Stormwater Management Advanced Exam
Questions And Correct Answers (Verified
Answers) Plus Rationales 2026 Q&A | Instant
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1. Which best describes the primary objective of a detention basin in
urban stormwater management?
A. Provide permanent water storage for irrigation
B. Reduce peak discharge rates and delay runof f to downstream
systems
C. Remove dissolved nutrients through biological uptake
D. Increase groundwater recharge through infiltration
Detention basins are designed primarily to attenuate peak flows
and reduce downstream flood risk by temporarily storing runoff
and releasing it slowly.
2. When designing an infiltration trench, which soil property is most
critical to evaluate?
A. Plasticity index
B. Hydraulic conductivity (infiltration rate)
C. Specific gravity
D. Atterberg limits
An infiltration trench’s performance depends on the soil’s ability to
transmit water; hydraulic conductivity determines whether the
trench will drain as intended.
3. The “first flush” concept in stormwater quality refers to:
A. The first rain after a drought that causes erosion
, B. The initial portion of runoff that carries disproportionately
high pollutant concentrations
C. The first event that saturates the watershed
D. The flush used to test stormwater pumps
Pollutants accumulated on surfaces are washed off early in a
storm, so the initial runoff often contains the highest contaminant
loads.
4. For sizing a bioretention cell, which factor most directly influences
required surface area?
A. Plant species selection
B. Target water quality volume and soil infiltration capacity
C. Color of mulch
D. Type of underdrain piping
Required area depends on the amount of runoff to treat (water
quality volume) and how quickly the soil can infiltrate that volume.
5. Which mechanism is least effective for removing dissolved
nutrients in a stormwater wetland?
A. Plant uptake
B. Sedimentation of dissolved constituents
C. Microbial transformations (e.g., denitrification)
D. Adsorption to organic matter
Dissolved nutrients do not settle by sedimentation; they are
removed mostly by biological uptake, adsorption, or biochemical
processes.
6. The Rational Method is typically appropriate for estimating peak
runoff in which situation?
A. Large river basin (>1,000 acres)
, B. Small urban catchments (usually <200 acres) with relatively
uniform runoff characteristics
C. Estimating groundwater recharge for a watershed
D. Long-duration, continuous simulation modeling
The Rational Method is a simple, event-based formula best suited
for small, homogeneous urban catchments for peak flow
estimation.
7. Which design storm is most commonly used for water quality
treatment sizing in many U.S. stormwater manuals?
A. 100-year, 24-hour storm
B. The 90th percentile/first 1-inch (or local equivalent volume)
design storm
C. 10-year, 10-minute storm
D. Tropical cyclone design storm
Many manuals use a relatively small, frequent storm or a volume-
based approach (e.g., the first inch) to size water quality controls
that capture typical pollutant loads.
8. Which Best Management Practice (BMP) primarily relies on
physical filtration through a vegetation/soil matrix?
A. Constructed wetland with deep open water
B. Bioretention (rain garden)
C. Extended detention basin without media
D. Underground detention vault
Bioretention systems filter runoff through engineered soils and
vegetation, removing particulates and associated pollutants.
9. In stormwater modeling, what does the Time of Concentration (Tc)
represent?
, A. Time until groundwater table recovers
B. Time required for runoff to travel from the most distant point
in the watershed to the outlet
C. Time for BMPs to dewater completely
D. Time between rain gauge readings
Tc determines how quickly a watershed responds to rainfall and is
critical for hydrograph timing and peak flow calculations.
10. Which pollutant is most effectively removed by
sedimentation-based BMPs?
A. Dissolved nitrates
B. Total Suspended Solids (TSS)
C. Dissolved phosphates
D. Heavy metals bound to dissolved organic carbon
Sedimentation removes particulate matter (TSS) as solids settle out
of the water column; dissolved pollutants are less affected.
11. A treatment train approach in stormwater management
means:
A. Designing a single oversized BMP to handle all flows
B. Using multiple BMPs in series to address different pollutants
and flow regimes
C. Employing only natural systems and avoiding engineered
devices
D. Using a train of detention basins connected by pumps
Treatment trains layer structural and non-structural practices so
each component targets specific pollutants or flow conditions for
improved performance.
