NORTH CAROLINA FLOODPLAIN MAPPING PROGRAM COOPERATING TECHNICAL STATE

Transcription

1 NORTH CAROLINA FLOODPLAIN MAPPING PROGRAM COOPERATING TECHNICAL STATE FINAL BASIN PLAN SAVANNAH RIVER BASIN Prepared by the: State of North Carolina and the Federal Emergency Management Agency Final: June 8, 2007

2 TABLE OF CONTENTS PAGE Contact Information... iv Abbreviations and Acronyms... v I. Introduction... 1 Why the State of North Carolina Created the Floodplain Mapping Program... 1 Components of the North Carolina Floodplain Mapping Program... 2 Floodplain Mapping Program Funding and Work Plan... 3 Program Benefits... 4 II. III. IV. Savannah River Basin Description... 5 Scoping Phase for the Savannah River Basin... 6 Step 1 Initial Research and Community Coordination... 9 Step 2 Initial Scoping Meetings Step 3 Draft Basin Plan Step 4 Final Scoping Meetings Step 5 Final Basin Plan Elevation and Flood Data Development and Digital FIRM Production for the Savannah River Basin Base Map Topographic Data Flood Hazard Data Detailed Study Riverine Redelineation Limited Detailed Study Use of Effective Information Variations from Community Identified Needs and Priorities Digital FIRMs V. Community Review and Due Process Date: June 8, 2007 Page i

3 TABLE OF CONTENTS PAGE List of Figures Figure 1. Three Phases of Development and Production... 3 Figure 2. Phases of the North Carolina Statewide Floodplain Mapping Program.. 3 Figure 3. North Carolina Portion of the Savannah River Basin Vicinity Map... 5 Figure 4. Process for Scoping the Savannah River Basin... 8 Figure 5. Components of a Digital FIRM List of Tables Table 1. Total Flood Claims and Repetitive Loss Claims... 1 Table 2. Community Information... 6 Table 3. USGS Gage Information Table 4. Initial Scoping Meetings for the Savannah River Basin Table 5. Summary of Riverine Flooding Sources to be Studied in Detail Table 6. Summary of Technical Methods for the Savannah River Basin Table 7. Summary of Digital FIRMs for the Savannah River Basin Appendices Appendix A. Attendance Sheets from Initial Scoping Meetings... A 1 Appendix B. Summaries of Community Identified Flood Mapping Needs... B 1 Appendix C. Attendance Sheet(s) from Final Scoping Meeting(s)... C 1 Appendix D. Summary of Flooding Sources to be Studied by Limited Detailed Methods.D 1 Appendix E. Summary of Variations from Community Identified Needs and Priorities.E 1 Date: June 8, 2007 Page ii

4 TABLE OF CONTENTS A. Attachments 1. Community Recommendations Savannah River Basin A. Jackson County, North Carolina B. Macon County, North Carolina C. Transylvania County, North Carolina 2. Final Basin Plan Savannah River Basin A. Jackson County, North Carolina B. Macon County, North Carolina C. Transylvania County, North Carolina Date: June 8, 2007 Page iii

5 CONTACT INFORMATION Questions or comments about this Basin Plan can be directed to: Randy Mundt, Community Development Planner North Carolina Floodplain Mapping Program (919) x119 or Questions about the National Flood Insurance Program (NFIP) and NFIP mapping can be directed to the Federal Emergency Management Agency s Map Assistance Center toll free information line at FEMA MAP ( ) or map.specialist@dewberry.com. Date: June 8, 2007 Page iv

6 ABBREVIATIONS AND ACRONYMS The following abbreviations and/or acronyms are used throughout this Basin Plan. Abbreviation/Acronym Description BFE Base Flood Elevation CGIA Center for Geographic Information and Analysis CTS DEMs Digital Elevation Models DFIRM Digital Flood Insurance Rate Map DOQs Digital Orthophoto Quadrangles FEMA Federal Emergency Management Agency FEMA MCC FEMA s Mapping Coordination Contractor (Dewberry) FIS Flood Insurance Study FIRM Flood Insurance Rate Map FMIS Floodplain Mapping Information System GIS Geographic Information Systems LIDAR Light Detection and Ranging MENCA Mapping and Engineering Needs Community Assessment NAVD 88 North American Vertical Datum of 1988 NCEM North Carolina Division of Emergency Management NCDENR North Carolina Department of Environment and Natural Resources NCFMP North Carolina Floodplain Mapping Program NFIP National Flood Insurance Program NGVD 29 National Geodetic Vertical Datum of 1929 TIN Triangulated Irregular Network USGS U. S. Geological Survey Date: June 8, 2007 Page v

7 I. INTRODUCTION The State of North Carolina, through the Federal Emergency Management Agency s (FEMA s) Cooperating Technical Community partnership initiative, has been designated as the nation s first (CTS). As a CTS, the State has assumed primary ownership and responsibility of the National Flood Insurance Program s (NFIP) Flood Insurance Rate Maps (FIRMs) for all North Carolina communities. This role has traditionally been fulfilled by FEMA. North Carolina faces extreme hazard and consequence from hurricanes and flooding. Since 1989, there have been 21 federally declared disasters in North Carolina. Damages from Hurricane Floyd alone have reached $3.5 billion. As a result of Hurricane Floyd, 4,117 uninsured and under insured homes were destroyed. Table 1 below shows the number of flood claims and repetitive loss claims in the Savannah River Basin between the years of 1978 and The State s vulnerability to hurricanes and flooding make it crucial that communities and property owners have accurate, up to date information about the flood risk. The updated DFIRMs produced through this Program will help to protect the lives and property, and contribute to the general well being, of North Carolina citizens. County No. of Claims (2002) Repetitive Loss Claims (as of 2003) Jackson 1 0 Macon 0 0 Transylvania 0 0 Table 1. Total Flood Claims and Repetitive Loss Claims Why the State of North Carolina Created the Floodplain Mapping Program There are several reasons why the State has initiated this Program; these include the following: Approximately 55% of North Carolina FIRMs were at least 10 years old. Approximately 75% of North Carolina FIRMs were at least 5 years old. FEMA s mapping budget is finite; on average, North Carolina received only one updated flood study for one county per year. Many counties and communities have indicated that they do not have the resources to take on this responsibility. Date: June 8, 2007 Page 1

