Not updating digital terrain map

Jim,
Here is the question we discussed earlier today:

I've drawn in new contours to represent levees on both sides of the
creek. The layer is in "use" under Elevation Layers, it shows up like I
want it to when I check the elevation of the contours I drew, it even
works as it is supposed to by holding the water in on the cross-sections
when I run the analysis.

The problem occurs when I run the Floodplain Map Results. The program
is not recognizing the additional contours for this function. When I
use Track Surface it does not give me the correct elevation in the areas
of the new contours. Is there something I need to do to activate these
additional contours that I'm not doing yet?

Any information you can give me to shed light on the situation would be
appreciated.

Thanks,
John A. Simcik, E.I.T.

Dear John :

This is discussed in the new RCAD 2000 User Manual. However, it is fairly easy to explain.

When RCAD generates a floodplain map, it only creates the ground digital terrain model once. This is because the ground terrain does not typically change. However, if you add contours to designate a levee, then the ground digital terrain model needs to updated. This is done by selecting "Always Regenerate Topo Surface" from the Floodplain Map Results dialog box. This will remedy the problem you are experiencing.

If you have any additional questions or need any further information, please contact me again.

Sincerely,

Chris E. Maeder, M.S.
Senior Technical Engineer
chris.maeder@bossintl.com

Chris,

Thanks for responding to my question. However, I have been using the "Always
Regenerate Topo Surface" function and it is not curing the problem. Do you have
any other suggestions?

Thanks,
John A. Simcik, E.I.T.

Dear John :

Umm.... It should work. Did you identify what layers the new contours are on? You need to select Modules | Configure | Elevation Layers, which will display the Configure Elevation Layers dialog box. Then, make certain to mark USE for the all the layers that contain elevation data.

Note, also, that the digital terrain model can get confused if you have overlapping elevation contours--such as original topography and proposed topography. You will need to merge the elevation data such that there is no overlapping elevation data prior to performing the floodplain mapping. Otherwise, RiverCAD will not be able to make sense out of what the "true" ground terrain is supposed to look like.

If you have any additional questions or need any further information, please contact me again.

Sincerely,

Chris E. Maeder, M.S.
Senior Technical Engineer
chris.maeder@bossintl.com

Chris,

I think you may have identified my problem: merging the existing with the
proposed topo. What exactly do I need to do to merge the two?

Thanks,
John A. Simcik, E.I.T.

Dear John :

To have a single terrain model, try to identify which contours are obsolete, and then delete these contours. You don't want the contours to overlap--this really messes with the digital terrain model.

If you have any additional questions or need any further information, please contact me again.

Sincerely,

Chris E. Maeder, M.S.
Senior Technical Engineer
chris.maeder@bossintl.com

Is that all there is to "merging" proposed and existing contours? The program
still refuses to update the topo map.

Dear John :

There is an old saying, garbage in is garbage out. RiverCAD is not a digital terrain modeling (DTM) application. We have another sister product that does that. You may need to use a DTM to merge these 2 data sources.

If you have any additional questions or need any further information, please contact me again.

Sincerely,

Chris E. Maeder, M.S.
Senior Technical Engineer
chris.maeder@bossintl.com