Flood Map Modernization
Detailed Thorough Precise.
Building to a Safer Standard
Flood hazard maps can be valuable tools in the effort to protect lives and property. The County’s flood maps are nearly 30-years old and seriously out-of-date. The new flood maps provide a much more accurate picture of flood risks and flood elevations to guide in land development and building decisions.
Engineers, Developers and Builders Can Plan for Safer Construction.
Now that the preliminary Digital Flood Insurance Rate Maps (DFIRMs) have been released, the building industry will need to know the differences between the preliminary maps and the current effective maps. The data from the more conservative map is typically used by communities for design and permitting purposes. This will remain the case until the preliminary maps become effective. When the preliminary map shows less restrictive information, it usually cannot be used until the map becomes effective.
The Vertical Datum is Changing.
As new maps are issued, they will no longer be using the National Geodetic Vertical Datum of 1929 (NGVD29) as the vertical datum (see FEMA’s Procedure Memorandum No. 41). Instead, they will use the North American Vertical Datum of 1988 (NAVD88). Floodplain managers, engineers, surveyors, builders, and other users of elevation data from multiple sources (e.g. FIRM and Elevation Certificate) must take care that the elevation values they use are based on the same vertical datum. If they are not the same, the values need to be converted to the same datum. Failure to do so can result in improper design (e.g. building at the wrong elevation). Note that the property owner’s risk is not affected by a vertical datum change because all elevations in the local area are changed by the same amount. To learn more, go to the Resources page.
Requests for Engineering or Surveying Services for Insurance Rating or Appeals
While the new maps use the latest technology and information available at the time of risk modeling, the maps can be improved if better information is available. FEMA will accept detailed topographic or hydrologic model information to support a change to the map during the 90-Day Public Comment Period. Property owners may be requesting services of engineers and surveyors to meet the requirements of insurance or to support an appeal. More information is available on the Public Comment Period page.