ASCE Water Resources and Environmental Engineering 2

Question 1

Using the Rational Method, what is the peak runoff from a 10-acre site with C = 0.6 and rainfall intensity i = 2 in/hr?

Accepted Answer

12 cfs

Answer

Q = CiA = 0.6 × 2 × 10 = 12 cfs, since 1 acre-in/hr is approximately 1 cfs.

Question 2

A hydraulic jump forms in an open channel when flow changes from:

Accepted Answer

Supercritical to subcritical

Answer

A hydraulic jump is the abrupt shift from fast, shallow supercritical flow to slower, deeper subcritical flow.

Question 3

In open channel flow, a Froude number exactly equal to 1.0 indicates:

Accepted Answer

Critical flow

Answer

Fr = 1 means flow velocity equals the shallow-water wave celerity, which is critical flow.

Question 4

If the Hazen-Williams C coefficient of a pipe drops because of aging and tuberculation, what happens at the same flow rate?

Accepted Answer

Head loss increases

Answer

A lower C means a rougher pipe, so friction head loss goes up for the same discharge.

Question 5

In the NRCS (SCS) Curve Number method, a higher curve number means:

Accepted Answer

Greater runoff potential

Answer

Higher CN values stand for less permeable surfaces and more direct runoff.

ASCE - American Society of Civil Engineers Certification Practice Test