how to create polyline of set elevation?

Question

I'm trying to create a polyline (which i can save as .kml) for a public land boundary.  The boundary runs along a river and is defined as the 1,144.3 foot elevation level.  Everything above that elevation is private property.  Everything at or below is public land.  I'm using 70cm lidar DEM that is clipped to the river corridor, only.  I'm using ArcMap 10.7.1.  Can anyone share a process for generating this polyline?

Tim_McGinnes · Accepted Answer

If you have either the 3D Analyst or Spatial Analyst extensions it is pretty easy:

Creating a single contour - this adds a single contour to the map as graphics

Deriving contour lines from a surface - the tools listed here create feature classes of the contours

I would recommend the Contour List tool, which allows you to specify the exact elevation values you want.