Upload
dwight-gaines
View
224
Download
0
Tags:
Embed Size (px)
Citation preview
North Carolina North Carolina White Oak River Basin White Oak River Basin
PlanPlanDecember 19, 2000
North CarolinaNorth CarolinaCooperating Technical Cooperating Technical State Flood Mapping State Flood Mapping Program OverviewProgram Overview
Purposes of the NFIPPurposes of the NFIP
1. Make flood insuranceavailable
2. Identify floodplainareas and flood risk zones
3. Provide framework for a community’s floodplain management ordinances
With up-to-date flood hazard data:
Map users can make prudent siting, design, and flood insurance purchase decisions
Communities can administer sound floodplain management programs
Importance of Updated Importance of Updated Flood Hazard InformationFlood Hazard Information
North Carolina’s North Carolina’s Flood Mapping Flood Mapping
ProgramProgram Program established to implement the
Cooperating Technical State (CTS) Partnership with FEMA, signed September 15, 2000
Ownership and responsibility for Flood Insurance Rate Maps (FIRMs) delegatedto State
Why North Carolina Is Why North Carolina Is Undertaking This Undertaking This
ProjectProject State’s vulnerability to hurricanes
and flooding 14 federally declared disasters since 1989 Hurricane Floyd damages = $3.5 billion 4,117 uninsured/under-insured homes
destroyed as result of Hurricane Floyd Accurate, up-to-date flood hazard
information crucial to protect livesand property
Why North Carolina Is Why North Carolina Is Undertaking This Undertaking This
ProjectProject Hurricane Floyd revealed flood hazard data
and map limitations Age of North Carolina FIRMS
55% at least 10 years old 75% at least 5 years old
FEMA’s mapping budget is finite North Carolina receives only one updated
flood study for one county per year Many counties and communities lack
resources to take on this responsibility
Program Program ComponentsComponents
Developing flood hazard studies through community mapping needs analysis (Scoping)
Acquiring high-resolution topographic data and accurate Digital Elevation Models (DEMs)
Conducting engineering studies Generating countywide digital FIRMs (DFIRMs) Designing and implementing state-of-the-art,
dynamic IT infrastructure Supporting real-time flood forecasting and
inundation mapping capability
Digital FIRMDigital FIRM
Digital FIRM=
Flood DataBase + Topography +
Funding for this Funding for this Program Program
In August 2000, North Carolina General Assembly approved funding for first six river basins ($23 million)
FEMA has contributed $6 million, as well as in-kind professional services
North Carolina is also working with other Federal partners to secure additional funding
Benefits of North Benefits of North Carolina’s CTS Carolina’s CTS
ProgramProgram Current, accurate data for sound
siting and design decisions Better floodplain management to
reduce long-term flood losses Updated data to alert at-risk
property owners of the need for flood insurance
Faster, less expensive FIRM updates
Benefits of North Benefits of North Carolina’s CTS Carolina’s CTS
ProgramProgram Digital format to allow:
More efficient, precise flood risk determinations
Geographic Information System (GIS) analysis and planning
Online access 24 hours a day DEMs will be useful for almost any
engineering or planning application
White Oak River White Oak River BasinBasin
Located in the southern coastal plainof North Carolina
Includes 4 separate river drainage systems (New, North, White Oak, Newport Rivers and tributaries)
Comprised of portions of 4 counties and 14 municipalities
Scoping Phase for Scoping Phase for White Oak River White Oak River
BasinBasinThe Scoping Phase determines: What areas are floodprone and
need flood hazard data developed What methods will be used to
generate flood hazard data How the data will be presented on
FIRMs
Scoping Phase for Scoping Phase for White Oak River White Oak River
BasinBasin Research/inventory all available
elevation, flood hazard, and digital base map data
Assess existing flood hazard data on effective FIRMs
Determine appropriate technical method for developing up-to-date flood hazard data and establish priority level
Five Steps of Scoping Phase
Step 1 — Initial Research Step 1 — Initial Research and Community and Community
CoordinationCoordination
State held “kickoff” meeting with county and local floodplain administrators
Obtained community mapping needs Effective Flood Insurance Study (FIS) and
FIRM information was researched Post-Hurricane Floyd data was evaluated Research and mapping needs were
entered into GIS-enabled scoping database
Step 2 — Initial Scoping Step 2 — Initial Scoping MeetingsMeetings
State held meetings with each county to present research results and discuss flood mapping needs
Input gathered from communities on proposed study priorities and analysis methods
Identified potential resources of local GIS base map data
Step 3 — Draft Basin PlanStep 3 — Draft Basin Plan
Plan for developing updated flood hazard data and countywide DFIRMs
Comprised of results from research and county and community input
Includes listing of flooding sources to be updated within the basin, technical methods, and projected schedule
Step 4 — Final Scoping Step 4 — Final Scoping MeetingMeeting
THIS IS WHERE WE ARE TODAY!
