MINNEHAHA COUNTY, SOUTH DAKOTA AND INCORPORATED AREAS Community Community Name Number BALTIC, TOWN OF 460058 BRANDON, CITY OF 460296 *COLTON, CITY OF 460166 *CROOKS, CITY OF 460314 DELL RAPIDS, CITY OF 460059 GARRETSON, CITY OF 460177 HARTFORD, CITY OF 460180 HUMBOLDT, TOWN OF 460118 MINNEHAHA COUNTY, SD UNINCORPORATED AREAS 460057 *SHERMAN, TOWN OF 460313 SIOUX FALLS, CITY OF 460060 VALLEY SPRINGS, CITY OF 460221 *Non-Floodprone Community REVISED: NOVEMBER 16, 2011 Federal Emergency Management Agency FLOOD INSURANCE STUDY NUMBER 46099CV000B NOTICE TO FLOOD INSURANCE STUDY USERS Communities participating in the National Flood Insurance Program have established repositories of flood hazard data for floodplain management and flood insurance purposes. This Flood Insurance Study (FIS) may not contain all data available within the repository. It is advisable to contact the community repository for any additional data. Part or all of this FIS may be revised and republished at any time. In addition, part of this FIS may be revised by the Letter of Map Revision process, which does not involve republication or redistribution of the FIS report. It is, therefore, the responsibility of the user to consult with community officials and to check the community repository to obtain the most current FIS report components. Selected Flood Insurance Rate Map (FIRM) panels for this community contain information that was previously shown separately on the corresponding Flood Boundary and Floodway Map (FBFM) panels (e.g., floodways, cross sections). In addition, former flood hazard zone designations have been changed as follows: Old Zone(s) New Zone A1 through A30 AE B X C X Initial Countywide FIS Report Effective Date: September 2, 2009 Revised Countywide FIS Report Date: November 16, 2011 TABLE OF CONTENTS Page 1.0 INTRODUCTION .................................................................................................................... 1 1.1 Purpose of Study .............................................................................................................. 1 1.2 Authority and Acknowledgements ................................................................................... 1 1.3 Coordination ..................................................................................................................... 2 2.0 AREA STUDIED...................................................................................................................... 4 2.1 Scope of Study ................................................................................................................. 4 2.2 Community Description ................................................................................................... 5 2.3 Principal Flood Problems ................................................................................................. 9 2.4 Flood Protection Measures ............................................................................................. 10 3.0 ENGINEERING METHODS ................................................................................................. 11 3.1 Hydrologic Analyses ...................................................................................................... 12 3.2 Hydraulic Analyses ........................................................................................................ 16 3.3 Vertical Datum ............................................................................................................... 18 4.0 FLOODPLAIN MANAGEMENT APPLICATIONS ............................................................ 20 4.1 Floodplain Boundaries ................................................................................................... 20 4.2 Floodways ...................................................................................................................... 21 5.0 INSURANCE APPLICATIONS ............................................................................................ 33 6.0 FLOOD INSURANCE RATE MAP ...................................................................................... 33 7.0 OTHER STUDIES .................................................................................................................. 36 8.0 LOCATION OF DATA .......................................................................................................... 37 9.0 BIBLIOGRAPHY AND REFERENCES ............................................................................... 37 10.0 REVISIONS DESCRIPTION ............................................................................................... 40 10.1 First Revision (Revised November 16, 2011) ............................................................... 41 FIGURES Page Figure 1 - Floodway Schematic .................................................................................................... 22 ii TABLE OF CONTENTS (Cont’d) TABLES Table 1 – Summary of Discharges .................................................................................................15 Table 2 – Floodway Data ...............................................................................................................23 Table 3 – Community Map History ...............................................................................................35 EXHIBITS Exhibit 1 – Flood Profiles Beaver Creek Panel 01P Big Sioux River Panels 02P-11P Big Sioux River Diversion Channel Panels 12P-13P Cherry Creek Panels 14P-17P Dells of the Big Sioux River Panel 18P Skunk Creek Panels 19P-21P Willow Creek Panels 22P-26P Exhibit 2 – Flood Insurance Rate Map Index Flood Insurance Rate Map iii FLOOD INSURANCE STUDY MINNEHAHA COUNTY, SOUTH DAKOTA AND INCORPORATED AREAS 1.0 INTRODUCTION 1.1 Purpose of Study This Flood Insurance Study (FIS) revised and supercedes the FIS reports and/or Flood Insurance Rate Maps (FIRMs) in the geographic area of Minnehaha County, South Dakota including: the Cities of Brandon, Colton, Crooks, Dell Rapids, Garretson, Hartford, Sioux Falls, and Valley Springs; the Towns of Baltic, Humboldt, and Sherman; and unincorporated areas of Minnehaha County (hereinafter referred to collectively as Minnehaha 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. This information will also be used by Minnehaha 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. Please note that the Cities of Colton and Crooks and the Town of Sherman are within Minnehaha County but are identified as non-floodprone. This designation is defined in detail within the NFIP documents. The information will also be used by local and regional planners to further promote sound land use and floodplain development. In some states or communities, floodplain management criteria or regulations may exist that are more restrictive or comprehensive than the minimum Federal requirements. In such cases, the more restrictive criteria take precedence, and the State (or other jurisdictional agency) will be able to explain them. 1.2 Authority and Acknowledgements The sources of authority for this FIS report are the National Flood Insurance Act of 1968 and the Flood Disaster Protection Act of 1973. The hydrologic and hydraulic analyses for the original study in Minnehaha County and the City of Sioux Falls were performed by the U.S. Army Corps of Engineers (USACE), Omaha District, for the Federal Insurance Administration (FIA), under Interagency Agreement No. IAA-H-7-76, Project Order No. 13. This study was completed in May 1977 and was originally published in the FIS report of the City of Sioux Falls dated March 1979 (Reference 1). 1 The hydrologic analysis for Skunk Creek and portions of the Big Sioux River were restudied by the USACE for the Federal Emergency Management Agency (FEMA), under Interagency Agreement No. EMW-95-E-475, Project Order No. 6. This restudy was completed in January 1997. The hydrologic and hydraulic analyses for Skunk Creek were first completed by the USACE, Omaha District, for FEMA, under Interagency Agreement No. EMW-95- E-4759, Project Order No. 6. This restudy was completed in May 1999. The hydraulic analyses for Skunk Creek, Cherry Creek, Willow Creek, and portions of the Big Sioux River were completed by ICON/G&O Joint Venture, for FEMA under contract EMS-2001-CO-0070-TO02. The hydrologic analysis for Cherry Creek and Willow Creek was also completed under this contract. This study was completed in September 2005. The hydrologic and hydraulic analyses for the Big Sioux River through the Town of Baltic and Beaver Creek through the City of Valley Springs study were performed by the Schemmer Associates, Inc., for the FIA under Contract No. H-4712. This work, which was completed in January 1979, covered all significant flooding sources affecting the Town of Baltic. The hydrologic and hydraulic analyses for the Big Sioux River and Dells of the Big Sioux River, through the City of Dell Rapids, were performed by Henningson, Durham & Richardson, for the FIA, under Contract No. H-4551. This work, which was completed in November 1978,