Charlotte-Mecklenburg Storm Water Services develops and maintains locally-adopted floodplain maps. These maps are used to regulate development in special flood hazard areas and to determine flood insurance rates.
Current Flood Insurance Rate Maps (FIRMs) provide flood hazard information for 330 miles of stream in 32 Charlotte-Mecklenburg watersheds. The FIRMs include floodplain maps in unincorporated Mecklenburg County, the City of Charlotte and the Towns of Cornelius, Davidson, Huntersville, Matthews, Mint Hill and Pineville.
Special Flood Hazard Areas are being remapped
Storm Water Services is now remapping all Charlotte-Mecklenburg floodplains. This will continue through 2016.
More about the status of floodplain remapping.
As before, the newest Charlotte-Mecklenburg floodplain maps show two floodplains--existing and future.
Electronic versions of the new maps also use layers with colors to show types of risk:
- Blue, green and yellow to show how deep the floodwater will be
- Red, orange and yellow to show how frequently a parcel is expected to flood
2012 Floodplain Analysis and Mapping Standards Document
2008 Floodplain Analysis and Mapping Standards Document
The Floodplain Analysis and Mapping Standards Documents provide guidance to contractors who create floodplain maps for Charlotte-Mecklenburg Storm Water Services.
How floodplain maps have changed over the years
Map showing existing
and future floodplains
"3D" map showing
varying flood depths
1970's Floodplain Map
One color shows
entire regulated floodplain
1999 Floodplain Map
Light blue indicates FEMA Floodplain.
Grey shows Community Floodplain.
2010 Floodplain Map
Different colors show how
deep the floodwater will be.
FEMA Floodplains and Community Floodplains
In 1999, Charlotte-Mecklenburg became the first community in the nation with Flood Insurance Rate Maps (FIRMs) containing two floodplains and two floodways. The floodplain maps identify both:
- current flood zones (called the Federal Emergency Management or FEMA Floodplain)
- areas likely to flood in the future when the watershed is fully developed (called the Community Floodplain.)
The FEMA Floodway has a surcharge of 0.5 foot in contrast to the typical 1.0 foot surcharge. In addition to the FEMA Floodplain and FEMA Floodway, the maps contain the Community Floodplain and the Community Encroachment Area.
The Community Floodplain is determined using the 100-year flood discharge applying future land use conditions. The Community Encroachment Area is a floodway with a surcharge of 0.1 foot. This creates a wider floodway than the FEMA Floodway. The purpose of the Community Floodplain is to estimate the future expansion of the floodplain based on zoning and predicted development.
Two documents summarize study findings and were used to guide policy decisions that became the foundation of Charlotte-Mecklenburg's floodplain mapping program:
Executive Summary of changes in flood elevations due to 1999 remapping
Flood loss analysis compares the financial impact of flooding with and without restrictions on additional development in the Community Floodplain
Regulating the Community Floodplain
All of the jurisdictions within Mecklenburg County except Cornelius and Matthews use the Community Floodplain information to regulate development. Cornelius and Matthews require structures to be constructed two feet above the FEMA Base Flood Elevation. There are additional regulatory requirements for development in the Community Encroachment Area. See each jurisdiction's Floodplain Regulations.
2000 Floodplain Maps
- Storm Water Services became Cooperating Technical Partner with FEMA
- Storm Water Services contributed $2,000,000 to develop Flood Insurance Study (FIS)
- Storm Water Services worked with FEMA to develop and adopt revised Flood Insurance Rate Maps (FIRMs) Revised maps replaced floodplain maps that were 5 to 20 years old
- Revised floodplain maps adopted for local regulatory purposes
- FEMA adopted FIS data and the revised Mecklenburg County FIRMS for insurance purposes
Newest Floodplain Maps
Updated Floodplain Maps for about one-third of Charlotte-Mecklenburg became effective on February 19, 2014. New maps for the remaining sections of the county will take effect in phases through 2016.
Charlotte-Mecklenburg experienced explosive growth in recent decades. Data used in the 1999 mapping initiative is out of date. Ongoing remapping of watersheds is necessary to maintain accurate floodplain information for proper floodplain management. As part of the map maintenance program, Storm Water Services intends to remap approximately 20% of the watersheds per year on a rotating basis.
For more information about the floodplain mapping/map maintenance program:
Bill Tingle, CFM
Charlotte-Mecklenburg Storm Water Services