Transcript No Slide Title

North Carolina
White Oak River Basin Plan
December 19, 2000
North Carolina
Cooperating Technical State
Flood Mapping Program
Overview
Purposes of the NFIP
1. Make flood insurance
available
2. Identify floodplain
areas and flood risk zones
3. Provide framework for a community’s
floodplain management ordinances
Importance of Updated Flood
Hazard Information
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With up-to-date flood hazard data:
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Map users can make prudent siting,
design, and flood insurance purchase
decisions
Communities can administer sound
floodplain management programs
North Carolina’s Flood
Mapping Program

Program established to implement the
Cooperating Technical State (CTS)
Partnership with FEMA, signed September
15, 2000
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Ownership and responsibility for Flood
Insurance Rate Maps (FIRMs) delegated
to State
Why North Carolina Is
Undertaking This Project

State’s vulnerability to hurricanes
and flooding
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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 lives
and property
Why North Carolina Is
Undertaking This Project
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Hurricane Floyd revealed flood hazard data
and map limitations
Age of North Carolina FIRMS
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FEMA’s mapping budget is finite
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55% at least 10 years old
75% at least 5 years old
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 Components
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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 FIRM
+
Base
=
Topography
+
Flood Data
Digital
FIRM
Funding for this Program
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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
Carolina’s CTS Program
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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
Carolina’s CTS Program
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Digital format to allow:
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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 Basin
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Located in the southern coastal plain
of 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
White Oak River Basin
The 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
White Oak River Basin
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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 and
Community Coordination
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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
Meetings
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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 Plan
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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 Meeting
THIS IS WHERE WE ARE TODAY!
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All impacted counties and communities
invited
Draft White Oak River Basin plan presented
Provides final opportunity for input
Step 5 — Final Basin Plan
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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
White Oak Basin Meeting
QUESTIONS ON THE
SCOPING PHASE
???
Draft White Oak
River Basin Plan
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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 Maps
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Countywide Digital FIRM Production
will be based on the following:
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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 Data
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Will be acquired using airborne Light
Detection and Ranging (LIDAR)
Will be acquired during the Winter
2000-2001 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
Recommended
Study Areas
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Five study options:
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Detailed study (riverine)
Detailed study (coastal)
Redelineate using updated topographic data
Approximate study
Use current effective information (not
selected for any areas)
Detailed Study — Riverine
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This method requires the following:
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DEMs
Field surveys
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Channel bathymetry
Bridge/culvert opening geometry
Channel and floodplain characteristics
Detailed Hydrologic and Hydraulic Analyses
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10%, 2%, 1%, and 0.2% annual chance flood
elevations and boundaries identified (Zone AE)
Floodways delineated
Areas to be Studied
in Detail
Flooding
Source
Cartwheel
Branch
New River
Newport
River
Southwest
Prong of
Newport
River
Total
Approx.
Reach
Length
(miles)
County
Reach Description
Onslow
From the confluence with
Holland Mill Creek to a point
approximately 1.5 miles
upstream
1.5
Onlsow
From the confluence of Blue
Creek upstream to the
confluence of Crawford
Branch
18.9
Carteret
From the upstream limit of
detailed study at Newport to
a point approximately 6.3
miles upstream
6.3
Carteret
From the confluence with the
Newport River to a point
approximately 6.1 miles
upstream
6.1
32.8
Detailed Study — Coastal
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This method produces the following:
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Floodplain mapping for areas along
open coast and embayments
Designations as Zones AE or VE
No detailed coastal studies are proposed
Redelineation
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This method requires the following:
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DEMs
Effective FIS flood elevations
Proposed for all areas currently shown on
effective FIRM as Zone AE or VE and not
being restudied
Approximate Study
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This method requires the following:
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DEMs
Delineation of 1% annual chance floodplain
boundaries using approximate methods
Does not include collection/use of fieldcollected 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
Information
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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 CommunityIdentified Needs & Priorities
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Necessary to deviate from communityidentified needs and priorities due to:
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Conflicting needs and priorities identified
by contiguous communities sharing a
flooding source
Less dense development
In these instances, the State used a
quantitative ranking system to determine
methods
Digital FIRMs
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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
Production
County
FIRM
Panels in
White Oak
Basin
Projected
Preliminary Date
for White Oak
Portion
Carteret
151
August 2001
Neuse River
(August 2002)
Craven
6
August 2001
Neuse River
(August 2002)
Jones
16
August 2001
Neuse River
(August 2002)
August 2001
Cape Fear River
(February 2002)
and Neuse River
(August 2002)
Onslow
147
Other Basin(s)/
Projected
Preliminary Date
Community Review and
Due Process
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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
Due Process
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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
White Oak Basin Meeting
QUESTIONS ON THE
DRAFT BASIN PLAN
???