Running a 1D-2D urban drainage simulation

Step-by-step guide

In InfoWorks ICM, direct rainfall modelling allows time-varying rainfall to be applied directly onto the 2D mesh to assess its drainage mechanism and potential storage on the surface.

This example applies a 2D infiltration surface type, runs a simulation, and analyzes the results.

1. Select Open transportable database.
2. Navigate to the downloaded files folder, and select Run_1D_2D_Urb_Drng_Sim.icmt.
3. Click Open.
4. If a popup appears about opening the database as read-only, click Yes.
5. In the transportable database window, right-click the top-level folder and select Copy.
6. In the popup, click Continue.
7. Right-click the Database and select Paste (with children).
8. Double-click 1D/2D Sewer Model to open it on the GeoPlan.

By default, a 2D zone with no information in the Infiltration surface field produces 100% runoff.

For this model, configure a 60% fixed runoff:

9. On the GeoPlan, select the 2D zone.
10. From the Windows toolbar, expand the Grid windows drop-down and select New polygons window.

11. In the polygons window, open the Infiltration surface (2D) tab.
12. Add a new surface ID of “Rural Area”.
13. Set the Infiltration type to Fixed.
14. Set the Fixed runoff coefficient to 0.6.

15. In the 2D Zone Properties window, in the Infiltration surface drop-down, select Rural Area.

16. Validate the network.
17. Click Commit changes to database.
18. Add a comment, such as "Infiltration setup".
19. Click OK.

Now, run the simulation:

20. From the Database, right-click the Model Group and select New InfoWorks > Run.

In the Run window, set the following parameters:

21. Set the Run title to Initial 1D2D Run.
22. From the Database, drag 1D/2D Sewer Model and drop it into the InfoWorks Network box.
23. From the Database, drag 10yr Design, Wastewater Profile, and Trade Profile, and drop them into their respective Rainfall event, Waste water, and Trade waste boxes.
24. Set the Timestep(s) to 5.
25. Set the Results timestep multiplier to 60.
26. Set the Duration to 6 hours.
27. Click Run simulations.

28. In the Schedule Job(s) dialog box, click OK.
29. From the Window menu, select Job control window to display the status of scheduled simulation jobs.
30. In the Explorer window, the Job Progress tab can also be selected to monitor information related to the 1D and 2D simulation engines.

The Job Control window shows the simulation complete, with warnings.

To investigate the warnings further:

31. In the Database, expand Initial 1D2D Run.
32. Right-click the M10-240 simulation icon and select Open as
33. In the Select Results popup, click Log results (text).
34. Click OK.
35. Inspect the log report—especially the volume balance summary—to ensure that the run was stable.

The volume balance summary looks good, but the warning relates to flow limiting having occurred. The node locations can be inspected in more detail once the results are open.

36. In the Database, double-click the simulation icon to open the simulation results on the GeoPlan.
37. In the Windows toolbar, expand the Grid windows drop-down and select New node results window.

38. In the node results window, locate the Total cumulative limited volume column.
39. Right-click the column header and select Sort descending.

There are three nodes which have large volumes. Volume limiting is a numerical check to prevent the generation of flow between the 1D and 2D engines. It is not problematic but may indicate an area of instability in the model.

40. Right-click the left-hand column in line with the first node and click Select and find in GeoPlan.

The GeoPlan zooms to the node.

41. In the Results toolbar, click Graph Pick.
42. On the GeoPlan, click the node.
43. In the Graph dialog box, select Flow from 2D zone.

44. Click OK.

The graph has oscillating positive and negative flow, which is something to try to avoid, especially in areas of interest. For this model, running at a 1 second timestep will stabilize the flow, but at the cost of increased simulation time.

45. From the Replay Control toolbar, click Show maxima.
46. To help visualize the results, from the Database, drag the pre-saved 1D2D Results theme onto the results.

To adjust the theme:

47. Right-click the model results and select Properties & Themes.
48. In the GeoPlan Properties and Themes dialog box, in the 2D zone row, Themes column, click Edit.
49. For the speed2d sub-theme, ensure that arrows are enabled, so that the direction of the flow can be seen.

50. Click OK.
51. If any changes were made to the theme, in the GeoPlan Properties and Themes dialog box, click Save.
52. Click OK to return to the simulation results.
53. Continue to inspect the results using the themes and graphing tools.