I suppose they occur too slowly to actually catch them forming. You can identify sites where they are in process, but you’d need to take regular photographs over years to get a set of pictures that could show it happening. But then again, the river might simply not perform like the theory says it should.
Reality has the right not to subscribe to our expectations of it – especially if that is to fulfil our clever, ambitious ideas.
One of the threads that makes sense of Jesus’ actions in the gospel is to see how he punctured people’s ideas about him. Through his actions, his dialogue, he remained consistent to his own reality. When he said “I am the truth” he was explaining that he came to invite us into the real world. To enable us to remain in the physical and human world, as they say in geography, but at the same time enter into the kingdom of God.
And once the river of God starts to flow through you, you might start to fashion features like ox-bow lakes that make others scratch their heads in wonder.