NEWPORT COUNTY, RHODE ISLAND (ALL JURISDICTIONS) COMMUNITY NAME COMMUNITY NUMBER JAMESTOWN, TOWN OF 445399 LITTLE COMPTON, TOWN OF 440035 MIDDLETOWN, TOWN OF 445401 NEWPORT, CITY OF 445403 PORTSMOUTH, TOWN OF 445405 Newport County TIVERTON, TOWN OF 440012 PRELIMINARY MARCH 21, 2012 Federal Emergency Management Agency FLOOD INSURANCE STUDY NUMBER 44005CV000B 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. The Federal Emergency Management Agency (FEMA) may revise and republish part or all of this Preliminary FIS report 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 community officials and check the Community Map Repository to obtain the most current FIS components. Initial Countywide FIS Effective Date: April 5, 2010 Revised Countywide FIS Date: TABLE OF CONTENTS Page 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 9 2.4 Flood Protection Measures 13 3.0 ENGINEERING METHODS 14 3.1 Riverine Hydrologic Analyses 15 3.2 Riverine Hydraulic Analyses 16 3.3 Coastal Hydrologic Analyses 18 3.4 Coastal Hydraulic Analyses 19 3.5 Vertical Datum 39 4.0 FLOODPLAIN MANAGEMENT APPLICATIONS 40 4.1 Floodplain Boundaries 40 4.2 Floodways 41 5.0 INSURANCE APPLICATIONS 47 6.0 FLOOD INSURANCE RATE MAP 48 7.0 OTHER STUDIES 51 8.0 LOCATION OF DATA 51 9.0 BIBLIOGRAPHY AND REFERENCES 51 i TABLE OF CONTENTS – continued Page FIGURES Figure 1 – Transect Schematic 23 Figure 2 – Transect Location Map 33 Figure 3 – Floodway Schematic 43 TABLES Table 1 – Initial and Final CCO Meetings 5 Table 2 – Flooding Sources Studied by Detailed Methods 5 Table 3 – Letters of Map Change 6 Table 4 – High-Water Mark Elevations 11-12 Table 5 – Summary of Discharges 15-16 Table 6 – Manning's "n" Values 18 Table 7 – Summary of Coastal Stillwater Elevations 19 Table 8 – Transect Descriptions 24-32 Table 9 – Transect Data 34-39 Table 10 – Floodway Data 44-46 Table 11 – Community Map History 49-50 EXHIBITS Exhibit 1 - Flood Profiles Bailey Brook Panels 01P-04P Beacon Avenue Tributary Panels 05P-06P Conanicut Brook Panels 07P-08P Jamestown Brook Panels 09P-10P Maidford River Panels 11P-16P Paradise Brook Panels 17P-20P Sheffield Cove Brook Panels 21P-22P ii FLOOD INSURANCE STUDY NEWPORT COUNTY, RHODE ISLAND (ALL JURISDICTIONS) 1.0 INTRODUCTION 1.1 Purpose of Study This countywide Flood Insurance Study (FIS) investigates the existence and severity of flood hazards in, or revises and updates previous FISs/Flood Insurance Rate Maps (FIRMs) for the geographic area of Newport County, Rhode Island, including: the City of Newport; and the Towns of Jamestown, Little Compton, Middletown, Portsmouth, and Tiverton (hereinafter referred to collectively as Newport County). This FIS aids in the administration of the National Flood Insurance Act of 1968 and the Flood Disaster Protection Act of 1973. This FIS has developed flood risk data for various areas of the county that will be used to establish actuarial flood insurance rates. This information will also be used by the communities of Newport County to update existing floodplain regulations as part of the Regular Phase of the National Flood Insurance Program (NFIP), and will also be used 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. 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. The April 5, 2010 FIS (Reference 1) was prepared to include the incorporated communities within Newport County in a countywide format. Information on the authority and acknowledgments for each jurisdiction included in the 2010 countywide FIS, as compiled from their previously printed FIS reports, is shown below. 1 Jamestown, Town of: The hydrologic and hydraulic analyses for the FIS report dated February 19, 1986, represent a revision of the original analyses performed by the Natural Resources Conservation Services (NRCS), formerly Soil Conservation Service (SCS), for the Federal Emergency Management Agency (FEMA). The updated version was prepared by Stone & Webster Engineering Corporation for FEMA, under Contract No. EMW-C-0405. That work was completed in February 1984. Little Compton, Town of: The hydrologic and hydraulic analyses for the FIS report dated August 15, 1984, represent a revision of the original analyses performed by Stone & Webster Engineering Corporation for FEMA, under Contract No. H-4604. The hydrologic and hydraulic analyses for Rhode Island Sound and the Sakonnet River were previously performed by the