CSM Data Collection & Analysis 4

Question 1

Which sensor technology is commonly used for continuous in-situ turbidity monitoring in stormwater channels?

Accepted Answer

Optical nephelometer or infrared scatter probe

Answer

Optical nephelometers measure light scattered by suspended particles at a defined angle and are routinely deployed as submersible probes for continuous turbidity monitoring.

Question 2

A stage-discharge rating curve becomes invalid when:

Accepted Answer

Channel cross-section geometry changes due to scour or deposition

Answer

Rating curves are developed for a specific channel geometry; scour, deposition, or vegetation changes alter hydraulic controls, requiring recalibration with new discharge measurements.

Question 3

In the context of stormwater data analysis, 'censored data' refers to:

Accepted Answer

Values reported only as less than the detection limit (non-detects)

Answer

Censored data are measurements below the method detection limit, reported as '<MDL'; special statistical techniques (e.g., Kaplan-Meier, substitution methods) are needed to handle them in analysis.

Question 4

Which remote sensing product is most commonly used to map impervious surface area across an entire watershed efficiently?

Accepted Answer

Multispectral satellite imagery classified using NDVI and spectral indices

Answer

Multispectral imagery (e.g., Landsat, Sentinel-2) distinguishes impervious surfaces from vegetation and soil using spectral indices, enabling watershed-scale impervious cover mapping at low cost.

Question 5

A stormwater manager finds a strong negative correlation (r = -0.85) between vegetated buffer width and outfall total suspended solids (TSS) concentrations. This means:

Accepted Answer

As buffer width increases, TSS concentrations tend to decrease

Answer

A negative correlation coefficient means the two variables move in opposite directions — wider buffers are associated with lower TSS, consistent with buffers trapping sediment before it reaches the outfall.

(CSM) Certified Stormwater Manager Practice Test

(CSM) Certified Stormwater Manager Practice Test

CSM Data Collection & Analysis 4