This set of Engineering Hydrology Multiple Choice Questions & Answers (MCQs) focuses on “Hydrologic Channel Routing”.
1. In hydrologic channel routing, storage is a function of which of the following?
a) Outflow only
b) Inflow only
c) Outflow and inflow
d) Outflow, inflow and length of reach
View Answer
Explanation: Unlike hydrologic reservoir routing in which the storage was a function of outflow only, in case of hydrologic channel routing, the storage is a function of both the outflow and inflow discharges. This makes it different from storage routing.
2. How many parts is the storage volume of a channel reach divided into?
a) 1
b) 2
c) 3
d) 4
View Answer
Explanation: The water level surface in a channel reach constantly varies with time. The slope of the water surface with the channel bottom also changes. So in case of a flood flow, it would be convenient to divide the storage of the reach into two parts.
3. What is the storage volume of a channel section whose surface is parallel to the channel bottom called?
a) Prism storage
b) Level storage
c) Parallel storage
d) Fixed storage
View Answer
Explanation: If the flow downstream of the channel section is uniform, the storage would be called as prism storage. It is a volume constrained by an imaginary plane parallel to the channel bottom at a fixed distance from it.
4. Which of the following best describes the location of the wedge storage for a channel reach?
a) Upstream of the prism storage
b) Downstream of the prism storage
c) Above the prism storage
d) Below the prism storage
View Answer
Explanation: In a channel reach, the volume of water that is present above the imaginary plane that defines the prism storage, is known as wedge storage. The name represents the fact that the shape of this volume most likely resembles a wedge.
5. Which of the following is true for the storage in a channel section?
a) Both prism and wedge storage remain constant
b) Prism storage changes and wedge storage is constant
c) Prism storage is constant and wedge storage changes
d) Both prism and wedge storage change
View Answer
Explanation: For a given channel section at a fixed depth, the prism storage is the base storage which remains constant while the wedge storage is constantly varying depending on the nature of the flood flow.
6. A flood wave dips before suddenly rising as it enters a channel reach. What is the change in wedge storage from upstream of the reach to the reach?
a) Negative to positive
b) Positive to negative
c) Remains negative
d) Remains positive
View Answer
Explanation: When a flood wave dips before entering the reach, the water surface goes below the imaginary surface of the prism storage. This represents negative wedge storage. When the wave rises, it comes above the prism storage and represents a positive wedge volume.
7. What is the shape of the prism storage of reach of 1 km length with a square channel of side 25 meters?
a) Cube
b) Cuboid
c) Trapezoid
d) Parallelepiped
View Answer
Explanation: The prism storage is represented by a volume constrained by an imaginary plane parallel to the channel bottom. Since it is not mentioned whether the channel is horizontal or sloped, the prism storage will be a parallelepiped volume. If the reach had been horizontal and the level water surface at the top, the prism storage would be a cuboid of volume = (1000*25*25) = 625000 m3.
8. The wedge storage in a stream section in the presence of a receding flood wave is negative.
a) True
b) False
View Answer
Explanation: A receding flood wave in a channel represents the falling phase of a flood wave which dips and goes below the level of the prism storage. This implies that the wedge storage in that section is negative.
9. If P is the prism storage, W is the wedge storage, I is the inflow discharge and Q is the outflow discharge, which of the following represents the correct function f?
a) P = f(I) and W = f(Q)
b) P = f(Q) and W = f(I)
c) P = f(I,Q) and W = f(Q)
d) P = f(Q) and W = f(I,Q)
View Answer
Explanation: The prism storage can be compared to routing a reservoir and hence it is only a function of outflow discharge Q. However, the wedge storage depends on the incoming flood wave and hence is a function of inflow discharge I. Therefore, the channel storage is a function of both inflow and outflow.
10. Which of the following represents the general equation for the storage in channel reach? I and Q represents the inflow and outflow, respectively. K, x and m are constants for a given channel reach.
a) x.Im+(1-x).Qm
b) Kx.Im+(1-x).Qm
c) K[x.Im+(1-x) .Qm]
d) Km [x.I+(1-x).Q]
View Answer
Explanation: The channel storage depends on both the inflow and outflow discharges, and a general function representing this relation is given as,
K[x.Im+(1-x) .Qm]
Where, K and x are routing constants determined based on observations from the reach and m is a constant depending on the channel type.
Sanfoundry Global Education & Learning Series – Engineering Hydrology.
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