The Stream Order function is used to rank the river, and the extracted Raster River System are numbered according to the river rank. SuperMap currently supports two grading methods: Strahler and Shreve.

Strahler Stream Order

The Strahler Stream Order method was proposed by Strahler in 1957. The rules are defined as follows: the river directly originating from the river source is a class 1 river; the grade of the river formed by the intersection of two rivers at the same level is increased by one grade; the grade of the river formed by the intersection of two rivers at different grades is equal to the higher grade of the original river.

Strahler method is the most common method for river network classification. However, because this method only raises the level when the same level intersects, this method only retains the level of the highest-level connector, and does not consider all the connectors of the drainage network.

Strahler's grading method

Shreve Stream Order

The Shreve Stream Order method was proposed by Shreve in 1966. The definition of the rule is that the grade of the river directly originating from the river source is grade 1, and the grade of the river formed by the confluence of two rivers is the sum of the grades of the two rivers. For example, two Class 1 rivers meet to form a Class 2 river, and a Class 2 river and a Class 3 river meet to form a Class 5 river.

The Shreve method considers all the connecting lines in the drainage network, and the magnitude of the connecting lines actually represents the number of upstream connecting lines.

Shreve grading method