To Calculate Surface Catchment Areas

1. Locate an area of interest in the drawing.
2. Optionally, perform the following steps:
   1. Click Analyze tabGround Data panelFlow Paths Water Drop Find.

      This command creates a polyline that represents the water drop path from a point on the selected region to the depression point in this region.

   2. Select the water drop path polyline, right-click, and choose Properties.
   3. In the Properties manager, under Geometry, navigate to the last vertex and copy and paste the X- and Y-coordinate values (comma-separated with no space) into a text file.
3. Click Analyze tabGround Data panelCatchments Catchment Area Find.
4. In the Catchment Area dialog box, click the Value column for the Catchment Layer property and click to select an existing layer, or create a layer in the Create Layer dialog box.
   BestPractice: It is useful to place the catchment region on a separate layer. Then you can control visual style elements, such as color and line types.
5. Click the Value column for the Catchment Object Type, and select a line type.
   Tip: If you select 2D Polyline, you can use the AutoCAD Area command on the catchment region. If you select 3D Polyline, you can use the level values of the polyline vertices for analysis.
6. Click the Value column for the Catchment Marker property, and specify whether you want to mark the catchment point.
7. Click in the Value column of the Catchment Marker Style property, and then select a style in the Catchment Marker Style dialog box. Click OK.
8. If more than one surface is available in the drawing, click the surface on which to perform the catchment region analysis, or press Enter to select a surface in the Select A Surface dialog box.
9. Specify a valley line. You can either paste the coordinates that you copied in Step 2 or click in the desired location.

   The catchment region boundary appears on the drawing, and the value of the region area displays at the command line.