Natural Erosion

Raining on and off for the past several days, Moon and Copper have become a little bored, I'm afraid.  When I went outside with them yesterday when the sun came out, they both made a bee-line for the edge of the creek.  This is what I saw.

Walking back over there about a half hour later, they were still at IT, frantically digging and digging into the bank beneath the Hosta that edges the entire creek.  I've worked hard for eight years getting that stuff to spead!  Don't they know that????

BUTT Mom, we're almost to his house!  You know one of the little chipmunks that lives beneath your front garden bed!

Is this what they mean by natural erosion?