CME Stormwater Management & Drainage Engineering 1 — Questions and Answers
Question 1: The Rational Method formula Q = CiA is used to estimate which quantity in stormwater design?
- Peak runoff discharge (Correct answer)
- Total runoff volume
- Time of concentration
- Pipe friction losses
Correct answer: Peak runoff discharge
The Rational Method calculates peak runoff discharge (Q) in cubic feet per second using runoff coefficient (C), rainfall intensity (i), and drainage area (A).
Question 2: What does NPDES stand for in the context of stormwater regulation?
- National Pollution Discharge Elimination System (Correct answer)
- National Permit for Drainage and Environmental Standards
- Natural Prevention of Debris and Erosion Systems
- National Program for Drainage Engineering Specifications
Correct answer: National Pollution Discharge Elimination System
NPDES (National Pollution Discharge Elimination System) is the EPA permit program that controls water pollution by regulating point sources that discharge pollutants into waters of the United States, including stormwater.
Question 3: In stormwater design, 'time of concentration' (Tc) is defined as:
- The time for runoff to travel from the hydraulically most remote point in a watershed to the design point (Correct answer)
- The duration of a design storm event
- The time required for a detention pond to drain completely
- The lag time between peak rainfall and peak discharge
Correct answer: The time for runoff to travel from the hydraulically most remote point in a watershed to the design point
Time of concentration is the travel time for runoff from the hydraulically most remote point in the watershed to reach the outlet, which determines the critical storm duration for peak flow calculations.
Question 4: What is the primary functional difference between a retention pond and a detention pond?
- Retention ponds hold a permanent pool of water; detention ponds drain completely between storms (Correct answer)
- Detention ponds are lined; retention ponds are unlined
- Retention ponds treat water quality only; detention ponds control quantity only
- Detention ponds are for groundwater recharge; retention ponds are for flood control
Correct answer: Retention ponds hold a permanent pool of water; detention ponds drain completely between storms
Retention ponds maintain a permanent pool of water (wet ponds) and provide additional storage above the permanent pool, while detention ponds (dry ponds) temporarily store runoff and drain completely between storm events.
Question 5: Manning's equation is primarily used in stormwater engineering to calculate:
- Flow velocity and discharge in open channels and pipes (Correct answer)
- Sediment transport capacity in streams
- Rainfall intensity from return period data
- Infiltration rate through permeable pavement
Correct answer: Flow velocity and discharge in open channels and pipes
Manning's equation (V = (1/n) R^(2/3) S^(1/2)) calculates flow velocity in open channels and pipes based on hydraulic radius, slope, and Manning's roughness coefficient, which allows discharge to be computed.
Question 6: A '100-year storm event' in municipal drainage design refers to:
- A storm with a 1% annual probability of exceedance (Correct answer)
- A storm that occurs once every 100 years with certainty
- The largest storm recorded in the past 100 years
- A storm lasting exactly 100 hours
Correct answer: A storm with a 1% annual probability of exceedance
A 100-year storm has a 1% probability of being equaled or exceeded in any given year, meaning it is a statistical return period rather than a guarantee of a 100-year recurrence interval.
Question 7: Which of the following best describes green infrastructure in the context of stormwater management?
- Practices that mimic natural hydrology by infiltrating, evapotranspiring, or harvesting stormwater near its source (Correct answer)
- Construction of large regional detention basins with vegetated side slopes
- Replacing all gray concrete infrastructure with recycled materials
- Installing permeable curbs and gutters along roadways
Correct answer: Practices that mimic natural hydrology by infiltrating, evapotranspiring, or harvesting stormwater near its source
Green infrastructure uses natural processes — such as bioretention, rain gardens, green roofs, and permeable pavements — to manage stormwater at or near its source, reducing runoff volume and improving water quality.
CME Stormwater Management & Drainage Engineering 1
The Rational Method formula Q = CiA is used to estimate which quantity in stormwater design?