8 Components of the North Carolina Floodplain Mapping Program The North Carolina Floodplain Mapping Program involves the following: Acquisition of high resolution topographic data and development of accurate DEMs. Development of up to date, accurate flood hazard data and floodplain mapping. Production of seamless digital FIRM coverage statewide: - Digital FIRMs will be produced on a statewide basis where all counties and incorporated communities are seamlessly shown across one set of state maps. - Digital Orthophoto Quadrangles (DOQs), produced in partnership by the State of North Carolina and the U.S. Geological Survey (USGS), will be used as the primary base map. In areas where there is a locally produced base map that is more current or accurate than the DOQs, the locally developed map may be used to supplement or in place of the DOQs as the base. - Flood Elevations on the DFIRMs will be converted to the North American Vertical Datum of 1988 (NAVD 88). The North Carolina Floodplain Mapping Program, administratively located in the North Carolina Division of Emergency Management (NCEM) oversees and manages the Program. NCFMP will work closely with several other state agency partners (North Carolina Geodetic Survey [NCGS], Center for Geographic Information and Analysis [CGIA], and the Floodplain Management Branch) to ensure quality map production. In the production of the Basin Plan, NCFMP has worked in close cooperation with the Floodplain Management Branch of the NCEM to ensure that all flood hazards and NFIP issues are addressed. Additionally, after the updated flood data and maps are produced, NCFMP coordination with Floodplain Management to conduct training and outreach to assist communities in utilizing the new data and maps to implement floodplain management and hazard mitigation activities. The North Carolina Floodplain Mapping Program has also implemented a state of theart, dynamic Floodplain Mapping Information System (FMIS) to analyze, maintain, and archive maps and associated flood hazard data. The FMIS also serves to present and distribute the mapping data and associated reports to the public via the Internet without the user needing to have sophisticated Geographic Information System (GIS) software. An additional component of the Program is a real time flood forecasting and inundation mapping capability. The North Carolina Flood Warning System is currently being piloted in the Tar Pamlico and Neuse River Basins. Date: June 8, 2007 Page 2

9 The development of topographic and flood data and production of statewide digital FIRM panels will have three phases (Figure 1): (1) scoping, (2) flood map production, and (3) Community Review and Due Process (post preliminary process). Scoping Flood Map Production Community Review and Due Process Figure 1. Three Phases of Development and Production Flood Mapping Program Funding and Work Plan In August 2000, the North Carolina General Assembly allocated $42.8 million to the Floodplain Mapping Program. FEMA has contributed an additional $30.65 million toward the Program as well as in kind contribution of engineering, mapping, and program management services. The State has also worked with other Federal partners to secure additional needed funding. Based on the General Assembly s directive, work began on the six eastern river basins as shown in Figure 2 (Phase I Cape Fear, Lumber, Neuse, Pasquotank, Tar Pamlico, and White Oak). Work was initiated on six additional river basins in 2003 (Phase II Chowan, Roanoke, Yadkin, Catawba, Watauga, and New). Work on the remaining five basins (Phase III Broad, French Broad, Little Tennessee, Hiawassee, and Savannah) began in the summer of 2005, in which the General Assembly of North Carolina provided an additional $10 million. Figure 2. Phases of the North Carolina Floodplain Mapping Program Date: June 8, 2007 Page 3

10 Program Benefits The North Carolina Statewide Floodplain Mapping Program will provide many benefits to North Carolina communities, property owners, and citizens. These include: The updated flood hazard data will provide current, accurate information for North Carolina communities and property owners to make safe siting and design decisions when rebuilding from flooding disasters, building new structures and infrastructure, and retrofitting existing structures. The use of the updated flood hazard data by communities for floodplain management will dramatically reduce long term flood losses to the State of North Carolina, its communities, and its citizens. Updated flood hazard data will alert those at risk to flooding of the need to purchase flood insurance protection. It will be faster and more cost effective to subsequently update DFIRMs. Current, updated base maps and the digital format of the FIRMs will allow users to make more efficient, precise flood risk determinations. The resultant DFIRMs will be the official NFIP maps; these DFIRMs will also be used by communities for floodplain management purposes. The digital format of the DFIRMs will allow use with GIS for analysis and planning. The digital Floodplain Mapping Information System will allow online access to all map users 24 hours a day without requiring sophisticated GIS software. The DEMs being developed will be useful for almost any engineering or planning application, such as site design, storm water management, transportation planning and design, and spill response. This report summarizes and provides details about the scoping phase that was completed for the Savannah River Basin and how the results of this scoping effort were used to develop a plan for developing updated flood data and statewide DFIRMs for counties and communities located within the Savannah River Basin. This report also describes the process and schedule for completing the map production and community review phases. Date: June 8, 2007 Page 4

