1.1 482.3 482.3 482.4 0.1 Z 120,912 864 10,853 1.9 86 486.1 486.1 486.2 0.1 1Feet above confluence with Mississippi River 2Combined Floodway width of Cahokia Creek and Indian Creek

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS CAHOKIA CREEK 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE AA 121,704 923 7,106 2.9 912 486.8 486.8 486.9 0.1 AB 126,931 2,195 8,422 2.5 490.5 490.5 490.6 0.1 AC 136,752 2,712 22,423 0.9 492.7 492.7 492.8 0.1 AD 139,761 2,112 13,505 1.6 493.3 493.3 493.4 0.1 AE 143,352 3,379 33,784 0.6 493.6 493.6 493.7 0.1 AF 149,635 3,179 9,385 2.1 495.2 495.2 495.2 0.0 AG 152,750 193 1,577 12.2 498.2 498.2 498.3 0.1 AH 153,753 1,868 15,817 1.2 502.7 502.7 502.8 0.1 AI 160,195 1,144 11,141 1.8 1132 506.3 506.3 506.4 0.1 AJ 160,670 1,572 10,572 1.9 407 506.6 506.6 506.7 0.1

1Feet above confluence with Mississippi River

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS CAHOKIA CREEK 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE A 13,464 3,371 2,237 2.5 422.4 422.4 422.5 0.1 B 18,850 1,050 1,675 3.4 434.4 434.4 434.5 0.1 C 26,664 1,301 2,452 3.5 450.3 450.3 450.4 0.1 D 36,168 386 2,151 3.6 470.3 470.3 470.3 0.0 E 38,544 406 2,267 3.4 473.6 473.6 473.7 0.1 F 39,178 380 1,933 4.1 51 474.6 474.6 474.7 0.1 G 42,293 472 2,133 3.5 480.2 480.2 480.3 0.1 H 42,768 365 1,319 5.6 481.1 481.1 481.2 0.1 I 44,352 512 2,722 2.7 484.5 484.5 484.5 0.0 J 46,728 342 2,684 2.8 149 488.3 488.3 488.3 0.0 K 47,784 48 566 13.2 489.5 489.5 489.5 0.0 L 48,048 498 4,190 1.8 493.9 493.9 493.9 0.0 M 49,262 250 1,660 3.9 494.9 494.9 494.9 0.0 N 53,856 497 3,219 2.0 58 501.0 501.0 501.1 0.1 O 57,816 294 2,085 2.2 507.9 507.9 508.0 0.1 P 62,410 200 930 4.2 517.0 517.0 517.1 0.1 Q 62,885 55 535 6.3 519.2 519.2 519.3 0.1 R 63,307 23 418 8.1 523.6 523.6 523.7 0.1 S 66,317 220 1,433 1.8 528.2 528.2 528.3 0.1

1Feet above Mouth

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS CANTEEN CREEK 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE A 0.49 190 1,126 3.2 458.2 458.2 458.3 0.1 B 0.60 160 659 5.5 459.5 459.5 459.6 0.1 C 0.85 380 1,353 2.7 465.4 465.4 465.5 0.1 D 1.00 179 1,368 2.7 466.1 466.1 466.2 0.1 E 1.15 75 405 9.0 470.3 470.3 470.4 0.1 F 1.49 129 813 4.5 316 480.1 480.1 480.2 0.1 G 1.69 388 1,221 3.0 486.4 486.4 486.5 0.1

1Miles above Mouth

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS COAL BRANCH CREEK 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE A 810 418 1,005 0.6 434.0 434.0 434.1 0.1 B 2,000 114 355 1.1 436.5 436.5 436.6 0.1 C 2,880 124 361 0.9 436.9 436.9 437.0 0.1 D 3,388 45 149 2.2 437.2 437.2 437.3 0.1

1Feet above South Flank Wood River Levee

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS EAST ALTON DITCH 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE A 15,238 121 1,184 12.9 456.3 456.3 456.4 0.1 B 15,845 1,721 14,529 1.0 460.6 460.6 460.7 0.1 C 16,875 2,349 24,356 0.6 461.6 461.6 461.7 0.1 D 20,740 1,126 10,425 1.5 462.0 462.0 462.1 0.1 E 22,857 1,616 12,787 1.2 463.3 463.3 463.4 0.1 F 23,533 1,024 10,706 1.4 463.6 463.6 463.7 0.1 G 31,812 1,735 13,271 1.2 465.2 465.2 465.3 0.1 H 37,356 1,417 10,721 0.8 466.9 466.9 467.0 0.1 I 45,984 1,319 5,600 1.6 97 468.4 468.3 468.4 0.1 J 51,385 1,229 4,935 1.8 472.1 472.1 472.2 0.1 K 53,254 830 3,352 2.7 474.5 474.5 474.6 0.1 L 60,414 1,224 8,284 1.1 478.3 478.3 478.4 0.1 M 72,125 684 4,233 2.1 485.0 485.0 485.1 0.1 N 102,126 138 1,760 5.1 508.5 508.5 508.6 0.1 O 107,526 836 5,362 2.0 510.7 510.7 510.8 0.1 P 112,327 263 1,952 5.7 515.8 515.8 515.9 0.1

1Feet above Mouth

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS EAST FORK SILVER CREEK 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE East Fork Wood River F 15,629 125 1,943 7.8 437.6 436.3 2 436.3 0.0 G 20,011 495 6,049 2.5 440.1 439.6 2 439.7 0.1 H 21,912 441 2,295 6.6 440.9 440.7 2 440.8 0.1 I 23,654 384 3,635 4.2 44 443.3 443.3 443.4 0.1 J 26,242 600 2,423 6.3 446.4 446.4 446.5 0.1 K 26,559 175 2,302 6.5 448.8 448.8 448.8 0.0 L 27,562 1,066 3 4,856 3.1 450.6 450.6 450.7 0.1 M 29,199 1,579 3 4,877 3.1 452.4 452.4 452.5 0.1 N 30,572 1,430 4,966 3.1 454.1 454.1 454.1 0.0 O 31,944 1,650 6,550 2.1 455.2 455.2 455.2 0.0 P 34,109 1,613 3,064 4.5 458.2 458.2 458.3 0.1 Q 36,221 1,362 5,782 2.4 460.5 460.5 460.6 0.1 R 40,023 996 3,000 4.7 466.4 466.4 466.5 0.1 S 44,828 599 3,789 3.8 474.0 474.0 474.1 0.1 T 47,943 594 3,573 4.1 478.8 478.8 478.9 0.1 U 56,496 1,130 5,058 3.0 491.7 491.7 491.8 0.1 V 59,981 107 1,538 9.8 498.8 498.8 498.9 0.1 W 61,935 723 5,232 2.9 502.3 502.3 502.4 0.1

1Feet above Mouth 2 Elevations computed without considering backwater effect from Wood River and Mississippi River 3 Combined floodway width of East Fork Wood River and Stanley Creek

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS EAST FORK WOOD RIVER 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE A 5,386 691 1,860 3.1 478.8 478.8 478.9 0.1 B 6,336 946 2,722 2.1 481.2 481.2 481.3 0.1 C 10,454 772 2,235 2.7 489.4 489.4 489.5 0.1 D 11,986 564 1,659 3.6 492.7 492.7 492.8 0.1 E 15,206 666 2,258 2.7 500.4 500.4 500.5 0.1 F 18,533 500 1,874 3.2 505.6 505.6 505.7 0.1 G 23,549 366 1,465 4.2 516.7 516.7 516.8 0.1

