CEPSCI Stormwater Management and Hydrology 2 — Questions and Answers
Question 1: A check dam installed in a swale is primarily designed to:
- Mark the boundary of the site
- Reduce flow velocity and promote sediment settling in the channel (Correct answer)
- Prevent vehicle access
- Direct water to storm drains
Correct answer: Reduce flow velocity and promote sediment settling in the channel
Check dams reduce the velocity of flow in drainage channels and swales, promoting sediment deposition and reducing the channel's erosive energy.
Question 2: What is the purpose of a diversion dike on a construction site?
- To separate different construction crews
- To redirect clean runoff away from disturbed areas or to route runoff to a BMP (Correct answer)
- To mark equipment exclusion zones
- To stockpile excavated material
Correct answer: To redirect clean runoff away from disturbed areas or to route runoff to a BMP
Diversion dikes are earthen berms that redirect surface runoff away from disturbed areas or channel it toward a sediment control BMP to prevent uncontrolled runoff.
Question 3: Which stormwater BMP provides the most effective long-term management of runoff quality after construction is complete?
- Silt fence
- Temporary sediment basin
- Permanent stormwater pond or bioretention area (Correct answer)
- Straw wattle
Correct answer: Permanent stormwater pond or bioretention area
Permanent stormwater management facilities like detention ponds or bioretention areas provide long-term water quality and quantity control after construction activities have ended.
Question 4: Sheet flow in stormwater hydrology describes:
- Flow through a pipe or culvert
- Thin, uniform flow across a broad surface with no defined channel (Correct answer)
- Flow in a concrete-lined channel
- Flow that has been filtered through a silt fence
Correct answer: Thin, uniform flow across a broad surface with no defined channel
Sheet flow is the thin layer of water that moves across a surface in a relatively uniform depth without concentrating into a defined channel, and it is less erosive than concentrated flow.
Question 5: A level spreader is used to:
- Measure the elevation of a site
- Convert concentrated flow back to sheet flow before it enters a vegetated buffer (Correct answer)
- Install silt fence at a consistent height
- Spread soil amendments uniformly
Correct answer: Convert concentrated flow back to sheet flow before it enters a vegetated buffer
Level spreaders convert concentrated runoff into sheet flow so it can be dispersed across a vegetated buffer strip or filter area, reducing erosive velocity and promoting infiltration.
Question 6: Why is it important to minimize runoff velocity on a construction site?
- Higher velocity improves sediment settling in basins
- Lower velocity reduces the erosive energy that detaches and transports soil particles (Correct answer)
- Velocity has no effect on erosion
- Higher velocity improves BMP performance
Correct answer: Lower velocity reduces the erosive energy that detaches and transports soil particles
Runoff velocity directly determines erosive energy; slower flows have less capacity to detach and transport soil particles, reducing overall sediment production and transport.
CEPSCI Stormwater Management and Hydrology 2
A check dam installed in a swale is primarily designed to: