CLAYTON COUNTY, IOWA AND INCORPORATED AREAS Community Name Community Number Clayton, City of 190072 Clayton County 190858 (Unicorporated Areas) * Edgewood, City of 190573 (Clayton and Delaware Counties) Elkader, City of 190073 Elkport, City of 190074 Farmersburg, City of 190075 Garber, City of 190076 Garnavillo, City of 190580 Guttenberg, City of 190077 Luana, City of 190767 Marquette, City of 195182 McGregor, City of 195183 Millville, City of 190081 Monona, City of 190620 North Buena Vista, City of 190082 Osterdock, City of 190083 ** Postville, City of 190641 Clayton Saint Olaf, City of 190084 County Strawberry Point, City of 190662 Volga, City of 190085 * NO SPECIAL FLOOD HAZARD AREAS IDENTIFIED ** COMMUNITY NOT INCLUDED IN CLAYTON COUNTY STUDY June 2, 2011 Federal Emergency Management Agency FLOOD INSURANCE STUDY NUMBER 19043CV000A 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. Part or all of this Flood Insurance Study may be revised and republished at any time. In addition, part of this Flood Insurance Study may be revised by the Letter of Map Revision process, which does not involve republication or redistribution of the Flood Insurance Study. It is, therefore, the responsibility of the user to consult with community officials and to check the community repository to obtain the most current Flood Insurance Study 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 Countywide FIS Effective Date: June 2, 2011 Revised FIS Report Dates: TABLE OF CONTENTS Page 1.0 INTRODUCTION 1 1.1 Purpose of Study 1 1.2 Authority and Acknowledgements 1 1.3 Coordination 3 2.0 AREA STUDIED 3 2.1 Scope of Study 3 2.2 Community Description 4 2.3 Principal Flood Problems 5 2.4 Flood Protection Measures 6 3.0 ENGINEERING METHODS 7 3.1 Hydrologic Analyses 8 3.2 Hydraulic Analyses 10 3.3 Vertical Datum 13 4.0 FLOODPLAIN MANAGEMENT APPLICATIONS 15 4.1 Floodplain Boundaries 15 4.2 Floodways 16 5.0 INSURANCE APPLICATIONS 23 6.0 FLOOD INSURANCE RATE MAP 23 7.0 OTHER STUDIES 24 8.0 LOCATION OF DATA 24 9.0 BIBLIOGRAPHY AND REFERENCES 26 i TABLE OF CONTENTS (continued) Page FIGURES FIGURE 1 – Floodway Schematic 17 TABLES TABLE 1 – Clayton County CCO Meetings 3 TABLE 2 – Limits of Previous Detailed Studies 3 TABLE 3 – Limits of New Detailed Studies 4 TABLE 4 – Mississippi River Floods at Guttenberg 6 TABLE 5 – Peak Discharge Values 9 TABLE 6 – Cross Section Data 11 TABLE 7 – Manning’s “n” Values 11 TABLE 8 – Starting Water-Surface Elevations 11 TABLE 9 – Datum Conversion Calculation 14 TABLE 10 – Floodway Data 18-22 TABLE 11 – Community Map History 25 EXHIBITS Exhibit 1 – Flood Profiles Mississippi River Panels 01P-02P Turkey River 03P-04P PUBLISHED SEPARATELY Flood Insurance Rate Map Index Flood Insurance Rate Maps ii FLOOD INSURANCE STUDY CLAYTON COUNTY, IOWA AND INCORPORATED AREAS 1.0 INTRODUCTION 1.1 Purpose of Study This countywide Flood Insurance Study (FIS) revises and supersedes the FIS reports, Flood Insurance Rate Maps (FIRMs) and/or Flood Boundary and Floodway Maps (FBFMs) in the geographic area of Clayton County, including the Cities of Clayton, Edgewood, Elkader, Elkport, Farmersburg, Garber, Garnavillo, Guttenberg, Littleport, Luana, Marquette, McGregor, Millville, Monona, North Buena Vista, Osterdock, Saint Olaf, Strawberry Point, and Volga; and the unincorporated areas of Clayton County (hereinafter referred to collectively as Clayton County), and aids in the administration of the National Flood Insurance Act of 1968 and the Flood Disaster Protection Act of 1973. Please note that the City of Edgewood is located in both Clayton and Delaware Counties and is included in its entirety in this FIS. No Special Flood Hazard Areas (SFHAs) were identified for the City of Edgewood. Also note that the City of Postville is located in both Allamakee and Clayton Counties and will be included in its entirety in the FIRM for Allamakee County, which is currently in progress. The City of Littleport is a former city in Clayton County. The City was officially disincorporated in 2005. This study has developed flood-risk data for various areas of the community that will be used to establish actuarial flood insurance rates and to assist the community in its efforts to promote sound floodplain management. Minimum floodplain management requirements for participation in the National Flood Insurance Program (NFIP) are set forth in the Code of Federal Regulations at 44 CFR. 60.3. 