(Solved): A trapezoidal channel, with vertical sides, has the geometry shown in the fig ...

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A trapezoidal channel, with vertical sides, has the geometry shown in the figure below. The bed slope is 1 in 500 . Local engineers need to undertake repair works on the channel. The proposed materials to be used are smooth conerete and brickwork. The engineers wish to ensure that the height of the water in the channel, outside of storm surges, never exceed the depth of the trapezoidal section of the pipe, and the design flow rate for normal operations is \( 80 m^{3} s^{-1} \). (a) Using the appropiate Manning's coefficient for each material, state, with reasons, which of the two materials is mest suited to perform the reparir works required. Due to climate change, it is predicted that the required flow rate in the channel during extreme rainfall events will increase to \( 200 \mathrm{~m}^{3} \mathrm{~s}^{-1} \). (b) Check that the existing channel is of sufficient size to cope with the predicted increase in required capacity.