Creating catchments in Civil 3D

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In Civil 3D, after you have your InfoDrainage drawing set up and the manholes and pipes inserted,

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you can create the catchment areas.

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Each catchment object is comprised of a boundary and a flow path.

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You can either create catchments from the surface,

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or, as is the case in this exercise,

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you can create catchments from objects by copying and pasting polygon objects onto the existing surface.

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Open the file Catchments.dwg.

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These seven polygons represent seven subcatchment objects.

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Highlight all the subcatchments, then copy them to the clipboard.

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Then, paste the copied subcatchments into the current surface drawing.

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Be sure to use PASTEORIG so that the origins align and the subcatchments appear in the correct place.

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Next, you need to tell Civil 3D that these polygons are catchments.

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On the ribbon, Analyze tab, Ground Data panel, expand Catchments.

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There are a few options here, but for this exercise, select Create Catchment from Object

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since you already have the subcatchment areas created.

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In the drawing, you are prompted to, “Select polyline for catchment area boundary.”

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Place your cursor over the first polygon, and after it highlights, click to select it.

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Now you are prompted to “Select a polyline on the uphill end to use as a flow path (or press ESC to skip)”.

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For now, press ESC, since you can always create a flow path in InfoDrainage.

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The Create Catchment from Object dialog box appears.

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Here, you can choose to designate the manhole for the new catchment object

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by adding the reference pipe network structure.

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However, you could choose to perform this step in InfoDrainage.

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To do so here, click Select reference structure,

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and when you are prompted to select a pipe network structure,

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in the drawing, select Structure – (1).

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Back in the Create Catchment from Object dialog, click the Catchment tab.

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Set the Catchment style to Standard, set the Catchment label style to Name Only,

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and set the Flow segment label style to None.

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Click the Flow Path tab.

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For the Time of Concentration, use TR-55 for the calculation.

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But again, InfoDrainage has more detailed tools for flow paths,

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so you can accept the defaults here in Civil 3D.

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Click OK.

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Notice that the highlight color for the subcatchment changes to show that the manhole has been assigned.

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Also, the Command line reports the calculated 2D area of the new catchment.

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Repeat this process for other catchment areas,

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being careful to reference each of them to the correct structure.

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Save the file as Withcatchments.dwg.