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 Federal Emergency Management Agency (FEMA) DFIRM database specifications and Geographic Information System (GIS) format requirements. The flood hazard information was created and is provided in a digital format so that it can be incorporated into a local GIS and be accessed more easily by the community. 1.2 Authority and Acknowledgments The sources of authority for this countywide 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 FIRMs for communities within Clayton County was compiled, and is shown below. 1 City of Clayton The hydrologic and hydraulic analyses for the March 1989 study were performed by the U.S. Army Corps of Engineers (USACE), St. Paul District, for FEMA, under Inter-Agency Agreement No. EMW-87-E-2509, Project Order No. 12. This work was completed in September 1987 (Reference 1). City of Elkader The hydrologic and hydraulic analyses for the July 1996 study were performed by Stanley Consultants, Inc. (SCI), for FEMA, under Contract No. H-4005. This work was completed in March 1977 (Reference 2). City of Guttenberg The hydrologic and hydraulic analyses for the September 1979 study were performed by SCI for the Federal Insurance Administration, under Contract No. H-4005. This work was completed in April 1978 (Reference 3). Additional areas of the Mississippi River were studied by detailed methods and have been incorporated in this countywide FIS. The hydrologic and hydraulic analyses for this study were performed by the USACE as part of the Upper Mississippi River System Flow Frequency Study (UMRSFFS) (Reference 4). This study was a collaboration of effort between the Rock Island, St. Louis, Kansas City, Omaha, and St. Paul districts and was completed in 2003. The 1-percent-annual-chance flood water-surface profile and floodway computations for the Mississippi River were performed for FEMA under Interagency Agreement No. EMW-2002-IA-0114 by the St. Paul, Rock Island, and St. Louis districts and were completed in 2004. The floodplain mapping for the Mississippi River was performed by Watershed Concepts for FEMA under Interagency Agreement No. HSFE07-07-C-0022. Additional approximate hydrologic and hydraulic analyses for this countywide FIS were performed by Stantec Consulting Services, Inc. (Stantec), for FEMA under Contract No. EMK-2001-CO-2018, Task Order No. 30. This work, which was completed in July 2007, covered unprotected flooding sources affecting Clayton County. In addition to incorporating the existing three FISs for communities within Clayton County, this countywide FIS includes new and restudied approximate studies, new detailed study areas, redelineation of all other effective profiles, and incorporation of approved Letter of Map Changes (LOMCs). The vertical datum was shifted to North American Vertical Datum of 1988 (NAVD88). The digital floodplain data was merged into a single, updated DFIRM. The DFIRM includes 2006 digital orthophotography (Reference 5), a digital terrain model (DTM) covering the Mississippi River floodplain with a vertical accuracy to support the creation of 4 foot contours (Reference 16); 20-foot contours developed from a United States Geological Survey (USGS) digital elevation model (DEM) covering the areas outside of the Mississippi River floodplain (Reference 6); topographic break lines and spot elevations, political boundaries, road centerlines with street names, railroads, airports, rivers, lakes, streams, bridges and other hydraulic structures, and elevation reference marks. 2 The coordinate system used for the production of the digital FIRMs is State Plane Iowa North Zone 1401 referenced to the North American Datum of 1983 and the Geodetic Reference System 1980 ellipsoid. 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 FISs for the incorporated communities within Clayton County’s boundaries are shown in TABLE 1 (References 1-3). TABLE 1 – Clayton County CCO Meetings Community Name Initial CCO Date Final CCO Date City of Clayton December 11, 1986 May 4, 1988 City of Elkader April 1976 August 18, 1976 City of Guttenberg April 1976 March 16, 1979 Clayton County January 4, 2009 October 20, 2009 Results of the technical aspects of this study were reviewed and accepted by representatives of Stantec, FEMA, and the community.