Practice Test Geeks(CFS) Certified Floodplain Surveyor Practice Test
← All CFS Flashcard Decks

Hydrologic & Hydraulic Analysis Flashcards

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

Read the first 7 Hydrologic & Hydraulic Analysis flashcards as text

  1. A floodplain surveyor finds that a stream cross-section has a main channel and two overbank areas with different Manning's n values. How should composite roughness be calculated for the entire section?

    Answer: Use a conveyance-weighted composite n for each subsection

    Total discharge is computed by summing conveyance (K = (1.486/n)AR^(2/3)) for each subsection; composite roughness reflects the conveyance-weighted combination.

  2. The concept of 'equal conveyance reduction' is used in HEC-RAS to determine:

    Answer: The effective flow area by excluding ineffective flow regions

    HEC-RAS uses ineffective flow areas to exclude portions of a cross-section where water is ponded or not actively conveying flow in the downstream direction.

  3. Which FEMA-accepted hydrologic method is specifically designed for ungauged, rural watersheds using USGS regression equations?

    Answer: Regional regression equations (StreamStats)

    USGS StreamStats provides regional regression equations for estimating flood frequencies on ungauged rural watersheds based on basin characteristics.

  4. In a Log-Pearson Type III frequency analysis, what does a negative skew coefficient indicate about the flood data distribution?

    Answer: The distribution has a longer tail on the low-flow side

    A negative skew coefficient means the data distribution is skewed toward lower values with the longer tail on the left (low-flow) side.

  5. When a culvert operates under inlet control, what factor primarily governs the flow capacity?

    Answer: The geometry of the culvert entrance (headwater depth and inlet geometry)

    Under inlet control, the culvert capacity is controlled by the inlet geometry, headwater depth, and opening size, not the barrel characteristics or tailwater.

  6. The 'effective reach length' in a HEC-RAS model is the distance used to compute friction losses between cross-sections. For overbank areas, how is this typically determined?

    Answer: Measured along the overbank flow path, which may differ from the main channel path

    Overbank reach lengths are measured along the actual overbank flow path, which is often shorter or different than the main channel centerline distance.

  7. According to Bulletin 17C guidelines, what is the recommended approach when historical flood data contains low outliers?

    Answer: Use the Conditional Probability Adjustment to handle potentially incomplete records

    Bulletin 17C recommends the Conditional Probability Adjustment when records may be incomplete at the low end, accounting for years when flows did not exceed a threshold.