# Engineering Hydrology Questions and Answers – Flood Routing Equations

This set of Engineering Hydrology Multiple Choice Questions & Answers (MCQs) focuses on “Flood Routing Equations”.

1. Which of the following is true with respect to the travel of flood waves through a river?
a) Its shape remains constant as it moves down a river
b) Flood peak is amplified as it passes through a river
c) Flood peak is attenuated as it passes down a river without lateral inflow
d) Lateral inflow in rivers causes flood peak attenuation

Explanation: As a wave moves down a river, its shape gets changed due to various factors like storage, resistance, etc. When lateral inflow is absent, the flood peak gets attenuated because of channel friction. Lateral inflows cause a reduction of attenuation or amplification of flood waves.

2. What happens when a flood wave passes through a reservoir?
a) Attenuated peak and shortened time base
b) Attenuated peak and enlarged time base
c) Amplified peak and shortened time base
d) Amplified peak and enlarged time base

Explanation: As a flood wave passes through a reservoir, the flood peak gets attenuated and the time base is extended as reflected from a hydrograph. This is due to the effect of storage of the reservoir.

3. Which of the following is closest in definition to the process of flood routing?
a) Determining flood hydrograph on upstream side with the use of upstream flood data
b) Determining flood hydrograph on upstream side with the use of downstream flood data
c) Determining flood hydrograph on downstream side with the use of upstream flood data
d) Determining flood hydrograph on downstream side with the use of downstream flood data

Explanation: Flood routing is the technique of generating a flood hydrograph of a river or channel at a point using the data of the flood at one or more sections upstream of the selected point. It includes functions like flood forecasting, flood protection, spillway design, etc.

4. How is flood routing categorized on the basis of its application?
a) Reservoir and channel routing
b) Hydrologic and reservoir routing
c) Channel and hydraulic routing
d) Hydraulic and hydrologic routing

Explanation: Flood routing can be divided into two categories on the basis of where it is applied. If it is used to study the flood wave entering a reservoir it is known as reservoir routing, and if it is used to study the effect of flood wave in a channel it is known as channel routing.

5. How many types of flood routing techniques are there based on the method used?
a) 2
b) 3
c) 4
d) 5

Explanation: Flood routing is categorized into two types based on the routing method used. Hydrologic routing uses only the continuity equation, whereas hydraulic routing uses continuity equation along with equation of motion.

6. Which of the following relationships should be known to predict the reservoir elevation and outflow variations with time using reservoir routing?
a) Discharge-elevation relationship of reservoir
b) Inflow-stage relationship of reservoir
c) Outflow-elevation relationship of spillway
d) Volume-elevation relationship of spillway

Explanation: For conducting reservoir routing, it is important to know the volume-elevation relationship of the reservoir and the outflow-elevation relationship for the outlet structures of the reservoir. Using this data, the effect of flood wave through the reservoir is studied to predict the required variations of reservoir elevation and outflow discharge with time.

7. Which of the following is not an application of reservoir routing?
a) Design of spillway capacity
b) Fixing location of reservoir
c) Selecting the size of reservoir
d) Cost-benefit analysis of reservoir

Explanation: Studying the effect of a flood wave passing through a reservoir through reservoir routing has the following applications – Design of capacity of spillway and other outlet structures of reservoir, deciding the location, size and capacity of reservoir to meet specific requirements.

8. Channel routing is used in flood forecasting by predicting the changes in shape of a flood hydrograph at different downstream point in a river.
a) True
b) False

Explanation: Channel routing is a type of flood routing where the shape of flood hydrograph is studied as it passes down a channel. An input hydrograph is considered at an upstream section. The data obtained on flood peak attenuation and elevation levels is used in flood forecasting and flood protection works.

9. How many basic equations does hydrologic flood routing use?
a) 1
b) 2
c) 3
d) 4

Explanation: Hydrologic flood routing essentially requires the use of only one equation, that is the continuity equation. On the other hand, hydraulic routing requires the use of two basic equations, collectively known as St. Venant equations.

10. Which of the following is not true with respect to hydraulic routing?
a) Simple and accurate method
b) Equation of motion of unsteady flow is required
c) Complex method
d) Use of high speed computers required

Explanation: Hydraulic routing methods require the use of both continuity equation and equation of motion of unsteady flow. It is a complex but accurate method which requires use of computers with advanced programming languages.

Sanfoundry Global Education & Learning Series – Engineering Hydrology.

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