I'm in Sonoma County CA too.  With drought conditions the gophers, that usually stay out in the field, did a number on my sheet mulched backyard growing area ( Toby Hemingway inspired). In a last ditch effort (before making formal wood and hardware clothl raised beds) I made 2 ft high and wide dirt beds and dug down a foot in the trough area and layed down flakes of rice straw in the trough area to see if it would stop the gophers.  Two weeks into it and seems to be working.  Has anyone else tried this?