Active Topology Management

Product(s): WaterGEMS, Hammer, StormCAD, CivilStorm, WaterCAD, SewerCAD, SewerGEMS, PondPack
Version(s):  CONNECT Edition, V8i, V8 XM
Area: Layout and Data Input


The purpose of this TechNote is to discuss active topology management in the Bentley OpenFlows products. Additional information on active topology management can be found by opening the product, going to the Help documentation, and searching for Active Topology.


See bottom of article for a video demonstration.

In the analysis of the water or wastewater system, it may be helpful for the modeler to assess future (or past) configurations of the system. This can include not only a change in data at a node, but also may include additional nodes and pipes that do not currently exist in the current system. For this reason, a modeler may need to add elements to the existing model. However, when this is done, the new elements are present in each scenario, even those that should depict only the existing elements. It is in these situations that you would use Active Topology management.

Due to the way that the data is stored in the database file, it is not possible to physically add or remove elements from one scenario with affecting all of them. Active Topology management enables the user to create alternatives in which specific elements are present or not present. When the elements are inactive, they are not included in the network hydraulic calculations. Inactive elements are also not evaluated when displaying results, such as contour plots and profiles.

Modelers will typically choose to hide the inactive elements so that they disappear from scenarios where they aren't included. For example, in your current year scenario, pipes laid in the future don't show up at all and you still have the ability to color code. Then when you switch to your future conditions scenario, those pipes appear and can be color coded. Those things couldn't happen if we treated Is active? as a typical property, which is why the display of active topology is controlled in the Options dialog as explained further below.

Active Topology Alternative

The active or inactive status of an element is stored in the Active Topology Alternative. To open the Alternatives manager in CONNECT Edition, browse to the Home tab and choose Alternatives.

In V8i or V8 XM versions, browse to Analysis > Alternatives or click the Alternatives icon in the toolbar.

Expand the list of alternatives for Active Topology to view the available alternatives. There will be at least one active topology alternative available. To open the alternative, you can double-click on the alternative, or right-click it and select Open.

The dialog will include a tab for each element type. When you click on one of the tabs, a list of all of the elements of that type will be shown. There will be one editable column available: “Is Active?” If there is a checkmark for a given element, it means that the element is active in the model. If you unclick the box, the element will be inactive.

If you make an element inactive in the model (see section below), this change will be applied to the Active Topology Alternative associated with the scenario associated with it. An unlimited number of active topology alternatives can be created.

For the steps to create new scenarios and alternatives, see the Scenarios and Alternatives TechNote or the Help menu for your program.

Selecting inactive elements in the model

There are a number of ways to make an element active or inactive. Besides making the changes directly to the active topology alternative, there are items available in the individual element’s properties dialog or in the element FlexTable. In either of these, there is an item called “Is active?” You can make the element active or inactive by changing the value of this item.

There is another method available for making changes to the active topology of the model: the Active Topology Selection Tool. In both the CONNECT Edition and the V8i/V8 XM versioins, this can be accessed by going to Tools > Active Topology Selection.

Note: Changing the active status using this tool only affects the Active Topology Alternative of the current scenario. If you want to change the active status for a different scenario other than the current one, you will need to change scenarios first.

After select the Active Topology Selection Tool, a Select tool will open.

Selecting elements with this can make them active or inactive. By default, the Add icon is selected. When this is selected, you can choose elements individually or drag a box around it with your mouse. When they are selected, they will appear red on the drawing pane.


Note: items that are already inactive will also appear in red.

When you click the green checkmark in the Select tool, the items will be made inactive for the active scenario.

This tool also allows you to remove items, making them active again. If you select the Remove icon, when you select items in the drawing and select the green checkmark, the items will be active in the active scenario.

Active Topology by selection set, query and other selection methods

The Active Topology Selection tool also allows for more advanced methods of selecting items in the drawing. The “Select by Polygon” icon allows the user to draw a polygon on the drawing. Depending on whether the Add or Remove icon is selected, the elements within the polygon will be added or removed from active topology.

The Query icon allows the user to select elements in the model based on a preexisting selection set, a custom query, or from a number of standard queries.

