Deer Repellent
Deer repellent is among the most effective ways to keep chipmunks away without harming them. You can spray it around trees, on the ground, and along the perimeter of your house. Be sure to re-spray every few weeks and after a hard rain.
Castor Oil
Pour castor oil around chipmunk holes. It smells terrible to chipmunks and won't harm them. Avoid pouring it into their holes. This can cause them to burrow further underground and cause damage to your house. Instead, completely saturate the ground surrounding their holes with castor oil.
Yard Debris
Eliminate nesting areas. If you have a woodpile or debris in your yard, this is an attractive location for chipmunks to build their homes. Clean up your yard to ensure there's no place for chipmunks to hide.
Sound Repellents
Use an ultrasonic repellent. Chipmunks are incredibly skittish because they are prey to so many predators. Ultrasonic machines are motion-activated and emit a high pitched sound that is frightening to chipmunks.
Pets
Allow your pets to play in the yard. Dogs and cats can be great chipmunk deterrents even if they never capture a chipmunk. The chipmunks will see and smell large predators in your yard and avoid building their homes there. If you don't have pets, inflatable snakes and stuffed owls can work wonders to deter chipmunks.