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Definitions

High-Risk Advisory Zones: : High-risk advisory zones – Preliminary NFHL, Advisory A, or Updated AE – are non-regulatory 1%-annual-chance flood zones represented as orange-colored flood zones in the WV Flood Tool. These advisory flood zones are generated from new model-backed flood studies or from redelineation mapping. Redelineation is the method of updating effective flood hazard boundaries to match updated topographic data based on the computed water surface elevations from effective models. The public should be informed that these non-regulatory zones will most likely become effective when new Flood Insurance Rate Maps (FIRM) are published, and thus any development in these zones should be regulated to the same standards as effective high-risk flood zones. In local floodplain ordinances, communities may choose to adopt high-risk advisory zones as "community-identified floodplains" and regulated the same as the Special Flood Hazard Area of the official Flood Insurance Rate Map (FIRM). Besides showing flood prone areas that are likely to be “mapped into the SFHA” in a future FEMA Flood Restudy, the high-risk advisory zones are also beneficial in identifying Letters of Map Amendment (LOMAs) for structures or property that should be “removed from the SFHA.”

  • Preliminary NFHL: Preliminary FEMA National Flood Hazard Layers (NFHL) are pending to become effective on new Flood Insurance Rate Maps (FIRMs). A Preliminary Flood Zone for a 1%-annual-chance-flood (100-year flood) event is displayed on the WV Flood Tool as a high-risk advisory zone until it becomes effective on the official FIRM.
  • Advisory A Flood Zone: : A model-backed Approximate A Zone is determined by using hydrology and hydraulics (H&H) analysis and the best available elevation data. Water Depth and Water Surface Elevation Grids are also companion products of Advisory A Zones. The Advisory Flood Heights or Advisory Base Flood Elevations are displayed in the Flood Query Results Panel of the WV Flood Tool. Although these high-risk advisory zones are non-regulatory flood zones, future FEMA Flood Studies most likely will incorporate these advisory zones on the official FIRM. In local floodplain ordinances, communities may choose to adopt high-risk advisory zones as "community-identified floodplains" and regulated the same as the Special Flood Hazard Area of the official FIRM.
  • Updated AE Boundary: A Non-Restudy where AE Zones undergo redelineation, a method of updating effective flood hazard boundaries to match updated topographic data based on the computed water surface elevations from effective models. Advisory AE Zones outside the SFHA are high-risk, non-regulatory flood zones. Future FEMA Flood Studies most likely will incorporate these Advisory AE Zones on the official FIRM. In local floodplain ordinances, communities may choose to adopt high-risk advisory zones as "community-identified floodplains" and regulated the same as the Special Flood Hazard Area of the official FIRM. Along with the Updated AE Floodplain Boundaries, the Depth and Water Surface Elevation Grids are products of the redelineation. Gridded Base Flood Elevations are displayed in the Flood Query Results Panel of the WV Flood Tool. Flood Heights in effective AE Zones should be confirmed with the Flood Profiles and Flood Elevation Tables, whereas flood heights delineated outside the effective AE Zones of the FIRM the base flood elevations are advisory; communities may choose to regulate Advisory Flood Heights (or Advisory Base Flood Elevations) in high-risk advisory zones the same as Base Flood Elevations in the SFHA.

Flood Height Grid: Gridded base flood heights are important for floodplain management and flood risk assessment activities. Presently, in the Flood Query Results Panel, model-backed flood height values are displayed for Approximate A Zones and AE Zones for 35 and 7 counties, respectively. FEMA now accepts the Advisory Flood Heights (or Advisory BFE) displayed on the WV Flood Tool for LOMA determinations and for Elevation Certificates. Gridded base flood elevations for AE Zones (Restudies/Non-Restudies) displayed in the Flood Query Results Panel of the WV Flood Tool should be confirmed with the Flood Profile in the Flood Insurance Study. Composite Water Surface Elevation Grids are organized and published separately by source methodology: Risk MAP Restudy, Non-Restudy (AE Zone Redelineation), and Advisory Flood Height (Approximate A Zone) studies.

Water Depth Grid: The base flood water depths are important for communicating flood risk. Water depths are published in the Flood Query Results Panel and used for computing the Water Depth-in-Structure for the building-level flood risk assessments. The Water Depth is the principal input for the 3D flood visualizations. The statewide Hazus depth grid created in 2010 is not very accurate, and thus a priority is to attain model-backed depth grids for full statewide coverage. Two statewide, composite Depth Grids are organized and published separately by the source software utilized: HEC-RAS engineering software and Hazus software.

LOMAs Verified: Letters of Map Amendment (LOMA) in which the positional accuracy of the x-y coordinates has been verified by legal descriptions, deed book/page number, parcel identifier, or E-911 address. Verified LOMAs are displayed in the EXPERT and RISK MAP Views of the WV Flood Tool. Current and historical LOMAs categorized as Structure Non-Removal, Removal, or Out as Shown.

West Virginia Flood Tool

Official FEMA Definitions and Resources

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Supported by all modern browsers: Please contact Eric Hopkins with questions or comments relating to the site. Copyright 2015.