Network width

• For a description of what the network width is and how RivEX calculates it, click here.  The rest of this page is about the operational use of RivEX for extracting network widths.

• RivEX can extract out the network width values of a network and store the results in a dbase file or send it directly to MS Excel.

• The whole river network is processed but the output is for each catchment, thus a large network with many catchments will generate a large number of tables\worksheets.

• To compute the network width you must complete the parameters section of the main interface and press Build to construct the dictionaries used to analyse the river network.

• Select the Analyse Network tab and tick the Network width check box.  The drop down to the right will activate and you must select the type of stepping distance used.

• If you choose Mean polyline length then the stepping distance will be calculated from the mean polyline length of the whole river network.

• If you choose Fixed distance then you will be asked the stepping distance in units of kilometres as shown below.

Note: Ensure your Data Frame Units are set correctly, especially if you have been displaying data which are in different projections (e.g. you were looking at Lat/Long but you are now processing a network in UTM).  The Data Frame remembers the last units and does not reset if you have cleared the contents and loaded new data.

• Click on Go! and you will then be ask to identify the catchment ID and distance from mouth fields as shown below.  These must exist. If they do not then cancel the dialog and build the fields.

• Once the process has finished, you will be asked where to direct the output as shown below.

• Select YES sends the output to MS Excel.  The Excel application will minimise when data transfer has completed, do not click on the window until this has happened!

• Select NO sends the output to the C:\RivEX\Output folder.  The number of dbase files created depends upon the number of catchments in your river network.  If your river network contains 1000 catchments then 1000 files will be generated!

• The file naming convention used is LayerName_CatchID_NetWidth.dbf.  For example if you processed a river network call riv and it contained 2 catchments with ID numbers 12 and 555 then two files will be created called riv_12_Netwidth.dbf and  riv_555_Netwidth.dbf.

• The output (dbase or Excel worksheet) will contain 2 fields for each catchment, Distance and count.

• The Mean polyline stepping distance is easy to identify it is simply the value in the first row of the distance field. In the example image below catchment 275 stepping distance is 1981.96.  Remember this value is calculated from the whole network and not the individual catchment which could potentially have quite a different mean polyline length.