Question on cut/fill nomenclature

[GreeneSWCD]

I'm drawing some shallow excavated wetlands.  My plan of attack is to draw a circular shape, turn that polygon into a feature line, lay the feature line on the existing surface, then grade that line down to a designed depth on a 10:1 slope.  It works fine, but when I put in 10:1 for the "cut" and 6:1 for the "fill" slopes, I get a cut down to the designed depth but on a 6:1. 

Why does C3D think that this is a fill and not a cut? 

I'm using 2010. 

Thanks. 

[wfberry]

A normal section has a fill line that goes down and a cut line that goes up.

Bill

[BrianHailey · Accepted solution]

Cut and fill is relative to your target, not your beginning point. If you are above the target, you are in fill. If you're below the target you are in cut.

[Jeff_M]

Are you entering a positive or negative number for the depth?

[Neilw_05]

Something doesn't make sense here. From your description of the objective, you should be using a relative or absolute elevation for your grading target. An elevation target does not have cut or fill parameters, only depth or elevation and slope. Would you please clarify your approach?

[BrianHailey]

If the feature line isn't level, an elevation target can be cut and fill. Relative elevation is either or.

[Neilw_05]

I stand corrected. Thanks Brian.

[GreeneSWCD]

A little morre in depth:

1. I'm drawing the outside of the proposed pool area with a polyline to draw a polygon on the surface. 

2. Change the polyline into a feature line.

3. Lay the feature line on the existing surface.  (EG)

4. Click the feature line, click on grading creation tools

5. Toggle to "grade to elevation" and then hit the "create grading" button. 

6. Click the feature line.

7. Click on the inside of the circlular feature line. 

8.  Entire lenght, yes.

9. Elevation (key in proposed bottom of the wetland)

10. Cut format (grade/slope) "slope" enter

11. cut slope (10:1) enter

12. fill format (grade/slope) "slope" enter

13. fill slope (3:1) enter

Then it cuts down to the elevation on a 3:1 instead of a 10:1.  If I want to cut down on a 10:1, I need to transpose my number for fill and cut. 

Then I put an infill in inside of the toe of the slope at the proposed bottom of the wetland. 

From there, I take the original feature line laying on the surface, and the line at the toe of the slope down at proposed bottom elevation and "add those to surface as breaklines" on a new surface.  For volume, I just run the volume tool in the analyze tabe using the new surface compared to EG. 

These aren't hard little wetlands to draw, and I'm doing fine with just the little quirk with the cut/fill numbers, but it bothers me that the projected slopes are green instead of red on my drawings.  In my opinion, since the new surface is lower than the existing, it should be red signifying a cut.  My volumes come out as pure cut, and zero fill.  So the volumes tool is working properly for what I want it to do. 

Thanks for the help. 

[Neilw_05 · Accepted solution]

As Brian Hailey implied, if any part of your footprint featureline is ABOVE the target elevation it is treated as a fill condition (the grading must slope DOWN to the target). When using an elevation as a target, the existing ground is irrelevant in determining a cut or fill condition. Thus in your grading scenario, since the target elevation is lower than the footprint, the FILL SLOPE parameter will be applied. I think what is puzzling you is you expect it to be a cut scenario since the bottom of the pond is below the existing terrain. If you leave the ground surface model out of the equation it should make sense.

To help put the cut/fill condition in persepctive, think of a road that is traversing a terrain. If the road is above the terrain, the sides slopes will project down in a fill condition. That is what you have with your pond. Since the target is below the footprint, it is a fill condition.

HTH