A 5.0 m wide rectangular channel carries a discharge of $10 \mathrm{~m}^3 / \mathrm{s}$ at a depth of 1.5 m under uniform flow. To produce critical flow conditions without affecting the upstream conditions, the channel bottom elevation should be raised (in m ) by _________ (rounded off to 2 decimal places).
Assume that there is no loss of head at the raise, kinetic energy correction factor is 1.0 , and acceleration due to gravity is $9.81 \mathrm{~m} / \mathrm{s}^2$.
A compound symmetrical open channel section as shown in the figure has a maximum of _______ critical depth(s).
Bm – Bottom width of main channel
Bf – Bottom width of flood channel
ym – Depth of main channel
y – Total depth of the channel
nm – Manning’s roughness of the main channel
nf – Manning’s roughness of the flood channel
The critical flow condition in a channel is given by _______.
[Note: 𝛼 – kinetic energy correction factor; 𝑄 – discharge; Ac – cross-sectional area of flow at critical flow condition; Tc – top width of flow at critical flow condition; 𝑔 – acceleration due to gravity]
The cross-section of a small river is sub-divided into seven segments of width 1.5 m each. The average depth, and velocity at different depths were measured during a field campaign at the middle of each segment width. The discharge computed by the velocity area method for the given data is _____ m3/s (round off to one decimal place).
| Segment | Average depth (D) (m) | Velocity (m/s) at 0.2D | Velocity (m/s) at 0.6D | Velocity (m/s) at 0.8D |
|---|---|---|---|---|
| 1 | 0.40 | -- | 0.40 | -- |
| 2 | 0.70 | 0.76 | -- | 0.70 |
| 3 | 1.20 | 1.19 | -- | 1.13 |
| 4 | 1.40 | 1.25 | -- | 1.10 |
| 5 | 1.10 | 1.13 | -- | 1.09 |
| 6 | 0.80 | 0.69 | -- | 0.65 |
| 7 | 0.45 | -- | 0.42 | -- |