They are all examples of land forms
The shape of a river channel can vary based on were it is located and what is around it the factors that control the shape of it is errioson from the water that passes through it, the vegitation that is growing around it, outside forces such as human impact, and things like sediment or other minerals that are passing through if murky water is passing through than it is more likely to leave behind minerals and dirt which could change the shape along with the other factors that i mentioned
