Extracting network connectivity

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Use these tools to write the network connectivity to file geodatabase tables. These can be used in "relates" or imported into another application for subsequent analysis. The two available tools are:

Upstream and Downstream connectivity

Upstream segment identifier

Extract network connectivity dialog

Upstream and Downstream connectivity

RivEX can identify and store the adjacent polyline ID's for all the polylines in the network.  Adjacency is defined as polylines that connect to the nodes of the polyline in question.

The output are two tables stored in a file Geodatabase in the default output location (..\RivEX_Workspace\Output\fGDB_NetworkConnectivity.gdb). The two table names are Upstream_Polylines and Downstream_Polylines. Please note that these tables can be very large with large networks.

For polylines that are sources there will be no upstream polyline and thus are excluded from the table.  The same situation happens for polylines that are mouths where there are no downstream polylines.

Before writing to the Geodatabase, RivEX will delete any existing upstream/downstream tables generated by this process.

The table structure is ObjectID, PolylineID and either US_PolyID or DS_PolyID. In the screen shot below the polyline with ID 225884 has two upstream polylines flowing into it they are 26122 and 21828.

Upstream polyline table

Upstream segment identifier

RivEX can extract for each polyline all upstream polyline ID's.

This tool will generate very large tables for large river networks and will therefore take a long time to process such networks.

The Geodatabase (..\RivEX_Workspace\Output\fGDB_NetworkConnectivity.gdb) is populated with tables listing the polyline IDs.    Each table uses the naming convention Catch_XXX_Upstream_IDs where XXX is the catchment ID.

RivEX finishes by building an attribute index to optimise any future querying.

In the screen shot below polyline 53318 has been highlighted, it has 5 polylines upstream, this includes itself.

Upstream segment identifier table

In the image below, the network is colour coded by catchment ID. Catchment ID was generated with the force longest route option turned on and we see the majority of the network is coloured blue whilst a small drain is coloured brown as it flows to an unconnected mouth (the magenta coloured node).  The furthest source is indicated by the red node and the arrow indicates the node at which the drain connects to the main catchment.

Incorrect processing

Upstream of the arrow, are the polylines part of the blue or brown segment ID tables?  The answer is both as the segment ID tables are only storing topological information and use the catchment ID as a convenient method of grouping the data.  Thus all polylines  upstream of the arrow appear in both segment ID tables.  If a survey site happened to be on the the brown drain then it's segment ID tables would allow you to search upstream to the source of the river and not terminate at the arrow.