Typically it is the upper course of the river
The origin of the Mississippi River is Lake Itasca, in Minnesota. The origin of a river is also called its headwaters.
it was formed by rain falling
river channels are formed when river water erodes into a larger opening
V-shaped valleys The river channel - vertical erosion, shallow but a very fast flow Waterfalls Gorges(which are formed by waterfalls) Bedload is also very big and angular.
Deltas are formed from the deposition of the sediment carried by the river as the flow leaves the mouth of the river.
Oxbow lake are usually formed in flat, low-lying plains close to where the river empties into another body of water. They are usually stillwater lakes and often they become swamps or bogs, not potholes.
Fluvial Erosion
When run-off water from rain, lakes, homes, rivers and other forms of water pass through the limestone it causes potholes to form in the limestone regions.
Create, probably not, but they do make them worse, once they're formed.
Nothing
I don't know all of them (21 I think), but I can mention the Rimac in Lima, Urubamba in Cuzco and of course the Amazon river in the rainforest formed by the Marañon river and the Ucayali river.
The Grand Canyon was formed mainly due to the Colorado river, and also due to uplift pronouncing the scale of the canyon; it is not formed due to a delta, as deltas are only formed at the mouth of the river, not in its middle course.
The Nile river is formed by the Blue river and the White river. ~ You're Welcome
the congo basin was formed by tectonic plates.
Potholes in My Lawn was created in 1988.
Potholes are mechanical weathering
A river raft was formed by the water eroding the river time after time