CFS Floodplain Mapping & Elevation Determination 3 — Questions and Answers
Question 1: In a FIRM revision, what is the significance of a 'Limit of Moderate Wave Action (LiMWA)' line?
- It separates Zone AE from Zone X
- It marks where wave heights transition from less than 1.5 ft to 1.5 ft or greater (Correct answer)
- It defines the landward edge of the SFHA
- It indicates the 0.2% annual chance flood boundary
Correct answer: It marks where wave heights transition from less than 1.5 ft to 1.5 ft or greater
The LiMWA separates coastal areas with moderate wave action (waves 1.5 ft or greater) from those with lesser wave action, distinguishing Zone AE from Zone VE construction standards.
Question 2: When performing a Hydraulic Structure Analysis for a culvert, which condition typically controls the design water surface elevation?
- Inlet control or outlet control, whichever produces the higher headwater elevation (Correct answer)
- Always inlet control for circular culverts
- Always outlet control for box culverts
- The Manning's equation result only
Correct answer: Inlet control or outlet control, whichever produces the higher headwater elevation
Both inlet and outlet control headwater elevations are computed, and the higher value governs the design since it represents the more restrictive condition.
Question 3: A surveyor finds that a structure's Lowest Adjacent Grade (LAG) is 342.1 ft NAVD 88 and the BFE is 341.5 ft NAVD 88. What is the freeboard above BFE?
- 0.6 feet below BFE
- 0.6 feet above BFE (Correct answer)
- 1.6 feet above BFE
- No freeboard; structure is in the SFHA
Correct answer: 0.6 feet above BFE
LAG (342.1) minus BFE (341.5) = +0.6 ft, meaning the lowest adjacent grade is 0.6 feet above the BFE.
Question 4: What does 'effective' versus 'amended' mean on a FIRM panel?
- Effective is the original FIRM; amended panels reflect only LOMA/LOMC changes
- Effective is the current legally adopted panel; amended refers to draft revisions not yet adopted (Correct answer)
- They are synonyms used interchangeably by FEMA
- Amended panels apply only in V zones
Correct answer: Effective is the current legally adopted panel; amended refers to draft revisions not yet adopted
The effective FIRM is the currently adopted, legally binding map, while an amended panel has been modified through a formal LOMA or LOMR but may still await community adoption.
Question 5: Which statement best describes the relationship between the 1% annual chance flood and the 100-year flood?
- They are different events — the 100-year flood is more severe
- They are equivalent terms describing a flood with a 1% probability of occurrence in any given year (Correct answer)
- The 1% flood is the average of the 50-year and 150-year floods
- The 100-year flood occurs exactly once per century
Correct answer: They are equivalent terms describing a flood with a 1% probability of occurrence in any given year
The '1% annual chance flood' and '100-year flood' are synonymous, both describing a flood magnitude with a 1-in-100 probability of being equaled or exceeded in any year.
Question 6: During a LOMR-F application, what document must a licensed engineer or surveyor provide to support fill-based elevation claims?
- A certified Elevation Certificate showing the structure's lowest floor elevation
- A grading plan and an Elevation Certificate or certified topographic data showing fill placement (Correct answer)
- Only a surveyor's letter on company letterhead
- A FEMA MT-1 form with photos only
Correct answer: A grading plan and an Elevation Certificate or certified topographic data showing fill placement
LOMR-F applications require certified topographic data or an Elevation Certificate demonstrating that legal fill has raised the property above the BFE.
Question 7: What is the primary purpose of the Flood Insurance Study (FIS) report that accompanies a FIRM?
- To list all structures in the SFHA requiring flood insurance
- To document the methodology, data, and BFEs used to produce the FIRM (Correct answer)
- To provide community floodplain ordinance language
- To track claims history for the NFIP
Correct answer: To document the methodology, data, and BFEs used to produce the FIRM
The FIS report is the technical backup document that details the hydrologic and hydraulic analyses, data sources, and computed BFEs shown on the FIRM.
CFS Floodplain Mapping & Elevation Determination 3
In a FIRM revision, what is the significance of a 'Limit of Moderate Wave Action (LiMWA)' line?