1Feet above Mouth

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS HONEYCUT BRANCH 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE A 800 2,336 2 20,665 1.2 441.1 438.8 3 438.9 0.1 B 7,286 911 5,115 2.1 441.1 440.2 3 440.3 0.1 C 10,032 136 1,609 7.0 444.3 444.3 444.3 0.0 D 10,929 800 7,081 1.6 446.3 446.3 446.3 0.0 E 11,088 800 7,110 1.6 446.3 446.3 446.3 0.0 F 12,038 326 2,986 3.7 448.1 448.1 448.1 0.0 G 15,312 1,049 7,775 1.4 450.7 450.7 450.8 0.1 H 16,790 595 4,947 2.2 452.2 452.2 452.3 0.1 I 21,648 484 3,864 2.9 454.3 454.3 454.4 0.1 J 26,716 734 5,532 2.0 457.4 457.4 457.5 0.1 K 30,782 1,138 5,327 2.1 459.1 459.1 459.2 0.1 L 33,897 992 3,571 2.7 461.5 461.5 461.6 0.1 M 37,435 1,305 5,690 1.7 464.6 464.6 464.7 0.1 N 40,128 922 3,562 2.1 467.2 467.2 467.3 0.1 O 43,982 893 3,671 1.9 471.6 471.6 471.7 0.1 P 48,100 921 3,024 2.1 19 476.2 476.2 476.3 0.1 Q 49,684 956 3,859 1.6 308 478.2 478.2 478.3 0.1 R 51,585 1,057 3,182 1.9 480.8 480.8 480.8 0.0 S 54,331 846 2,827 2.1 484.8 484.8 484.9 0.1 T 58,565 903 3,141 1.9 490.2 490.2 490.3 0.1 U 62,040 91 774 7.6 497.5 497.5 497.6 0.1

1Feet above Mouth 2 Combined floodway width of Cahokia Creek and Indian Creek 3 Elevations computed without considering backwater effect from Cahokia Creek

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS INDIAN CREEK 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE A 1,267 47 290 3.8 203 476.4 476.4 476.5 0.1 B 12,672 179 733 4.5 510.2 510.2 510.3 0.1 C 14,890 299 1,076 3.1 516.2 516.2 516.3 0.1 D 24,235 94 208 4.3 561.7 561.7 561.7 0.0

1Feet above Mouth

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS JOULTERS CREEK 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE A 397 46 156 5.2 486.4 486.4 486.5 0.1 B 901 65 245 5.9 487.6 487.6 487.7 0.1 C 915 64 263 6.5 487.5 487.5 487.6 0.1 D 965 46 246 3.9 488.4 488.4 488.5 0.1 E 990 38 181 4.5 488.4 488.4 488.4 0.0 F 1,935 33 139 5.8 490.5 490.5 490.5 0.0 G 2,589 24 131 8.7 492.6 492.6 492.6 0.0 H 2,642 35 185 5.0 493.7 493.7 493.7 0.0 I 2,772 40 161 5.0 493.9 493.9 493.9 0.0 J 2,898 37 175 4.6 494.1 494.1 494.1 0.0 K 2,937 38 220 4.4 494.3 494.3 494.3 0.0 L 3,003 43 218 4.0 494.5 494.5 494.5 0.0 M 3,096 43 165 4.9 494.5 494.5 494.5 0.0 N 3,846 36 157 5.1 496.7 496.7 496.7 0.0 O 5,012 45 161 3.6 500.2 500.2 500.2 0.0 P 5,846 42 125 4.7 503.1 503.1 503.2 0.1 Q 6,871 45 133 4.4 508.0 508.0 508.0 0.0

1Feet above confluence with Lindenthal Creek

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS LAUREL BRANCH 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE A 219 10 15 2.1 497.7 497.7 497.7 0.0 B 435 12 7 4.9 501.4 501.4 501.4 0.0 C 534 32 69 2.2 505.3 505.3 505.3 0.0 D 1,321 66 13 2.5 531.3 531.3 531.3 0.0

1Feet above confluence with Laurel Branch

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS LAUREL BRANCH TRIBUTARY 1 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE A 3,383 266 475 5.9 474.1 474.1 474.2 0.1 B 4,400 335 887 3.1 476.8 476.8 476.9 0.1 C 5,464 313 853 3.3 479.1 479.1 479.2 0.1 D 6,454 85 518 5.4 481.7 481.7 481.8 0.1 E 7,214 266 855 3.2 483.6 483.6 483.7 0.1 F 8,145 369 1,113 2.4 485.7 485.7 485.8 0.1 G 9,294 401 856 2.0 487.2 487.2 487.3 0.1 H 10,178 239 490 3.4 488.5 488.5 488.6 0.1 I 10,438 158 324 10.1 489.3 489.3 489.4 0.1 J 11,131 187 507 3.3 492.4 492.4 492.5 0.1 K 11,160 195 885 1.9 494.6 494.6 494.6 0.0 L 11,336 235 1,294 1.3 494.6 494.6 494.7 0.1 M 11,833 160 790 2.1 494.7 494.7 494.7 0.0 N 12,830 231 678 2.5 495.7 495.7 495.7 0.0 O 12,901 196 535 10.4 495.2 495.2 495.2 0.0 P 12,971 219 1,549 1.1 498.5 498.5 498.5 0.0 Q 13,534 235 1,075 1.3 498.6 498.6 498.6 0.0 R 14,003 39 250 5.8 498.9 498.9 498.9 0.0 S 14,071 203 634 2.3 501.5 501.5 501.5 0.0 T 14,334 179 764 1.9 501.7 501.7 501.7 0.0 U 15,277 65 308 6.3 502.6 502.6 502.6 0.0 V 15,393 77 506 4.0 504.6 504.6 504.6 0.0 W 16,271 55 314 6.8 505.6 505.6 505.7 0.1 X 16,645 198 1,647 0.9 515.0 515.0 515.0 0.0 Y 16,731 875 10,866 0.1 529.1 529.1 529.1 0.0 Z 16,786 827 10,498 0.1 529.1 529.1 529.1 0.0 1Feet above confluence with Sugar Creek

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS LINDENTHAL CREEK 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE AA 17,312 760 8,517 0.1 529.1 529.1 529.1 0.0 AB 18,146 483 4,594 0.1 529.1 529.1 529.1 0.0 AC 18,241 470 3,112 0.2 529.1 529.1 529.1 0.0 AD 19,156 524 2,285 0.2 529.1 529.1 529.1 0.0 AE 19,560 380 1,412 0.4 529.1 529.1 529.1 0.0 AF 19,914 242 755 0.7 529.1 529.1 529.1 0.0 AG 20,066 410 1,082 0.5 529.8 529.8 529.8 0.0 AH 20,907 211 505 1.1 529.8 529.8 529.9 0.1

1Feet above confluence with Sugar Creek

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS LINDENTHAL CREEK 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE A 146 1,115 8,341 0.1 529.1 529.1 529.1 0.0 B 289 610 5,719 0.1 529.1 529.1 529.1 0.0 C 615 470 4,914 0.1 529.1 529.1 529.1 0.0 D 885 330 2,528 0.2 529.1 529.1 529.1 0.0 E 919 320 2,457 0.2 529.1 529.1 529.1 0.0 F 1,019 470 4,135 0.1 530.9 530.9 530.9 0.0 G 1,609 850 7,033 0.1 530.9 530.9 530.9 0.0 H 1,990 900 4,712 0.1 530.9 530.9 530.9 0.0 I 2,236 590 3,786 0.1 530.9 530.9 530.9 0.0 J 3,200 300 869 0.3 530.9 530.9 530.9 0.0 K 4,131 66 212 1.2 531.0 531.0 531.0 0.0 L 5,013 105 250 1.5 531.1 531.1 531.2 0.1 M 5,140 207 443 0.6 534.5 534.5 534.5 0.0 N 5,527 170 200 1.3 534.6 534.6 534.6 0.0 O 6,444 199 109 3.2 536.0 536.0 536.0 0.0

