Imagine that you live in a $450,000 home situated along a stream out in the country. With very heavy rains, the stream rises about three feet, but your home is two feet above that level.One day, though, upstream, a landslide changes the flow of another stream. It previously fed into your stream below your home. Now it feeds into it upstream. So now your stream’s normal level is three feet higher than before, which means that with a three-foot rise from a heavy rain you’ll have a foot of water in your home. You’ve seen enough of the heavy rains...