Minimum slope

[GeoTrek]

i have a drainage ditch that i want to have a minimum slope of -0.8%. (no positive slopes but ok to have more than 0.8%- dont want to fill anything)

what is the best way to achieve this.

[TerryS]

From your description, it is difficult to tell what you are really trying to do. Is this an existing ditch to be be regraded? Is this a new ditch you are designing?

A typical approach would be:
1. Solve a profile of existing grades.
2. Create a proposed profile with desired grades.

In the Input/edit Profile routine, you can load the proposed file for editing and select the existing for a reference profle to view along with design.

[GeoTrek]

It is not an exisiting ditch. I am creating an interceptor ditch above pad to catch water and drain away from pad.

The criteria for ditch is min -0.8% grade (no positive grades) if it is more than 0.8% that is okay, we would not fill it.

I can do it manually on the profile but I was looking for something more automated do to the length of the ditch

[TerryS]

While the method I mentioned is still my preferred approach (use Profile to 3d polyline to draw the ditch and Design Pad Template to catch to existing TIN for top of bank).

You could also use 3d polyline tools to draw the ditch.
a. one approach would be to draw the polyline by snapping to an upstream and downstream surface grade and then just using MOVE to lower the 3dpoly to create a depth.

b. another approach would be to draw a 2d polyline and then convert it to 3d using "2d to 3d polyline by start-end elevations". One has the option of specifying a slope with this routine.

There are lots of ways of acheiving your goal with various tools in Carlson Civil. Be sure to check out "Edit polyline Vertex" as well. It gives you slope control of vertex elevation too.