![At the foot of a spillway, water flows at a depth of 23 cm with a velocity of 8.1 m/s, as shown in the figure](https://www.gkseries.com/blog/wp-content/uploads/2023/08/At-the-foot-of-a-spillway-water-flows-at-a-depth-of-23-cm-with-a-velocity-of-8.1-m-s-as-shown-in-the-figure.jpg)
Q. At the foot of a spillway, water flows at a depth of 23 cm with a velocity of 8.1 m/s, as shown in the figure.
![](https://www.gkseries.com/blog/wp-content/uploads/2023/08/Screenshot-475.png)
The flow enters as an M-3 profile in the long wide rectangular channel with bed slope = 1/1800 and Manning’s n = 0.015. A hydraulic jump is formed at a certain distance from the foot of the spillway. Assume the acceleration due to gravity, g = 9.81 m/s2. Just before the hydraulic jump, the depth of flow 𝑦1 (in m, round off to 2 decimal places) is
Solution:
Given, At a given section, y = 0.23 m and velocity (v) = 8.1 m/s
q (discharge per unit width) = 8.1 × 0.23 = 1.863 m2/s
Now, For a wide rectangular channel (B ≫≫ y)
A = B × y
P = B + 2y
![](https://www.gkseries.com/blog/wp-content/uploads/2023/08/Screenshot-476.png)