Strange Formation On Road Cut

[ethnfreeman]

This on a high wall on a road cut along side of the end of rt 34 in Hamlin Lincoln CO WV, its about 20 ft above the road about 625ft above see level and about 60ft above the mud river am i correct in assuming that this hole was caused by a torrent of water whipping that boulder around inside there its about the size of a medicine ball. Ive seen these on the bottoms of creeks but never up on hillside like that. What kind of flow would it take to do this as far as feet per second i know theres a formula just cant think of it

 

[abyssunder]

Percolating water may shape sediments like limestone, to make them look like that.