CSM Assessment & Monitoring Methods 2 — Questions and Answers
Question 1: Which parameter is measured by a totalizing flow meter in a stormwater monitoring program?
- Instantaneous flow rate only
- Cumulative volume over a storm event (Correct answer)
- Turbidity at peak flow
- pH of stormwater runoff
Correct answer: Cumulative volume over a storm event
A totalizing flow meter accumulates and records the total volume of flow passing through the monitoring point over the duration of a storm event.
Question 2: What is the primary purpose of using a Manning's n roughness coefficient in stormwater assessment?
- Estimating pollutant load in runoff
- Calculating open-channel flow velocity (Correct answer)
- Determining soil infiltration capacity
- Measuring sediment particle size distribution
Correct answer: Calculating open-channel flow velocity
Manning's n is a roughness coefficient used in the Manning's equation to calculate flow velocity and discharge in open channels and pipes.
Question 3: During a field assessment, you observe a V-notch weir in a detention pond outlet. What does the angle of the notch primarily affect?
- Sensitivity of flow measurement at low flows (Correct answer)
- Sediment trapping efficiency of the pond
- Water quality sampling frequency
- Outlet pipe diameter requirements
Correct answer: Sensitivity of flow measurement at low flows
Narrower V-notch angles increase sensitivity and accuracy at low flow rates, while wider angles accommodate higher flows.
Question 4: A stormwater manager needs to assess the condition of a buried culvert without excavation. Which method is most appropriate?
- Dye tracer test
- CCTV pipe inspection (Correct answer)
- Sediment core sampling
- Infiltrometer testing
Correct answer: CCTV pipe inspection
Closed-circuit television (CCTV) inspection allows visual assessment of culvert interior condition, defects, and blockages without excavation.
Question 5: What does an elevated Chloride (Cl⁻) concentration in stormwater runoff most likely indicate in a northern US climate?
- Sewage infiltration into storm drains
- Road salt application from winter maintenance (Correct answer)
- Agricultural fertilizer runoff
- Industrial discharge from a nearby facility
Correct answer: Road salt application from winter maintenance
Road deicing salts contain sodium chloride or calcium chloride, and elevated chloride levels in stormwater are a common indicator of winter road salt use.
Question 6: Which sampling strategy collects individual discrete samples at fixed time intervals regardless of flow conditions?
- Flow-proportional composite sampling
- Time-composite sampling (Correct answer)
- Grab sampling at peak flow
- Event mean concentration sampling
Correct answer: Time-composite sampling
Time-composite sampling collects aliquots at set time intervals (e.g., every 15 minutes), independent of the actual flow rate during the storm event.
Question 7: What is the significance of the 'first flush' phenomenon in stormwater monitoring?
- The first rainfall event of the year has the highest volume
- Initial runoff typically carries the highest pollutant concentrations (Correct answer)
- First flush describes the peak discharge in a hydrograph
- Early rain events have lower temperature than later events
Correct answer: Initial runoff typically carries the highest pollutant concentrations
The first flush effect describes the tendency for the initial portion of stormwater runoff to carry disproportionately high pollutant loads accumulated during dry weather periods.
CSM Assessment & Monitoring Methods 2
Which parameter is measured by a totalizing flow meter in a stormwater monitoring program?