Questions And Correct Answers (Verified
Answers) Plus Rationales 2026 Q&A | Instant
Download Pdf
1. Which best describes the primary objective of a detention basin in
urban stormwater management?
A. Provide permanent water storage for irrigation
B. Reduce peak discharge rates and delay runof f to downstream
systems
C. Remove dissolved nutrients through biological uptake
D. Increase groundwater recharge through infiltration
Detention basins are designed primarily to attenuate peak flows
and reduce downstream flood risk by temporarily storing runoff
and releasing it slowly.
2. When designing an infiltration trench, which soil property is most
critical to evaluate?
A. Plasticity index
B. Hydraulic conductivity (infiltration rate)
C. Specific gravity
D. Atterberg limits
An infiltration trench’s performance depends on the soil’s ability to
transmit water; hydraulic conductivity determines whether the
trench will drain as intended.
3. The “first flush” concept in stormwater quality refers to:
A. The first rain after a drought that causes erosion
, B. The initial portion of runoff that carries disproportionately
high pollutant concentrations
C. The first event that saturates the watershed
D. The flush used to test stormwater pumps
Pollutants accumulated on surfaces are washed off early in a
storm, so the initial runoff often contains the highest contaminant
loads.
4. For sizing a bioretention cell, which factor most directly influences
required surface area?
A. Plant species selection
B. Target water quality volume and soil infiltration capacity
C. Color of mulch
D. Type of underdrain piping
Required area depends on the amount of runoff to treat (water
quality volume) and how quickly the soil can infiltrate that volume.
5. Which mechanism is least effective for removing dissolved
nutrients in a stormwater wetland?
A. Plant uptake
B. Sedimentation of dissolved constituents
C. Microbial transformations (e.g., denitrification)
D. Adsorption to organic matter
Dissolved nutrients do not settle by sedimentation; they are
removed mostly by biological uptake, adsorption, or biochemical
processes.
6. The Rational Method is typically appropriate for estimating peak
runoff in which situation?
A. Large river basin (>1,000 acres)
, B. Small urban catchments (usually <200 acres) with relatively
uniform runoff characteristics
C. Estimating groundwater recharge for a watershed
D. Long-duration, continuous simulation modeling
The Rational Method is a simple, event-based formula best suited
for small, homogeneous urban catchments for peak flow
estimation.
7. Which design storm is most commonly used for water quality
treatment sizing in many U.S. stormwater manuals?
A. 100-year, 24-hour storm
B. The 90th percentile/first 1-inch (or local equivalent volume)
design storm
C. 10-year, 10-minute storm
D. Tropical cyclone design storm
Many manuals use a relatively small, frequent storm or a volume-
based approach (e.g., the first inch) to size water quality controls
that capture typical pollutant loads.
8. Which Best Management Practice (BMP) primarily relies on
physical filtration through a vegetation/soil matrix?
A. Constructed wetland with deep open water
B. Bioretention (rain garden)
C. Extended detention basin without media
D. Underground detention vault
Bioretention systems filter runoff through engineered soils and
vegetation, removing particulates and associated pollutants.
9. In stormwater modeling, what does the Time of Concentration (Tc)
represent?
, A. Time until groundwater table recovers
B. Time required for runoff to travel from the most distant point
in the watershed to the outlet
C. Time for BMPs to dewater completely
D. Time between rain gauge readings
Tc determines how quickly a watershed responds to rainfall and is
critical for hydrograph timing and peak flow calculations.
10. Which pollutant is most effectively removed by
sedimentation-based BMPs?
A. Dissolved nitrates
B. Total Suspended Solids (TSS)
C. Dissolved phosphates
D. Heavy metals bound to dissolved organic carbon
Sedimentation removes particulate matter (TSS) as solids settle out
of the water column; dissolved pollutants are less affected.
11. A treatment train approach in stormwater management
means:
A. Designing a single oversized BMP to handle all flows
B. Using multiple BMPs in series to address different pollutants
and flow regimes
C. Employing only natural systems and avoiding engineered
devices
D. Using a train of detention basins connected by pumps
Treatment trains layer structural and non-structural practices so
each component targets specific pollutants or flow conditions for
improved performance.