11 II. SAVANNAH RIVER BASIN DESCRIPTION The Savannah River Basin is bordered to the south by the state of Georgia and South Carolina, and it is bordered to the north, east, and west by the Little Tennessee and Hiwassee River Basins. Beginning in the Blue Ridge Mountains of southern North Carolina and northern Georgia, the Savannah River flows for more than 300 miles to the Atlantic Ocean and drains more than 10,577 square miles. However, only approximately 172 square miles of the upper reaches of the Savannah River Basin are located within the state of North Carolina, making it the smallest basin in the state. Figure 3 below shows the location of the counties within the Savannah River Basin. Figure 3. North Carolina Portion of the Savannah River Basin Vicinity Map The total distance of freshwater flooding sources in North Carolina sums up to equal approximately stream miles, and 1,366 acres of lakes in the Savannah River Basin. The Savannah River Basin is comprised of portions of Clay, Macon, Jackson, and Transylvania and the Town of Cashiers and the Town of Highlands. According to the 2000 Census data, the population is approximately 11,482. The population density of the Savannah River Basin was 23 persons per square mile, compared to the statewide Date: June 8, 2007 Page 5

12 average of 139 persons per square mile. Significant growth is expected in the Savannah River Basin in the next five years. A large portion of the Savannah River Basin situated within North Carolina lies within the Nantahala National Forest. The topography of the Savannah River Basin consists of forest land and urban and developed land. The approximate land use in the basin is as follows: 87.6% forestland and Federal Land, 9.6% urban and developed land, and 2.8% other land. Since 1982, land use identification shows a 27.7% increase in urban and developed land area and a 100% decrease in pasture land. The Savannah River Basin is located where the steep eastern face of the Blue Ridge Mountains faces south, and with its relatively wet climate (over 80 inches of rain per year), there are over 87 rare plant species. Additionally, there are many rare acquatic and wetland dwelling animal species, such as the rosyface chub, turquoise darter, redeye bass, yellowfin shiner, and green salamander. Clay, Macon, Jackson, and Transylvania Counties are all located partially within the Savannah River Basin. Table 2 below summarizes the counties and communities located partially or entirely within the Savannah River Basin and their current NFIP participation and mapping status. No mapped flooding sources from Clay County lie within the Savannah River Basin. Table 2. Community Information Community Name County Participation Status Date of Current NFIP Map Unincorporated Areas Clay Participating 4/1/1999 Unincorporated Areas Jackson Participating 5/17/1989 Cashiers, Town of Jackson Not Participating Not Mapped Unincorporated Areas Macon Participating 6/1/2001 Highlands, Town of Macon Not Participating Not Mapped Unincorporated Areas Transylvania Participating 3/2/1998 III. SCOPING PHASE FOR THE SAVANNAH RIVER BASIN The State worked closely with FEMA and Dewberry, to complete the scoping phase for the Savannah River Basin counties and communities in the Spring of Stated simply, scoping involves determining what areas are floodprone and need to have flood hazard data developed, what methods will be used to generate that hazard data, and how the data will be presented on the DFIRMs. For the Savannah River Basin, the comprehensive scoping phase entailed: Date: June 8, 2007 Page 6

13 Researching and inventorying available elevation, flood hazard, and digital base map data that may be useful for preparing updated DFIRMs; Assessing existing flood hazard data (for example: flood elevation profiles, floodplain boundaries, floodways, coastal hazard zones) on effective FIRMs for adequacy; Providing outreach to, and receiving input from, counties and communities regarding their needs for updated DFIRMs; Identifying data that needs to be developed or acquired, such as digital base maps, DEMs, or field surveys of stream channels, hydraulic structures, and coastal transects; Determining the proposed scales and paneling scheme for statewide digital FIRM production; and Developing a schedule for completion of updated flood hazard data and digital FIRM production. For flooding sources within the basin, the flood hazard data from the effective FIRMs were assessed for adequacy in consultation with the impacted counties and communities. For areas where the existing flood hazard data was deemed to be inadequate or outdated, a priority level was established and the most appropriate method of developing updated data was selected based on the: Type and extent of man made and natural changes within the floodplain and/or watershed; Quality of data available; and Existing and/or proposed levels of development affected by the flooding source. Date: June 8, 2007 Page 7

14 The process followed for completing the scoping is shown in Figure 4 and is described further below. Scoping Flood Map Production Step 1 Step 2 Step 3 Step 4 Step 5 Initial Research & Community Coordination Initial Scoping Meeting Draft Basin Plan Final Scoping Meeting Revise Draft Basin Plan Technical & Cost Proposals for Contractors Finalize Basin Plan Figure 4. Process for Scoping the Savannah River Basin Distribute Final Basin Plan to Communities Analysis and Mapping Date: June 8, 2007 Page 8