Note: an alternative way to make elements active or inactive, is to filter the respective element flextable, then global edit the "is active" attribute.

The Find icon is helpful if you know which element you would like to make active or inactive, but do not know exactly where it is in the drawing. This will open a new dialog in which you can type the name of the element or choose from a list after selecting the icon in the upper right.

If you are selecting items and choose the wrong elements, you can choose the Clear icon on the right, which will clear all of the selections.

It is important to remember that changing the "is active" status using this tool only affects the Active Topology Alternative of the current scenario. If you want to change the active status for a different scenario other than the current one, you will need to change scenarios first.

Note: Selecting a node element to become Inactive will also select all adjacent pipes to become Inactive. This is because all pipes must end at a node.

Displaying Inactive Elements

Inactive elements are differentiated visually from Active ones in the main drawing pane. This is controlled in the Options menu found in the Tools pulldown.

Find the item “Display inactive topology.” If this is checked, the inactive elements will appear in the drawing pane as the color identified to the right of the “Display inactive topology” item. If this item is not checked, the inactive elements will not be displayed in the drawing pane at all.

Inactive elements will appear in FlexTables but calculated values will be set to N/A. Inactive elements are also available for inclusion in selection sets. If you do not want inactive elements to be displayed in the FlexTables or reports, you will need to filter the column "Is Active?" to only elements with the entry "True" are included.

Common procedures

The user can set up different active topology alternatives any number of ways. Different users may be more comfortable using one method over another. As you work with a model, you may end up using different methods for making certain elements active or inactive. Below are two possible instances.

Consider a situation where you have a model that has the current layout of the model elements. The scenario is called “Current Layout.” The base active topology alternative is called “Current active elements.”

You now would like to model a future scenario in which additional demand nodes are added to the right side of the model. In order to model this, you will need to create a new Active Topology alternative and a new scenario.

Create a new child Active Topology alternative called “Future active elements.” Then create a child scenario called “Future Layout.” Double-click on the scenario “Future Layout” to open the properties and set the active topology alternative to “Future active elements.” Then make “Future Layout” the current scenario.

Once this is complete, add the new elements to the model. Notice that they are active in the drawing pane.

Now change the scenario back to “Current Layout”. Notice that the new elements are now inactive. This is because the default setting when is inactive when the alternative cannot be identified by the active scenario.

Now consider a case where you add the future elements before creating the new scenario and active topology alternative for the future layout of the system. In this case, all of the elements are active in both scenarios.

You now want to make the elements in the red box in the screenshot above inactive. You can do this through the FlexTables or the properties of the individual elements, but the most efficient way to make these inactive would be to Active Topology Selection tool. Using one of the steps above, make the items in the red box above inactive.

The drawback to this method is that the same elements are inactive in the scenario “Future Layout” as well. This is because child alternatives inherit data from the base alternative. This can be fixed quickly by going to the “Future Layout” scenario and opening the Active Topology Selection tool again. The inactive elements will appear in red. Select the Remove icon and select the elements you want to make active. When you select the green checkmark, the will be active again. Switch back to the scenario “Current Layout” and you will see that the elements are still inactive in that scenario.

Active topology + Customer meter elements

When customer meters are attached to the pipes and you are making those pipes inactive using active topology, connected customer elements are still active in that case, which has been logged as a defect as of Connect Edition update 2, reference number is # 145793.

However, if there are other elements attached to pipe like hydrant it becomes inactive in the process along with the pipes, so it is just issue with the customer elements as of version and should be fixed in the future versions.


  • Select the inactive pipes, then run the “Find Associated Customer Meters” query.
  • Open customer meter flextable on that selection of customer meters, and global-edit to set Is Active false.


  • User notifications are generated when referenced pipes of customer elements become inactive
  • Right click on this error of customer meter, this should select all the related customer meters, right click in the drawing > Group Edit > Make the customer meters inactive.

 This should make the associated customer meters inactive as well.

See Also

How do I use and display Active Topology for elements on the ArcGIS/ArcMap platform?

Filter FlexTable to only show active elements