3.5. Network following tools

3.5.1. Refresh network topology

• Before using the network following tools, be sure that your network topology is updated

• To refresh the network topology, click the Refresh network topology tool (Button with SQL and drip)

• If ok, there is a message: Success: Network successfully updated

3.5.2. Upstream

• It does not matter, which layer is selected

• To start upstream network following select the Upstream TWW button

• TWW opens then profile window at the bottom of the map. Click on your start node.

• If there is more than one node in this area, you choose the one you want form the mouse-list

• After a few seconds all upstream reaches will be highlighted and you can see where the water is coming from.

• If you want to select the highlighted reaches, then click on the Select current path button in the profile window

• You can now work with your reach selection in the attribute table or zoom to the selected reaches (if the vw_tww_reach layer is selected)

• Use this tool to check if the topology of your network is correct.

Note

In the button select current path, you have a menu Configure Select. This feature is not working with the actual twwplugin.

3.5.3. Downstream

• Downstream network following works similar as the Upstream network following described above.

• You can see where the water is going to.

• Control, if TWW finds also the overflows

• Use this to check whether the topology of your network is correct or to find out where you could intervene in case of an accident.

3.5.4. Sum up upstream

• This is a tool in the TWW-toolbox.

• The idea for this tool is to sum up a value over the whole network of channels, e.g. the flowtime for each point to the outlet of the network.

• For this tool you need a field in the layer vw_tww_reach with the values to sum up. Because interesting values are normally not part of this layer, you have first to join the value-field (e.g flowtime or flow rate) to the layer vw_tww_reach.

• As example look at this small network, labeled with reach-identifier, length and flow direction arrow

• We need a table (in the example called sum up tool) with at least two fields: field identifier for the join and field flow rate (in the example in [m/s]) to sum up.

• Open the properties of layer vw_tww_reach, choose Joins and Add new join (green + Button) and define the join with the join field (identifier) and the joined fields (field to sum up).

• Start the tool with double-click one Sum up upstream

• In the window you have to enter/to choose

  • an expression as shown in the title of the field (COALESCE(“field_name”,0). If you do not use the coalesce command, you will get an error when running the tool and there are NULL-values in the field to sum up. In the figure is as example the calculation for the flow time in [minutes], calculated with length effective and the flow rate in [m/s].

  • the branch behavior (Minimum, Maximum, Average): which value will be used after when two branches join to continue the summing.

  • the advanced parameters are preconfigured for TWW and should not need to be changed.

  • Summed up: if you let this field empty, there will be a temporary point layer with the results in your project. Otherwise you can save the results to a new point vector layer.

The resulting point-vector layer has the fields of the vw_wastewater_node layer and an additional field value with the sum for each wastewater node. * In the figure below you see the result of the example with all three branch behaviors: minimum = normal style, maximum = bold, average = underscored

3.5.5. Flow times downstream

• This is a tool in the TWW-toolbox.

• The idea for this tool is to get the flowtime between a startpoint (where e.g.is an accident) and an interesting wastewater structure downstreams. It is not the idea to create a flowtime plan for a whole network with this tool (use the SumUpTool_ tool for this task).

• For this tool you need a layer (table) in the TWW-project with the flowtime per reach and the obj_id of the reach.

• You have to select the start-reach (where the accident is) in the vw_tww_reach-layer

• Start the tool with double-click one Flow times downstream

• In the window you have to choose

  • as reach layer: vw_tww_reach

  • as flow time layer: your table with the reach obj_id and the flowtimes (or the values you want to sum-up downstream)

  • as reach id field: the field in your table that is the obj_id of the reach

  • as Flow times field: the field in your table, that you want to sum-up

  • as Flow times: if you let this field empty, there will be a temporary file with the results in your projects. Otherwise you can save the results to a vector layer.

• The tool makes a downstream network search starting with the selected reach and creates for every reach a record in the (temporary) vector layer with just one field (the sum of the Flow times).

Attention

If there is more than one downstream-way, the results are wrong after the branch.

• There are some cases, where you get an empty flow time-Layer and red (error) text in the Log-window:

  • Do not select more than one reach to start

  • Do not select vw_tww_reach as flow time layer (to sum-up the length, use the vw_network_segment layer)

  • If the reach id field has no values that match the reach obj_id, you will also get an error