15 Step 1 Initial Research and Community Coordination The State held two central kickoff meetings in 2005 with county and community floodplain administrators, engineers, and planners on August 8 and 9 in Cullowhee and Marion, North Carolina, respectively. The objectives of the meetings were to overview the State s CTS Agreement with FEMA and the North Carolina Floodplain Mapping Program, inform the floodplain administrators of the process that will be followed to develop updated mapping, and encourage them to be an active participant in the process. A questionnaire regarding the communities mapping needs was mailed prior to the meeting and distributed to those community representatives in attendance. This questionnaire contained pointed questions designed to help each community systematically ascertain its flood mapping needs. The county and municipal officials were encouraged to complete the questionnaire and submit it back to the NCFMP either digitally via e mail or via hardcopy. Technical support was available for completion of the questionnaire through the State. Completed questionnaires were received by the State from the following county and community in the Savannah River Basin: Jackson County and the Town of Highlands. Additionally, the State completed research of community mapping needs as per its September 1999 Cooperating Technical Community agreement with FEMA, Assessment of Community Mapping Needs. Further, FEMA and Dewberry conducted research of effective Flood Insurance Study (FIS) and FIRM information and other relevant data available for each community in the FEMA Flood Mapping Archives and FEMA s Mapping Needs Update Support System database. This database contains information on community mapping needs collected over the past few years through community surveys. As part of the initial research, the State and Dewberry also evaluated post Hurricane Floyd data, such as gage information, high water marks, and inundation mapping, obtained from FEMA, the U.S. Army Corps of Engineers, and the USGS. The purpose of this evaluation was to identify areas where actual flooding elevations and inundation limits experienced did not match the flood hazard data in the effective FIS and FIRM, thereby indicating a mapping need. Date: June 8, 2007

16 U.S. Geological Survey Gage Data Up to date analyses for stream gages located in the Savannah River Basin were obtained from the USGS. The revised gage analyses were compared with effective FIRM information to determine the need for restudy of the flooding sources on which these gages are located. As part of this assessment, the 1% annual chance (100 year) discharge and water surface elevation were compared. Table 3 outlines this information for all stream gages in the Savannah River Basin. There are no USGS gages within the North Carolina portion of the Savannah River Basin. Table 3. USGS Gage Information USGS 100 year Discharge (cfs) 100 year WSEL (ft) Gage Flooding Source Effective Gage Effective Gage * * * * * * * Data Not Available The results of the initial research and responses to the community questionnaires were entered into a GIS enabled scoping database: Mapping and Engineering Needs Community Assessment (MENCA). This database was used to generate Initial Scoping Projects for each community; these projects were used to conduct the Initial Scoping Meetings (Step 2). Step 2 Initial Scoping Meetings The State held meetings with each of the four counties (Clay, Jackson, Macon, and Transylvania) that are within the Savannah River Basin to present the results of the initial research to the county and its communities and to discuss their flood mapping needs. Elected officials, floodplain administrators, emergency managers, and GIS staff were invited from the county and each incorporated community, including those communities that do not participate in the NFIP. The meetings were held at the Asheville Buncombe Community College, Enka Candler campus, Macon County Courthouse in Franklin, NC, Southwestern Community College in Sylva, NC, and Tri County Community College in Murphy, due to their central location and ease of accessibility within the river basins jurisdictions. Dewberry staff attended to provide program and technical support during the meetings. NCEM Floodplain Management Branch staff attended the meetings to exchange contact information with community Floodplain Administrators, establish contact with non participating communities, and distribute copies of the current North Carolina model Flood Damage Prevention Ordinance. Table 3 summarizes the initial scoping meeting dates with each community. Meeting attendance sheets are included as Appendix A. Please note that portions of some counties (Clay, Jackson, Macon, and Transylvania) in the Savannah River Basin are situated in other river basins. The initial scoping meetings were conducted on a countywide basis and covered all areas of each county and Date: June 8, 2007 Page 10

17 community in the county irrespective of the basin. Table 4 contains a list of communities with the location and date of initial scoping meetings held for each community. Only those communities located entirely or partially within the Savannah River Basin are listed in Table 4. Table 4. Initial Scoping Meetings for the Savannah River Basin Community Meeting Location Meeting Date (s) Transylvania County Clay County Jackson County Town of Highland Macon County Asheville Buncombe Technical Community College Enka Campus Asheville, NC Tri County Community College, Small Business Center; Murphy, NC Southwestern Community College, Jackson Campus, The Pines Building Library; Sylva, NC Macon County Courthouse, Old Commissioners Board Room; Franklin, NC Macon County Courthouse, Old Commissioners Board Room; Franklin, NC September 21, 2005 November 8, 2005 November 9, 2005 November 10, 2005 November 10, 2005 At the initial scoping meetings, the State, NCEM Floodplain Management Branch, and Dewberry representatives met individually, or in groups, with the county and its incorporated communities representatives to: Provide a brief overview of the Floodplain Mapping Program purpose, objectives, and goals; Review the research results for each community using the Initial Scoping Package; Discuss the community s mapping needs and response to the questionnaire; and Identify available local data such as base maps, topographic data, ongoing studies, etc. In assessing the communities flood mapping needs, emphasis was placed on: Areas of future development; Date: June 8, 2007 Page 11

