It only takes one night of rain to knock an entire neighborhood's fences down. This is what happens when people knowingly build structure in a flood plain.
Here's the entrance to my yard. This section of fence is completely missing.
http://img832.imageshack.us/img832/5522/1001633m.jpg
...and here's the exit. The chain link fence didn't escape the destruction, either.
http://img845.imageshack.us/img845/4392/1001632.jpg