CPESC Hydrology & Hydraulics 3

Question 1

The 'return period' (recurrence interval) of a storm event represents:

Accepted Answer

The average number of years between occurrences of a storm of equal or greater magnitude

Answer

How often a storm of that magnitude occurs every calendar year

Answer

The duration in hours of the design rainfall event

Answer

The number of years a BMP must remain functional

Question 2

Which hydraulic parameter directly determines the erosive force exerted on a channel boundary by flowing water?

Accepted Answer

Boundary shear stress (tractive force)

Answer

Hydraulic gradient

Answer

Froude number

Answer

Reynolds number

Question 3

In the context of sediment basin design, the concept of 'fall velocity' (or settling velocity) of a sediment particle is governed by:

Accepted Answer

Stokes' Law for small particles settling in still water

Answer

Darcy's Law for flow through porous media

Answer

Manning's equation for open channel flow

Answer

The Rational Method for peak discharge

Question 4

A culvert is designed to pass a 10-year peak flow without overtopping the road. If the design storm peak discharge is 150 cfs, which sizing approach is used to determine the required culvert diameter?

Accepted Answer

Weir and orifice equations depending on headwater depth and control conditions

Answer

Manning's equation assuming inlet control conditions

Answer

The Rational Method applied inside the culvert

Answer

Darcy-Weisbach equation for pressure flow only

Question 5

What is the primary purpose of a rip-rap apron or energy dissipator placed at the outlet of a pipe or culvert?

Accepted Answer

Reduce outlet velocity and prevent scour by dissipating kinetic energy

Answer

Filter fine sediment from the discharge before it enters the channel

Answer

Increase flow velocity to transport sediment through the reach

Answer

Measure the discharge rate using a calibrated weir

Question 6

In watershed hydrology, the term 'baseflow' refers to:

Accepted Answer

Groundwater contribution to streamflow during dry weather periods

Answer

The minimum design flow used to size drainage structures

Answer

The average annual runoff volume from a watershed

Answer

Direct surface runoff from impervious areas during a storm

Question 7

Which of the following best describes the hydrograph response of a highly urbanized watershed compared to a forested watershed of the same size?

Accepted Answer

Higher peak discharge with a shorter time to peak and greater runoff volume

Answer

Lower peak discharge with a longer time to peak

Answer

Similar peak discharge but significantly lower runoff volume

Answer

Lower runoff velocity but equal total discharge volume