Identifying Pipe Network Connectivity Issues with Map Topology in Civil 3D/Map 3D 2020

August 23, 2019 Randy McCollum

For a small pipe network, you might be able to tell it is fully connected and logically flowing in the right direction just by doing a simple visual inspection of the drawing.  But what if you are tasked with verifying the connectivity of a storm/sanitary pipe network for an entire community?  Consider the sanitary sewer map below.


It would take hours, if not days, to inspect the entire network for connectivity issues and determine all the issues that could exist within this map.  Luckily, AutoCAD Map 3D (and Civil 3D) can determine this on a mass scale using Topology.

Before we create a topology, we must recognize two things:

  1. Because this is a gravity network, the logical flow direction of each pipe (called “links”) should all have been drawn upstream to downstream or vice/versa. If the pipes where drawn haphazardly with no thought as to the direction of flow, then the analysis will require considerably more work to correct.
  2. Each pipe “link” endpoint must be connected to one “node”. In this case, our manholes will serve as our “nodes” and the pipes will serve as our “links”.

02From either Map 3D or Civil 3D, go the Planning and Analysis workspace.


From the Create tab, go to the Topology panel and select New.  This will open a new dialog window.


From the Create Topology dialog box, on the right hand side, select the radio button next to Network.  Give the topology a name and click “Next”.


In the next two windows, select the layers upon which the links and nodes reside.


Lastly, on the “Create New Nodes” tab.  Select a point style and layer upon which Civil 3D will place additional nodes if your network topology is incomplete.  Click “Finish” to save your topology.

With the Advanced Properties panel open, select one of your pipes.  Scroll to the bottom of the properties panel with that pipe selection and you will see a new section called “Topo”.  By default, the pipes were drawn in the direction of flow from upstream to downstream.  Therefore, select all of the pipes at once and change the flow direction value from “Bi-direction” to “Forward”.


As soon as you click Finish, by default AutoCAD will load this newly created network topology into memory.  Go to the Analyze tab, Drawing Object panel and click Network Analysis to run this analysis.


In the Network Topology Analysis window, select a “Flood Trace” analysis and click “Next”.   Select the tributary point that you wish to start from.


Lastly, map the link flow direction before launching the analysis by pressing “Finish”. 


The analysis will go downstream and highlight the network in red until it reaches a point past which it is not able to flow.  In this example, if we zoom in to see why the analysis failed, can clearly see the there is a connection that is missing between two manholes.  Once we correct this geometry and rerun the analysis, we should be able to confirm that this reach is valid and properly connected.



About the Author

Randy McCollum

Civil Solutions Applications Expert<br><br>As a professionally licensed civil engineer Randy provides training, process optimization, and technical support in water resource and site designs. His involvements include a wide range of product types including AutoCAD, Civil 3D, Map 3D, Autodesk Storm and Sanitary Analysis, Raster Design, and Infraworks.

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