Inadequate means to handle human waste is one of the greatest risks in the event of a SHTF situation. Not only can it be unpleasant, but disease can spread very quickly.
If the water/pumping system breaks down, the first thing to do is to seal-up your indoor toilet so it cannot be used. There are two reasons for this:
1. After weeks of no use, the water in the trap will evaporate, allowing gases to rise up from the sewer system.
2. If there is no water to flush waste away, you are going to have to manually clean it out at some point.
Simply cover the bowl with a few layers of cling film, close the lid and tape it down.
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You now need to find another method to handle waste. Digging a hole and allowing the waste to drain away into the ground water is not ideal, especially if you might be digging a well in the future. The waste should be stored in some sort of container, where it will compost, and after a year or so, it can be sprinkled on your vegetable patch.
A common system, and the one we use at the cottage, is to collect all solid human waste in a large 20-30 litre container. After each visit, dried leaves, sawdust or dry mulch is added to absorb excess liquid. But don't add too much, it means the container fills too quickly.
Once full, the container is emptied into a composter (ours happens to be an old chest freezer, painted green
). After a year or so, it composts down and becomes extremely lightweight. I won't give any design for compost toilet building, you can find lots of options on google. One thing to remember: Try to limit the amount of pee you add to your composting poo. Pee slows down the composting and greatly increases the smell. A compost toilet without pee has practically no smell. If you can pee somewhere else, it is much better. (One good option is to pee on a bale of straw, which helps to safely break it down.)
Finally, for anyone who has never defacated anywhere else but a flush toilet or a nappy, you should practice as part of your preps. Some "city people" who visit us find it surprisingly difficult. Best to break your "outside poo" virginity now, rather than finding it a challenge during a future time of stress.
I would rather pull them out with pliers!!! 
