Pocket Gophers???

I live in Duncan Oklahoma & my front yard has been taken over by pocket gophers. I have actually flooded one out and killed it. Thinking I had solved the problem the mounds of dirt & sinking ground continued... I have tried everything poisonous granules, sprays, smoke bombs, and even strictnine! My yard has actually gotten so bad I had dirt brought in to semi-level it again. I'm to the point do I keep trying to water & feed my lawn or just let it die so they might move? Hopeful thinking.