Designing ponds

Step-by-step:

When a catchment is overlaid with an impermeable surface, such as concrete or tarmac, it will create more (and faster) runoff. A traditional solution to this problem is to build a storage or attenuation structure (i.e., a pond) upstream of the discharge point, store the water there, and release it slowly into the receiving watercourse.

1. In the model, double-click pipe 016 to open the Connections dialog box and view its attributes.
2. Note the Upstream Cover Elevation for the selected pipe.
   
3. Close the Connections dialog box.
4. In the Tree View, right-click the Surface node and select Load Surface.
5. In the Surface Data dialog box, click Load From.
6. Select the surface data file import surface trimmed.iddx and click Open.
7. A notification appears, asking if you want to update all or keep all existing surface data, or manually maintain specific levels. Select Keep All.
8. In the Tree View, toggle the visibility of the Surface node.
   
   
9. To remove the pipe where the pond is to be located, in the model, with the Select tool active, click pipe 015.
   
10. Press DELETE to delete the pipe.
11. To import the CAD drawing of the pond, in the Tree View, right-click the CAD Data node and select Import Data.
12. In the Load CAD Wizard, click Select.
13. Select the file pond outline.dwg and open it.
    
14. In the Load CAD Wizard, click Next. Note that the imported data includes multiple layers.

The Load CAD Wizard showing a preview of the pond outline as it will appear in the InfoDrainage model once it is imported, and the Finish button called out.

15. Click Finish.
16. On the ribbon, click the Plan tab and select Snap mode to enable it.
17. In the Toolbox, expand the Stormwater Controls node to see a list of control systems.
18. Click and drag the Pond option into the Plan View and drop it into the polygon representing the pond outline.
19. Click each of the polygon’s vertices, then right-click anywhere inside the polygon to finish it.
    
20. In the model, double-click the Pond icon to view its attributes in the Pond dialog box.
    
21. In the Pond dialog box, set the pond’s Exceedance level to 32.309 (the Upstream Cover Elevation from step 2.)
22. Set the Freeboard to 200 mm.
23. Toggle ON the Depth field.
24. Enter a Base Level (Elevation) of 30.434.
25. In the Depth (m) column, enter a depth of 1.875 (the pond’s exceedance level minus its base level) into the second row, and press ENTER.
26. Copy and paste the Area value of 449.43 from the first row into the second row and press ENTER.
    
27. Open the Sizing Calculator.
28. Expand the Method drop-down and click Side Slope.
29. Enter a Side Slope value of 4.
30. In the Maintain drop-down, ensure Top Area is selected.
31. Click OK to close the Sizing Calculator.
    
32. Click OK to close the Pond dialog box.

The pond updates in the Plan View to include a dashed line that represents its base area.

33. Double-click the Pond icon to reopen the Pond dialog box.
34. Click the Advanced tab.
35. Enter a Manning’s n value of 0.030.
    
36. Click OK to close the Pond dialog box.