Indirect Methods of River Gauging

Q. A current meter is used to measure the velocity at a certain depth in a flow cross-section . The date obtained is as follows-
then what are the number of revolutions corresponding to the velocity 0.35 m/s?

$\begin{array}{cc}\text{Number of}& \text{Velocity}\\ \text{revolutions}\left(s^{-1}\right)& \left(m/s\right)\\ 24& 0.3\\ 50& 0.6\end{array}$

1. 20
2. 35
3. 30
4. 40

Q. In a river, discharge is $173{\text{m}}^3/\text{s}$; water surface slope is 1 in 6000; and stage at the gauge station is $10.0m$. If during a flood, the stage at the gauge station is same and the water surface slope is 1 in 2000, the flood discharge in ${\text{m}}^3/\text{s}$, is approximately

1. 371
2. 100
3. 519
4. 300

Q. The number of revolutions of a current meter in 50 seconds were found to be 12 and 30 corresponding to the velocities of 0.25 and 0.46 m/s respectively. What velocity (in m/s) would be indicated by 50 revolutions of that current meter in one minute?

1. 0.42
2. 0.50
3. 0.60
4. 0.73

Q. How is the average velocity along the vertical in a wide stream obtained?

1. By averaging the velocities at 0.2 and 0.8 depth from surface.
2. By measuring velocity at 0.6 depth below the surface.
3. By measuring velocity at half the depth.
4. By measuring velocity at 0.1 times the depth below the surface.

Q. Two point method is used for measurement of velocity in a triangular channel having top width equal to 5 m and depth equal to 2 m. The measured velocities along the center line at 0.4 m, 1.5 m and 1.6 m below the surface are 0.8 m/s, 0.5 m/s and 0.4 m/s respectively. The discharge through the stream is

1. 6
2. 9
3. 10
4. 3

Q. The slope area method is extensively used in

1. development of rating curve
2. estimation of flood discharge based on high­ water marks
3. cases where shifting control exists
4. cases where back-water effect is present

Q. The stage-discharge relation in a river during the passage of flood is measured. If $q_f$ is the discharge at the same stage when water surface is falling and $q_r$ is the discharge at the same stage when water surface is rising, then

1. $q_f=q_r$
2. $q_f<q_r$
3. $q_f>q_r$
4. $\frac{q_f}{q_r}=\text{constant for all stages}$

Q. Calibration of a current meter for use, in channel flow measurement is done in a

1. wind tunnel
2. water tunnel
3. towing tank
4. flume

Q. The top width and depth of flow in a triangular channel are 3.5 m and 2 m respectively. The velocities at 0.4 m and 1.6 m vertically below the water surface of the channel are 0.8 m/s and 0.4 m/s respectively. Using two point method of velocity measurement, the discharge in the channel is

1. $1.3m^3/s$
2. $1.8m^3/s$
3. $2.1m^3/s$
4. $2.7m^3/s$

Q. A stilling well is required when the stage measurement is made by employing

1. Bubble gauge
2. Float gauge recorder
3. Vertical staff gauge
4. Inclined staff gauge

Q. In the case of large rivers, a number of equidistant vertical sections of the total width of flow are identified, for the purpose of finding the discharge on any day by numerical integration. On each section, the mean velocity is taken as the arithmetic average of two typical depths on that section. Then the mean velocity is worked out for that section. Usually, the mean velocity of any section, corresponds to which one of the following? (V represents the point velocity at the given section and the depth such as $0.1d,0.2d\cdots etc.$

1. $\frac{V_{0.1d}+V_{0.9d}}{2}$
2. $\frac{V_{0.2d}+V_{0.8d}}{2}$
3. $\frac{V_{0.3d}+V_{0.7d}}{2}$
4. $\frac{V_{0.4d}+V_{0.6d}}{2}$

Q. In a river carrying a discharge of $142m^3/s$ , the stage at a station A was 3.6 m and the water surface slope was 1in 6000. If during a flood, the stage at A was 3.6m and the water surface slope was 1 in 3000, what was the flood discharge (approximately)?

1. $284m^3/s$
2. $200m^3/s$
3. $164m^3/s$
4. $96m^3/s$