Adding bridges to a river

Step-by-step guide

Bridges are critical structures in river modelling and can significantly influence hydraulics. Bridges in ICM have 5 sections:

• Contraction reach: Cross section upstream of the bridge
• US bridge section: Cross section directly upstream side of the bridge
• DS bridge section: Cross section directly downstream side of the bridge
• Expansion reach: Cross section downstream of the bridge
• Deck: Cross section of the bridge deck

Cross section lines are required for each of these sections. For this example, cross-section survey data has already been imported. To complete this exercise, open the transportable database .icmt file for this tutorial or continue from the previous lesson.

1. In the Explorer, under the Database, double-click the 1D River Model to open it on the GeoPlan.
2. In the GeoPlan Tools toolbar, click Find in GeoPlan.
3. In the Quick Find dialog box, in the Name field, type “16DECK”.
4. Click Find.

5. Once the deck is located, Close the Quick Find window.
6. From the GeoPlan Tools toolbar, expand the New Object Type combo box.
7. Select Link.

8. On the GeoPlan, draw a new link between the two break nodes, from upstream node 16!US to downstream node 17DS.

9. In the Create New Link popup, set the Type to Bridge.
10. Click OK.

In the Properties window for the new bridge link, inline validation errors appear against all of the empty section data.

11. Using the Select tool, on the GeoPlan, select the new bridge link.
12. From the Model menu, select Bridge > Build sections from lines.

The Bridge Operation report displays information on how it has associated the cross section data.

13. Close the report window.
14. From the Properties window, in the US link section data field, click the ellipsis (…) button to view the imported data.

The inline validation messages remain due to the missing roughness values.

The next step is to add bridge openings, so that water can flow through.

15. From the GeoPlan Tools toolbar, expand the New Object Type combo box.
16. Select Line.
17. Click Create New Object.
18. On the GeoPlan, draw a bridge opening downstream from left to right parallel to, or on top of, the bridge link—as close as you can to the center line.

Note: This line must extend slightly beyond both the upstream 16US and downstream 16DS cross sections.

19. Double click the final point to finish digitizing the line.
20. In the New Line popup, add the name “Opening_1”.
21. Set the Type to Bridge opening.
22. Click OK.

In the Properties window for the new Bridge opening, set the following parameters:

23. Set the Shape ID to RECT.
24. Set the Width to 23.000.
25. Set the Height to 1.200.
26. Set the Roughness Manning's n to 0.0110.
27. Set the Length to 22.1.
28. Set the US invert level to 32.762.
29. Set the DS invert level to 32.750.

The upstream and downstream invert levels are the same as those of the upstream and downstream bridge face cross sections.

There is still one validation error in the Bridge US node ID field.

To resolve this error, insert the opening into the bridge section:

30. On the GeoPlan, select the bridge link.
31. In the Properties window, under Bridge, enable the Skew openings and piers option.
32. Using the Select tool, on the GeoPlan, select both the bridge and the bridge opening.
33. From the Model menu, select Bridge > Insert selected openings into sections.

Notice that the opening is now trimmed to the bridge face cross sections.

The Bridge opening can now be viewed by going to the Bridge Properties window. There are roughness validation errors for the US bridge section data and DS bridge section data fields. There may also be another error, such as “d/s bed is at or above soffit of opening”. In this example, the error is on the DS bridge section data.

34. In the DS bridge section data field, click the ellipsis (…) button to open the Bridge section data window.
35. In the graph, make sure the bridge opening is within the channel.

In this example, the opening is not shown in the graph, which means that no flow will be transferred through the opening.

To fix the error, alter the opening position by first removing the old one, and then redefining it:

36. Remove the rows with entries in the Opening and Side columns by right-clicking and selecting Delete Row.

37. In the graph, locate the true left side of the opening.
38. In the table, find the corresponding row. Here, the row is at Offset 3.475 m.
39. For this row, expand the Opening drop-down and select Opening_1.
40. In the Side column, select Left.
41. Right-click the row ID and select Insert Row at Offset.
42. Since the bridge opening is 23 meters wide, add 23 to the amount in the popup field. In this case, change 3.475 to 26.475.

43. Click OK.
44. In the table, scroll down to the row with Offset value 26.475.
45. For the Opening column, select Opening_1.
46. In the Side column, select Right.

On the graph, the opening now appears in the new position, represented by a rectangle.

Now that the location of the bridge opening is placed properly within the cross sections, the next step is to build a boundary for the bridge.

47. From the Model menu, select Bridge > Build boundary from section ends.

This boundary signifies that the bridge is not meshed as part of any 2D meshing process and is the region that will be used for the flood theme.