Floodplain Mapping
Update
December 3, 2013
Robert Billings, PE, PH, CFM
The Risk is Real… Be PREPARED!
Why are we here?
The Purpose of this meeting:
 To update flood hazard data in Mecklenburg
County
 Explain the FEMA floodplain mapping process
 Discuss the Impact of New Maps
 Discuss Floodplain Management Standards
The Risk is Real… Be PREPARED!
Cooperating Technical Partner CTP
FEMA’s Cooperating
Technical programs
 North Carolina is a
Cooperating Technical
State
 Mecklenburg County is a
Cooperating Technical
Partner
The Risk is Real… Be PREPARED!
Floodplain Statistics:
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The Risk is Real… Be PREPARED!
320 miles of streams
4000+ structures in the
floodplain
Average Precipitation: 40
inches per year
Record Maximum
Precipitation: 22 inches in
24 hours (1916 estimate)
Current 100-Year
Precipitation is 7.29 inches
Probable Maximum
Precipitation: About 33
inches
What is a Floodplain ?
Floodplains are those areas commonly
inundated by flooding. Floods result when
water runoff exceeds the capacity of stream
and river channels or lake basins.
FEMA Map Drains
One Square Mile
Area
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Floodplains vs Buffers
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Buffer - Improve Water Quality
- Limit Impervious Areas
- Limit Vegetation/Tree Removal
- Zoning
 Floodplain - Safety From Flood Damage
- Restrict Placement of Fill In
Floodway
- Ensure Buildings are Elevated
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DEFINITIONS
 Digital Flood Insurance Rate Map (DFIRM)
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A digitally-produced FIRM, whether viewed in hardcopy or in
digital form
Flood Insurance Study (FIS)
Details the examination, evaluation, and determination of flood
hazard areas
FIRMs are part of the FIS
Base Flood Elevation (BFE)
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As shown on the FIRM, represents whole-foot elevations of the
1% annual chance flood
Regulated to the nearest tenth of a foot; detailed information
provided in the FIS
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Flood Plain Mapping

Floodplain Mapping is regulated by FEMA if
the community participates in the NFIP
 Floodplain Mapping must follow a regimented
process
 Floodplain Maps generally progress through
three levels: Draft, Preliminary, and Effective
 Floodplain Maps may take as long a five years
to progress from terrain data acquisition to
Effective
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PURPOSE OF NFIP

To make flood insurance available
 Flood insurance is a requirement if there is a
mortgage on the home
 To identify floodplains and areas at risk of
flooding
 To provide standards, guidance, and a
framework to help communities manage
floodplains
The Risk is Real… Be PREPARED!
Floodplain Mapping History
Why are “Floodplains” Mapped?
 Protecting Life and Property
 Community Sustainability & Resiliency
 Communicate
& Reduce Flood Risk
USES FOR FLOOD RISK INFORMATION
 Flood Preparedness
Flood Insurance
 Regulate New Development
 Planning
 Mitigation
 And more…..
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Background: Floodplains
Evolution of Floodplain Maps & Regulations
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1978 – First Charlotte Ordinance and Maps
2002 -NC Floodplain Mapping – 99 Counties
2004 – FEMA published updated Maps
2009 – Charlotte maps reformatted to meet
NC Mapping Grid
2012 and beyond – New Floodplain Maps
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Why Floodplain Maps Change
Flood Risk Changes Over Time
Climatological
Changes
Technological
Advancements
Natural &
Man Made
Land Changes
• Extended Historic
Rainfall Records
• Changes in Rain
Intensity, Duration,
Frequency, etc.
• Better Data
• Improved
computer models
• Enhanced Map
Products
• Natural Geomorphic
Stream Changes
• Development within
the Watershed
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The Risk is Real… Be PREPARED!
NC – CTS Panel
NGS
Benchmark
Zone
X
Zone
AE
BFE
Floodway
(white hatched
area)
Stream
Name
Cross
Section
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Floodplains
Community (Future Conditions) Floodplain
FEMA (Existing
Conditions) Floodplain
FEMA Floodway
Community Encroachment Area
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Floodplain
Regulations and
the Flood
Insurance Rate
Map (FIRM)
FEMA Floodplain
Area
Community Floodplain
Area
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The Risk is Real… Be PREPARED!
2016
2014
February 19,
2014
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Phase 1
Mapping
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The Risk is Real… Be PREPARED!
UPPER LITTLE SUGAR
BRIAR
LOWER LITTLE SUGAR
BACK
REEDY
McKEE
CALDWELL
McALPINE
CLEAR
GOOSE
McMULLEN
CROOKED
FOUR MILE
TWELVE MILE
SIX MILE
CLEM
Phase 2
Mapping
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Watersheds along and
west of I-77:
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The Risk is Real… Be PREPARED!
McDowell
Upper Mtn Island
Gar
Long
Lower Mtn Island
Irwin
Paw
Catawba
Sugar
Beaverdam
Steele
Does not include Lake
Norman or Lake Wylie
POST-PRELIMINARY PROCESSING

