CFS Floodplain Mapping & Elevation Determination 2

Question 1

On a FIRM, what does a Zone AE designation indicate?

Accepted Answer

Special Flood Hazard Area with Base Flood Elevations determined

Answer

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

Question 2

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

Accepted Answer

NAVD 88

Answer

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

Question 3

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

Accepted Answer

Natural ground elevation is at or above the BFE

Answer

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.

Question 4

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

Accepted Answer

Manning's roughness coefficient

Answer

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

Question 5

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

Accepted Answer

Provides the downstream boundary condition from which computations proceed upstream

Answer

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

(CFS) Certified Floodplain Surveyor Practice Test

(CFS) Certified Floodplain Surveyor Practice Test

CFS Floodplain Mapping & Elevation Determination 2