The stream order function is used to classify rivers and assign numbers to the extracted raster river system based on stream order. SuperMap currently supports two classification methods: the Strahler method and the Shreve method.

Strahler Stream Order Method

The Strahler stream order method was proposed by Strahler in 1957. Its rules are defined as follows: Streams originating directly from sources are classified as first-order; when two streams of the same order converge, the resulting stream's order increases by 1; when two streams of different orders converge, the resulting stream retains the higher order of the two.

The Strahler method is the most common stream classification approach. However, since it only increases the order when streams of the same level converge, this method preserves the highest-order connections while not accounting for all links in the drainage network.

Strahler classification method

Shreve Stream Order Method

The Shreve stream order method was proposed by Shreve in 1966. Its rules are defined as follows: Streams originating from sources are classified as first-order; the order of a converged stream equals the sum of its two tributaries' orders. For example, two first-order streams converging form a second-order stream, while a second-order and a third-order stream converging form a fifth-order stream.

The Shreve method considers all links in the drainage network, where the magnitude of a link actually represents the number of upstream links.

Shreve classification method