Calculating Best Hydraulic Section for Composite Channel - Flow Rate 6.5(m^3/s)

[fonseh]

Homework Statement

Determine the depth of the flow of channel if the best hydraulic channel is needd for composite channel in figure to convey flow rate of 6.5(m^3/s) , Manning coefficient n on bed slope are 0.015 and 0.0015 respectively .

Homework Equations

The Attempt at a Solution

I assume the total flow rate of composite channel is 6.5(m^3/s) .. so From the table , i gt z = 1 / sqrt(3) , A = (sqrt(3) + 2 ) (y^2) = 3.73(y^2)
P = 4y +2sqrt(2) = 6.83 y
So , From manning equation , Q = (1/n)(A)(R^(2/3))(sqrt bed slope) ,

so , n = 0.015 , bed slope = 0.0015 , i found that y = 2.4 , is my ans and concept correct ?

 

[fonseh]

Anyone can try to help ?