1Feet above confluence with Lindenthal Creek

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS LINDENTHAL CREEK TRIBUTARY 1 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE A 148 1,125 7,711 0.0 530.9 530.9 530.9 0.0 B 995 520 2,775 0.1 530.9 530.9 530.9 0.0 C 1,050 820 1,861 0.1 530.9 530.9 530.9 0.0 D 1,848 71 54 0.9 531.2 531.2 531.2 0.0 E 2,393 435 230 4.1 534.9 534.9 534.9 0.0 F 2,516 650 3,757 0.0 540.1 540.1 540.2 0.1 G 2,859 1,076 5,915 0.0 540.1 540.1 540.2 0.1

1Feet above confluence with Lindenthal Creek Tributary 1

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS LINDENTHAL CREEK TRIBUTARY 2 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE A 332 428 918 0.1 530.9 530.9 530.9 0.0 B 1,138 146 82 1.1 531.3 531.3 531.3 0.0

1Feet above confluence with Lindenthal Creek Tributary 2

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS LINDENTHAL CREEK TRIBUTARY 3 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE A 337 1,107 2,804 0.0 530.9 530.9 530.9 0.0 B 968 260 230 0.3 530.9 530.9 530.9 0.0 C 1,680 69 27 2.3 534.5 534.5 534.5 0.0

1Feet above confluence with Lindenthal Creek Tributary 1

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS LINDENTHAL CREEK TRIBUTARY 4 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) WIDTH2 SECTION MEAN (FEET) AREA VELOCITY WIDTH2 REGULATORY DISTANCE1 WITHIN (SQUARE (FEET PER (FEET) FROM UNET WITHOUT WITH CROSS SECTION (MILES) ILLINOIS FEET) SECOND) TOTAL MODEL FLOODWAY FLOODWAY INCREASE 182.44 182.44 1,343 N/A N/A 2,322 427.9 N/A N/A N/A 182.50 182.50 1,399 N/A N/A 2,586 427.9 N/A N/A N/A 182.52 182.52 1,376 N/A N/A 2,496 427.9 N/A N/A N/A 182.53 182.53 1,400 N/A N/A 2,492 427.9 N/A N/A N/A 182.90 182.90 1,807 N/A N/A 2,811 428.2 N/A N/A N/A 183.26 183.26 2,134 N/A N/A 2,919 428.6 N/A N/A N/A 183.27 183.27 2,104 N/A N/A 2,991 428.5 N/A N/A N/A 183.28 183.28 2,105 N/A N/A 3,030 428.5 N/A N/A N/A 183.30 183.30 2,118 N/A N/A 3,084 428.5 N/A N/A N/A 183.38 183.38 2,215 N/A N/A 3,008 428.5 N/A N/A N/A 183.98 183.98 2,210 N/A N/A 3,128 429.1 N/A N/A N/A 184.56 184.56 2,876 N/A N/A 3,851 429.6 N/A N/A N/A 185.18 185.18 5,263 N/A N/A 6,236 430.0 N/A N/A N/A 185.76 185.76 7,577 N/A N/A 8,986 430.2 N/A N/A N/A 186.36 186.36 9,100 N/A N/A 10,531 430.4 N/A N/A N/A 186.82 186.82 10,080 N/A N/A 11,575 430.5 N/A N/A N/A 187.41 187.41 10,693 N/A N/A 12,068 430.7 N/A N/A N/A 188.00 188.00 10,489 N/A N/A 11,843 430.9 N/A N/A N/A 188.43 188.43 9,965 N/A N/A 11,082 431.2 N/A N/A N/A 188.88 188.88 9,457 N/A N/A 10,621 431.4 N/A N/A N/A 189.47 189.47 6,020 N/A N/A 7,457 431.8 N/A N/A N/A 190.29 190.29 3,071 N/A N/A 5,139 432.3 N/A N/A N/A 190.32 190.32 3,049 N/A N/A 5,135 432.3 N/A N/A N/A 190.37 190.37 3,048 N/A N/A 5,035 432.3 N/A N/A N/A 190.46 190.46 3,002 N/A N/A 5,307 432.3 N/A N/A N/A 190.47 190.47 2,985 N/A N/A 5,176 432.3 N/A N/A N/A 1Miles above mouth of the Ohio River 2Widths are reported as width to state line and composite width from the USACE floodway model. *Floodway Data Tables for the Mississippi River are a special case. See Flood Insurance Study Text for full explanation.

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS MISSISSIPPI RIVER* 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) WIDTH2 SECTION MEAN (FEET) AREA VELOCITY WIDTH2 REGULATORY WITHIN (SQUARE (FEET PER (FEET) FROM UNET WITHOUT WITH CROSS SECTION DISTANCE1 ILLINOIS FEET) SECOND) TOTAL MODEL FLOODWAY FLOODWAY INCREASE 190.48 190.48 2,995 N/A N/A 5,153 432.3 N/A N/A N/A 190.50 190.50 3,012 N/A N/A 5,071 432.3 N/A N/A N/A 190.64 190.64 3,037 N/A N/A 5,204 432.4 N/A N/A N/A 190.79 190.79 3,067 N/A N/A 5,212 432.4 N/A N/A N/A 190.81 190.81 3,069 N/A N/A 5,162 432.5 N/A N/A N/A 190.82 190.82 3,081 N/A N/A 5,191 432.5 N/A N/A N/A 190.85 190.85 3,141 N/A N/A 5,366 432.5 N/A N/A N/A 191.36 191.36 3,995 N/A N/A 6,561 432.7 N/A N/A N/A 191.92 191.92 3,596 N/A N/A 8,838 432.9 N/A N/A N/A 192.41 192.41 3,082 N/A N/A 9,148 433.0 N/A N/A N/A 192.91 192.91 2,667 N/A N/A 9,785 433.3 N/A N/A N/A 193.28 193.28 2,820 N/A N/A 11,296 433.4 N/A N/A N/A 193.79 193.79 1,745 N/A N/A 11,798 433.6 N/A N/A N/A 194.16 194.16 2,537 N/A N/A 13,235 433.8 N/A N/A N/A 194.63 194.63 3,221 N/A N/A 14,131 433.9 N/A N/A N/A 194.97 194.97 4,141 N/A N/A 15,110 434.0 N/A N/A N/A 195.56 195.56 4,062 N/A N/A 23,470 434.3 N/A N/A N/A 196.09 196.09 3,884 N/A N/A 17,731 434.4 N/A N/A N/A 196.48 196.48 3,121 N/A N/A 17,788 434.6 N/A N/A N/A 196.82 196.82 2,832 N/A N/A 17,027 434.7 N/A N/A N/A 197.31 197.31 3,084 N/A N/A 20,410 434.8 N/A N/A N/A 197.71 197.71 3,147 N/A N/A 19,342 434.9 N/A N/A N/A 198.28 198.28 2,467 N/A N/A 20,288 435.0 N/A N/A N/A 198.81 198.81 1,695 N/A N/A 18,704 435.1 N/A N/A N/A 199.34 199.34 1,320 N/A N/A 17,998 435.2 N/A N/A N/A 199.83 199.83 1,217 N/A N/A 7,039 435.3 N/A N/A N/A 1Miles above mouth of the Ohio River 2Widths are reported as width to state line and composite width from the USACE floodway model. *Floodway Data Tables for the Mississippi River are a special case. See Flood Insurance Study Text for full explanation.

