Regulatory Implications

Hillsborough County uses the results of the most current set of Flood Insurance Rate Maps and its accompanying Flood Insurance Study to guide compliance and site planning. The new, revised Flood Maps will be considered the "best available data" and used for new construction when they illustrate more restrictive (higher base flood elevations) than the current effective flood maps. The unincorporated County's flood hazard data are based on the studies completed for 17 watersheds. The watershed master plans have all been adopted by FEMA and the County, and have been used for design purposes for the past two years. Now, the flood hazard maps are complete and will work in conjunction with the 100-year model output created by the 17 studies to illustrate the high-risk areas, known as Special Flood Hazard Areas. Use the Proposed Flood Map Viewers to locate property within Hillsborough County.

Watershed Master Plans

Information from and relating to the Watershed Master Plans can be obtained by contacting the Stormwater Section of the County's Public Works Department Engineering Division.

Changes to the Vertical Datum

Base Flood Elevations on the new maps are in North Atlantic Vertical Datum of 1988 (NAVD 88).

In years past, Hillsborough County would use the National Geodetic Vertical Datum of 1929 (NGVD 29) as the base for vertical measurements. The Federal Government adopted the NAVD 88 as a more accurate vertical measurement in the early 1990's and requested local governments to follow suit. The County has used both measurements while transitioning to NAVD 88 as the official standard. (Please note that the datum used in the watershed master plans is in NGVD 29 and will be transitioned to NAVD 88 over the next two years as the model is updated.). More information is available on the Vertical Datums page.

View the FEMA fact sheet for Industries Involved with Development ( PDF, 175KB ) .

The Preliminary Flood Insurance Studies are available.