What determines the directional flow of rivers in the US?
It is an irregular division of the US between the western side and the eastern side, and it is much closer to the Pacific coast. It is the point at which some rivers flow east and others flow west. On the Pacific side the rivers flow west or north or south. On the Atlantic side the rivers flow north or south or east. The continental divide is roughly contiguous with the Rocky Mountains.
Vor is an abbreviated form of VHF Omni-directional Range and is a kind of radio navigation system for aircraft that emanates two types of signals - one directional and the other a 360 degree radial omni-directional. The Phase comparison gives what radial you are on by the position of the needle while DME determines the distance based on timing. It kind of works like a GPS.
The major rivers in the US that are located west of the Great Divide are the Colorado, Colombia, American, Sacramento, Snake, and San Joaquin. The Great Divide is the natural boundary line separating waters that flow into the Atlantic Ocean or Gulf of Mexico from those that flow into the Pacific Ocean.