Buffer a polygon based on a raster

[PawanThapa]

Dear Experts,

I'm using ArcGIS 10.6.1.

I have a polygon shape file along a river stretch (represents maximum flooding area) and a DEM (30m x 30m raster) reperesnting the eelvation in and around the area.

Now what I need is to extend that boundary-polygon or buffer it towards outside (from the riverline on both sides/banks) such that the new boundary polgon is away from earlier boundary polygon by 3meter increase in elevation (based on the udnerlying DEM) - which means in vertical cliff both boundary line will be same, in high slope the new boundary line will be little further away and in flat slope it will be much furtehr away.

I hope I could make my task clearer. Hoping for the hints from the expert on how to get this done?

Thanking you all!

[PawanThapa]

Any hint please?

[MehdiPira1]

Pawan Thapa‌ One of the options you have is to:

• first create contour lines out of the raster file using  Contour Tool (Spatial Analyst or 3D Analyst).
• Check the closest contour line or the next one to your flooding area which surrounds this area to see what the elevation is. (e.g 3 meters higher)
• Based on that, you can extract the most suitable contour line (it might a closed or an open line).
• then measure the distance between the flooding area boundary and the selected contour line
• you can use this linear unit (measured distance) in your buffer tool (this is not going to be the exact e.g 3 meter higher than the flooding area) or alternatively use the same contour line as a new boundary.