Ownership of rivers is a broad legal topic. The different ways by which we speak of rivers can confuse the layperson. In many jurisdictions and in certain situations property owners on both sides of a river each own the fee to the center of the river. Center lines of rivers form the boundaries of cities and states in many areas. The center of the river describes the limits to the property lines. The language used does not mean the abutters "own" the river. They own the land underneath it and their ownership is subject to the rights of the public to the use of the waters of the river. Federal and state laws govern rivers with federal law being the higher authority. "The public does not have a general right to cross private land to get to and from rivers, but such a right exists at traditional access routes . . . (according to) the legal doctrines of custom and prescription." You can study the many legal aspects of river use and public ownership at The National Organization for Rivers website provided below.
A canyon
Canyons are formed from running water. Very slowly but steadily, a river flowing through it carves it out.
A stream of water cutting through land is a river.
old river
river
The Rhine river flows through Europe, which is part of the Eurasian land mass.
Land drained by a river is a watershed. This is an area of land that feeds all the water running under it and draining off of it into a body of water.
A river.
Marine Land
a river
You could be referring to the River NIle
The flat land region running from Texas to Florida is the Gulf Coastal Plain. The flat to rolling topography is broken by many streams, river riparian areas, and marsh wetlands.