18 New or proposed crossings, encroachments, and flood controls; Historically flooded areas; Out of date or inadequate data on current FIRMs; Existing data mismatches with contiguous communities; and Out of date FEMA analyses (detailed or approximate). For flooding sources identified in the meeting as having a flood mapping need, the community was asked to provide input on proposed study analysis methods and priorities. Appendix B contains tables summarizing the community identified flood mapping needs, suggested type of study, and priorities for each community within the Savannah River Basin. Attachments 1A through 1C depict these community identified needs and priorities. Also, as part of the initial scoping effort, CGIA met with county GIS staff to inventory the availability of local GIS data to identify potential base map data resources for the Floodplain Mapping Program. Information collected from the survey form was entered into MENCA for each Phase III county. Step 3 Draft Basin Plan Based on the results of the Initial Scoping Meetings, the State synthesized the research and the community input. These results were used to develop the Draft Basin Plan for developing updated flood hazard data for the basin and for producing statewide DFIRM panels for the affected counties and communities within the Savannah River Basin. Section IV of the Draft Basin Plan included a list of flooding sources to be updated within the basin, including the technical method of update (detailed, limited detailed, or redelineation) and reach limits and stream miles to be updated. Section IV also included a comprehensive list of counties for which statewide DFIRM panels will be produced including digital base map source to be used and proposed DFIRM paneling and tiling scheme. Lastly, Section IV also included a projected schedule for completing the basin studies and statewide preliminary DFIRMs. Step 4 Final Scoping Meetings The draft Savannah River Basin Plan was sent to affected counties and communities and posted on the State s website on March 23, Subsequently, after a 30 day review period, the State will typically hold a Final Scoping meeting for the Savannah River Basin counties and communities. The communities Chief Elected Officer, floodplain administrators, planners, Engineers, GIS staff, building and zoning officials will typically be invited from each county and incorporated community in the basin for the Final Scoping Meetings. Date: June 8, 2007 Page 12

19 The objective of the final scoping meeting is for the State to overview the Draft Basin Plan, including the proposed scope, schedule for the project, and provide an opportunity for additional county and community input or suggested changes to the Draft Basin Plan. Typically, individual meetings for each county will be scheduled for community leaders to meet with representatives from the State and Dewberry. However, in this case, jurisdictions were notified by letters and phone calls in order to confirm the jurisdictions acceptance of the Draft Basin plan and the proposed scope of flood hazard studies. The Final Basin Plan summarizes the comments and/or feedback received from these letters and phone calls. Step 5 Final Basin Plan After the jurisdiction s acceptance of scope was verified, the Draft Basin Plan was revised, as necessary, to produce this Final Basin Plan. The Final Basin Plan contains specific information regarding comments that were received and how the Draft Basin Plan was revised and why. The State then requested that its Flood Mapping Contractor prepare a technical and cost proposal to execute the components of the revised draft Savannah River Basin Plan. After negotiations between the State and the Flood Mapping Contractor, if the cost estimate indicates that the Basin Plan can be executed within the State s available budget for the Savannah River Basin, the Basin Plan will be finalized. However, if the negotiated cost estimate indicates that the Basin Plan cannot be executed within the State s available budget, the State may have to modify the scope of the project. Once the Hiwassee River Basin Plan was finalized, the Final Basin Plan is posted on the State website, with a description and explanation of any changes made from the Draft Basin Plan. Date: June 8, 2007 Page 13

20 IV. ELEVATION AND FLOOD DATA DEVELOPMENT AND DIGITAL FIRM PRODUCTION FOR THE SAVANNAH RIVER BASIN The State s flood mapping contractor will develop digital elevation data, conduct engineering flood hazard analyses, and prepare floodplain delineations for the flooding sources in the Savannah River Basin and produce statewide preliminary DFIRMs for the affected communities within the Savannah River Basin. Figure 5 shows how the base map, topographic data, and flood data will be used to build a DFIRM. Each component is discussed further in the following sections. + + Base Topography Flood Data = Digital FIRM Figure 5. Components of a Digital FIRM Base Map Locally produced digital orthophotography will be used as the base map for statewide DFIRM production, provided that it meets FEMA s base map standards. If local imagery is not available, the U.S. Geological Survey (USGS) Digital Orthophoto Quadrangles (DOQs), based on 1998 aerial photography, will be used. The base maps will be supplemented with stream and river centerlines, shoreline, political boundaries, and road name data from other sources; this may include locally available GIS data. The specific local GIS data to be used to supplement the DOQs will be determined on completion and assessment of the CGIA s GIS surveys as discussed in Section III of this Final Basin Plan. Topographic Data Watershed Concepts, under contract with the State, acquired digital topographic data of the Savannah River Basin using airborne Light Detection and Ranging (LIDAR). This LIDAR data was acquired during the Spring 2006 flying season. For Phase III of the NCFMP, the state has specified Fundamental Vertical Accuracy of 1.2 ft (36.3 cm) in open terrain, and Consolidated Vertical Accuracy of 1.6 ft (49.0 cm) in all land cover categories combined, including open terrain, weeds and crops, scrub, Date: June 8, 2007 Page 14

21 forests, and urban terrain (built up areas). (See the North Carolina Floodplain Mapping Program s Issue Paper 50: Phase III Quality Control of Light Detection and Ranging (LIDAR) Elevation Data in North Carolina for more information). These topographic data will be primarily used for floodplain modeling and mapping for counties and communities in the Savannah River Basin (described below). However, the data will also be useful for other State and county engineering and planning applications using ARC/INFO and other GIS software and will be available through the State s online Information Management System described earlier in this plan. It is planned for these data to be available online in Flood Hazard Data In developing flood hazard data for each of the flooding sources in the Savannah River Basin the State s Flood Mapping Contractor will utilize one of four options available. These are described below. All flood elevations will be referenced to the NAVD 88. All analyses and mapping will comply with FEMA s regulations, guidelines, and specifications for NFIP mapping. 1. Detailed Study Riverine This method entails using the TINs, supplements them with field surveys for channel bathymetry, bridge/culvert opening geometry, and channel and floodplain characteristics, to conduct fully detailed hydrologic and hydraulic analyses and floodplain mapping. This will include analyses of the 10%, 2%, 1%, and 0.2% annual chance flood peak discharges, water surface elevations, profiles, and determination of a floodway. Riverine areas studied in detail will be designated as Zone AE on the updated DFIRMs. Flood profiles and base flood elevations will be referenced to NAVD 88. Table 5 summarizes the riverine flooding sources and reach descriptions within the Savannah River Basin that will be studied using detailed methods. The estimated number of hydraulic structures is an approximation of the number of culverts, bridges, dams, and weirs along the reach to be studied in detail. These estimates were made based on the number of major road crossings using CGIA data and from the flood profiles in the current FIS report. Attachments 2A through 2C depict the specific reaches to be studied in detail. Date: June 8, 2007 Page 15

