Plant a marigold next to every plant- gophers hate the smell and will leave your plants alone.
Alternatively there is a product called "critter ridder" which is made from peppers and spices which deters most ground mamals. You do need to reapply after each rain though.
Of course the old chicken wire trick around the base of each plant works well, but is alot of work if you have hundreds out.....
there are sonic transmitters that piss them off......i poison them but make sure i take care of the dead so higher predators dont eat them........"hello mr gofer lets be friends Boom".....shoot them......you can flood them out .........either way u really gotta kill em. sorry kids.........but the only happy gopher i know is a dead one. root eating bastards dont get me started on deer and wood and pack rats ....do not want
kill killl killlllllll.............sorry its a personal battle.....the furry creatures are mine enemy. i have lost too many tap roots to their mayhem......but if its a small garden the marigold as chimera said, but they will still raid...............destroy them
get some Gopher Getter at Home Depot. Get Stick or something Pointy and poke the area were the dirt comes up find tunnel path, pour the Gopher getter in.. but if you are next to a hill areas you cant get rid of them, just try to keep up and do your best.hope this helps ya.