Thanks much for the tips!
Cell size is 1ft so fairly straightforward.
I also got some hints elsewhere that led me to perform following general steps.
- Generate surface/slope raster
- Generate aggregated slope raster to give general flow direction arrows
- Generate surface/aspect raster from aggregated raster, then changed symbol to a flow arrow that rotates to direction of slope. This allows for easy indication of slope direction for later tracing.
- Create reclass raster of steep slopes over 40% so that I can create a mask of only steep slope areas
- Use the reclass to extract a mask of the surface
- Generate Hydrology/flow direction and flow length from the masked surface
Now I had a raster of flow length only of steep slopes which I shaded with desired break values. Flow length is calculated along the slope starting from zero and counts up with each cell. This is fine but I need to define the whole region of the slope whenever the length is over the 25ft. Being this close, and since the area was limited enough, I just traced polygons over the appropriate regions using the flow direction arrows as a guide to defining the edges of the slope.
Perhaps you have better ideas of how to arrive at the end result like maybe a mathematical expression that would weed out the steep slope areas that didn't have the threshold length, but this worked well enough for me.