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS MISSISSIPPI RIVER* 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) WIDTH2 SECTION MEAN (FEET) AREA VELOCITY WIDTH2 REGULATORY WITHIN (SQUARE (FEET PER (FEET) FROM UNET WITHOUT WITH CROSS SECTION DISTANCE1 ILLINOIS FEET) SECOND) TOTAL MODEL FLOODWAY FLOODWAY INCREASE 200.31 200.31 1,468 N/A N/A 5,182 435.4 N/A N/A N/A 200.54 200.54 1,335 N/A N/A 4,521 435.5 N/A N/A N/A 200.70 200.70 1,299 N/A N/A 4,225 435.6 N/A N/A N/A 200.85 200.85 1,298 N/A N/A 4,196 435.7 N/A N/A N/A 201.29 201.29 1,454 N/A N/A 4,768 435.9 N/A N/A N/A 201.85 201.85 1,535 N/A N/A 4,215 436.2 N/A N/A N/A 202.50 202.50 1,605 N/A N/A 3,379 436.6 N/A N/A N/A 202.63 202.63 1,436 N/A N/A 2,913 436.6 N/A N/A N/A 202.66 202.66 1,417 N/A N/A 3,189 436.6 N/A N/A N/A 202.68 202.68 1,383 N/A N/A 2,400 436.6 N/A N/A N/A 203.04 203.04 1,309 N/A N/A 3,132 436.7 N/A N/A N/A 203.36 203.36 1,892 N/A N/A 3,762 436.7 N/A N/A N/A 203.86 203.86 2,062 N/A N/A 5,416 436.8 N/A N/A N/A 204.38 204.38 1,702 N/A N/A 6,820 436.8 N/A N/A N/A 204.96 204.96 1,631 N/A N/A 7,294 436.9 N/A N/A N/A 205.48 205.48 1,656 N/A N/A 7,721 437.0 N/A N/A N/A 206.07 206.07 1,943 N/A N/A 7,994 437.0 N/A N/A N/A 206.60 206.60 2,220 N/A N/A 8,134 437.0 N/A N/A N/A 207.12 207.12 2,221 N/A N/A 8,645 437.0 N/A N/A N/A 207.72 207.72 3,169 N/A N/A 8,482 437.1 N/A N/A N/A 208.29 208.29 3,498 N/A N/A 7,095 437.2 N/A N/A N/A

1Miles above mouth of the Ohio River 2Widths are reported as width to state line and composite width from the USACE floodway model. *Floodway Data Tables for the Mississippi River are a special case. See Flood Insurance Study Text for full explanation.

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS MISSISSIPPI RIVER* 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE A 4,171 3,403 11,748 0.5 457.6 453.2 453.3 0.1 B 7,550 842 2,627 2.4 460.7 460.7 460.7 0.0 C 8,026 24 320 19.4 462.8 462.8 462.8 0.0 D 8,818 1,366 6,814 1.0 184 472.8 472.8 472.8 0.0 E 10,032 531 1,032 4.5 472.8 472.8 472.8 0.0 F 14,309 194 627 2.6 474.3 474.3 474.3 0.0 G 14,628 137 366 6.1 474.4 474.4 474.5 0.1 H 15,021 386 788 2.8 477.1 477.1 477.1 0.0 I 15,135 326 933 2.4 479.9 479.9 480.0 0.1 J 15,733 355 1,437 1.6 480.5 480.5 480.5 0.0 K 16,544 88 541 4.9 480.9 480.9 480.9 0.0 L 16,729 139 927 2.6 482.4 482.4 482.4 0.0 M 16,784 140 734 3.1 482.4 482.4 482.4 0.0 N 17,123 270 1,282 2.8 484.3 484.3 484.3 0.0 O 17,561 490 1,404 1.6 484.5 484.5 484.5 0.0 P 17,658 152 660 3.4 486.1 486.1 486.1 0.0 Q 17,764 112 559 4.0 486.1 486.1 486.1 0.0 R 18,077 162 641 3.5 486.5 486.5 486.5 0.0 S 18,217 135 4,269 0.5 512.9 512.9 512.9 0.0 T 26,339 195 910 2.5 514.5 514.5 514.6 0.1 U 26,363 58 221 5.8 514.4 514.4 514.4 0.0 V 26,423 180 728 2.4 519.7 519.7 519.7 0.0 W 27,126 243 1,351 0.6 519.8 519.8 519.8 0.0 X 27,263 220 1,295 0.6 521.6 521.6 521.6 0.0 Y 27,713 88 469 1.7 521.6 521.6 521.6 0.0 Z 27,773 49 384 2.1 521.9 521.9 521.9 0.0 1Feet above Mouth

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS MOONEY CREEK 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE AA 28,089 315 1,513 0.5 522.0 522.0 522.0 0.0 AB 28,952 113 472 1.7 522.1 522.1 522.1 0.0 AC 29,632 145 380 2.1 522.4 522.4 522.4 0.0 AD 30,951 25 105 7.5 524.9 524.9 524.9 0.0

1Feet above Mouth

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS MOONEY CREEK 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE A 246 131 283 1.1 514.7 514.7 514.8 0.1 B 355 135 374 2.4 516.1 516.1 516.2 0.1 C 1,295 39 125 2.7 516.7 516.7 516.7 0.0 D 1,379 51 147 2.5 517.1 517.1 517.1 0.0 E 2,149 22 53 6.0 519.9 519.9 519.9 0.0

1Feet above confluence with Mooney Creek

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS MOONEY CREEK TRIBUTARY 1 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE A 161 260 1,299 0.1 519.8 519.8 519.8 0.0 B 284 130 602 0.2 520.1 520.1 520.1 0.0 C 822 15 63 4.1 520.2 520.2 520.2 0.0 D 910 22 74 3.1 521.5 521.5 521.5 0.0 E 1,804 25 22 5.6 528.9 528.9 528.9 0.0 F 2,715 20 25 4.9 538.3 538.3 538.4 0.1

1Feet above confluence with Mooney Creek

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS MOONEY CREEK TRIBUTARY 2 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE A 7,286 368 1,287 5.3 475.0 475.0 475.0 0.0 B 8,448 1,019 3,363 1.7 477.2 477.2 477.3 0.1 C 12,307 502 2,009 2.8 117 482.9 482.9 483.0 0.1 D 13,675 1,004 2,829 2.0 486.1 486.1 486.2 0.1 E 18,955 656 2,711 2.1 493.9 493.9 494.0 0.1 F 23,284 175 2,311 2.6 586 502.3 502.3 502.3 0.0 G 26,400 674 3,187 1.9 505.8 505.8 505.9 0.1 H 30,676 596 2,407 2.5 512.0 512.0 512.1 0.1 I 33,158 750 2,015 2.9 514.8 514.8 514.9 0.1 J 37,065 423 1,592 3.6 521.7 521.7 521.8 0.1 K 39,230 43 1,329 4.3 307 528.1 528.1 528.2 0.1 L 42,187 580 1,588 3.6 531.3 531.3 531.4 0.1 M 44,932 543 1,755 3.2 536.0 536.0 536.1 0.1 N 46,516 448 1,068 5.1 540.0 540.0 540.1 0.1 O 53,539 384 1,996 2.6 552.8 552.8 552.9 0.1 P 56,390 279 1,613 3.2 43 559.6 559.6 559.7 0.1 Q 57,340 498 2,471 2.1 561.6 561.6 561.6 0.0

1Feet above Mouth

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS PADDOCK CREEK 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE Sherry Creek A 3,537 1,338 4,727 2.4 479.3 479.3 479.4 0.1 B 3,960 1,221 2,594 4.3 480.9 480.9 481.0 0.1 C 5,544 1,256 6,178 1.8 483.3 483.3 483.4 0.1 D 10,507 891 2,661 4.2 489.4 489.4 489.5 0.1 E 15,946 1,059 5,569 2.0 494.4 494.4 494.5 0.1 East Fork Sherry Creek F 18,902 845 4,289 2.6 497.1 497.1 497.2 0.1 G 23,866 1,362 6,589 1.8 500.8 500.8 500.9 0.1 H 24,446 1,800 3,360 3.5 440 502.4 502.4 502.5 0.1

