I am trying to create polygons around rivers that extend all the way up to the top of the surrounding slopes.
I am currently able to do this using stream data and contour data, but I would have to digitize it by hand. Because this would be a very time consuming process, I was wondering if there was an automated process of identifying ridges within ArcGIS or QGIS. I have attached two figures to show what I mean.
In Figure 1, you can see the contour lines surrounding the river. From this, it is very clear from the contours that there is a steep slope on either side of the river.
In Figure 2, I have filled in the area with red showing the desired polygon I would like to make.
Does anyone know if the software can identify these areas of steep elevation change using contour data and create a polygon of the area between them? Or, would my only choice be to digitize?