Transcript No Slide Title

Utilizing a Basinwide Approach
for the North Carolina Flood
Mapping Program
John Dorman, Program Director,
NC CTS Flood Mapping Program
Gib Jones, P.E., Dewberry & Davis LLC
Background
Why North Carolina Is Undertaking
This Project

NC 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 NC lives
and properties
Why North Carolina Is Undertaking
This Project (Continued)


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
 NC receives only one updated flood study
for one county per year

Many counties and communities lack
resources to take on this responsibility
North Carolina CTS Flood
Mapping Program


Cooperating Technical State (CTS)
partnership with Federal
Emergency Management
Agency (FEMA)
State ownership and responsibility
for Flood Insurance Rate Maps
(FIRMs)
Mapping Products



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
High-resolution topographic data
and accurate Digital Elevation
Models (DEMs)
Engineering studies
Countywide digital FIRMs
State-of-the-art, dynamic Information
Technology (IT) infrastructure
Real-time flood forecasting and
inundation mapping capability
Basinwide Approach to
Floodplain Mapping
Three Phases to Mapping Project
Phase I—blue
Phase II—gold
Phase III—green
Phase I — Eastern Six River Basins

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
Addressing eastern six basins first
Basins most affected by
Hurricane Floyd
Comprise approximately half
of State
Phase I — Eastern Six River Basins

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Affect 48 counties and 334
incorporated municipalities
(in whole or in part)
Encompass approximately 21,200
linear miles of streams and rivers
Flood hazard mapping for remaining
11 basins to be discussed with
General Assembly in 2001
Project “Scoping”

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Meetings held with every
community in 6 eastern basins
Their needs synthesized into
basinwide objectives
Basinwide work plans developed
Flood Map Production Process

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Topographic Data Collection and
DEM Creation
Hydrologic & Hydraulic (H&H)
Analyses
DFIRM Production
Community Review and Due Process
Two Study Contractors

Each to perform
 Topographic data collection
and DEM production
 H&H Analyses
 DFIRM production

Work broken out by basin
Topographic Data Collection
and DEM Creation

Includes
 LIDAR surveys
 Field surveys of structures and channels
 Automated and manual post-processing
 DEM creation

Conducted on a basinwide approach
 Efficiency of scale realized in surveying
large geographic areas
Topographic Data Collection
and DEM Creation
Example: Status of
Bare Earth DEM
Creation
Engineering Analyses

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Hydrology and stream hydraulics
do not follow corporate boundaries
Set up H&H models using basinwide
approach
 Allows large areas to be study
contiguously
 Minimizes discontinuities and
mismatches
Digital FIRM Production

“Carve” up data into countywide
maps
 Countywide maps more user friendly
 Corresponds to community-based
approach to floodplain management

Merge data for counties in more
than one basin
Community Review and
Due Process

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Community meetings held on
county or basinwide basis
Due Process
 90-day appeal period
 Evaluate and resolve community
comments and concerns
 Update community ordinances

Printing and distribution of maps
Multi-Basin Counties

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Many
counties are
in more than
one basin
Basins will be
completed at
different
times
Insert figure with
schedule for
different basins
Multi-Basin Counties
Tar-Pamlico Basin
Neuse Basin
Processing Multi-Basin Counties

Process different portions of
county separately
 Produce separate preliminary maps
 Separate due process
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Merge different portions after all
portions have gone through due
process
Prioritize multi-basin counties
Preliminary Map for Multi-Basin
County
Lumber
River Basin
BLADEN COUNTY
AND INCORPORATED AREAS
Cape Fear River
Basin
FIRM panel neatlines
“Preliminary revised flood hazard information
not yet available for Cape Fear Basin. Please
refer to effective FIRM.”
Timeline for Multi-Basin County
6 month compliance period
1st
Public
Notice
90-day appeal
period (Lumber)
period (Cape Fear)
2nd
Public
Notice
Preliminary
Issued
(Lumber)
9-28-01
90-day appeal
10-5-01 10-12-01
1st
Public
Notice
Final
Meeting
(Lumber)
End of
Appeal Period
(Lumber)
Preliminary
Issued
(Cape Fear)
10-26-01
1-10-02
8-28-02
Effective
Countywide
FIRM
2nd
Public
Notice
Final
Meeting
(Cape Fear)
9-6-02
9-13-02
9-27-02
End of
Final
Appeal Period Elevation
(Cape Fear) Determin.
12-12-02
12-26-02
2-28-03
4-25-03
Utilizing a Basinwide Approach
for the North Carolina Flood
Mapping Program
QUESTIONS
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