1Feet above Mouth

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS SHERRY CREEK- EAST FORK SHERRY CREEK 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE A 193,501 5,139 74,669 0.5 453.5 453.5 453.6 0.1 B 199,959 4,615 40,082 0.8 453.7 453.7 453.8 0.1 C 206,960 4,615 43,360 0.8 454.2 454.2 454.3 0.1 D 214,162 5,340 54,981 0.4 454.5 454.5 454.6 0.1 E 219,859 2,219 19,026 1.2 454.7 454.7 454.8 0.1 F 225,762 398 3,626 6.1 458.3 458.3 458.4 0.1 G 227,510 1,600 3,818 5.8 459.0 459.0 459.1 0.1 H 236,861 2,826 22,021 1.0 461.1 461.1 461.2 0.1 I 245,314 2,394 18,607 1.2 462.7 462.7 462.8 0.1 J 251,133 2,176 11,764 1.9 464.3 464.3 464.4 0.1 K 251,750 2,275 16,263 1.4 464.8 464.8 464.9 0.1 L 260,753 2,195 21,740 1.0 472.1 472.1 472.2 0.1 M 262,004 1,966 16,811 1.4 474.1 474.1 474.2 0.1 N 264,855 1,174 12,576 1.8 475.0 475.0 475.1 0.1 O 274,006 889 9,704 2.4 478.9 478.9 479.0 0.1 P 280,664 346 5,657 4.1 481.9 481.9 482.0 0.1 Q 285,537 1,529 13,949 1.7 483.4 483.4 483.5 0.1 R 288,346 1,959 19,297 1.2 484.2 484.2 484.3 0.1 S 290,226 1,030 10,669 2.2 484.7 484.7 484.8 0.1 T 301,625 1,675 15,814 1.5 488.4 488.4 488.5 0.1 U 308,727 2,181 18,839 1.2 490.3 490.3 490.4 0.1 V 313,727 2,632 14,806 1.6 492.9 492.9 493.0 0.1 W 318,796 270 3,523 7.1 496.1 496.1 496.2 0.1 X 325,327 1,355 11,362 2.0 498.7 498.7 498.8 0.1 Y 334,023 266 2,511 9.1 504.6 504.6 504.7 0.1 Z 343,327 1,493 13,924 1.7 508.7 508.7 508.8 0.1 1Feet above Mouth

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS SILVER CREEK 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE AA 354,124 1,200 21,769 1.1 514.7 514.7 514.8 0.1 AB 357,324 1,154 8,637 2.6 515.7 515.7 515.8 0.1 AC 359,035 1,495 10,577 2.1 517.7 517.7 517.8 0.1 AD 366,384 1,262 9,513 2.0 522.0 522.0 522.1 0.1 AE 372,034 1,422 11,980 1.6 529.1 529.1 529.2 0.1 AF 374,035 1,126 9,014 1.6 529.7 529.7 529.8 0.1 AG 380,134 902 5,605 2.6 533.0 533.0 533.1 0.1 AH 386,934 1,188 8,133 1.8 538.0 538.0 538.1 0.1 AI 390,894 1,217 5,007 2.9 541.4 541.4 541.5 0.1

1Feet above Mouth

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS SILVER CREEK 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE A 3,802 692 1,853 2.6 507.5 503.3 2 503.3 0.0 B 7,392 113 680 6.7 510.3 510.3 510.4 0.1 C 12,514 478 1,385 2.8 519.0 519.0 519.1 0.1 D 17,318 275 1,162 3.1 528.0 528.0 528.1 0.1

1Feet above Mouth 2 Elevations computed without considering backwater effect from Silver Creek

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS SILVER CREEK TRIBUTARY NO. 1 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE A 3,379 485 1,647 3.0 517.9 517.2 2 517.2 0.0 B 9,177 413 1,339 3.1 528.0 528.0 528.1 0.1 C 10,254 532 2,823 1.5 529.1 529.1 529.2 0.1 D 13,480 488 1,566 2.4 15 533.3 533.3 533.4 0.1 E 16,901 150 711 5.3 539.4 539.4 539.5 0.1 F 19,177 40 376 7.4 543.6 543.6 543.7 0.1 G 23,190 226 729 3.8 552.2 552.2 552.3 0.1 H 25,170 79 375 6.4 556.8 556.8 556.9 0.1 I 25,798 35 318 7.5 559.8 559.8 559.9 0.1 J 26,717 221 804 3.0 563.2 563.2 563.2 0.0 K 27,857 63 519 4.6 565.2 565.2 565.3 0.1 L 28,855 15 127 16.0 566.2 566.2 566.2 0.0

1Feet above Mouth 2 Elevations computed without considering backwater effect from Silver Creek

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS SILVER CREEK TRIBUTARY NO. 2 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE A 1,220 1,066/ 775 2 4,856 3.1 450.5 449.9 3 449.9 0.0 B 2,165 1,579/1,400 2 1,753 1.3 452.4 451.8 3 451.8 0.0 C 4,171 299 602 3.7 456.7 456.7 456.8 0.1 D 6,283 500 1,014 2.2 465.7 465.7 465.7 0.0 E 7,973 78 273 4.8 474.6 474.6 474.7 0.1 F 9,662 68 376 3.5 485.6 485.6 485.6 0.0

1Feet above Mouth 3 Elevations computed without considering overflow effect from Wood River 2 Combined floodway width of East Fork Wood River and Stanley Creek

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS STANLEY CREEK 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE A 2,376 855 4,434 1.7 468.3 468.3 468.4 0.1 B 2,476 1,100 6,710 1.1 468.4 468.4 468.5 0.1 C 4,176 818 4,853 1.6 52 469.2 469.2 469.3 0.1 D 10,127 985 3,963 1.9 473.7 473.7 473.8 0.1 E 14,061 95 4,511 1.7 705 476.6 476.6 476.7 0.1 F 20,412 566 5,114 1.5 134 482.1 482.1 482.1 0.0 G 20,824 145 1,115 6.4 482.1 482.1 482.2 0.1 H 22,002 650 7,347 1.0 485.8 485.8 485.8 0.0 I 27,424 124 1,076 6.6 489.1 489.1 489.2 0.1 J 31,263 690 5,707 1.0 492.8 492.8 492.9 0.1 K 36,078 680 2,796 2.0 496.0 496.0 496.1 0.1

1Feet above Mouth

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS SUGAR FORK 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE A 4,012 582 648 2.7 451.0 451.0 451.1 0.1 B 4,646 381 553 3.1 455.6 455.6 455.7 0.1 C 5,069 400 898 1.8 460.1 460.1 460.2 0.1 D 6,600 66 374 4.6 470.2 470.2 470.3 0.1 E 8,026 140 331 4.0 492.8 492.8 492.8 0.0 F 9,134 93 710 1.0 108 495.5 495.5 495.6 0.1 G 9,715 23 165 4.5 44 499.8 499.8 499.8 0.0

1Feet above Mouth

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS TRIBUTARY E 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE A 3,326 478 754 2.4 451.4 451.4 451.5 0.1 B 4,171 112 675 2.5 458.7 458.7 458.8 0.1 C 5,174 32 162 5.6 467.8 467.8 467.8 0.0 D 6,019 24 133 6.3 475.1 475.1 475.1 0.0

1Feet above Mouth

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS TRIBUTARY F 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE A 475 25 123 6.0 466.3 466.3 466.3 0.0 B 1,478 40 88 5.9 491.8 491.8 491.8 0.0

1Feet above Mouth 2 Combined floodway width of West Fork Wood River and Tributary X 3 Elevations computed without considering backwater effect from West Fork Wood River