Preliminary panels are issued
 2 notices in local newspaper
 90-day Appeal/Protest Period
 Educational Meetings
 Resolution of Appeals and Protests
 The 6-month Compliance Period
 Letter of Final Determination from FEMA
 Map Adoption and Update of Flood Damage
Prevention Ordinance
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CMSWS
Recognition of Preliminary FIRM
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FEMA requires maps to be released as
Preliminary for a period of about one year prior
to the final approval by FEMA.
 The Preliminary maps may show increased flood
elevations along some streams
 MCSWS regulates construction of new buildings
using the preliminary elevations, but only if the
new elevations are higher than the flood
elevations shown on the current flood maps.
The Risk is Real… Be PREPARED!
Regulate Where Floodplains are
Increasing On Preliminary Maps
The Risk is Real… Be PREPARED!
Cannot Use Preliminary Maps
Where Floodplains Decreasing
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DEVELOPMENT
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Development means any man-made change to
improved on unimproved real estate, including, but
not limited to:
 Buildings or other structures
 Mining
 Dredging
 Filling
 Grading
 Paving
 Excavating or drilling operations
 Storage of equipment or materials
The Risk is Real… Be PREPARED!
NO IMPACT CERTIFICATION
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A no-impact certification is required for any
proposed development in the floodway or
community encroachment area.
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A professional engineer must conduct a study and
certify that the proposed development will have no
impact on flood elevations.
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Community can issue a Floodplain Development
Permit only after receiving the engineer’s
certification.
The Risk is Real… Be PREPARED!
IMPACT ON DEVELOPMENT
REQUIREMENTS
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When FEMA publishes new flood maps or new
regulations are adopted, any existing compliant
development is grandfathered based on the
flood maps and regulations that were in effect at
the time of the building permit was issued, the
date of construction, or the date of last
substantial damage and/or substantial
improvement – whichever is later
The Risk is Real… Be PREPARED!
USE OF PRELIMINARY DATA
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The use of Preliminary Data will be treated on a
case by case process:
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Because Preliminary Data is the best
available data, it may be used in some
circumstances
Because Preliminary Data is not recognized
by FEMA until it becomes Effective, it cannot
be used in certain LOMC applications
If communities wish to enforce more stringent
data, they are encourage to adopt the
Preliminary data
The Risk is Real… Be PREPARED!
Online Flood Map Review
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http://mapserver.mecklenburgcountync.gov/fmr/
 ftp://ftp1.co.mecklenburg.nc.us/luesa/stormwater
/Floodplain%20Mapping/
The Risk is Real… Be PREPARED!
The Risk is Real… Be PREPARED!
The Risk is Real… Be PREPARED!
What is Flood Risk
Likelihood of
Event
Total
Risk
Consequences /
Impact
(Physical, Emotional,
Financial)
(Probability)
Probability over 30 years
40%
20%
26%
1%
0%
Likelihood of
Flood
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Likelihood of
Fire
What is Changing
Flood Insurance
Rate Maps
New Flood Risk
Products
New Floodzone
Website
• FEMA Floodplain
(Flood Insurance)
• Community Floodplain
(local use)
• Floodways
• 3D Flood Depth Maps
• Annual likelihood of
flooding
• Change Comparisons
• Delivery of Flood Risk
Information
• Mapping
• Risk Assessment
• Risk Reduction
The Risk is Real… Be PREPARED!
Using New Flood Map Products
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Knowing your flood risk is the first step in
taking actions toward Reducing your risk.
• Flood Likelihood
• Flood Insurance Rate
Maps
• Interactive Floodzone
Maps
• Property data
• Understanding
Consequences
• Potential Damage ($)
• Home, Car, HV/AC
Systems, Shed,
Personal Property, Etc.
• Floodplain Buyouts
• Flood Mitigation
Projects
• Preparedness and
Planning
• Flood proofing
• Elevation
• Audible Alarms
Show
Flood Risk
Know
Flood Risk
Reduce
Flood Risk
The Risk is Real… Be PREPARED!
Useful Information
Mecklenburg County’s Flood Map Review Application:
http://mapserver.mecklenburgcountync.gov/fmr/
Mecklenburg County’s Flood Map Review Application:
http://maps.co.mecklenburg.nc.us/website/floodzone/
Mecklenburg County’s ftp site:
ftp://ftp1.co.mecklenburg.nc.us/luesa/stormwater/Floodplain%20Mapping/
North Carolina Flood Map Application:
http://floodmaps.nc.gov/fmis/
North Carolina DOT GIS:
http://www.ncdot.org/it/gis/
The Risk is Real… Be PREPARED!
Thank You
Robert Billings, PE, PH, CFM
Floodplain Mapping
Project Manager
(704) 432-0907
Robert.Billings@
MecklenburgCountyNC.gov
The Risk is Real… Be PREPARED!