The flow in a very wide channel tends to a freefall at which the depth is reduced to 0.67 times the normal depth. The channel conveys a specific discharge of 4  /s and has a bed slope of 10 cm/km....

The flow in a very wide channel tends to a freefall at which the depth is reduced to 0.67 times the normal depth. The channel conveys a specific discharge of 4
 /s and has a bed slope of 10 cm/km. Estimate the distance upstream of the fall where the water depth is 0.9 times the normal depth. Take the Manning coefficient as 0.025 and use the step-by-step method.