Example 1

Water flows in an open channel of trapezoidal cross section with a velocity of 0.9m/s at a rate . The bed slope and side slopes are 1:2500 and 1:1 respectively. Find the depth and bottom width of the channel. Take Chezy's constant as 40.4.

Given that,
Discharge,   ;       Velocity, ;       Bed slope, ;       Side slope,
Area of the flow,       
By Chezy's formula,
The area of the flow and wetted perimeter for a trapezoidal section is given by,
                        
By definition of hydraulic radius,