Marshall County, Minnesota and Incorporated Areas
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MARSHALL COUNTY MARSHALL COUNTY, MINNESOTA AND INCORPORATED AREAS Community Community Name Number ALVARADO, CITY OF 270267 ARGYLE, CITY OF 270268 GRYGLA, CITY OF 270269 *HOLT, CITY OF 270811 MARSHALL COUNTY (UNINCORPORATED AREAS) 270638 MIDDLE RIVER, CITY OF 270270 NEWFOLDEN, CITY OF 270271 OSLO, CITY OF 270272 STEPHEN, CITY OF 270273 *STRANDQUIST, CITY OF 270813 *VIKING, CITY OF 270814 WARREN, CITY OF 270274 *NO SPECIAL FLOOD HAZARD AREAS IDENTIFIED Revised Preliminary: FLOOD INSURANCE STUDY NUMBER 27089CV000A NOTICE TO FLOOD INSURANCE STUDY USERS Communities participating in the National Flood Insurance Program have established repositories of flood hazard data for floodplain management and flood insurance purposes. This Flood Insurance Study (FIS) report may not contain all data available within the Community Map Repository. Please contact the Community Map Repository for any additional data. The Federal Emergency Management Agency (FEMA) may revise and republish part or all of this FIS report at any time. In addition, FEMA may revise part of this FIS report by the Letter of Map Revision process, which does not involve republication or redistribution of the FIS report. Therefore, users should consult with community officials and check the Community Map Repository to obtain the most current FIS report components. 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 Zone(s) New Zone Al through A30 AE B X C X Initial Countywide FIS Effective Date: To Be Determined TABLE OF CONTENTS 1.0 INTRODUCTION ................................................................................................................ 1 1.1 Purpose of Study ............................................................................................................. 1 1.2 Authority and Acknowledgments ................................................................................... 1 1.3 Coordination ................................................................................................................... 4 2.0 AREA STUDIED .................................................................................................................. 5 2.1 Scope of Study ................................................................................................................ 5 2.2 Community Description .................................................................................................. 6 2.3 Principal Flood Problems ................................................................................................ 7 2.4 Flood Protection Measures ........................................................................................... 10 3.0 ENGINEERING METHODS ............................................................................................ 11 3.1 Hydrologic Analyses ..................................................................................................... 11 3.2 Hydraulic Analyses ....................................................................................................... 14 3.3 Vertical Datum .............................................................................................................. 17 4.0 FLOODPLAIN MANAGEMENT APPLICATIONS ..................................................... 19 4.1 Floodplain Boundaries .................................................................................................. 20 4.2 Floodways ..................................................................................................................... 20 5.0 INSURANCE APPLICATIONS ....................................................................................... 30 6.0 FLOOD INSURANCE RATE MAP ................................................................................. 31 7.0 OTHER STUDIES .............................................................................................................. 32 8.0 LOCATION OF DATA ...................................................................................................... 32 9.0 BIBLIOGRAPHY AND REFERENCES ......................................................................... 32 i TABLE OF CONTENTS (Continued) FIGURES Figure 1 – Floodway Schematic ..................................................................................................... 30 TABLES Table 1 – Initial and Final Community Meetings ............................................................................. 4 Table 2 – Streams Studied by Detailed Methods .............................................................................. 5 Table 3 – Incorporated LOMCs ........................................................................................................ 6 Table 4 – Red River of the North Flooding Events .......................................................................... 8 Table 5 – Snake River Flooding Events ........................................................................................... 8 Table 6 – Middle River Flooding Events .......................................................................................... 9 Table 7 – Mud River Flooding Events .............................................................................................. 9 Table 8 – Summary of Discharges .................................................................................................. 13 Table 9 – Manning’s “n” Values .................................................................................................... 17 Table 10 – Vertical Datum Conversion .......................................................................................... 18 Table 11 – Floodway Data .............................................................................................................. 22 Table 12 – Community Map History .............................................................................................. 33 EXHIBITS Exhibit 1 - Flood Profiles Middle River Panels 01P-07P Mud River Panel 08P Red River of the North Panels 09P-14P Snake River Panels 15P-19P Snake River Diversion Channel Panels 20P-21P Tamarac River Panels 22P-24P Exhibit 2 - Flood Insurance Rate Map Index Flood Insurance Rate Map ii FLOOD INSURANCE STUDY MARSHALL COUNTY, MINNESOTA AND INCORPORATED AREAS 1.0 INTRODUCTION 1.1 Purpose of Study This Flood Insurance Study (FIS) revises and updates information on the existence and severity of flood hazards in the geographic area of Marshall County, including the Cities of Alvarado, Argyle, Grygla, Holt, Middle River, Newfolden, Oslo, Stephen, Strandquist, Viking, and Warren, and the unincorporated areas of Marshall County (referred to collectively herein as Marshall County), and aids in the administration of the National Flood Insurance Act of 1968 and the Flood Disaster Protection Act of 1973. This study has developed flood-risk data for various areas of the community that will be used to establish actuarial flood insurance rates and to assist the community in its efforts to promote sound floodplain management. Minimum floodplain management requirements for participation in the National Flood Insurance Program (NFIP) are set forth in the Code of Federal Regulations at 44 CFR, 60.3. Please note that no special flood hazard areas have been identified in the Cities of Holt, Strandquist, and Viking. This does not preclude future determinations of SFHAs that could be necessitated by changed conditions affecting the community (i.e., annexation of new lands) or the availability of new scientific or technical data about flood hazards. 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 FIS are the National Flood Insurance Act of 1968 and the Flood Disaster Protection Act of 1973. 1 Precountywide Analyses Information on the authority and acknowledgements for each jurisdiction included in this countywide FIS, as compiled from their previously printed FIS reports, is shown below: Alvarado, City of: The hydrologic and hydraulic analyses for the Snake River for the July 16, 1980, FIS were performed by the U.S. Army Corps of Engineers (USACE), St. Paul District, for the Federal Insurance Administration (FIA), under Interagency Agreement No. IAA-H-10- 77, Project Order No. 25 (FIA, 1980a). The work was completed in February 1979. For the April 3, 1996, FIS revision (FEMA, 1996), the hydraulic analyses for the Snake River were prepared by the USACE, St. Paul District, for the City of Alvarado to reflect the completion of a flood control project. The work was completed in July 1994. Argyle, City of: The hydrologic