First, do you have a bird feeder? Typically, chipmunk populations explode due to the availability of non-natural food sources, such as a bird feeder that spills seed. See below for information on managing your bird feeder.
Trapping is still the most effective means of reducing the resident chipmunk population. Use more traps. Understand that after initially reducing the population, you may get reinvasion from neighboring yards until the population in the area restabilizes. Always employ multiple traps to increase efficiency. Check with your state wildlife agency to see whether there are any restrictions about trapping or traps.
Free-roaming cats should NOT be used due to their proclivity to harm valuable species. Additionally, free-roaming cats will be exposed to diseases that may be transmittable to their owners. Poison, even if it was legal, is not a wise option due to the tendency for chipmunks to cache the poison, which then poses a threat to desirable species.
Finally, keep the garage door closed, and consider changing the black landscaping edging around your flower beds. This sounds like a permanent problem, so why not seek a permanent solution?
Resources: (online)
Chipmunk Control
Bird Feeder Management
