Using Hydrology Tools

Civil 3D provides two very useful tools to help you analyze the drainage performance of your surface: Water Drop and Catchment. The Water Drop tool shows you the theoretical path of a drop of rain as it flows downhill from a location that you specify. By analyzing this path, you can determine the direction of flow and find low spots where water will stop flowing and begin to accumulate. A catchment shows you the area that drains to a point that you specify. This is helpful for stormwater management design, such as determining how large an inlet opening needs to be based on the size of the area contributing runoff to it.

To use the hydrology tools to analyze the design surface for the example project, follow these steps:

The Exercise File can be downloaded at the end of the article  

1. Open the drawing named Using Hydrology Tools.dwg located in the Chapter 18 class data folder. In this drawing, the feature line layers have been turned off. Also, a new surface named EG-FG Composite has been provided. This surface was made by creating a new surface and pasting EG and FG Final into it. The purpose of this surface is to enable the analysis of the entire project as though it has already been built.

2. Click the Analyze tab of the ribbon, and then click Flow PathsWater Drop. You are prompted to select a surface.
3. Press Enter to indicate that you would like to select the surface from a list. The Select A Surface dialog box opens.
4. Click EG-FG Composite, and then click OK. The Water Drop dialog box opens.
5. Click OK to close the Water Drop dialog box. In the left viewport, click a point within lot 29 near the road. A blue water drop path is drawn from lot 29, runs down the curb line, and then stops at the inlet near station 2+50 (0+080). You can see the path in the lowerright 3D viewport as well.
6. With the Select point: prompt still active, click a point near the southeast corner of lot 23. This water drop path travels toward the west along the curb line of Madison Lane. It ends at the inlet near station 7+25 (0+220) on Madison Lane.

7. Press Esc to clear the current command. On the Analyze tab of the ribbon, click CatchmentsCreate Catchment From Surface. You are prompted to specify a discharge point.
8. In the left viewport, use the Center object snap to choose the center of the red circle at the end of the second water drop path you created. The Create Catchment From Surface dialog box opens.
9. Select EG-FG Composite for Surface and click OK. A blue outline indicates the shape of the catchment area that drains to the inlet at the location you selected.

   Tips:Catchments are visible only in plan view, so you won’t see the catchment in the lowerright model view.

Analyzing Design Surfaces

• Using Surface Analysis
• Using Hydrology Tools
• Using a Quick Profile

Download Exercise File :

• Analyzing Design Surfaces - Metric     --- ( 14.02 MB )
• Analyzing Design Surfaces - Imperial  --- ( 13.73 MB )