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS TRIBUTARY G 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE A 1,320 742 2 3,916 2.7 490.2 489.8 3 489.8 0.0 B 2,429 520 1,903 3.1 491.9 491.9 492.0 0.1 C 3,168 127 2,000 3.0 493.8 493.8 493.9 0.1 D 3,854 500 1,706 3.5 496.0 496.0 496.1 0.1 E 7,814 623 2,049 3.0 507.5 507.5 507.6 0.1 F 12,461 465 2,451 2.6 523.7 523.7 523.8 0.1 G 13,147 97 943 5.3 524.9 524.9 525.0 0.1 H 14,467 453 1,310 3.8 528.8 528.8 528.9 0.1 I 15,365 109 999 5.0 533.2 533.2 533.3 0.1 J 17,160 116 758 6.2 539.1 539.1 539.2 0.1 K 18,586 268 935 4.5 546.2 546.2 546.3 0.1

1Feet above Mouth 2 Combined floodway width of West Fork Wood River and Tributary X 3 Elevations computed without considering backwater effect from West Fork Wood River

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS TRIBUTARY X 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE A 2,006 206 500 4.2 477.1 477.1 477.2 0.1 B 2,957 309 1,028 2.0 63 481.7 481.7 481.8 0.1 C 4,910 270 591 3.3 487.7 487.7 487.8 0.1 D 6,547 241 822 2.2 181 493.9 493.9 493.9 0.0

1Feet above Mouth

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS TRIBUTARY Z 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE A 1,742 727 7,659 2.3 437.9 437.9 437.9 0.0 B 4,013 1,318 6,889 2.6 439.3 439.3 439.3 0.0 C 7,128 455 2,584 6.8 442.2 442.2 442.3 0.1 D 7,920 693 3,945 4.6 444.6 444.6 444.7 0.1 E 9,134 200 2,561 7.1 446.5 446.5 446.6 0.1 F 11,774 1,586 11,207 1.6 449.5 449.5 449.6 0.1 G 15,998 1,205 5,414 3.1 451.6 451.6 451.7 0.1 H 21,173 1,233 6,470 x 459.0 459.0 459.1 0.1 I 22,757 1,648 7,198 2.4 460.1 460.1 460.2 0.1 J 26,347 561 3,314 4.8 464.7 464.7 464.8 0.1 K 29,568 1,300 4,757 3.4 468.0 468.0 468.1 0.1 L 32,472 1,618 4,903 2.2 470.9 470.9 471.0 0.1 M 33,898 1,927 3,748 2.8 473.2 473.2 473.2 0.0 N 34,056 1,551 6,635 1.6 474.2 474.2 474.2 0.0 O 34,690 1,576 5,713 1.8 474.3 474.3 474.3 0.0 P 39,706 896 3,074 3.4 483.7 483.7 483.8 0.1 Q 40,762 998 3,805 2.8 485.8 485.8 485.9 0.1 R 41,026 458 1,954 5.4 486.5 486.5 486.5 0.0 S 42,504 742 2 3,916 2.7 490.4 490.4 490.5 0.1 T 42,874 101 830 7.3 490.7 490.7 490.8 0.1 U 47,784 254 1,379 4.4 501.5 501.5 501.5 0.0 V 53,592 487 2,253 2.7 519.2 519.2 519.3 0.1 W 55,757 272 1,843 3.3 522.7 522.7 522.8 0.1

1Feet above Mouth 2 Combined floodway width of West Fork Wood River and Tributary X x - data is illegible (County of Madison, IL 10/15/81 FIS 170436V000 )

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS WEST FORK WOOD RIVER 1-PERCENT-ANNUAL-CHANCE FLOOD FLOODING SOURCE FLOODWAY WATER SURFACE ELEVATION (FEET NAVD88) SECTION MEAN AREA VELOCITY WIDTH REDUCED WIDTH (SQUARE (FEET PER FROM PRIOR WITHOUT WITH CROSS SECTION DISTANCE1 (FEET) FEET) SECOND) STUDY (FEET) REGULATORY FLOODWAY FLOODWAY INCREASE Wood River A 8,765 146 2,319 13.4 435.2 426.9 2 427.0 0.1 B 9,240 190 2,757 11.3 435.2 429.2 2 429.3 0.1 C 9,451 137 2,591 12.0 435.2 430.9 2 431.0 0.1 D 9,821 174 3,263 9.5 435.2 432.5 2 432.5 0.0 E 11,352 250 3,716 8.1 435.2 434.9 2 435.0 0.1

1Feet above Mouth 2 Elevations computed without considering backwater effect from Mississippi River

TABLE 10 FEDERAL EMERGENCY MANAGEMENT AGENCY FLOODWAY DATA MADISON COUNTY, IL AND INCORPORATED AREAS WOOD RIVER 5.0 INSURANCE APPLICATIONS

5.1 Flood Insurance Zones

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

Zone A

Zone A is the flood insurance risk zone that corresponds to the 1-percent-annual-chance floodplains that are determined in the FIS by approximate methods. Because detailed hydraulic analyses are not performed for such areas, no BFEs or base flood depths are shown within this zone.

Zone AE

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

Zone AH

Zone AH is the flood insurance risk zone that corresponds to the areas of 1-percent- annual-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 AO

Zone AO is the flood insurance risk zone that corresponds to the areas of 1-percent- annual-chance shallow flooding (usually sheet flow on sloping terrain) where average depths are between 1 and 3 feet. Average whole-foot base flood depths derived from the detailed hydraulic analyses are shown 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 flood control system that was subsequently decertified. Zone AR indicates that the former flood-control system is being restored to provide protection from the 1-percent-annual- chance or greater flood event.

Zone X

Zone X is the flood insurance risk zone that corresponds to areas outside the 0.2-percent- annual-chance floodplain, areas within the 0.2-percent-annual-chance floodplain, areas of 1-percent-annual-chance flooding where average depths are less than 1 foot, areas of 1- percent-annual-chance flooding where the contributing drainage area is less that 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.

75 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 described in Section 5.0 and, in the 1-percent-annual-chance floodplains that were studied by detailed methods, shows selected whole-foot BFEs or average depths. Insurance agents use the zones and BFEs in conjunction with information on structures and their contents to assign premium rates for flood insurance policies.

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

The current FIRM presents flooding information for the entire geographic area of Madison County. Previously, separate FIRMs were prepared for each identified floodprone incorporated community and the unincorporated areas of the county. Historical data relating to the maps prepared for each community are presented in Table 11.

7.0 OTHER STUDIES

This 2004 FIS incorporates all previously published FISs and FIRMs for the incorporate and unincorporated areas within Madison County.

This FIS report either supersedes or is compatible with all previous studies published on streams studied in this report and should be considered authoritative for purposes of the National Flood Insurance Program.

FEMA has published FIS reports and FIRMs for Bond County Unincorporated Area (Reference 65), Clinton County (Reference 66), Jersey County Unincorporated Area (Reference 67), Macoupin County Unincorporated Area (Reference 68), Montgomery Unincorporated Area (Reference 69), St. Clair County (Reference 49), and the City of Staunton, Macoupin County (Reference 70).

Additional studies performed in Madison County are the "Plan for Major Drainage: The Piasa Creek, Wood River, and Cahokia Creek Planning Basins," by the Southwestern Illinois Metrolpolitan and Regional Planning Commission (Reference 25), a study on the Canteen Creek watershed by the Illinois Department of Transportation (Reference 59), and studies by the COE and IDNR to determine flooding problems on the land side of the levee. The results presented in this 2004 FIS are in agreement with any results produced by the above studies.

