I added riprap to my levee when I first built it...for erosion control as well as to discourage muskrats. Seems to have done the job so far. I would recommend landscaping cloth underneath...seems to have really helped in my case, rocks are still in place and haven't sunk much at all.

Dale

[Linked Image from i90.photobucket.com]

"When tempted to fight fire with fire, remember that the Fire Department usually uses water." - anonymous