All impacted counties and communities invited
Draft White Oak River Basin plan presented
Provides final opportunity for input
Step 5 — Final Basin PlanStep 5 — Final Basin Plan
Draft Basin Plan will be revised following the Final Scoping Meeting
Watershed Concepts, Inc., will develop proposals for the State
White Oak River Basin Plan will be finalized and distributed to impacted counties and communities
Production phase will then begin
North Carolina North Carolina White Oak Basin MeetingWhite Oak Basin Meeting
QQUESTIONS ON THE UESTIONS ON THE SCOPING PHASESCOPING PHASE
? ? ?? ? ?
Draft White Oak Draft White Oak River Basin PlanRiver Basin Plan
Summarizes scoping phase Outlines how base maps and
topography will be acquired Proposes engineering methods by
which each flooding source reach will be studied
Describes the process and schedule for completing the map production
Base MapsBase Maps
Countywide Digital FIRM Production will be based on the following: U.S. Geological Survey (USGS) Digital
Orthophoto Quadrangles (DOQs), based on 1998 Aerial Photography
Local GIS data for streams, political boundaries, and roads may be used to supplement the DOQs
Topographic DataTopographic Data
Will be acquired using airborne Light Detection and Ranging (LIDAR)
Will be acquired during the Winter2000-2001 flying season
Will produce an equivalent to a approximately 2-foot contour interval map in floodplains
Digital Elevation Models (DEMs) will be generated to be used for modeling
RecommendedRecommendedStudy AreasStudy Areas
Five study options: Detailed study (riverine) Detailed study (coastal) Redelineate using updated topographic
data Approximate study Use current effective information (not
selected for any areas)
Detailed Study — Detailed Study — RiverineRiverine
This method requires the following: DEMs Field surveys
Channel bathymetry Bridge/culvert opening geometry Channel and floodplain characteristics
Detailed Hydrologic and Hydraulic Analyses 10%, 2%, 1%, and 0.2% annual chance flood
elevations and boundaries identified (Zone AE) Floodways delineated
Areas to be StudiedAreas to be Studiedin Detailin Detail
Detailed Study — Detailed Study — CoastalCoastal
This method produces the following: Floodplain mapping for areas along
open coast and embayments Designations as Zones AE or VE
No detailed coastal studies are proposed
RedelineationRedelineation
This method requires the following: DEMs Effective FIS flood elevations
Proposed for all areas currently shown on effective FIRM as Zone AE or VE and not being restudied
Approximate StudyApproximate Study
This method requires the following: DEMs Delineation of 1% annual chance
floodplain boundaries using approximate methods
Does not include collection/use of field-collected topographic data or bridge/culvert data
Proposed for all areas currently shown on effective FIRM as Zone A and not being restudied in detail.
Use of Effective Use of Effective InformationInformation
This method involves no new analyses or floodplain mapping
Effective FIS and FIRM data is digitized and fitted to updated base map
This method is not anticipated to be used for any communities in the White Oak River Basin
Variations from Variations from Community-Identified Community-Identified
Needs & PrioritiesNeeds & Priorities
Necessary to deviate from community-identified needs and priorities due to: Conflicting needs and priorities
identifiedby contiguous communities sharing a flooding source
Less dense development In these instances, the State used a
quantitative ranking system to determine methods
Digital FIRMsDigital FIRMs
Digital FIRMs will be produced in a countywide format
Will depict all flood hazard data FIRM panels will be consistent with
USGS DOQ tiling scheme
Schedule for FIRM Schedule for FIRM ProductionProduction
Community Review and Community Review and Due ProcessDue Process
Preliminary FIRMs provided when White Oak River Basin Study is complete
90-day appeal period Preliminary Countywide FIRMs provided
when adjacent basin studies are complete
All appeals evaluated and resolved Final Effective FIRMs provided and
made available by the State on its Information Management System
Community Review and Community Review and Due ProcessDue Process
Many counties and communities will need to update their floodplain management ordinances
Communities will be given a 6-month period to do so
NCDEM and FEMA will coordinate this effort with affected communities
North Carolina North Carolina White Oak Basin MeetingWhite Oak Basin Meeting
QQUESTIONS ON THE UESTIONS ON THE
DRAFT BASIN PLANDRAFT BASIN PLAN
? ? ?? ? ?