Special Flood Hazard Areas
- Category: Water
- Data Type: GIS Data Layer
- Steward(s): Utah Division of Emergency Management and FEMA
- Abstract: The Floodplains dataset refers to the Digital Flood Insurance Rate Map (DFIRM) Database depicting flood risk information and supporting data used to develop the risk information. The primary risk classifications used are the 1-percent-annual-chance flood event, the 0.2-percent-annual-chance flood event, and areas of minimal flood risk. The DFIRM Database is derived from Flood Insurance Studies (FISs), previously published Flood Insurance Rate Maps (FIRMs), flood hazard analyses performed in support of the FISs and FIRMs, and new mapping data, where available. The FISs and FIRMs are published by the Federal Emergency Management Agency (FEMA). The file is georeferenced to earth's surface using the UTM projection and coordinate system. The specifications for the horizontal control of DFIRM data files are consistent with those required for mapping at a scale of 1:12000.
Special Flood Hazard Areas
Anywhere it rains it can flood. Mapped floodplains or “Special Flood Hazard Areas (SFHA’s)” represent areas in Utah that are at a higher risk of flooding. In these areas there is a 1-percent annual chance that flood waters will reach or surpass a base flood elevation in any given year. The 1-percent annual chance flood is also referred to as the base flood or 100-year flood and the SFHA is commonly referred to as the "100-year floodplain.”
The 1-percent-annual-chance floodplain (or SFHA) is the area where the National Flood Insurance Program's (NFIP's) floodplain management regulations must be enforced through flood hazard building codes and the area where the mandatory purchase of flood insurance applies.
This layer was created using criteria as defined by the Flood Insurance Rate Maps (FIRM) and produced by the Federal Emergency Management Agency (FEMA). These mapped zones are regulatory. FIRMs are the basis for floodplain management, mitigation, and insurance activities for the National Flood Insurance Program (NFIP).
Insurance applications include enforcement of the mandatory purchase requirement of the Flood Disaster Protection Act, which "... requires the purchase of flood insurance by property owners who are being assisted by Federal programs or by Federally supervised, regulated or insured agencies or institutions in the acquisition or improvement of land facilities located or to be located in identified areas having special flood hazards," Section 2 (b) (4) of the Flood Disaster Protection Act of 1973. Special Flood Hazard Areas (SFHAs) identified on the map are the risk zones shown on the FIRMs and are the basis for the establishment of premium rates for flood coverage offered through the NFIP.
The Digital Flood Insurance rate Map (DFIRM) Database presents the flood risk information depicted on the FIRM in a digital format suitable for use in electronic mapping applications. The DFIRM database is a subset of the Digital Flood Insurance Study (FIS) database that serves to archive the information collected during the FIS.
One thing to keep in mind with the zone designations is the difference between "Shaded X" and "Unshaded X". In the link above, Shaded X represents the 0.2% annual chance floodplain (the 500-year flood). In almost all of the DFIRMs, the ZONE field will read: 0.2 PCT ANNUAL CHANCE FLOODPLAIN or something like that, and in some DFIRMs it will just read: Shaded X. Confusingly, when the ZONE field is just "X", that means Unshaded X, which is outside of the 500-year floodplain.
LiDAR can be used to support FEMA Map Amendments. This fact sheet describes the information and process necessary to use LIDAR data when applying for FEMA Map Amendments.
- National Flood Hazard Layer (NFHL) Web Map
- National Flood Hazard Layer (NFHL) Resources
- FEMA Flood Map Service Center
- Definitions of FEMA Flood Zone Designations
- Utah’s Risk Map (flood Mapping) Program
Downloads and Web Services
- This dataset has a varied update schedule and is updated continuously.