22 Table 5. Summary of Riverine Flooding Sources to be Studied in Detail County/Community Flooding Source Downstream Limit Upstream Limit Transylvania Deep Ford Creek Transylvania Deep Ford Creek Trib 1 Transylvania Deep Ford Creek Trib 1.1 Transylvania Deep Ford Creek Trib 1.2 Transylvania Toxaway River At the confluence with Toxaway River At the confluence with Deep Ford Creek At the confluence with Deep Ford Creek Trib 1 At the confluence with Deep Ford Creek Trib 1 Approximately 1,000 feet upstream of US 64 Approximately 1.51 miles upstream of the confluence with Toxaway River Approximately 980 feet upstream of the confluence with Deep Ford Creek Approximately 0.70 mile upstream of the confluence with Deep Ford Creek Trib 1 Approximately 0.45 mile upstream of the confluence with Deep Ford Creek Trib 1 Approximately mile upstream of North Club Blvd Approx. Reach Length (miles) Estimated Number of Hydraulic Structures TOTAL Date: June 8, 2007 Page 16

23 2. Redelineation This method involves no new analyses; rather, the effective FIS and FIRM data will be fitted to the updated base map using the new LIDAR derived topographic data. Floodways and cross section locations are digitized from the effective FIRMs and Flood Boundary and Floodway Map. Flood profiles and base flood elevations are converted from NGVD 29 to NAVD 88. Areas where this technique is used will be designated as Zone AE on the updated DFIRMs. This technique is useful for riverine and lacustrine flooding sources where the effective FIS engineering analyses are adequate but the topographic data used to delineate the floodplain boundaries is not sufficiently detailed or up to date. The redelineation method will be used for all flooding sources within the Savannah River Basin that are currently studied in detail on current FIRMs and that are not being restudied in detail as part of this Basin Plan. Currently, there are no streams in the Savannah River Basin that will be studied using redelineated methods. 3. Limited Detailed Study This method entails using the TINs being produced as part of the North Carolina Floodplain Mapping Program, without adding field surveyed bathymetric or bridge/culvert opening geometric data, to conduct hydrologic and hydraulic analyses. In addition, this method does not include field surveys that determine specifics on channel and floodplain characteristics. However, bridge and culvert opening data from North Carolina Department of Transportation maintenance records is incorporated into the hydraulic analysis models. Limited detailed study will result in the delineation of the 1% annual chance floodplain boundaries and base flood elevations. These will be designated as Zone AE on the newly generated DFIRMs. Limited detailed study will also determine widths of the non encroachment area at all studied cross sections. The nonencroachment widths given at modeled cross sections can be used by communities to enforce floodplain management ordinances that meet the requirement defined in 44 CFR 60.3(c)(10). This information will be provided in the Flood Insurance Study report to facilitate local floodplain management. The limited detailed study is a buildable product with a supporting engineering model that can be upgraded to full detailed study at a later date by adding field surveyed river or stream channel and bridge/culvert opening geometric data. All flooding sources currently designated as Zone A on the effective FIRMs that are not being studied by detailed study methods will be reanalyzed using either this limited detailed study method or the use of effective information explained below. In most Date: June 8, 2007 Page 17

24 cases, currently unmapped areas identified by communities as being a priority will be studied by the limited detailed study method unless they are otherwise being studied by detailed methods. Attachments 2A through 2C depict the specific reaches to be studied using limited detailed methods. Additionally, limited detailed study will be considered for unmapped flooding sources, with an emphasis on those in developed areas with a drainage area larger than 1 square mile. However, some floodprone areas with lesser drainage areas may also be mapped based on known hazards, level of development, and community identified needs. Appendix D summarizes the flooding sources and descriptions within the Savannah Basin that will be studied using limited detailed methods. 4. Use of Effective Information The study type "use of effective information" has been scoped for small effective Zone A areas that are likely backwater fingers that will be replaced with the backwater from the new or limited detailed study already scoped for the main stem. NCFMP will evaluate these reaches on a case by case basis after the main stem is studied to determine if the backwater replaces the effective Zone A fingers or if the tributary should be studied by limited detailed study. If the area is completely covered by backwater, NCFMP will not develop a "limited detailed" model for the reach. If the Zone A area extends beyond backwater and the contributing upstream drainage area is greater than 1 square mile in rural areas or 1/2 square mile in urban areas, NCFMP will study the reach using "limited detailed" methods. If the contributing drainage area is less than the urban and rural criteria, NCFMP will digitize the effective Zone A floodplain and map as a shaded Zone X. Several areas within the Savannah River Basin, totaling 6.88 stream miles, have been identified during scoping to be studied as Use of Effective Information. Table 6 summarizes the estimated number of linear miles for each method to be applied in the Savannah River Basin. Attachments 2A through 2C depict the technical methods to be applied to each flooding source within the Savannah River Basin. Table 6. Summary of Technical Methods for the Savannah River Basin Technical Method Estimated Linear Miles Detailed Study Riverine 5.41 Redelineation 0.00 Limited Detailed Study Use of Effective Information 6.88 Total Date: June 8, 2007 Page 18

