Re-orientate network polylines

RivEX can re-orientate a network of polylines such that all polylines point in a source to sea direction. For this tool to work you need to provided a point layer of snapped mouth nodes. For each mouth node RivEX will travel upstream and if required flip a polylines direction.

Multi-threaded and loops	Single channel

Why can't this tool deal with bifurcations? The algorithm is not robust enough to deal with multi-threading channels and will fail to process them correctly. This is because the tool uses the topology (connectivity) of the network and a known starting point (the snapped mouth points) to traverse the network. There are scenarios such a drain linking across sub-catchments which mean that direction cannot be logically determined. Currently the algorithm is unable to flag which polylines are indeterminate.

In the image below the single channelled network has been re-orientated so all polylines flow in a source to sea direction, a prerequisite for Strahler stream order.