Check Strahler and click OK. Progress can be followed in the status bar. Large networks will have large topological dictionaries and will take longer to process.

Strahler order

RivEX implements a fast recursive algorithm to calculate Strahler stream order, stream segments and can dealing with multi-channelled networks.  The algorithm that RivEX implements was developed by Gleyzer et al., 2004 and is documented in the Journal of the American Water Resources Association.  Click here to visit the web page for this paper.

The output of a Strahler stream order are two new fields in the river networks attribute table: Strahler and Segment.

The difference between Strahler and segment is best described in the images below.

This network achieves 3rd Order

Here are the same polylines encoded as segments, one segment for each Strahler reach

Stahler Order

Strahler segment

It is possible for RivEX to produce ZERO value stream orders, these are the results of polylines pointing from a mouth to source direction.  To deal with these you must:

oFlip the polyline.

oRebuild from- and to- node fields

oRe-run the stream ordering

Click here to be shown how to flip a single polyline.

Warning To apply stream ordering on artificial grid-like channels can produce some very strange results and should be interpreted with extreme caution.