25 The Savannah River Basin Study, which will include completion of the DEMs and preparation of updated flood hazard data, is scheduled to be completed by September Variations from Community Identified Needs and Priorities In some instances, it was necessary to deviate from the needs and technical methods identified by a county or community in developing this Final Basin Plan. The State used a quantitative ranking system to address all community needs identified for detailed study based on several factors. These factors included: The age of the effective FIRM analyses (studies based on older analyses receive a higher ranking) Likely flood mapping impacts (the greater the anticipated change to the flood elevation and/or floodplain boundary, the higher the ranking) Level of development (areas of more dense existing or anticipated development receive a higher ranking, or conversely, for flooding sources situated within public lands such as a National Forest, where the potential for development is severely limited) Historical flood information (if gage data, high water marks, inundation mapping, or community experience indicate a mapping problem, the higher the ranking) Mismatches with contiguous communities (significant mismatches in flood elevations and/or floodplain boundaries between adjacent communities receive a higher ranking) Whether any mitigation planning has been developed or is in the process of being developed (if so, the community receives a higher ranking) Appendix E summarizes the areas where the flood data development described above as part of this Final Basin Plan differs from the community identified needs and priorities. Digital FIRMs Using the base maps and flood hazard data described above, DFIRMs will be produced in seamless statewide format, including the unincorporated areas of each county in the Savannah River Basin and its incorporated communities on one set of DFIRM panels. The DFIRMs will depict flood hazard and related data (floodplain and floodway boundaries, base flood elevations, cross sections, and flood insurance zone designations) and non engineering reference features (road names and locations, stream and river centerlines, shorelines, corporate boundaries, airports, schools, and bench marks). Because several of the counties within the Savannah River Basin are at least partially located in adjacent river basins (French Broad, Hiwassee, and Little Tennessee), completion of the final effective statewide DFIRMs will be dependent on completion of the basin studies for the adjacent basins. However, when the Savannah River Basin Date: June 8, 2007 Page 19

26 Study is completed, statewide preliminary DFIRMs will be issued for the portions of counties and communities within the Savannah River Basin. (The community review and due process phases are discussed in more detail in Section V of this Final Basin Plan.) DFIRM panels will be tiled using the NCFMP tiling scheme and will be produced at either 1 =500 (for panels with detailed study or urban areas) or 1 =1,000 (for panels with only limited detailed study or rural areas). Table 7 summarizes the number and scale of DFIRM panels, the proposed schedule, and other basins affecting each county. (Panel information will be provided in the Final Basin Plan.) Table 7. Summary of Digital FIRM Panels for the Savannah River Basin County Total DFIRM Panels * 1 = 500 * 1 = 1,000 * Projected Preliminary Date for Savannah Portion Clay None Jackson Fall 2008 Macon Fall 2008 Transylvania Fall 2008 Other Basin(s) Projected Preliminary Date This county will be processed entirely with the Hiwassee River Basin Little Tennessee = Fall 2008 Little Tennessee = Fall 2008 French Broad = September 2007 *Includes total estimated DFIRM panels in county, not including adjacent basins. Also includes multi county panels that are also counted for contiguous counties. V. COMMUNITY REVIEW AND DUE PROCESS As discussed in Section IV of this Basin Plan, when the Savannah River Basin Study is completed, statewide preliminary DFIRMs will be issued to the impacted counties and communities for the portion of the county within the Savannah River Basin. As shown in Table 7 in Section IV, the statewide preliminary DFIRM panels for the Savannah River Basin are anticipated to be issued by Subsequently, a preliminary DFIRM meeting will be held for county and community officials to present the results of the Savannah Date: June 8, 2007 Page 20

27 River Basin Study and statewide preliminary DFIRM panels, answer questions, and explain administrative procedures. Shortly after the preliminary DFIRM panels are issued, a statutory 90 day appeal period will be initiated to allow counties, communities, and/or citizens to submit technical or scientific data to FEMA and the State to refute or contest new or revised base flood elevations shown on the preliminary DFIRMs and otherwise provide comments on the preliminary DFIRMs. Any and all appeals will be evaluated and resolved by FEMA in close coordination with the State, Dewberry, and the State s Flood Mapping Contractor. As the other basin studies impacting a county are completed, statewide preliminary DFIRM panels will be issued for the remaining portion(s) of the county. A preliminary DFIRM meeting will be held for those basins and the statutory 90 day appeal period will be provided and all appeals will be evaluated and resolved. After issuing preliminary DFIRM panels for all areas of a county and evaluating and resolving all appeals and community comments, the statewide preliminary DFIRM panels will be finalized. FEMA s Map Service Center will print and distribute the official DFIRMs to be used for flood insurance rating purposes. Additionally, the State will post the final statewide DFIRMs on its Floodplain Mapping Information System for distribution and access to communities and the public via the Internet. During the community review and due process phase, many counties and communities will need to update their floodplain management ordinances; the communities will be given a 6 month period to adopt the updated DFIRMs and incorporate the DFIRMs into their ordinances. The NCEM Floodplain Management Branch and FEMA will coordinate this effort with the counties and communities that need to update their ordinances. Date: June 8, 2007 Page 21

