I'm mapping quick clay risk areas and have extracted areas which could trigger slides (slope > 1:2.5; height (min/max) > 5m). The areas are separated into zones of roughly equal aspect (30 deg), giving me a direction for each area.
Now I want to map the respective release areas, which are defined as 20x the length of the trigger area.
I thought of resolving this by adding a line (or many) to each area, in the direction of the (rounded) aspect -> cutting the line at the border -> adding a new line 20x the lenght of the line inside starting at the end point.
My problem is, how (if possible at all) do I add lines with a direction to a polygon? Simply min/maxing (using the min and max elevation point inside each polygon) didn't work out, as it often gives a different direction than the aspect due to the nature of, well, nature.
Data available is the DTM, and based on that my trigger areas, aspect etc.
Screenshot plus drawing for explanation: