CSM Best Management Practices (BMPs) & Design 4

Question 1

Green roofs provide stormwater benefits primarily through which mechanism?

Accepted Answer

Retaining rainfall in growing media and releasing it through evapotranspiration

Answer

Green roofs absorb rainfall into the growing medium and return the majority of it to the atmosphere through evapotranspiration, reducing both runoff volume and peak flow.

Question 2

When calculating the design infiltration rate for an infiltration BMP, a safety factor is commonly applied to measured field Ksat values. What is the typical safety factor used?

Accepted Answer

0.50 (one-half of measured Ksat)

Answer

Designers typically apply a safety factor of 0.5, using half the measured Ksat to account for variability, clogging over time, and construction disturbance of native soils.

Question 3

Which of the following represents a structural BMP rather than a non-structural (source control) BMP?

Accepted Answer

Detention pond

Answer

Detention ponds are engineered, constructed facilities (structural BMPs), while the other options are programmatic or regulatory measures (non-structural BMPs).

Question 4

A stormwater management plan includes a rainwater harvesting cistern. Which design consideration is most important to ensure the cistern provides both water quality and volume reduction benefits?

Accepted Answer

Sizing the cistern with sufficient drawdown between storms to provide available storage capacity

Answer

A cistern only provides volume reduction if it has available capacity when the next storm arrives; adequate drawdown through planned reuse is essential for stormwater management benefits.

Question 5

In a low impact development (LID) approach, which strategy best mimics the pre-development hydrograph by reducing both runoff volume and peak discharge?

Accepted Answer

Distributing multiple small-scale infiltration and retention BMPs throughout the site

Answer

Distributed small-scale LID practices intercept and treat runoff near its source, collectively mimicking pre-development conditions by promoting infiltration, evapotranspiration, and slow release.

(CSM) Certified Stormwater Manager Practice Test

(CSM) Certified Stormwater Manager Practice Test

CSM Best Management Practices (BMPs) & Design 4