Question 1

Which of the following statements best describes the difference between a floodplain and a floodway?&#10;A)A floodplain may span across a vast area while a floodway is generally contained within the channel of a river&#10;B)A floodplain is generally contained within a specific footage on either side of a stream centerline, while a flood way may span across a vast area&#10;C)A floodplain is generally contained within the channel of a river while a floodway is generally contained within a specific footage on either side of a stream centerline&#10;D)There is no difference - they are the same

Accepted Answer

The statement that best describes the difference between a floodplain and a floodway is that a floodplain may span across a vast area while a floodway is generally contained within the channel of a river. Floodplains include any land area that may be inundated by floodwater from any source (river, lake, or ocean). A floodway is defined as the channel of a river and a portion of the overbank floodplain that carries most of the base flood. Federal regulations require that the construction of structures in a floodway will not obstruct flood flows or increase the elevation of floodwaters.

Question 2

Which of the following best describes the term &#34;base flood&#34;?&#10;A)The elevation of the crest of the base or 100-year flood&#10;B)The flood having a 1% chance of being equaled or exceeded in any given year&#10;C)A general and temporary condition of partial or complete inundation of normally dry land areas&#10;D)A condition of flooding where there is moving water, but no identifiable channel

Accepted Answer

A base flood is best described as the flood having a 1% chance of being equaled or exceeded in any given year. The Federal Emergency Management Agency (FEMA) refers to this flood as the "100-year" or "1% chance" flood. The base flood delineation is only a statistically based boundary developed using HEC-RAS or other computerized hydraulic and hydrologic model and is developed for the National Flood Insurance Program to ensure all participating properties are protected to the same degree against flooding.

Question 3

Which of the following is a common purpose for installing a stilling basin?&#10;A)Energy dissipation&#10;B)Scour prevention&#10;C)Channel erosion control&#10;D)All of the above

Accepted Answer

Stilling basins are commonly installed for energy dissipation, scour prevention, and channel erosion control purposes. Stilling basins are used at culvert outfalls to dissipate kinetic energy to prevent or mitigate scour holes and downstream channel erosion. Stilling basins are often a low-cost alternative to other in-stream modifications that can be made to address erosion and ecosystem restoration issues.

Question 4

For an open channel, the flow may be laminar or turbulent. To determine if open channel flow is laminar, the Reynolds Number, Re, must be which of the following? A)Re < 500 B)Re < 1,000 C)Re > 2,000 D)Re > 4,000

Accepted Answer

To determine if open channel flow is laminar, Re must be less than 500. The limit for turbulent flow in an open channel is Re >1,000. For pipe flow, the limits are as follows:
Laminar: Re < 2,000
Turbulent: Re > 4,000

Question 5

Which of the following fundamental laws of physics does not describe the flow of fluids?&#10;A)Conservation of matter (mass)&#10;B)Conservation of energy&#10;C)Conservation of electrical charge&#10;D)Conservation of momentum

Accepted Answer

The conservation of electrical charge law, one of the fundamental laws of physics, does not describe the flow of fluids. In fluid mechanics, the conservation of matter reduces to the conservation of mass as matter is not created, destroyed, or converted by a chemical process. Energy may be converted, and in the case of friction losses, mechanical energy of a fluid is converted to heat. The conservation of momentum applies to fluid mechanics as fluids constantly change shape while moving.

Question 6

Which of the following statements describes uniform steady flow characteristics?&#10;A)Discharge remains the same and the depth does not change&#10;B)Surface of the water is parallel to the bed of the channel&#10;C)Velocity of flow can be computed using Manning's equation&#10;D)All of the above.

Accepted Answer

Uniform steady flow characteristics can be described by the all of the statements listed. In steady flow conditions, the velocity measurements taken at a specific point does not change over time. In unsteady flow conditions, the depth of flow varies with both time and space.

Question 7

What is the velocity (in ft/sec) in a rectangular concrete channel with a width of 3 feet (ft), a hydraulic grade line slope of 0.002 ft/ft, a flow depth of 1.5 ft and an assumed Manning's coefficient n = 0.014?

A)0.15 ft/sec
B)1.50 ft/sec
C)3.92 ft/sec
D)None of the above

Accepted Answer

the velocity in a rectangular channel with the given dimensions is 3.92 ft/sec³/sec. Solution: Use Manning's Equation and solve for Q Q = (K/n) R ^2/3S_f^1/2 Where: K = conversion coefficient (1.486 for English units, 1.0 for SI) n = 0.014, the Manning coefficient d = depth of flow = 1.5 ft w = width of channel = 3.0 ft S_f= channel slope = 0.002 ft/ft A = Area = d x w = 1.5 ft x 3 ft = 4.5 ft² P = wetted perimeter = w + 2d = 3 ft + 3 ft = 6 ft R = hydraulic radius = A/P = (4.5 ft²)/ (6 ft) = 0.75 ft Q = (1.486/0.014) x (0.75 ft)^2/3 x (0.002 ft/ft)^/1/2 = 3.92 ft/sec

Question 8

Which of the following materials is not commonly used in the construction of drainage culverts?&#10;A)Asbestos cement (AC) pipe&#10;B)Corrugated metal pipe (CMP)&#10;C)Cast iron and steel pipe&#10;D)Reinforced concrete

Accepted Answer

Asbestos cement pipe is not commonly used in the construction of drainage culverts. PVC pipe is commonly used for culverts and storm sewers. Precast culverts are typically available in a variety of cross-sectional shapes, and are often not circular.

Question 9

When placing a weir in an open channel, the measurement of the head should be taken upstream from the crest. The measurement location should be at least how far away from the weir?&#10;A)At the weir crest&#10;B)Twice the head&#10;C)Four times the head&#10;D)Just behind the crest

Accepted Answer

The measurement location of the head should be at least four times the head. Measurements of stream flow that are made with weirs are only accurate when the weirs are properly set and calibrated. It is important to read the head measurement at a point upstream of the weir crest that is not affected by the downward curve of the water as it approaches the weir.

Question 10

The rate of flow through a Parshall flume is determined by the measurement of which of the following?&#10;A)Water velocity&#10;B)Flume configuration&#10;C)Water depth&#10;D)Water area

Accepted Answer

The rate of flow through a Parshall flume is determined by the measurement of water depth. Parshall flumes are specially shaped channel flow sections that are installed in gravity conveyance systems. These flumes conform to sizing standards set by the U.S. government. With recent advancements in flow monitoring technologies, Parshall flumes are not as widely used now as they had been in the past.

Question 11

Drawdown is a hydraulics term that refers to which of the following conditions in a typical sewer?&#10;A)Siphoning&#10;B)The surface curve at a free flowing outlet of a pipe&#10;C)Draining the line&#10;D)An area where the flow slows

Accepted Answer

The answer of Drawdown is a hydraulics term that refers...

Question 12

A hydraulic jump is likely to occur at which of the points in an open channel?&#10;A)Velocity of flow suddenly increases&#10;B)The flow depth is greater than the critical depth&#10;C)Water moving at a high velocity at shallow depth strikes water with a substantially deeper depth&#10;D)All of the above

Accepted Answer

The answer of A hydraulic jump is likely to occur...

Deck 7: Hydraulics Open