Using Catchment Area In Civil 3d 2009
In the world of land development, it is often helpful to
to accurately measure the area of drainage basins for both
pre-development and post-development conditions. This will
allow the designer to size storm drainage inlets and pipes
and to create a detention pond. AutoCAD Civil 3D offers a
simple tool to accomplish this.
The command is found under the Surfaces > Utilities pulldown
menu.
Once the command is launched, a dialog box will appear so
that the user can apply specific settings.
Catchment Layer is used to set the layer for the basin
outline the program is about to draw. It is often helpful to
set up beforehand two different layers for these outlines,
one for pre-development conditions and another for
post-development conditions.
Catchment Object Type specifies what kind of entity is going
to be used. The choices are 2D Polylines which are all drawn
at elevation zero and 3D Polylines which have elevations set
at each vertex from the surface used to draw the object.
Catchment Marker simply specifies whether or not a marker is
used at the downstream (or catchment) point and Catchment
Marker Style dictates what style is applied to the marker. A
Marker Style can be set up to show a dot or an "X" or
virtually anything the designer wishes.
Once these settings are adjusted and OK is hit, the user may
now select any location on a surface and the catchment area
is drawn.
If desired, default settings for Layer, object type and
Marker can be adjusted for the user who does not want to
have to set them every time the utility is employed within a
specific drawing. Simply go the the Settings tab > Surfaces
collection > Commands then find Catchment Area. Right-click
then choose Edit Command Settings. The following dialog box
will appear where the default values can be set. Remember
that these can be adjusted in a drawing template so that all
new drawings can be pre-set with these adjustments.
Other considerations must be made for use in actual
design, including any contributing areas from beyond the
coverage of the surface, C-factors and time of
concentration. A good tool to use for calculating time of
concentration is the Water Drop utility found just above the
Catchment Area command on the Surfaces pulldown menu. I have
written an article on this topic found here:
http://newsletters.hagerman.com/newsletters/ebul64-CIVIL.htm
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