28 APPENDIX A ATTENDANCE SHEETS FROM INITIAL SCOPING MEETINGS Clay County and Communities November 8, 2005 Name Title/Agency Phone Sam R. Beck, II Peggy Evans Steve Garrett Charity Peterson Tom Cadwallader Randy Mundt Katie Hess Fred Knight David Lentzner Danny Gee Floodplain/Building Code Inspector/Clay County Clerk/Finance Officer/Town of Hayesville Community Development Planner/ NCFMP GIS Specialist/NCFMP Engineer/NCFMP Community Development Planner/NCFMP Hazard Mapping Analyst/Dewberry Hazard Mapping Analyst/Dewberry NFIP Planner/NCEM NCEM/Area 15 Coordinator (828) sbeck@claync.org (828) hayesville@webworkz.com (919) x 118 sgarrett@ncem.org (919) x 113 cpeterson@ncem.org (919) x 109 tcadwallader@ncem.org (919) x 119 rmundt@ncem.org (703) khess@dewberry.com (703) fknight@dewberry.com (919) ext. 351 dlentzner@ncem.org (828) dgee@ncem.org Jackson County and Communities November 9, 2005 Name Title/Agency Phone John Wittekind Michael Ensley Flood Plain Manager, Building Inspection Division, Jackson County Emergency Management Coordinator, Jackson County (828) (828) mikeensley@jacksonnc.org Date: June 8, 2007 Page A 1

29 APPENDIX A ATTENDANCE SHEETS FROM INITIAL SCOPING MEETINGS Jackson County and Communities November 9, 2005 (continued) Name Title/Agency Phone Ken Westmoreland Linda Cable Bobby McMahan Jay Denton Jim Aust Steve Garrett Charity Peterson Tom Cadwallader Randy Mundt Katie Hess Fred Knight David Lentzner Jackson County Manager Planning/Jackson County Tax Administrator/GIS/Jackson County Town Manager/Town of Sylva Planner/Zoning Administrator/Town of Sylva Community Development Planner/ NCFMP GIS Specialist/NCFMP Engineer/NCFMP Community Development Planner/NCFMP Hazard Mapping Analyst/Dewberry Hazard Mapping Analyst/Dewberry NFIP Planner/NCEM (828) jacksoncomgr@jacksonnc.org (828) lindacable@jacksonnc.org (828) bobmcmahan@jacksonnc.org (828) jdenton@townofsylva.org (828) jaust@townofsylva.org (919) x 118 sgarrett@ncem.org (919) x 113 cpeterson@ncem.org (919) x 109 tcadwallader@ncem.org (919) x 119 rmundt@ncem.org (703) khess@dewberry.com (703) fknight@dewberry.com (919) ext. 351 dlentzner@ncem.org Macon County and Communities November 10, 2005 Name Title/Agency Phone David Key Emergency Management/Macon County (828) dkey@maconnc.org Date: June 8, 2007 Page A 2

30 APPENDIX A ATTENDANCE SHEETS FROM INITIAL SCOPING MEETINGS Macon County and Communities November 10, 2005 (continued) Name Title/Agency Phone Josh Pope Jim Gulisano Andy Muncey Art Provencher GIS Analyst/Macon County GIS Administrator/Macon County Network Administrator/Macon County Mapping/Macon County (828) jpope@maconnc.org (828) jgulisano@maconnc.org (828) amuncey@maconnc.org (828) aprovencher@maconnc.org Jack Morgan Codes Administrator/Macon County (828) Stacy J. Guffey Planner/Macon County (828) Rebecca Crawford Mike Decker Matt Shuler Steve Garrett Charity Peterson Tom Cadwallader Randy Mundt Katie Hess Fred Knight Planner/Town of Franklin Town Administrator/Town of Franklin GIS Field Technician/Town of Highland Community Development Planner/ NCFMP GIS Specialist/NCFMP Engineer/NCFMP Community Development Planner/NCFMP Hazard Mapping Analyst/Dewberry Hazard Mapping Analyst/Dewberry (828) rcrawford@franklinnc.org (828) mdecker@franklinnc.org (828) highgis@earthlink.net (919) x 118 sgarrett@ncem.org (919) x 113 cpeterson@ncem.org (919) x 109 tcadwallader@ncem.org (919) x 119 rmundt@ncem.org (703) khess@dewberry.com (703) fknight@dewberry.com Date: June 8, 2007 Page A 3

31 APPENDIX A ATTENDANCE SHEETS FROM INITIAL SCOPING MEETINGS Macon County and Communities November 10, 2005 (continued) Name Title/Agency Phone David Lentzner NFIP Planner/NCEM (919) ext. 351 dlentzner@ncem.org Transylvania County and Communities September 21, 2005 Name Title/Agency Phone Mike Thomas Jeff Fisher Josh Freeman Brad Burton Nancy Murr Planner/Planning and Economic Development/Transylvania County Building, Permitting and Inspections Department Director/Transylvania County Planning and Zoning Department/City of Brevard Planning and Zoning Department/City of Brevard Planning and Zoning Department/City of Brevard (828) tcedcmike@citcom.net (828) jfbldg@citcom.net (828) (828) (828) Johnny Rogers Town of Rosman (828) Steve Garrett Charity Peterson John Gerber Randy Mundt Joan Craft Colleen Swales Community Development Planner/ NCFMP GIS Specialist/NCFMP Engineer/NCFMP Community Development Planner/NCFMP Hazard Mapping Analyst/Dewberry Hazard Mapping Analyst/Dewberry (919) x 118 sgarrett@ncem.org (919) x 113 cpeterson@ncem.org (919) x 106 jgerber@ncem.org (919) x 119 rmundt@ncem.org (703) jcraft@dewberry.com (703) cswales@dewberry.com Date: June 8, 2007 Page A 4