What if the width of the x-section isn't given.. Only depth, bed slope, n is given. And in question it is asked to estimate discharge. Its a rectangular channel.
I am currently working on a new hydraulics lesson series, using models and real world examples. The first part of the first lesson can be found here: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-EYvudBeHhWQ.html
It’s a good question, but it is fairly standard in hydraulics and (as far as I know) applied fluid dynamics. In hydraulics, u is normal the velocity in the primary direction and v in the secondary. So in the context of pipe flow, u would be velocity along the pipe and v across the pipe.
