RivEX

Step

Processing Task

1

You have prepared your river network and added the required attribution to the network, in this example you have added Strahler and Shreve order.

2

The survey sites locations were chosen before you conducted the in-channel sampling.  The sites were captured as points aligned to the river network.  In this example the person who created your survey sites had done a poor job and not used snapping when capturing the site locations as points.  In this example we use the data as-is but in reality you would snap the sites to the river network and use the snapped data in subsequent processing.

3

Invertebrate Sampling Sites labelled with their site ID. At this scale it visually appears that all sites are aligned (snapped) to the network, a pre-requisite to using the Transfer network metrics tool.

4

The Transfer network metrics tool is completed as shown below, note the error log table will be added to the map if any errors were encountered.

5

The Transfer network metrics tool ran but warned you that the error log table was created and added to the map. Upon opening the attribute table of your sampling sites you observe sites 6, 7 and 9 have been given a -1 for Shreve and Strahler order. -1 is an indication of a failed transfer of the network metric.

Having observed these failed results, you open the error log table tblFailedSites_NetworkTransfer and it is immediately obvious why these 3 sites failed, they were not intersecting the network.

With only 3 sites failing the quickest solution is to edit your site data and move the point with snapping turned on.  If you had many sites fail then the best solution is to run your dataset through the snap sites to network tool then re-run the Transfer network metrics tool.

You have transferred the attributes Strahler and Shreve order, encoded into the river network, to your biological monitoring sites.  You can transfer other attributes such as catchment ID or distance from network mouth, in fact any other value encoded into your river network.  Such information may reveal further understanding in the biological make up of your sites.

You have seen the importance of preparing your site data and ensuring the sites are snapped to the river network.  If encountered, non-intersecting sites are excluded from analysis and in some cases will have a significant influence on the returned results.  You must always ensure sites are snapped to the network whilst avoiding tributary junctions (nodes).