Learn about the different types of flood hazard areas and where to locate them in Transect.
This article provides a breakdown of the different flood zone types and how Transect visualizes this data to help developers quickly assess risk and make informed decisions about project locations.
In this article, we’ll review:
Types of Flood Hazard Areas
- Special Flood Hazard Area (SFHA): The base floodplain displayed on FEMA maps, including A and V zones.
- Zone A: This is the 100-year floodplain. The Special Flood Hazard Area (except coastal V Zones) is shown on a community's Flood Insurance Rate Map.
- Zone A: SFHA, where no base flood elevation is provided.
- Zone A#: Numbered A Zones (e.g., A7 or A14), SFHA, where the FIRM shows a base flood elevation in relation to NGVD.
- Zone AE: SFHA, where base flood elevations are provided. AE Zone delineations are now used on new FIRMs instead of A# Zones.
- Zone AO: SFHA with sheet flow, ponding, or shallow flooding. Base flood depths (feet above grade) are provided.
- Zone AH: Shallow flooding SFHA. Base flood elevations in relation to NGVD are provided.
- Zone B: This is the 500-year floodplain. This is an area of moderate flood hazard, usually depicted on Flood Insurance Rate Maps as between the limits of the base and 500-year floods. B Zones are also used to designate base floodplains of little hazard, such as those with average depths of less than 1 foot.
- Zone C: Area of minimal flood hazard, usually depicted on Flood Insurance Rate Maps as above the 500-year flood level. B and C Zones may have flooding that does not meet the criteria to be mapped as a Special Flood Hazard Area, especially ponding and local drainage problems.
- Zone D: The Zone D designation is used for areas where there are possible but undetermined flood hazards, as no analysis of flood hazards has been conducted.
- Zone V: The Special Flood Hazard Area is subject to coastal high-hazard flooding. There are three types of V Zones: V, V#, and VE, which correspond to the A Zone designations.
- Zone X: Newer Flood Insurance Rate Maps show Zones B and C (see above) as Zone X.
Flood Hazard Zones in the Map
Within the Map, the Flood Hazard Zones layer visualizes areas that contain regulatory flood zones designated by FEMA. You can right-click on a map feature for more information
Flood Hazard Zones in Reports
After running a report, you can visualize the flood hazard zones in the Report Map by checking the box to activate the Floodplains layer. This will indicate which zones were found within the area of interest and their location.
The Executive Summary provides an overview of the Waters found within the AOI. This is broken down into wetlands, waterways, and floodplains, where you can click Learn More for additional information.
You will see a concern level based on the following information:
- High Concern: The concern level will be high if the project area intersects any wetland areas, waterbody areas, or streams, or if it was indicated waters will be impacted from the context questions*.
- Moderate Concern: The concern level will be moderate if there are no NWI wetlands or NHD streams within the project area, but it is within a FEMA 100-year floodplain.
- Low Concern: The concern level will be low if the project area does not intersect or contain with wetland areas, streams, or waterbody areas, or if it was indicated waters will be not impacted from the context questions*.
*As defined by the report creator in the context questions in the report creation process. Click here to learn more about Concern Levels.
The Waters > Data page further breaks down the water sources located within the area of interest, including wetlands, waterways, flood hazard areas, and FIRM panels. From this page, you can see the type, sub-type, area within the location, and whether it is located in the buffer or the AOI. This information can also be exported by right-clicking in the table and selecting Export.
