<P> Where tributaries have the same name as the river into which they feed, they are called forks . These are typically designated by compass direction . For example, the American River receives flow from its North, Middle, and South forks . The Chicago River's North Branch has the East, West, and Middle Fork; the South Branch has its South Fork, and used to have a West Fork as well (now filled in). </P> <P> Forks are sometimes designated as right or left . Here, the "handedness" is from the point of view of an observer facing upstream . For instance, Steer Creek has a left tributary which is called Right Fork Steer Creek . </P> <P> Tributaries are sometimes listed starting with those nearest to the source of the river and ending with those nearest to the mouth of the river . The Strahler Stream Order examines the arrangement of tributaries in a hierarchy of first, second, third, and higher orders, with the first - order tributary being typically the least in size . For example, a second - order tributary would be the result of two or more first - order tributaries combining to form the second - order tributary . </P> <P> Another method is to list tributaries from mouth to source, in the form of a tree structure, stored as a tree data structure . </P>

Whats the difference between a river and creek