76 FLOOD HAZARD COMMUNITY INITIAL BOUNDARY MAP FIRM FIRM NAME IDENTIFICATION REVISIONS DATE EFFECTIVE DATE REVISIONS DATE

Alhambra, Village of N/A none N/A none Alton, City of March 8, 1974 January 9, 1976 July 2, 1980 May 1, 1984 Bethalto, Village of May 3, 1974 February 20, 1976 July 2, 1980 none Collinsville, City of May 24, 1974 April 2, 1976 February 18, 1981 none E Alton, Village of May 17, 1974 April 9, 1976 March 18, 1980 none Edwardsville, City of April 5, 1974 July 2, 1976 January 18, 1984 none December 26, 1980 Glen Carbon, Village of N/A none N/A none Godfrey, Village of N/A none N/A none Granite City, City of November 16, 1973 none June 1, 1978 none Grantfork, Village of N/A none N/A none Hamel, Village of N/A none N/A none Hartford, Village of November 30, 1973 none May 1, 1979 none Highland, City of March 8, 1974 May 21, 1976 November 5, 1986 none Livingston, Village of March 22, 1974 June 11, 1976 February 27, 1984 none Madison , City of November 23, 1973 August 27, 1976 July 16, 1980 none Madison Unincorporated Areas, County of January 31, 1975 October 1, 1976 April 15, 1982 none Marine, Village of N/A none N/A none Maryville, Village of N/A none N/A none New Douglas, Village of N/A none N/A none Pierron, Village of N/A none N/A none TABLE 11 FEDERAL EMERGENCY MANAGEMENT AGENCY MADISON COUNTY, IL COMMUNITY MAP HISTORY AND INCORPORATED AREAS FLOOD HAZARD COMMUNITY INITIAL BOUNDARY MAP FIRM FIRM NAME IDENTIFICATION REVISIONS DATE EFFECTIVE DATE REVISIONS DATE

Pontoon Beach, Village of November 22, 1974 none July 16, 1980 February 5, 1982 Roxana, Village of May 1, 1979 none May 1, 1979 none South Roxana, Village of October 1, 1976 none May 15, 1980 November 26, 1982 St. Jacob, Village of N/A none N/A none Troy, City of N/A none N/A none Venice, City of February 15, 1974 none January 5, 1978 none Williamson, Village of N/A none N/A none Wood River, City of February 15, 1974 none May 1, 1979 none Worden, Village of N/A none N/A none TABLE 11 FEDERAL EMERGENCY MANAGEMENT AGENCY MADISON COUNTY, IL COMMUNITY MAP HISTORY AND INCORPORATED AREAS 8.0 LOCATION OF DATA

Information concerning the pertinent data used in the preparation of this study can be obtained by contacting the Flood Insurance and Mitigation Division, Federal Emergency Management Agency, 536 South Clark Street, Sixth Floor, Chicago, Illinois 60605.

9.0 BIBLIOGRAPHY AND REFERENCES

1. Federal Emergency Management Agency, Federal Insurance Administration, Flood Insurance Study, City of Alton, Madison County, Illinois, January 1980.

2. Federal Emergency Management Agency, Federal Insurance Administration, Flood Insurance Study, Village of Bethalto, Madison County, Illinois, January 1980.

3. Federal Emergency Management Agency, Federal Insurance Administration, Flood Insurance Study, City of Collinsville, Madison County, Illinois, August 1980.

4. Federal Emergency Management Agency, Federal Insurance Administration, Flood Insurance Study, Village of East Alton, Madison County, Illinois, September 1979.

5. Federal Emergency Management Agency, Federal Insurance Administration, Flood Insurance Study, City of Edwardsville, Madison County, Illinois, July 1983.

6. U.S. Department of Housing and Urban Development, Federal Insurance Administration, Flood Insurance Study, City of Granite City, Madison County, Illinois, December 1977.

7. U.S. Department of Housing and Urban Development, Federal Insurance Administration, Flood Insurance Study, Village of Hartford, Madison County, Illinois, November 1978.

8. Federal Emergency Management Agency, Federal Insurance Administration, Flood Insurance Study, City of Highland, Madison County, Illinois, November 1986.

9. Federal Emergency Management Agency, Federal Insurance Administration, Flood Insurance Study, City of Madison, Madison County, Illinois, January 1980.

10. Federal Emergency Management Agency, Federal Insurance Administration, Flood Insurance Study, Village of Pontoon Beach, Madison County, Illinois, January 1980.

11. U.S. Department of Housing and Urban Development, Federal Insurance Administration, Flood Insurance Study, Village of Roxana, Madison County, Illinois, November 1978.

12. Federal Emergency Management Agency, Federal Insurance Administration, Flood Insurance Study, Village of South Roxana, Madison County, Illinois, November 1979.

13. U.S. Department of Housing and Urban Development, Federal Insurance Administration, Flood Insurance Study, City of Venice, Madison County, Illinois, July 1977.

14. U.S. Department of Housing and Urban Development, Federal Insurance Administration, Flood Insurance Study, City of Wood River, Madison County, Illinois, November 1978.

7 9 15. Federal Emergency Management Agency, Federal Insurance Administration, Flood Insurance Study, Madison County, Illinois, Unincorporated Area, April 1982.

16. Illinois Department of Transportation, Division of Water Resources, "Drainage Improvements Wood River and East Alton, Illinois, Madison County," FR-285, Stage III, 1977.

17. U.S. Department of Commerce, Bureau of the Census, April 1, 2000 Census Population; Retrieved April 14, 2006, from www.census.gov.

18. U.S. Department of Commerce, National Oceanic and Atmospheric Administration, Environmental Data Service, Monthly Average Temperatures and Precipitation for State of Illinois, Washington, D.C., 1977.

19. Southeastern Metropolitan Area Planning Commission, Land Characteristics Study, Madison County, Illinois, June 1970.

20. Norton, W.T., Centennial History of Madison County, Illinois, 1812-1912. Chicago and New York: Lewis Publishing Company, 1912.

21. 74th Congress of the United States, Public Law No. 738, Flood Control Act of 1936, H.R. 8455, 1936.

22. U.S. National Weather Service, Technical Paper No. 40, Rainfall Intensity-Duration- Frequency Curves, Washington, D.C.: U.S. Government Printing Office, 1961.

23. U.S. Department of the Interior, Geological Survey, Water-Supply Paper 1681, 1975.

24. U.S. Geological Survey, Water Data Report IL-76-1, Water Resources Data for Illinois, Water Year 1976, Champaign, Illinois, 1977.

25. Southwestern Illinois Metropolitan and Regional Planning Commission, Plan for Major Drainage: The Piasa Creek, Wood River, and Cahokia Creek Planning Basins, Collinsville, Illinois, March 1976.

26. U.S. Geological Survey, Water Data Report IL-75-1, Water Resources Data for Illinois, Water Year 1975.

27. U.S. Army Corps of Engineers, St. Louis District, Levee Profiles, Upper Mississippi River Levees - Alton to Gale, Illinois, Wood River Drainage and Levee District, Madison County, Illinois, 1973.

28. U.S. Army Corps of Engineers, St. Louis District, Madison County (Preliminary) Flood Survey Wood River, and East Fork Wood River, February 1977.

29. Madison County, Illinois (Wood River Drainage and Levee District), House Document 150, 88th Congress, 2nd Session, Washington, D.C.: U.S. Government Printing Office, 1964.

30. Illinois Department of Transportation, Division of Water Resources, Personal Communication on Improvements to the 6th Street Detention Area, Wood River Drainage

80 Project, Mr. Robert L. Culli, Hydraulic Engineer, Bureau of Project Development, July 27, 1977.

31. U.S. Department of Housing and Urban Development, Federal Insurance Administration, Flood Hazard Boundary Map, City of Wood River, Madison County, Illinois, February 1974.

32. City of Wood River, Municipal Code of the City of Wood River, Flood Plain Management Regulations, Ordinance 60-1, Chapter XIII, Article V, March 1977.

