Why does waves only occurs on seas and not on the rivers?

Answer 1

I can't be certain where you got this question, but I'm currently sitting twenty feet from a small lake with a surface covered by waves. These waves are not crashing on the shoreline, but are waves nonetheless. I live 30 miles from Lake Michigan, a much larger lake mind you, where the waves at times do crash upon the shoreline, and having lived 5 miles from the Pacific Ocean, I can attest that Lake Michigan's waves can at times be as or more impressive than the world's largest ocean.

As far as rivers, I live within 10 miles of the largest river in Michigan. It isn't as impressive as the Mississippi or other major rivers of the world, but even tiny, little Grand River gets waves. Most of these are caused by wind, but down stream there are some smaller rapids that cause waves to form. As far as streams, well same thing on an even smaller scale.

Answer 2

Ocean waves are the result of large masses of water conducting a wave of energy through a fluid. Rivers are fluid which is in motion. The motion prevents any wave from forming.

Answer 3

They do.