Question

Question 2 a. A new gauging station in a rectangular 30m wide channel requires the construction of a broad crested weir with a sill height of 1.8m. The channel slope is 0.002 and has a Manning coefficient of 0.04. The discharge rate in the river is approximately 500m'/s and the equation for the weir is 0.1.705CoBh3 where the discharge coefficient is 0.88.
Determine the critical and norrnal depth of the channel.
ii. Determine the depth over the weir.
(5)
(2)
iii. Using the gradually vaned flow equation with 4 intervals compute the backwater profile behind the weir up to the point where the channel retums to normal depth and determine how far upstrearn this occurs. (12)
iv. Produce a scaled drawing of the profile showing critical and normal depth.
(6)
Page 2 of 7

Answer 1