The causes for a complete site failure can be anything from a natural disaster to any other bigger accident or incident. You can, for example, have a break in the water pipe that runs through the walls of the server room. Once the water builds up enough pressure, the wall bursts, and the water leaks into the server room. This can cause short circuits and water damage.

A natural disaster linked to water would be flooding. Flash floods are not easy to predict, and can happen in regions where big rivers are located.