LARE LARE Stormwater Management 5 — Questions and Answers
Question 1: Which design element is essential to prevent 'short-circuiting' in a constructed stormwater wetland?
- A high length-to-width ratio with inlet and outlet at opposite ends (Correct answer)
- Deep open water zones throughout the wetland
- A recirculation pump to mix the water
- Dense emergent vegetation planted throughout
Correct answer: A high length-to-width ratio with inlet and outlet at opposite ends
A high length-to-width ratio (minimum 2:1, ideally 4:1) with inlet and outlet at opposite ends maximizes water travel distance and prevents short-circuiting flow paths.
Question 2: What is 'hydromodification' in the context of stormwater management in California?
- Chemical modification of stormwater before discharge
- Changes to natural hydrologic processes caused by land development that alter stream morphology (Correct answer)
- Modification of storm drain pipe materials to reduce corrosion
- The process of converting stormwater to potable water
Correct answer: Changes to natural hydrologic processes caused by land development that alter stream morphology
Hydromodification refers to the alteration of natural hydrologic processes — flow duration, volume, and timing — by development, leading to stream channel instability and erosion.
Question 3: A designer is selecting plants for a bioswale in a cold climate. Which characteristic is most critical beyond aesthetics?
- Fall foliage color
- Tolerance of periodic inundation and drought cycles (Correct answer)
- Height during summer growing season
- Root depth for soil aeration
Correct answer: Tolerance of periodic inundation and drought cycles
Bioswale plants must tolerate both periodic inundation during storms and dry periods between events, making flood-drought tolerance the primary selection criterion.
Question 4: Which stormwater regulation requires municipalities in urbanized areas to obtain NPDES stormwater permits for their storm sewer systems?
- Clean Water Act Section 404
- MS4 (Municipal Separate Storm Sewer System) permit program (Correct answer)
- Safe Drinking Water Act
- RCRA Subtitle D regulations
Correct answer: MS4 (Municipal Separate Storm Sewer System) permit program
The MS4 permit program under the Clean Water Act requires municipalities operating separate storm sewer systems in urbanized areas to obtain NPDES permits and implement stormwater management programs.
Question 5: What is the primary purpose of a 'level spreader' at the outlet of a stormwater practice discharging to a filter strip?
- To measure the volume of flow leaving the BMP
- To convert concentrated pipe flow into sheet flow across the filter strip (Correct answer)
- To aerate the discharge and improve dissolved oxygen
- To prevent clogging of the outlet structure
Correct answer: To convert concentrated pipe flow into sheet flow across the filter strip
A level spreader converts concentrated flow from a pipe or channel into uniform sheet flow distributed across the width of a filter strip to maximize its treatment effectiveness.
Question 6: In green infrastructure planning at the watershed scale, what is a 'drainage area delineation' used to determine?
- The legal boundaries of stormwater easements on private property
- The land area that contributes runoff to a specific point or water body (Correct answer)
- The minimum lot size required for on-site stormwater retention
- The zone within which construction activity is prohibited near streams
Correct answer: The land area that contributes runoff to a specific point or water body
Drainage area delineation identifies the topographic boundary of all land that drains to a specific outlet point, which is essential for calculating runoff volumes and designing BMPs.
Question 7: Which factor most influences whether a stormwater infiltration practice will fail over time due to clogging?
- Seasonal variation in groundwater depth
- Fine sediment loading from the contributing drainage area (Correct answer)
- Plant root intrusion into the infiltration zone
- Freeze-thaw cycles in the soil
Correct answer: Fine sediment loading from the contributing drainage area
Fine sediment loading is the leading cause of clogging and failure in infiltration practices; pretreatment to remove sediment before it reaches the infiltration zone is critical to longevity.
LARE LARE Stormwater Management 5
Which design element is essential to prevent 'short-circuiting' in a constructed stormwater wetland?