How to clip polyline with z value where it would intersect DEM value?

Question

I hope the question is pretty straightforward.  What would be the workflow if I had a polyline with a certain z value that represents an elevation and I wanted to clip it where it's value is greater than the underlying DEM?   Imagine, if you will, a polyline drawn across a river valley, for instance.  If it had an value of 800 ft, I would like to clip it to length where the DEM values are less than the polyline z value....essentially creating an elevation top width.

Thanks,

Gene

SepheFox · Answer

I'm not sure how feasible your idea is, just because DEMs don't usually contain bathymetry information, ie. the elevation under the water. Some sort of spatial analysis of your DEM might work better, perhaps looking for the breakpoint where the DEM becomes flat at the surface of the water, and then using Con, or a Reclass to separate out just those water areas, and converting those to polygons. Just a thought.

Gene_D · Answer

To expand upon this.  I have a DEM of a river valley and I know the depth of water at many locations on the river (decreasing as I go downstream).  These would be point values on the river.  What I would like to do is come up with a polygon of depth of water that would represent the area under water, based off the DEM and know water depth.  Essentially this would be a very crude inundation map, without advanced hydraulic analysis.  The polygon is a hatched area representing the inundation area.

Gene_D · Answer

Kishor,

I am also going to look at your approach.  If the workflow seems plausible, I should be able to do this with python scripting.