Altering the design:
If woodchucks are a serious problem, make the wire-lined trench a foot or more deep and up to 3 feet wide. If you're trying to keep gophers out, dig the trench 2 feet deep and 6 inches wide, line it with 1/4-inch mesh hardware cloth, and/or fill it with coarse gravel.
Raccoons are good climbers. To foil them, extend the top part of the fence to at least 4 feet, and don't attach the topmost 1 foot of fencing to the posts. When the burglars clamber up, the loose section will flop backward and keep the raccoons from climbing over the top.
continue to raid your garden despite the chicken-wire barrier, you can add a single-strand electric fence.
Most garden supply stores sell easy-to-install electric fence kits, with solar-powered or conventional plug-in battery-powered chargers, 100 feet of wire, and plastic posts. You'll find a wealth of options on the Internet for purchasing individual components designed with the home gardener in mind.
Fencing deer out of a garden
requires a more sophisticated approach. A six-strand high-voltage electric fence, with the wires spaced 10 inches apart and the bottom one 8 inches off the ground, is an effective deterrent. But it is an impractical choice for many small-scale growers because of the high cost and complex installation.
Another alternative is to build a fence that is simply too high for a deer to jump over. The absolute minimum height for a jump-proof nonelectric deer fence is 8 feet. Standard woven-wire farm fencing comes 4 feet tall, so it's a common practice to stack one course on top of another to create an 8-foot fence. This method is neither inexpensive nor easy. Yet another option is weather-resistant polypropylene mesh fencing, which is sold as deer fencing and is available in kits for home garden use. Polypropylene mesh is available in several strengths: Use the highest strength if deer are a problem in your area.
Yet another option is to erect two fences, 3 feet or 4 feet high and spaced 3 feet apart, of welded-wire or snow fencing. Deer seldom jump a fence when they can see another fence or obstacle just on the other side. If you already have a fence around your garden and deer become a problem, add a 3-foot nonelectric or a 2-foot single-strand electric fence 3 feet outside the existing one.