33. U.S. Army Corps of Engineers, Hydrologic Engineering Center, HEC-1 Flood Hydrograph Package, Davis, California, January 1973.

34. U.S. Army Corps of Engineers, Routing of Floods Through River Channels, EM 1110-2- 1408, March 1960.

35. U.S. Army Corps of Engineers, St. Louis District, Regional Frequency Analysis for Streams in the St. Louis District, St. Louis, Missouri, 1974.

36. U.S. Geological Survey, Water Resources Data for Illinois, Part 1, Surface Water Records, 1939 to present.

37. Gray, Don M., "Synthetic Unit Hydrographs for Small Watersheds," Journal of the Hydraulics Division, American Society of Civil Engineers, July 1961.

38. U.S. Department of Agriculture, Soil Conservation Service, Technical Report No. 20, Computer Program for Project Formulation Hydrology, Washington, D.C., May 1965.

39. Illinois Department of Transportation, Division of Water Resources, Magnitude and Frequency of Floods in Illinois, Jack M. Carns, 1973.

40. U.S. Department of Agriculture, Soil Conservation Service, Technical Release No. 55, Urban Hydrology for Small Watersheds, 1975.

41. U.S. Army Corps of Engineers, Hydrologic Engineering Center, HEC-HMS Hydrologic Modelins System Version 2.2.1, Davis, California, October 2002.

42. Illinois Department of Natural Resources, Frequency Distributions and Hydroclimatic Characteristics of Heavy Rainstorms in Illinois, Illinois State Water Survey Bulletin 70, 1989.

43. Illinois State Water Survey Division, and Illinois Division of Water Resources, Circular 172, Frequency Distributions of Heavy Rainstorms in Illinois, Floyd A. Huff and James R. Angel, Champaign, 1989.

44. U.S. Army Corps of Engineers, Upper Mississippi River System Flow Frequency Task Force, Upper Mississippi River System Flow Frequency Study, January 2004.

45. U.S. Department of Agriculture, Soil Conservation Service, National Engineering Handbook, Section 4, Supplement A, Hydrology, 1957.

81 46. U.S. Geological Survey, Water Resources Investigations Report 87-4207, Technique for Estimating Flood-Peak Discharges and Frequencies on Rural Streams in Illinois, Urbana, 1987.

47. U.S. Geological Survey, 7.5 Minute Series Topographic Maps, Scale 1:24000, Contour Interval 10 feet: Alton, Illinois-Missouri, 1954, Photorevised 1968 and 1974; Bethalto, Illinois, 1954, Photorevised 1968 and 1974; Collinsville, Illinois, 1954, Photorevised 1968 and 1974; Columbia Bottom, Missouri-Illinois, 1951, Photorevised 1968 and 1974; Edwardsville, Illinois, 1954, Photorevised 1968 and 1974; Elsah, Illinois-Missouri, 1954, Photorevised 1968 and 1974; Granite City, Illinois-Missouri, 1954, Photorevised 1968 and 1974; Grantfork, Illinois, 1974; Highland, Illinois, 1957; Marine, Illinois, 1954; , Illinois, 1954, Photorevised 1968 and 1974; New Douglas, Illinois, 1974; Pocahontas, Illinois, 1974; Prairietown, Illinois, 1954, Photorevised 1968 and 1974; St. Jacob, Illinois, 1954, Photorevised 1968 and 1974; St. Rose, Illinois, 1962; Wood River, Illinois-Missouri, 1955, Photorevised 1968 and 1974; Worden, Illinois, 1954, Photorevised 1968 and 1974.

48. U.S. Army Corps of Engineers, Hydrologic Engineering Center, HEC-2 Water-Surface Profiles, Generalized Computer Program, Davis, California, August 1977.

49. Federal Emergency Management Agency, Federal Insurance Administration, St. Clair County, Illinois and Incorporated Areas, November 2003 (FIS), November 2003 (FIRM).

50. U.S. Army Corps of Engineers, Hydrologic Engineering Center, HEC-RAS River Analysis System Version 3.0.1, Davis, California, March 2001.

51. U.S. Army Corps of Engineers, Hydrologic Engineering Center, HEC-RAS River Analysis System Version 3.1.2, Davis, California, April 2004.

52. Surdex Corporation, Aerial Photographs, Scale 1:2400, South Roxana, Illinois, 1975.

53. Surdex Corporation, Aerial Photographs, Scale 1:4800, Pontoon Beach, Illinois, 1976.

54. City of Granite City, "Storm Sewer Map of Granite City," Granite City, Illinois 1962.

55. U.S. Army Corps of Engineers, St. Louis District, Topographic Mapping, Scale 1:4800, Contour Interval 2 feet: East St. Louis and Vicinity, Illinois, 1975.

56. U.S. Army Corps of Engineers, St. Louis District, Topographic Mapping, Scale 1:4800, Contour Interval 2 feet: Wood River Drainage and Levee District, 1975.

57. Illinois Department of Transportation, Division of Water Resources, Orthophotographic Mapping, Scale 1:2400, Contour Interval 2 feet: Wood River and East Alton, Illinois, 1975.

58. U.S. Army Corps of Engineers, St. Louis District, East St. Louis and Vicinity, Illinois, Interior Flood Control Project, (unpublished).

59. Illinois Department of Transportation, Division of Water Resources, Strategic Planning Study, Canteen Creek Watershed, Madison and St. Clair Counties, Illinois, September, 1978.

82 60. Federal Emergency Management Agency, Map Modernization, Guidelines and Specifications for Flood Hazard Mapping Partners, April 2003.

61. Madison County Information Systems, Countywide Digital Base Mapping Information, Illinois State Plane, Illinois West, North American Datum, NAD83, North American Vertical Datum 1988 (NAVD88), U.S. survey feet, 1995.

62. Illinois Department of Transportation, Division of Water Resources, Rules and Regulations, Regulation of Construction Within Flood Plains Established Pursuant to Section 65f, Chapter 19, Illinois Revised Statutes, Springfield, Illinois, 1973.

63. 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.

64. U.S. Army Corps of Engineers, St. Paul District, Rock Island District, St. Louis District, Upper Mississippi River Floodway Computation, June 2004.

65. Federal Emergency Management Agency, Federal Insurance Administration, Bond County, Illinois, Unincorporated Area, January 1985 (FIRM).

66. Federal Emergency Management Agency, Federal Insurance Administration, Clinton County, Illinois, June 2004 (FIS), June 2004 (FIRM).

67. Federal Emergency Management Agency, Federal Insurance Administration, Jersey County, Illinois, Unincorporated Area, August 1983 (FIS), February 1984 (FIRM).

68. U.S. Department of Housing and Urban Development, Federal Insurance Administration, Macoupin County, Illinois, Unincorporated Area, January 1978 (FIRM).

69. Federal Emergency Management Agency, Federal Insurance Administration, Montgomery County, Illinois, Unincorporated Area, January 1981 (FIRM).

70. Federal Emergency Management Agency, Federal Insurance Administration, City of Staunton, Macoupin County, Illinois, July 1981 (FIRM).

Southwestern Illinois Metropolitan and Regional Planning Commission, A Long Range Development Plan for Granite City, Illinois, Collinsville, Illinois, 1968.

Southwestern Illinois Metropolitan Area Planning Commission, A Comprehensive Community Plan, Venice, Illinois, Collinsville, Illinois, 1969.

Southwestern Illinois Metropolitan Area Planning Commission, Water and Sewer Inventory and Basin Data Collection, Collinsville, Illinois, 1971.

U.S. Army Corps of Engineers, North Central Division, Water Resources Development in Illinois, 1973.

U.S. Geological Survey, Addendum to Magnitude and Frequency of Floods in Illinois, 1975.

U.S. Geological Survey, Water Resources Investigations 13-75, Drainage Areas for Illinois Streams, 1975.

83