Our sliding property

A lot of mud has been washing off our garden and onto the sidewalks, and when I saw this tree root exposed at the top of the right-side garden for the first time, I had to admit that it appears that our whole yard is sliding downhill. I suppose without the trees to hold it in place, it is just eroding. Not sure what to do about that, apart from planting more stuff (twist my arm).

The deer are lately making a path directly across our front lawn, in the dark of night.