A frequent recommendation I make in geology hazard reports for steep bluff slopes is not to place yard waste on the steep slope. The yard waste will eventually build up mass as more material is added, kills the plants and roots under the waste, and when wet will slide down the slope. Hence the frequency of slope failures increases. It is a common practice and I suspect that there is either a mistaken belief that the yard waste will improve the slope (make it bigger?) or steep slopes are viewed as wasted land suitable for garbage disposal.
I had a field day a couple weeks ago where I encountered slides initiated by yard waste and some other generally poor slope management at multiple sites.
Slide of yard waste pile including the Christmas tree
Tree cutting for the view but with all the material left.
This will kill much of the under brush.
Also is terrible to traverse as a geologist trying to assess the slope.
Another yard waste failure.
This one had covered the train tracks.