Cob: cob and rocks

[Angela Broach]

I was wondering...  If you built a cob wall about 3 feet thick and had the outside of it with embedded rocks (about grapefruit sized) so that the outside looked like a stone wall with cob mortar, would that help or hurt with possible erosions problems?  On one hand it would seem like it would help because less cob would be exposed, but the rocks may create channels that concentrate any run off.  Also would that cause problems with breathability?  

thanks,
Angela