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LARE Drainage System Design Flashcards

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

Read the first 7 LARE Drainage System Design flashcards as text

  1. What is the primary purpose of a check dam installed in a vegetated swale?

    Answer: To slow flow velocity, promote infiltration, and trap sediment

    Check dams slow stormwater velocity in swales, allowing sediment to settle and promoting infiltration between successive pools.

  2. A site requires a 48-inch diameter reinforced concrete pipe (RCP) to convey the 25-year design storm. What minimum cover depth is typically required over the pipe in a roadway application?

    Answer: 24 inches

    Most design standards require a minimum of 24 inches of cover over RCP under roadways to prevent pipe failure from surface loads.

  3. Which condition creates a 'surcharged' storm sewer system?

    Answer: When hydraulic grade line rises above the pipe crown due to downstream backwater

    A surcharged system occurs when the hydraulic grade line exceeds the top of the pipe, causing pipes to flow under pressure rather than as open-channel flow.

  4. A landscape architect is designing a low-impact development (LID) site. Which combination of practices best addresses both runoff volume reduction and water quality improvement?

    Answer: Bioretention cells, permeable pavement, and green roofs in series

    Bioretention, permeable pavement, and green roofs each reduce runoff volume and filter pollutants, making them complementary LID strategies.

  5. When applying the SCS/NRCS Curve Number method, which land cover and soil type combination produces the highest runoff potential (highest CN)?

    Answer: Commercial district on Group D soils

    Commercial land cover (high imperviousness) combined with Group D soils (lowest infiltration rate) produces the highest CN values, approaching 95.

  6. An urban redevelopment project must achieve 'no net increase' in stormwater runoff volume. Which strategy most directly satisfies this requirement?

    Answer: Providing on-site volume reduction through infiltration and evapotranspiration equal to the increase in runoff volume

    Volume neutrality requires reducing runoff on-site through infiltration or ET to offset the increase caused by new impervious surfaces.

  7. A stormwater swale is designed with a 3:1 (H:V) side slope. What is the primary reason for this design standard?

    Answer: To provide safe mowable slopes and reduce erosion potential on channel banks

    A 3:1 side slope is stable, reduces erosion, and allows maintenance equipment such as mowers to safely operate on channel banks.

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