โ† All CFS Flashcard Decks

Floodplain Mapping & Elevation Determination Flashcards

7 cards from real CFS practice questions. Tap to flip, then mark Knew It or Still Learning โ€” missed cards come back until you master them.

Read the first 7 Floodplain Mapping & Elevation Determination flashcards as text
  1. On a FIRM, what does a Zone AE designation indicate?

    Answer: Special Flood Hazard Area with Base Flood Elevations determined

    Zone AE is a Special Flood Hazard Area where BFEs have been determined through detailed hydraulic analysis.

  2. What vertical datum is currently used for most FEMA FIRMs produced after 1991?

    Answer: NAVD 88

    NAVD 88 (North American Vertical Datum of 1988) replaced NGVD 29 as the standard datum for modern FIRMs.

  3. A Letter of Map Amendment (LOMA) is appropriate when a structure is removed from a SFHA based on what condition?

    Answer: Natural ground elevation is at or above the BFE

    A LOMA is used when the natural ground (not fill) at or around a structure is at or above the BFE, indicating the FIRM incorrectly included that property.

  4. Which cross-section data element is most critical for determining the BFE at a specific river reach using the HEC-RAS model?

    Answer: Manning's roughness coefficient

    Manning's n values define channel and floodplain roughness, directly controlling computed water-surface elevations in HEC-RAS.

  5. What is the purpose of a 'Starting Water Surface Elevation' (starting WSEL) in a step-backwater analysis?

    Answer: Provides the downstream boundary condition from which computations proceed upstream

    In subcritical flow, HEC-RAS computes upstream from a known downstream starting WSEL, which serves as the boundary condition.

  6. A floodway is defined as the channel plus the portion of the floodplain needed to convey the 1% annual chance flood while not increasing the BFE by more than how many feet?

    Answer: 1.0 foot

    FEMA's standard allows a maximum 1.0-foot surcharge (encroachment increase) when establishing the regulatory floodway.

  7. Which FEMA product provides the official flood zone determination for a specific parcel when the FIRM panel boundary falls through the property?

    Answer: Flood Zone Determination from a certified flood zone researcher

    When a FIRM panel boundary bisects a property, a certified flood zone determination is used to identify the applicable flood zone(s) for that parcel.