Since dogs dig for many different reasons, determining the reason for your dogs digging will make the problem much easier to solve. Ask yourself if your dog is:

• Digging to bury toys, etc.? Tie her toys with cable to a stationary object in a comfortable spot.
• Digging to make a cool spot? Purchase a hose mister and/or wading pool to make a new shady cool spot. If you have a long hair dog, get her a summer haircut.
• Digging at gophers? Call an exterminator.
• Digging just because it's fun? Fill all existing and new holes with your dog's solid waste and then cover with approximately 1" of dirt. Do not let her see you filling the holes. Never dig or plant in front of her. Exercise her much more than you are now. Give her new and interesting toys to keep her busy.
• Digging to escape? Spend more time playing with your dog in the backyard. Make every effort to have the backyard a fun place to be. Hide food treats all over the yard and let her spend hours trying to find them all. Exercise her much more than you are now. Each time you catch her digging, interrupt her with a noise that would startle her, but not frighten her. Never let her know the noise came from you or she may just continue digging when you are not around. Make sure to fortify the fence line to ensure that she can't actually escape.