I don't think a cat is wrecking your veggie garden. What exactly is the
damage being done?

Citrus peels are supposed to repel cats.

It might take a couple of days, but a sure fire way to rid the critter is to
entice the booger with several sardines next to a bowl of antifreeze. Works
every time.

PS - It also works well with skunks, dogs, raccoons, opossums, and other
varmints.

You can also try:

You should also be able to buy some pet/child/garden safe animal
deterrent that is sprinkled on your garden. Watch out for non-safe
products.

Plastic mesh (1cm-2cm squares, that's 1/2 inch - 1 inch for our
metricapped american friends :-) ) from the hardware store placed on
the ground stops them digging and you can cut holes where you want
plants to grow. It is best to this one before the garden is planted.

If you use a decent mulch it will create a matt over the top-soil
which will also deterr them. Some people use old newspapers laid flat
on the garden bed then covered with leaf-litter of mulch.

Dedicate a square of garden to your cat visitors and keep it freshly
turned (which is what attracts the cats). Obviously it is best to do
this a little away from your vege patch.

Good luck...

(snip)

After you harvest and before you replant, rake a few inches of topsoil
to the side.  Lay flat sheets of chickenwire over the area to be planted
and secure with wire stakes.  Conceal the chicken wire with your loose
topsoil or mulch.  Seed through the chickenwire, (This method will deter
birds, as well), or cut holes in the chickenwire for started seedlings.
Enlarge holes as the plants grow.  You will need to mulch for weed
control, since the chickenwire makes manual weed removal difficult.

When a cat tries to dig in the loose topsoil, it will catch its claws in
the chickenwire.  Cats hate this and will soon find another more
comfortable spot to conduct business.

In the meantime, surround your planted area with a swath of closely
spaced vertical sticks, (chopsticks work well).  Make sure the swath is
wide enough to be an obstacle for an athletic cat.  

I've grown organic vegetables and fruit in community garden plots for
years.  A small colony of feral cats share the space and do a great job
of controlling rodents.  The methods above have successfully kept the
cats away from growing areas without harm.

Throw cat toys over in the neighbor's yard to keep them busy over there
instead of in your yard.

Many good suggestions. Another option till the soil in another
area...basically make an area you keep a bit of fresh soil etc. Move some of
the previously left mater into the area might help as well.