CPESC Hydrology & Hydraulics 2

Question 1

What is the hydraulic radius of a channel cross-section, and how is it calculated?

Accepted Answer

The ratio of flow area to wetted perimeter; A/P

Answer

Hydraulic radius (R) = cross-sectional flow area (A) divided by the wetted perimeter (P), and is a key parameter in Manning's equation for channel design.

Question 2

A 2-year, 24-hour storm event is commonly used for which type of erosion and sediment control design?

Accepted Answer

Designing temporary diversion channels and sediment basins during construction

Answer

Many state stormwater regulations require temporary BMPs such as diversions and sediment basins to be designed for the 2-year, 24-hour storm to provide adequate protection during construction.

Question 3

In stormwater hydrology, the term 'imperviousness' refers to:

Accepted Answer

The percentage of a watershed surface that does not allow water infiltration

Answer

Imperviousness is the fraction of land surface covered by impervious materials (pavement, rooftops) that prevent infiltration and generate direct runoff.

Question 4

Which flow regime is considered most erosive and is characterized by a Froude number greater than 1.0?

Accepted Answer

Supercritical (rapid) flow

Answer

Supercritical flow (Fr > 1.0) has high velocity and shallow depth, producing significant shear stress on channel beds and banks, making it highly erosive.

Question 5

The unit peak discharge (qu) used in the TR-55 graphical peak discharge method is expressed in units of:

Accepted Answer

Cubic feet per second per inch of runoff per square mile (csm/in)

Answer

In the TR-55 method, unit peak discharge (qu) is expressed as csm/in (cubic feet per second per square mile per inch of runoff), used to compute peak discharge from small watersheds.

(CPESC) Certified Professional in Erosion and Sediment Control Practice Test

(CPESC) Certified Professional in Erosion and Sediment Control Practice Test

CPESC Hydrology & Hydraulics 2