CSM CSM Urban Stormwater Systems & Infrastructure 2 — Questions and Answers
Question 1: What is green infrastructure in the context of urban stormwater management?
- An approach that uses natural processes and vegetation to manage stormwater at or near its source, mimicking the natural water cycle (Correct answer)
- Installing solar panels on top of stormwater detention facilities
- Using recycled materials in the construction of storm sewer pipes
- Painting stormwater infrastructure green to indicate environmental compliance
Correct answer: An approach that uses natural processes and vegetation to manage stormwater at or near its source, mimicking the natural water cycle
Green infrastructure uses vegetated systems such as rain gardens, bioretention cells, and green roofs to infiltrate, evapotranspirate, or filter stormwater close to where rain falls, reducing runoff volume and improving water quality.
Question 2: What is a bioretention cell (also known as a rain garden) and what pollutants does it remove?
- A landscaped depression filled with engineered soil and plants that filters stormwater, removing sediment, nutrients, heavy metals, and bacteria (Correct answer)
- A sealed underground tank that stores runoff for irrigation reuse only
- A chemical dosing system that neutralizes acid rain before discharge
- A concrete vault that filters solids using screens and baffles
Correct answer: A landscaped depression filled with engineered soil and plants that filters stormwater, removing sediment, nutrients, heavy metals, and bacteria
Bioretention cells use a soil media-plant system to filter and infiltrate stormwater, removing suspended solids, excess nutrients, heavy metals, hydrocarbons, and pathogens through physical, chemical, and biological processes.
Question 3: How does permeable pavement reduce stormwater runoff compared to conventional pavement?
- By allowing rainfall to infiltrate through the pavement surface into the subbase and underlying soil, reducing runoff volume and peak flow (Correct answer)
- By heating the pavement surface to evaporate rainfall before it can run off
- By collecting runoff in sub-surface tanks that pump water back onto the road surface
- By using rough surface texture to slow runoff velocity without allowing infiltration
Correct answer: By allowing rainfall to infiltrate through the pavement surface into the subbase and underlying soil, reducing runoff volume and peak flow
Permeable pavement has an open pore structure that lets rainfall pass through to a stone storage bed below, where it infiltrates into native soils, significantly reducing surface runoff volume and peak discharge rates.
Question 4: What is the primary stormwater management function of a vegetated swale?
- To convey stormwater runoff while slowing its velocity, promoting infiltration, and filtering pollutants through the vegetation and soil (Correct answer)
- To rapidly convey runoff off-site at maximum velocity to prevent flooding
- To store large volumes of runoff for extended periods for water quality improvement
- To sample runoff for pollutant analysis at regular monitoring stations
Correct answer: To convey stormwater runoff while slowing its velocity, promoting infiltration, and filtering pollutants through the vegetation and soil
Vegetated swales are shallow, grass-lined channels that slow runoff, allow infiltration into the soil, and filter suspended solids and nutrients through contact with vegetation and soil media.
Question 5: What is the purpose of a stormwater outfall structure in an urban drainage system?
- To provide the controlled discharge point where the storm sewer system releases collected runoff to a receiving water body or channel (Correct answer)
- To recycle stormwater back into the municipal water supply system
- To measure the pollutant loading entering the storm sewer at street level
- To divert stormwater into sanitary sewers during dry weather
Correct answer: To provide the controlled discharge point where the storm sewer system releases collected runoff to a receiving water body or channel
An outfall is the terminal structure of a storm sewer where collected stormwater is discharged to a receiving water body, stream, or other drainage feature under the authority of an NPDES permit.
Question 6: What is a green roof and how does it contribute to urban stormwater management?
- A vegetated rooftop system that absorbs and evapotranspirates rainfall, reducing the volume and peak rate of runoff from buildings (Correct answer)
- A roof design that channels all rainfall to a single downspout for monitoring
- An elevated green space over a parking structure that collects rainwater for irrigation
- A solar-panel-covered roof that powers the building's stormwater pump system
Correct answer: A vegetated rooftop system that absorbs and evapotranspirates rainfall, reducing the volume and peak rate of runoff from buildings
Green roofs consist of growing media and plants on a rooftop that absorb rainfall, significantly reducing runoff volume and attenuating peak flows from building rooftops in urban areas.
CSM CSM Urban Stormwater Systems & Infrastructure 2
What is green infrastructure in the context of urban stormwater management?