Streamorder

Stream Order is a “top down” system of ordering streams as defined by Strahler (1957). The [streamorder] =1 are the outermost tributaries. If two flowlines of the same order merge, the resulting flowline is given a number that is one higher. If two flowlines with different stream orders merge, the resulting stream is given the higher of the two numbers.  Stream order provides an approximation of stream size and upstream drainage area, but is sensitive to changes in the scale of the cartographic source.