Stream Order function

Available with Spatial Analyst license.

Overview

Creates a raster layer that assigns a numeric order to segments of a raster representing branches of a linear network.

For more information, see the How Stream Order works topic.

This is a global raster function.

Notes

The output of the Stream Order function will be of higher quality if the input stream raster layer and input flow direction raster layer are derived from the same surface. If the stream raster is derived from a rasterized streams dataset, the output may not be usable because, on a cell-by-cell basis, the direction will not correspond with the location of stream cells.

The results of the Flow Accumulation function can be used to create a raster stream network by applying a threshold value to select cells with a high accumulated flow. For example, cells that have more than 100 cells flowing into them are used to define the stream network. Use the Con or Set Null function to create a stream network raster where flow accumulation values of 100 or greater go to one, and the remainder are put to the background (NoData). The resulting stream network can be used in the Stream Order function.

This function only supports a D8 input flow direction raster layer. D8 flow directions can be created using the Flow Direction function and run with the default flow direction type D8.

Parameters

Parameter name	Description
Stream Raster	An input stream raster that represents a linear stream network.
Flow Direction Raster	The input raster that shows the direction of flow out of each cell. The flow direction raster can be created by running the Flow Direction function.
Order Method	The method used for assigning stream order. STRAHLER—The method of stream ordering proposed by Strahler in 1952. Stream order only increases when streams of the same order intersect. The intersection of a first-order and second-order link will remain a second-order link, rather than creating a third-order link. This is the default. SHREVE—The method of stream ordering by magnitude, proposed by Shreve in 1967. All links with no tributaries are assigned a magnitude (order) of one. Magnitudes are additive downslope. When two links intersect, their magnitudes are added and assigned to the downslope link.