Human beings often make plans. We do it to find comfort from the terrible unknown that is the future. Plans make us feel safe, give us a sense of control over our lives. That is until the circumstances change and we are left dangling by rocks and roots because our nifty plans just got washed away in the metaphorical flood we had no way of predicting.
Ain’t life grand?
Our characters are (most times) also people. They should also form plans. Then, when they are feeling all cozy, you can change the circumstances of the world they live in, conjure up that flood in whatever form you like and shatter their plans. Nothing gives human beings more shock than re-acquainting ourselves with that one basic fact: we don’t know what the future brings. We can only suspect.
Plans for the future often include missions your character wants to fulfill to deal with a minor problem. The flood distracts said character, making him forget the old plans… but that minor problem she tried to solve is still there and, like all problems left unattended, it is growing. With our character’s attention averted by the effects of the flood, that small problem has time to grow into a large problem.
Devious. That’s what writers are paid to be.