A. because it's legal; B. I'm doubtful your hound is digging around in a root tangle; C. there is NO WAY a hound is going to get its' head in a 110; D. there is VERY, VERY LITTLE chance your hound is going to get its' head in a 160. E. that's where the mink are.
I advocate safe, ethical and legal use of bodygrip traps. Setting little holes in root systems IN A WATERCOURSE is not endangering your dogs. I worry more about abandoned barb wire and my dog jumping over a treetop and impaling itself on a branch than traps.