New England Division of the U.S. Army Corps of Engineers (USACE). The original work was completed in May 1979. The updated version was also prepared by Stone & Webster Engineering Corporation for FEMA. The revised work was completed in June 1983. Middletown, Town of: The hydrologic and hydraulic analyses for the FIS report dated October 17, 1983, represent a revision of the original analyses performed by the New England Division of the USACE for FEMA. The updated version was prepared by Harris-Toups Associates for FEMA, under Contract No. H-4776. That revised work was completed in November 1979. The hydrologic and hydraulic analyses for Maidford River were conducted by the NRCS. The wave height and wave runup analyses for this study were performed by Dewberry & Davis for FEMA, under Contract No. EMW-C-0543. That work was completed in April 1983. Newport, City of: The hydrologic and hydraulic analyses for the FIS report dated May 17, 1990, represent a revision of the original analyses performed by the USACE for FEMA, under Contract No. H- 4776. A further revision of the study was performed by Harris-Toups Associates in 2 Newport, City of - continued: October 1979. The hydrologic and hydraulic analyses in the 1990 revision were prepared by the USACE, under Inter-Agency Agreement No. EMW-84-E-1506, Project Order No. 1, Amendment No. 28. That study was completed in July 1987. The original wave height and wave runup analyses for the 2010 countywide study were performed by Dewberry & Davis for FEMA, under Contract No. EMW-C-0543 and was completed in July 1981. Zone boundaries and base flood elevations for Newport Harbor were subsequently revised by Dewberry & Davis in 1984. The USACE reviewed the original work, with no changes in existing wave height analysis recommended, and conducted the wave runup analysis along the Atlantic Ocean. Portsmouth, Town of: The hydrologic and hydraulic analyses for the FIS report dated September 2, 1982, represent a revision of the original analyses performed by the New England Division of the USACE for FEMA. The updated version was prepared by Harris-Toups Associates for FEMA, under Contract No. H-4776. That work was completed in August 1979. The wave height and wave runup analyses for the 2010 countywide study were performed by Dewberry & Davis for FEMA, under Contract No. EMW-C-0543. That work was completed in July 1981. Tiverton, Town of: The hydrologic and hydraulic analyses for the FIS report dated September 15, 1983, represent a revision of the original analyses performed by Tippetts-Abbett-McCarthy-Stratton for FEMA, under Contract No. H-4604. The updated version was prepared by Stone & Webster Engineering Corporation under agreement with FEMA. The stillwater flooding portion of this study was completed in May 1979. The hydrologic and hydraulic analyses in the updated study were computed by the USACE. The wave height and wave runup analyses were completed in April 1982. 3 For the 2010 countywide study, floodplains within the Town of Middletown for coastal areas, as well as for Maidford River and Bailey Brook, were redelineated using updated topographic data provided to FEMA by Town of Middletown Geographic Information Systems (GIS). This work was done for FEMA by Dewberry (the study contractor) under FEMA Contract No. HSFE01-07-D-0037, Task Order 0001 in 2008. The coastal and riverine floodplain redelineation effort was performed using the information contained in the previously published FIRMs and FIS report. No new analyses was performed to define the coastal special flood hazard areas. Base map information shown on the 2010 countywide study FIRM panels was provided by the Rhode Island Geographic Information System (RI GIS). This information was derived from digital orthophotos produced at a scale of 1:5,000 with 2-foot Ground Sample Distance (GSD) from photography dated April 2003 (Reference 2). The coordinate system used for the production of FIRM panels for the 2010 study was Rhode Island State Plane, FIPSZONE 3800, North American Datum of 1983 (NAD 83), GRS80 spheroid. Corner coordinates shown on the FIRM are in latitude and longitude referenced to the UTM projection, NAD 83. Differences in the datum, spheroid, projection or State Plane zones used in the production of FIRMs for adjacent counties may result in slight positional differences in map features at the county boundaries.